• TABLE OF CONTENTS
HIDE
 Title Page
 Copyright
 Dedication
 Acknowledgement
 Table of Contents
 Abstract
 Introduction
 Review of literature
 Climatology
 Evapotranspiration
 Soil characteristics
 Agricultural production
 Irrigation equipment
 Water quality
 System analysis
 Summary and conclusions
 Weather data
 Soil data
 Corn data
 Coastal bermudagrass data
 Soybean data
 Water quality data
 Laboratory procedures
 Reference
 Biographical sketch
 Copyright














Title: Effects of municipal effluent irrigation on agricultural production and environmental quality
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Title: Effects of municipal effluent irrigation on agricultural production and environmental quality
Series Title: Effects of municipal effluent irrigation on agricultural production and environmental quality
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Creator: Allhands, Marcus N.,
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Table of Contents
    Title Page
        Page i
    Copyright
        Page ii
    Dedication
        Page iii
    Acknowledgement
        Page iv
        Page v
    Table of Contents
        Page vi
        Page vii
    Abstract
        Page viii
        Page ix
    Introduction
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
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        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
    Review of literature
        Page 18
        Page 19
        Page 20
    Climatology
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
    Evapotranspiration
        Page 32
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        Page 60
        Page 61
    Soil characteristics
        Page 62
        Page 63
        Page 64
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    Agricultural production
        Page 109
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    Irrigation equipment
        Page 230
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    Water quality
        Page 241
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    System analysis
        Page 299
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    Summary and conclusions
        Page 315
        Page 316
        Page 317
        Page 318
        Page 319
    Weather data
        Page 320
        Page 321
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    Soil data
        Page 323
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    Corn data
        Page 340
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    Coastal bermudagrass data
        Page 344
        Page 345
        Page 346
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    Soybean data
        Page 348
        Page 349
    Water quality data
        Page 350
        Page 351
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        Page 353
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    Laboratory procedures
        Page 356
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    Reference
        Page 368
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        Page 377
    Biographical sketch
        Page 378
        Page 379
        Page 380
    Copyright
        Copyright
Full Text














EFFECTS OF MUNICIPAL EFFLUENT
IRRIGATION ON AGRICULTURAL PRODUCTION
AND ENVIRONMENTAL QUALITY


















By

MARCUS N. ALLHANDS


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA


1989



































Copyright 1989

by

Marcus N. Allhands




































I DEDICATE THIS DISSERTATION TO
THE FOUR JOYS OF MY LIFE: AMY,
TAMMY, ABBY, AND ESPECIALLY MY
DEVOTED AND TOLERANT WIFE, PAM


















ACKNOWLEDGMENTS

My abilities, strength, and patience all come from God. I,

therefore, humbly acknowledge Him as Lord and Provider of my life.

Through Jesus Christ He has made me His son.

I express my appreciation to the United States Department of

Agriculture whose Needs Fellowship made it possible for me to return

to college and work on my Ph.D. degree. James Peters, John Dean, Bill

Leseman, and Randy Bond (City of Tallahassee) are acknowledged for the

great aid they gave in providing me with historical data. Walter

Vidak (Pascua Florida Corporation) is recognized and thanked for the

freedom he gave me to conduct my research at the Tallahassee Southeast

Sprayfield. I thank Richard Thompson and Dan Downey for their help

which I could not have done without on our weekly visits to the spray-

field. I wish to thank my supervisory committee members: Dr. Kenneth

Campbell, Dr. Paul Chadik, Dr. Ben Koopman, and Dr. Daniel Spangler.

They were a great help to me both in and out of the classroom.

Special appreciation is given to my parents whose belief in me has

carried me through some very trying times.

I especially extend my appreciation to Christy Neff. The

technical assistance she gave me was invaluable. Her many hours

before the computer screen contributed greatly to the quality of this

work.

My greatest heartfelt appreciation goes to the one I've kept

until last. As my committee chairman, Dr. Allen R. Overman has

iv











guided, encouraged, and supported me throughout my research. The

knowledge he has imparted will serve me well throughout my profes-

sional career. He has been, and always will be, my great mentor. But

above all this, he is my friend.

Use of trade or company names is not an endorsement by the author

or the University of Florida but is for clarification or identifica-

tion only.



















TABLE OF CONTENTS
page
ACKNOWLEDGMENTS.................................................. iv

ABSTRACT ......................................................... viii

CHAPTERS

1 INTRODUCTION............................................... 1

Historical Record........................................... 1
Site Description.. ............................. ............. 8
Geography ................................................ 8
Geology................................................. 8
Wastewater System......................................... 10

2 REVIEW OF LITERATURE........................................ 18

3 CLIMATOLOGY................................................ 21

Historical Record........................................... 21
1988 Record................................................ 23

4 EVAPOTRANSPIRATION ......................................... 32

5 SOIL CHARACTERISTICS ....................................... 62

Physical Properties ........................................ 62
Chemical Properties........................................ 66
pH....................................................... 66
Organic Matter............................................ 69
Available Phosphorus ..................................... 72
Exchangeable Acidity..................................... 73
Extractable Bases........................................ 76
Cation Exchange Capacity.................................. 87

6 AGRICULTURAL PRODUCTION..................................... 109

Corn........................................................ 109
Coastal Bermudagrass....................................... 162
Soybeans ............................................... .... 221
Grazing................................................. .... 227

7 IRRIGATION EQUIPMENT........................................ 230

8 WATER QUALITY.............................................. 241











9 SYSTEM ANALYSIS ............................................ 299

10 SUMMARY AND CONCLUSIONS .................................... 315

APPENDICES

A WEATHER DATA ............................................... 321

B SOIL DATA .................................................. 324

C CORN DATA .................................................. 341

D COASTAL BERMUDAGRASS DATA .................................... 345

E SOYBEAN DATA............................................... 349

F WATER QUALITY DATA ......................................... 351

G LABORATORY PROCEDURES..................................... 357

REFERENCES....................................................... 368

BIOGRAPHICAL SKETCH.............................................. 378


















Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

EFFECTS OF MUNICIPAL EFFLUENT
IRRIGATION ON AGRICULTURAL PRODUCTION
AND ENVIRONMENTAL QUALITY

By

Marcus N. Allhands

August 1989

Chairman: Allen R. Overman, Ph.D.
Major Department: Agricultural Engineering

The performance of a 700 ha wastewater spray irrigation system

located southeast of Tallahassee, Florida, was analyzed to determine

the influence of management practices on system performance. The

sprayfield lies in a karst topography overlain with a deep, drouthy

Lakeland fine sand. This uniform sand forms a layer up to 12 m deep

below which lies a breached, discontinuous clay layer above the Flori-

dan aquifer. Changes in soil characteristics, groundwater quality,

and production yields were studied over an eight-year period. Growth

rate and nutrient assimilation of corn (Zea mays L.), Coastal bermuda-

grass [Cynodon dactylon (L) Pers.], and soybeans (Glycine max.) were

modeled along with a nitrogen balance in the root zone to guide

supplemental nitrogen decisions. Cattle grazing was investigated to

determine its warrant in such a system. Insight was sought to opti-

mize agricultural production, wastewater treatment, and environmental

quality yet stay within regulatory limits.


viii











Soil characteristic changes were positive for both wastewater

treatment and agricultural production. Soil pH has changed from 5.2

to 7.0 within the root zone, while the organic matter has increased

over 2 1/2 times in the top 30 cm. Phosphorus has penetrated only the

top 120 cm as the cation exchange capacity increased quite favorably.

A study was done to investigate the design of irrigation hardware

for use with wastewater effluent. Clogging due to turtle shells,

fish, and pieces of plastic in the effluent influence the selection of

nozzles and regulators.

Groundwater samples from the surficial aquifer 12 m below the

surface were analyzed over the life.of the sprayfield, and it was

found that nitrate concentration trends were tied to historical agri-

cultural management decisions. Excessive supplemental nitrogen as

high as 436 kg/ha/yr yielding a total annual load greater than 1 200

kg-N/ha was applied in the past to corn and Coastal bermudagrass

fields resulting in surficial aquifer nitrate concentrations reaching

36 mg-N/L with 1988 averaging 17 mg-N/L. A management scheme to

reduce supplemental nitrogen application by nearly 60% yet maintain

crop yields was developed.


















CHAPTER 1

INTRODUCTION

Historical Record

We live in a closed system. Nature prevents us from destroying

resources but allows us to modify and relocate. Therefore, our philo-

sophy of viewing waste products as useless things to eliminate must

change to seeing them as resources out of place.

George W. Rafter of the U.S. Geological Survey wrote the follow-

ing paragraph as an introduction to a series of published technical

papers:

Owing to the rapid growth of urban population during the past
few decades, and the consequent increase of pollution of
streams from which water supplies are obtained, the subject
of sewage purification and its relation to the purity of
streams has attracted general attention. In view of the
large number of people concerned and the benefits to be
derived from the dissemination of information on this
subject, there is probably no topic . which is of greater
importance to the country as a whole (Stevens, 1974, p. 23).

This paragraph with its timely message was written in 1897. Seeing

this need in America, George W. Rafter traveled the globe assembling

information on land treatment systems for municipal wastes.

When did organized land treatment of wastes begin?

Designate a place outside the camp where you can go to
relieve yourself. As part of your equipment have some-
thing to dig with and when you relieve yourself, dig a
hole and cover up your excrement (Deuteronomy 23:12,13).

The earliest documented municipal waste irrigation system began

in Bunzlau, Germany, in the year 1531 and operated for over 300 years











(Reed and Crites, 1984). Edinburgh, Scotland, was the site of a land

application system in 1650 where municipal wastes were used to grow

vegetables.

Stevens (1974) reports that Berlin, Germany, began land applica-

tion in 1861, and by 1892 the city, with a population of 1 578 794,

was utilizing 7 700 ha (19 000 ac) of cropped land for sewage dispo-

sal. Two treatment methods were used with continuous success. Part

of the raw sewage was released from ditches along the tops of gently

sloping fields of grass where it trickled slowly through the plants to

collection ditches at the slope bottom and eventually to nearby

streams (the modern overland flow system). The second method (slow

rate irrigation) consisted of row crops being planted in flat diked

terraces which were flooded with sewage. Underdrain pipes were buried

approximately 1 m (40 in) below the terraces to collect the percolate

and release it to adjacent streams.

When Paris, France, began piping its wastes to the plain of Gen-

nevilliers in 1870 for farm irrigation, the people of Paris protested

in alarm because the produce grown on such farms found its way to

Parisienne tables. The objections quickly subsided, and by 1880 the

demand by farmers for irrigation sewage was so great that the city had

to begin selling wastewater to the farmers to regulate its distribu-

tion (Stevens, 1974, p. 36).

The city of Melbourne, Australia, began irrigating the 11 660 ha

(28 810 ac) Werribee Farm System with primary municipal waste in the

1890s. Presently the farm, located only 35 km (22 mi) from a metro-

polis of 22 million people, represents the most productive agricul-

tural land in Australia (Write and Rovey, 1979).











In 1963 the Bortnichy State Farm outside of Kiev, U.S.S.R. began

irrigating 24 300 ha (60 000 ac) of cereal grains, potatoes, fodder,

and pasture with wastewater. This water is 60% chemically treated

industrial waste and 40% secondary activated sludge municipal efflu-

ent. The flow rate exceeded 7.2 m3/s (164 mgd) in 1975. There is no

disinfection of the wastewater before land application, yet the ill-

ness rate of farm workers is no greater than that of the general

public (Write and Rovey, 1979).

Much of the world has had wide success and acceptance of land

treatment of wastes for hundreds of years. This has not been so in

the United States. Unfortunately, the first planned land treatment in

America was attempted at Augusta, Maine in 1872 at the State Insane

Asylum. The system worked so flawlessly that other asylums began

treating their wastes in the same way. Soon land treatment became

associated with such institutions (Stevens, 1974, p. 41).

The first farm for the treatment of municipal wastes was for the

model town of Pullman, Illinois located 24 km (14 mi) south of Chicago

in 1880. Agricultural tile drains were buried 1.4 m (4.5 ft) deep in

the rich black prairie soil to intercept and carry away the percolated

effluent. For many years crops such as cabbage, cauliflower, and

celery returned an 8 to 10% profit in Chicago markets. The farm

eventually failed due to poor management, and the city of Chicago

engulfed the site (Stevens, 1974, p. 42).

Reed and Crites (1984) point out that most of the 143 sewage

treatment facilities in the United States and Canada in 1899 were land

treatment systems. Table 1-1 shows that many systems from that era

are still in use today.











TABLE 1-1. EARLY U.S. LAND TREATMENT SYSTEMS.


Location


Boulder, CO
Calumet City, MI
Woodland, CA
Fresno, CA
San Antonio, TX
Vineland, NJ
Lubbock, TX
South Framingham,


Source: Reed and
* System still in
# Data unavailable


Date Started


1890
1888*
1889*
1891*
1895
1901*
1915*
1889


Crites, 1984, p. 3.
use as of 1984.


Area
ha

#
5
97
1 620
1 620
6
#
#











At the turn of the century, the popularity of land treatment in

America declined rapidly. Technology became the buzz word and engi-

neers began divorcing themselves from traditional ties with the land

in favor of contained biological systems. By the 1930s, municipal

land treatment farms were all but gone in America.

The pendulum began to reverse its direction nearly two decades

ago when federal legislation, known as the Clean Water Act of 1972 (PL

92-500), proposed a zero discharge concept which encouraged the philo-

sophy of reuse and recovery. Thus, much intensive research, of which

this dissertation is one, has been initiated into land application of

wastes for the purpose of waste treatment, pollution abatement, efflu-

ent disposal with future reuse, and agricultural production.

Total population for the state of Florida increased from 2.8

million in 1950 (Pride, 1973) to over 12 million in 1987 (Florida

Statistical Abstract, 1988). Fresh water withdrawn for all uses in

Florida in 1950 was about 39 m3/s (900 mgd) ( Pride, 1973), while

total freshwater withdrawal in 1980 was 319 m3/s (7 300 mgd) (Baldwin

and Carriker, 1985). Per capital use of freshwater in Florida today

exceeds 2 250 1/d (600 gpd) or nearly 10 km3 (2.4 mi3) per year.

Baldwin and Carriker (1985) report that 33.4% of this amount, 3.34 km3

(0.8 mi3), is used consumptively where consumptive use is defined as

water withdrawn from a freshwater source that is not returned to a

useable source, thus being unavailable for reuse except by way of the

hydrologic cycle. This is a tremendous amount of water being made

unavailable each year, especially for a landmass with a peninsular

configuration. Leon County alone withdraws over 1.6 m3/s (36.6 mgd)











of freshwater, 94% of which comes from ground sources. Such a mining

operation must be replaced by reuse and recovery.

The City of Tallahassee embarked on such a course almost thirty

years ago. A 227 m /d (0.06 mgd) high-rate trickling filter was built

in 1961 near the municipal airport. Field tests at the site showed

that an irrigation rate of 100 mm/d (4 in/d) could be applied continu-

ously to the soil. In 1966 the city put into operation a 9 300 m3/d

(2.5 mgd) high-rate trickling filter system at this southwest site to

treat part of the city's ever increasing wastewater load. A pilot

irrigation system was part of this facility to dispose of 3 700 m3/d

(1 mgd) of secondary effluent. Research showed no observable hydrau-

lic problems resulted from the application of 250 mm/d (10 in/d) over

a four-day rotation.

The same facility, now called the Thomas P. Smith Wastewater

Renovation Plant, was enlarged in 1974 with the addition of a 28 000

m /d (7.5 mgd) conventional activated sludge system. Today, this

plant and the smaller Bradford Plant serve the entire city of 123 000

people.

Overman (1979) began an intensive investigation in 1971 to evalu-

ate the effects of wastewater irrigation of a sandy soil on 1) growth

and yields of forage crops, 2) changes in soil and groundwater charac-

teristics, and 3) coupling among transport processes in the soil. The

U.S. Geological Survey did a geological and groundwater study of this

site from 1972 to 1974. Slack (1975) reports on the results of this

study where 68 wells were investigated in the vicinity.

A parcel of land, 750 ha (1 850 ac), was leased by the City of

Tallahassee from a paper company and began receiving wastewater











affluent for irrigation in 1980. This site will be referred to from

\ow on as the TSESF (Tallahassee Southeast Spray Field). In 1981

icua Florida Corporation began managing the land for agricultural

action under contract with the city. The U.S. Geological Survey

'd 52 wells on the site prior to any wastewater application and

intained an extensive groundwater monitoring program since that

Beginning in 1989, the Tallahassee Water Quality Laboratory,

under the direction of William G. Leseman, will assume the responsi-

bility of the groundwater monitoring program. The Agricultural Engi-

neering Department at the University of Florida will continue investi-

gating this dynamic system under the leadership of Dr. A.R. Overman.

Many interwoven disciplines and interests are in operation in a

system such as the TSESF. The Florida Department of Environmental

Regulation requires the system to adhere to strict groundwater quality

standards, the City of Tallahassee has 60 000 m3 (15 800 000 gal) of

wastewater effluent to dispose of each day, and the farmer produces

useable crops such as corn and soybeans. Other major factors in the

success of the system include maintenance, available labor, seed and

fertilizer decisions, weather, effluent constituents, amount of irri-

gation and timing, commodity prices, and changes in surrounding land

uses.











Site Description

Geography

Tallahassee, the capital of Florida, is positioned near the geo-

graphic center of Leon County in the north central panhandle section

of Florida. The City lies 240 km (150 mi) west of Jacksonville and 280

km (175 mi) east of Pensacola. The center of the City is positioned

32 km (20 mi) north of Apalachee Bay on the Gulf of Mexico and just 29

km (18 mi) south of the Georgia state line. Refer to the map located

in the upper right corner of Figure 1-1.

The TSESF lies 13.7 km (8.5 mi) east-southeast of the Thomas P.

Smith Wastewater Renovation Plant (refer to Figure 1-1). The TSESF

site consists of 750 ha (1 850 ac) of rolling sand formerly planted in

pine trees for the pulp industry. Surface elevations range 6-21 m

(20-70 ft) above mean sea level with a general decline toward the

south. Figure 1-2 shows a topographic contour map of the site.

Geology

Hendry and Sproul (1966) divided Leon County into three physio-

graphic divisions: 1) the Northern Highlands, 2) the Gulf Coastal

Lowlands, and 3) the River Valley Lowlands. The TSESF is found in the

Gulf Coastal Lowlands. Cooke (1939, 1945) surmised that the ocean

level dropped during each glacial age, causing the seas to recede from

the land. Between the glacial stages the sea level rose and the seas

advanced upon the land. Each time the sea advanced, a gently seaward-

sloping plain or terrace was formed. The most widely accepted theory

today is that the greatest rise in sea level occurred during the

earliest part of the Pleistocene Epoch, with each succeeding rise

being lower than the previous one (Hendry and Sproul, 1966, p.26).











This leaves a terrace record today scarred by thousands of years of

erosion. Leon County contains two of these marine Pleistocene ter-

races as described by Vernon (1942, 1951). These are the Okefenokee

and Wicomico terraces. The TSESF is located in the Wicomico terrace

formation.

The Coastal Lowlands area was divided by Hendry and Sproul (1966)

into two major units called the Apalachicola Coastal Lowlands and the

Woodville Karst Plain. The Apalachicola Coastal Lowlands covers the

southwest portion of Leon County, while the Woodville Karst Plain lies

southeast of Tallahassee and includes the TSESF.

The sinkhole-sand dune topography of the Woodville Karst Plain is

composed of loose, quartz sands thinly covering a limestone substrata.

This substrata from the Miocene Epoch forms the St. Marks Formation.

Below this is the Oligocene Suwannee Limestone covering the Ocala

Limestone-Avon Park Formation originating in the Eocene Age. These

limestone formations make up the Floridan aquifer system including the

Upper Floridan aquifer (Pruitt et al., 1988, p. 15). Because of qui-

escent crescent-shaped barchan dunes seen on the topographic quad-

rangle for this area, Hendry and Sproul (1966) suggested that pre-

vailing winds came from the northeast, thereby contributing to the

shaping of the land surface.

The permeable overlying sands have allowed rapid infiltration and

percolation of rainwater into the underlying limestones. These solu-

ble limestones have undergone considerable solutioning, thereby lower-

ing the land surface over time much below its original level. Sellards

(1910, p. 50-52) states that this limestone surface may sink at the











rate of 30 cm (12 in) each 5 000 to 6 000 years by solutioning due to

percolating water.

Due to rapid infiltration and high permeabilities, few streams

exist in the Woodville Karst Plain. Clay lenses are found in the

overlying sands, but their thickness and areal extent vary consider-

ably. Elder et al. (1985, p. 15) states that these clay lenses "do

not constitute an effective, continuous confining bed because of

interfingering with the sand and because of breaching by sinkhole

development." Figure 1-3 shows the thickness of unconsolidated

deposits above the Floridan aquifer system. Cross section A-A' shown

in Figures 1-3 and 1-4 demonstrates the upper geologic variability at

the TSESF site.

Wastewater System

The City of Tallahassee maintains two wastewater treatment facil-

ities. The Lake Bradford Treatment Plant uses both trickling filters

and activated sludge processes to treat municipal wastewaters. The

Thomas P. Smith Wastewater Renovation Plant utilizes the activated

sludge process with a design capacity of 66 200 m3/day (17.5 mgd).

The average 1988 daily flows were 14 700 m3/day (3.88 mgd) and 45 120

m /day (11.92 mgd) (personal communication from John L. Dean, Sewer

Division Superintendent, Tallahassee, Florida) for the Lake Bradford

and Thomas P. Smith plants, respectively. Payne (1987) found combined

flows to have been 24 100 m3/day (6.37 mgd) for 1981, 34 700 m3/day

(9.17 mgd) for 1982, 38 400 m3/day (10.14 mgd) for 1983, 49 600 m3/day

(13.10 mgd) for 1984, 49 200 m3/day (13.00 mgd) for 1985, and 52 600

m3/day (13.90 mgd) for 1986.











Secondary effluent from the Lake Bradford and Thomas P. Smith

plants is released to holding ponds, with a maximum 7-day storage

capacity, at the Thomas P. Smith site where average retention time is

2 days. From these ponds it is pumped 13.7 km (8.5 mi) to holding

ponds at the TSESF. An average 1-day retention time at this site

raises the average total retention time after chlorination at the

treatment plants to 3 days. The effluent is then pumped through the

irrigation system by four 331 L/s (5 250 gpm) pumps.

Thirteen center pivot irrigation units ranging in size from 38-67

ha (94-166 ac) make up the sprayfield irrigation system. This puts

695 ha (1 720 ac) under actual irrigation. Figure 1-5 shows the

layout of these pivots and Table 1-2 presents a description of the

pivots.

Effluent application rates for 1988 varied from less than 5.0

cm/week (2.0 in/week) per pivot to over 10.0 cm/week (3.9 in/week) per

pivot with an average rate of 6.1 cm/week (2.4 in/week). The design

loading rate for the entire system is 7.6 cm/week (3 in/week).











PIVOT DESCRIPTION AT TSESF.


Beginning of
Operation


Pivot
Number


1
2
3
4
5
6
7
8
9
10
11
12
13


Area Under
Irrigation
ha ac


1980
1980
1980
1980
1980
1980
1980
1982
1982
1982
1982
1982
1986


94
138
138
138
138
138
138
166
138
138
106
138
106


Design Flowrate
of Center Pivot
L/s gpm


101
92
92
92
92
92
92
110
92
92
69
92
69


600
450
450
450
450
450
450
740
450
450
090
450
090


TABLE 1-2


Nov.
Nov.
Nov.
Nov.
Nov.
Nov.
Nov.
March
March
March
March
March
March





























































FIGURE 1-1. MAP OF THE TSESF LOCALE.


Source: Pruitt, 1988, p. 3.












84*12'40"




65
a~ 0 I 84'10'36'
3022' 50" ,0 BO -

o O,


o o S 6 o ho a
no




o *











EXPLANATION
-30-- TOPOGRAPHIC CONTOUR--Shows attitude of land surface Contour interval 10 feet Hachures
indicate depressions Datum is sea level
0 1.000 2.000 3,000 4.000 5,000 FEET
| I 4 1 I I I
0 500 1.000 METERS



FIGURE 1-2. TOPOGRAPHIC MAP OF THE TSESF.
FIGURE 1-2. TOPOGRAPHIC MAP OF THE TSESF.


Source: Pruitt, 1988, p. 11.













b641240'



HOLDNG
PONDS
12 A
30=22'07 r SES
T4e



A40 EB
\ 40









044

464
\ 2 22 9 10
0 6 4 ,.
o-2* 6 49 44 SPRAYFIELD BOUNDARY
02*3 4 W O-
4 7 3 2 "
EXPLANATION
-60- UNE OF EQUAL THICKNESS OF UNCONSOUDATED DEPOSITS
ABOVE FLORIDAN AQUIFER SYSTEM-Irtefrv 20 feet
A A' LINE OF GEOLOGIC SECTION

94 CONTROL POINT--Upper figure is well numb. lower figure is
thickness, in feet

0 1.000 2.000 3.000 4.000 5.000 FEET
0 500 1.000 METERS


FIGURE 1-3. THICKNESS OF UNCONSOLIDATED DEPOSITS AT TSESF.


Source: Pruitt, 1988, p. 12.














L.
A to
IFEET P- _
FEET5-. -. -


FIGURE 1-4. NORTH-SOUTH CROSS SECTION AT TSESF.


Source: Elder, 1985, p. 18.













84'12'40"



HOLDING


30*22'07. C ^ eS1Es


46,7,36


40,41,42 0 4

AREA A 1,35 AREA B











,23,4 02,31
33 46,470



,8 17,34 14e22,30 0 9 0 0,21,229 SPRAYFIELD BOUNDA

*23, 50 4 *24,51
EXPLANATION

*24,51 WATER-QUAUTY SITE AND INDIVIDUAL WELL NUMBERS

4 PIVOT SPRAY UNIT NUMBER--Area f circles indicates approximate area
where spray irrigation water is applied
0 1.000 2.000 3.000 4000 5.000 FEET
0 500 1.000 METERS





FIGURE 1-5. TSESF LAYOUT.


Source: Pruitt, 1988, p. 4.

















CHAPTER 2

REVIEW OF LITERATURE

The scope of research such as this encompasses many disciplines,

each with its host of literature. The Federal Water Pollution Control

Act Amendments of 1972 (P1 92-500) state that "it is the national goal

that the discharge of pollutants into the navigable waters (natural

streams and lakes) be eliminated by 1985." This act, better known as

the Clean Water Act of 1972, led to a profuse array of publications

concerning land treatment of municipal and industrial wastes. Stevens

(1974), Jewell and Seabrook (1979), and Rafter and Baher (1894) cover

the history of land treatment of wastes very thoroughly. Many early

and existing systems have been reviewed by Wright and Rovey (1979),

Stevens (1972), Sullivan et al. (1973), and Kardos et al. (1974).

There are many books now available to aid in the design of land

treatment systems. Several of the more widely used references come

from the U.S. Environmental Protection Agency (1976, 1978, and 1981).

Metcalf and Eddy, Inc. (1979, pp. 760-828), discuss the design of

irrigation, rapid infiltration, overland flow, wetlands, and aquacul-

ture systems for the treatment of wastewater. Other useful books on

these techniques are Loehr et al. (1979), Reed and Crites (1984), Ful-

ler and Warrick (1985), McGowan (1975), and Reed and Buzzell (1975).

Before the TSESF was put into operation, the hydrogeology of the

area was investigated by Hendry and Sproul (1966) and Slack (1975).

Research into groundwater changes since the operation began in 1980

18











has been conducted by Elder et al. (1985), Yurewicz and Rosenau

(1986), Payne and Overman (1987), and Pruitt et al. (1988).

The general topic of groundwater and its associated geology is

extensively covered by Bouwer (1978), Freeze and Cherry (1979), and

Fetter (1980), while Leet and Judson (1971) treat the subject of phys-

ical geology in a thorough manner. Willrich and Smith (1970) and

Fairchild (1987) delve deeply into the relationships between agricul-

ture and water quality. They cover not only cause and effect but also

modeling and predicting water quality based on the environment and

management. Lamb (1985) provides a comprehensive guide to water chem-

istry as it relates to water quality and potability as does Metcalf

and Eddy, Inc. (1979).

A large number of good references are available today on soils

and soil physics. Included in these are Buckman and Brady (1969),

Hillel (1982), Sposito and Jury (1985), and Chong et al. (1982).

Along these same lines is the topic of solute movement through the

soil. Works by Rao et al. (1976) and Davidson et al. (1983) treat

this area well. More specifically, Starr et al. (1974) and Misra et

al. (1974) address the movement of nitrogen through the soil and its

transformations. This subject is indeed important to the successful

operation of the TSESF.

Agricultural production and plant physiology are key matters in a

system such as land treatment. Classic aid here comes from Salisbury

and Ross (1985), while Heath et al. (1973), Mays (1974), Burton et al.

(1963), and Prine and Burton (1956) lend expertise in forage crop

growth and management. Aldrich et al. (1975) provide a source of

information on corn (Zea mays) production, while Karlen et al. (1987)











and Hanway (1962) have looked at corn nutrient uptake and partitioning

of plant parts.

Extensive modeling pertinent to this research has been done by

Barber (1984) in the area of plant nutrient uptake and by Walton

(1985) on groundwater movement.

Hortenstine (1976) investigated chemical changes in the soil

solution of a spodosol irrigated with secondary wastewater effluent.

The effluent nitrogen in that study was 88% Kjeldahl nitrogen, while

that at the TSESF is 65% nitrate. The study by Hortenstine (1976)

showed no nitrate problems, but phosphorus moved quickly downward

until reaching the spodic horizon at which time it was effectively

immobilized.

Israelsen and Hansen (1962) covered general aspects of irrigation

principles and Payne and Overman (1987) analyzed the performance of

the pivot irrigation system at the TSESF. Due to the diversity of

topics involved in this research, many references are incorporated

into the text as each subject is addressed.


















CHAPTER 3

CLIMATOLOGY

Perhaps the greatest natural resource in Florida is the climate.

The extreme northern region of the state reflects a transitional

climatic zone between temperate and subtropical, while the Florida

Keys experience a truly tropical climate. The unique climate in

Florida is molded by the state's latitude, elevation, and proximity to

the Gulf of Mexico and the Atlantic Ocean. Cold arctic air masses can

move down from the north, bringing snow along with subfreezing temper-

atures. Morris (1983, p. 451) points out seventeen major snowfall

events between the years 1774 and 1977. Four inches of snow fell on

Lake Butler on February 12-13, 1899 with flurries as far south as Fort

Myers (Morris, 1983, p. 451).

The TSESF, at latitude 30021', receives large doses of incoming

solar radiation throughout the year. However, being only 24 km (15

mi) from the Gulf results in cooling convective rains during the

summer and warm breezes during the winter, yielding a mild, moist

climate.

Historical Record

Weather statistics are recorded by the National Weather Service

station number 8-8758 housed at the Tallahassee Regional Airport loca-

ted 15 km (9 mi) west-northwest of the TSESF. The exact location is

30023' north latitude, 84022' west longitude, and 16.8 m (55 ft) above

mean sea level. Table 3-1 shows that average monthly temperatures

21











TABLE 3-1. THIRTY-YEAR AVERAGE CLIMATIC CONDITIONS FOR TALLAHASSEE,
FLORIDA.


Average Monthly Temperaturet


Time Maximum
month F C


Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.


63.4
65.9
72.7
80.0
86.0
90.1
90.9
90.6
87.8
80.4
71.5
65.3


17.4
18.8
22.6
26.7
30.0
32.3
32.7
32.6
31.0
26.9
21.9
18.5


Minimum
UF C


39.9
41.2
47.7
54.0
62.0
68.8
71.5
71.6
68.8
56.4
46.0
40.7


4.4
5.1
8.7
12.2
16.7
20.4
21.9
22.0
20.4
13.6
7.8
4.8


Mean
oF C


51.6
53.6
60.2
67.1
74.0
79.5
81.2
81.1
78.3
68.4
58.8
53.0


Average Monthly
Precipitationt
in mm


10.9
12.0
15.7
19.5
23.3
26.4
27.3
27.3
25.7
20.2
14.9
11.7


4.66
5.00
5.60
4.13
5.16
6.55
8.75
7.30
6.45
3.10
3.31
4.58


118
127
142
105
131
166
222
185
164
79
84
116


t Source: National Climatic Center, 1983.


Yearly 78.7 25.9 55.7 13.2 67.2 19.6 64.59 1 639











vary less than 170C (310F) throughout the year. The lowest official

temperature in Florida, -18.9 C (-20F), was recorded at Tallahassee in

February, 1899 (Mitchell, 1928).

Average monthly precipitation amounts are also shown in Table

3-1. Nearly 50% of the average yearly rainfall occurs during the four

months of June through September as a result of convective thunder-

storms. These are followed by the 2 driest months of the year, Octo-

ber and November. Cyclonic rains are possible throughout the year,

but occur most frequently from November through March (Mitchell and

Ensign, 1928, p. 110). The Tallahassee region has a more uniform

distribution of precipitation over an average year than most parts of

the state. This region receives an average rainfall amount of 1 640

mm/yr (64.6 in/yr).

1988 Record

Temperatures and relative humidities were recorded by a Belfort

5-594 Series Hygrothermograph equipped with a seven-day chart. This

was installed outside the pivot areas away from any buildings or

obstructions. The instrument was housed inside a standard weather

shelter on high ground at a height of 1.5 m (60 in) above the land

surface. Table 3-2 contains the average maximum, minimum, and mean

temperatures for each of the months in 1988. Figure 3-1 shows 1988 to

have been a cooler year than normal with only the months of September,

November, and December having average or above-average temperatures.

Appendix A shows other temperatures for each week of 1988. The

National Weather Service station at the Tallahassee Regional Airport

also recorded average daily wind speed and percent cloud cover.

Appendix A contains climatic data for 1988.











TABLE 3-2. AVERAGE CLIMATIC CONDITIONS AT TSESF, 1988.


Average Monthly Temperature


Time Maximum
month F
month F C


57.4
63.3
70.6
78.8
84.5
90.5
90.1
90.8
87.4
78.7
74.7
68.3


14.1
17.4
21.4
26.0
29.2
32.5
32.3
32.7
30.8
25.9
23.7
20.2


Minimum
-F C


36.8
37.8
46.5
54.5
57.3
66.1
69.3
70.7
69.4
51.6
49.5
40.7


2.7
3.2
8.1
12.5
14.1
18.9
20.7
21.5
20.8
10.9
9.7
4.8


Mean
F C


47.1
50.6
58.6
66.7
70.9
78.3
79.7
80.8
78.2
65.2
62.1
54.5


8.4
10.3
14.8
19.3
21.6
25.7
26.5
27.1
25.7
18.4
16.7
12.5


Average Monthly
Precipitation
in mm


3.50
7.40
5.47
3.66
2.17
1.10
5.39
3.62
9.10
1.34
3.43
1.26


89
188
139
93
55
28
137
92
231
34
87
32


Yearly 77.9 25.5 54.2 12.3 66.1 18.9 47.44 1 205


Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.











Precipitation was recorded by a Weather Measure P501 Tipping

Bucket Rain Gage and seven-day Weather Measure P521 Event Recorder

located in the vicinity of the hygrothermograph and by a Belfort 5-780

Series Recording Weighing Bucket Rain Gage located inside Pivot-11.

Rainfall events are quite localized in this area. Times were observed

in 1988 when heavy rainfall occurred at one area of the sprayfield,

while 100 m (330 ft) away there was no precipitation. The rainfall

recorded at the tipping bucket rain gage showed the amount in 1988 to

be 23% below normal, while the National Weather Service records show

rainfall at the Tallahassee Regional Airport to have been 5% above

normal. The weighing bucket rain gage, located within Pivot 11

approximately 800 m (2 600 ft) east-southeast of the tipping bucket

rain gage, recorded total precipitation to be 25% below normal in

close agreement with the tipping bucket rain gage. Weekly data from

these three recording stations are shown in Table 3-3. Figures 3-2

and 3-3 graphically compare 1988 rainfall at the TSESF to 30-year

averages for Tallahassee.

During the course of this study, rainfall and effluent applica-

tion data for Pivot-11 were taken from the weighing bucket rain gage.

The tipping bucket rain gage, located at the weather station outside

the irrigated area, and a ten inch Taylor rain gage, located within

Pivot-11 near the weighing bucket gage, were used as a check (Table

3-3). Calendar weeks for this data ran from Friday through Thursday

since January 1, 1988 was on Friday.

Pivot-5 was equipped with a ten inch Taylor rain gage within the

same pivot span and at approximately the same elevation as the area

where corn and soybean samples were taken. This rain gage was











TABLE 3-3. PRECIPITATION DATA AT TSESF FOR 1988.


TB
mm in


15
7


3
12
136
25
71
51
0



7
72
3
26
1
13
30
0
29
0
3
2
49
46
1
42
17
6
27
22
32



82
22
0
0
0


0.58
0.27


0.13
0.47
5.37
1.00
2.79
2.01
0



0.29
2.85
0.11
1.03
0.02
0.53
1.20
0
1.15
0
0.12
0.06
1.94
1.82
0.05
1.64
0.66
0.23
1.06
0.87
1.26



3.21
0.87
0
0
0


Precipitation


WB#
mm in


13
7
63
6
4
12
128
37
55
50
0
8
23
1
1
86
1
26
1
7
30
0
23
0
3
2
62
38
0
33
13
5
34
22
39
113
66
11
50
36
0
0
1
0
37
4


NWS
mm in


0.50
0.26
2.48
0.25
0.15
0.46
5.03
1.45
2.18
1.98
0
0.30
0.90
0.05
0.05
3.40
0.05
1.01
0.03
0.28
1.18
0.01
0.90
0
0.13
0.08
2.45
1.50
0
1.28
0.53
0.18
1.33
0.85
1.55
4.45
2.60
0.42
1.95
1.40
0
0
0.05
0
1.45
0.15


40
15
83
23
11
17
50
62
18
30
6
62
141
10
1
0
0
0
35
115
6
0
26
156
109
28
85
12
3
48
23
11
200
4
1
37
34
21
0
9
0
0
0
21
25
111


1.57
0.60
3.27
0.91
0.44
0.68
1.97
2.45
0.71
1.20
0.25
2.45
5.56
0.38
0.05
0.01
0
0
1.39
4.53
0.25
0
1.02
6.13
4.28
1.11
3.36
0.48
0.10
1.90
0.91
0.45
7.88
0.16
0.05
1.45
1.33
0.84
0
0.34
0
0
0
0.84
0.98
4.36


Time
week











TABLE 3-3--continued.

Precipitation
Time TB WB NWS
week mm in mm in mm in

47 12 0.47 1 0.03
48 37 1.47 35 1.38 4 0.14
49 0 0.01 1 0.02 0 0
50 27 1.08 28 1.10 21 0.81
51 2 0.06 0 0 4 0.14
52 3 0.10 3 0.11 2 0.06
52.3 1 0.03 0 0 0 0


t Weeks are Friday through Thursday.
TB Tipping Bucket Rain Gage
# WB Weighing Bucket Rain Gage
NWS National Weather Service, Tallahassee, FL







28



recorded and emptied every Tuesday, so weekly rainfall and effluent

amounts for Pivot-5 were recorded by weeks running from Tuesday

through Monday. Rainfall from the weighing bucket rain gage, located

about 1 200 m (4 000 ft) east of the gage in Pivot-5, was subtracted

from the Taylor rain gage volume for the appropriate days to give

effluent application on Pivot-5.













30 -



25 -
u


U 20 -



-"5 -
L, 15

L.J







Mean 1988 Temperature at TSESF
0 1I I I I1 1 I-I
J F M A M J J A S 0 N D

MONTH


FIGURE 3-1. THIRTY-YEAR AVERAGE TEMPERATURE DATA FOR TALLAHASSEE, FLORIDA.









250


200
E /\



S 150 / \ / I



5 \/
w I



S/ '\
"-' 10




III I I




0
J F M A M J J A S 0 N D
MONTH


AVERAGE PRECIPITATION DATA FOR TALLAHASSEE, FLORIDA.


FIGURE 3-2.









1800
30 Year Average Precipitation
1988 Precipitation at TSESF

1500



E
E 1200

z

< g00 /
I- / /



r 600



300



0
0 I I I I I I I
J F M A M J J A S 0 N D
MONTH


FIGURE 3-3. ACCUMULATED PRECIPITATION FOR TALLAHASSEE, FLORIDA.

















CHAPTER 4

EVAPOTRANSPIRATION

Plants absorb water from the soil through their root systems.

This water is drawn up through the plant xylem eventually reaching the

stomates in the leaves where it evaporates into the atmosphere. This

unidirectional flow of water from the soil through the plant to the

atmosphere, proportional to the vapor pressure gradient at the stomate

-atmosphere interface, is called transpiration. The process does not

constitute an essential function of plant physiology. It is rather a

disadvantageous consequence of the carbon dioxide absorption mechanism

(Salisbury and Ross, 1985. p. 66). Barber (1984) refers to three

mechanisms for supplying water and certain nutrient ions to the root

surface: 1) root interception, 2) mass flow (convection), and 3) dif-

fusion. Root interception and diffusion do not depend on transpira-

tion. Yet, under dry-land farming practices or infrequent irrigation,

transpiration is the driving mechanism for mass flow. Barber (1984,

p. 96) lists the proportion of major plant nutrients supplied by each

of the above three processes. For nutrients such as phosphorus and

potassium, diffusion plays the major role. On the other hand, mass

flow accounts for the greatest supply of nitrogen, calcium, magnesium,

and sulfur. For this reason, transpiration does provide a benefit to

plant growth. However, under conditions of this research, an average

of 76 mm (3.0 in) of water were applied weekly with Pivot-11 reaching

123 mm (4.8 in) over the 1988 calendar year, accounting for more mass

32











flow from percolation to root surfaces than transpiration would

provide. If stomatal evaporation exceeds root uptake, a too negative

water potential arises within the plant causing the condition known as

water stress. Water stress initially restricts water from moving into

cells thereby retarding cell growth. Increasing water stress

adversely affects photosynthesis, synthesis of proteins, and the

building of cell walls. Under the same environmental conditions,

different plant types and species manifest widely diverse soil

moisture demands. Trees may transpire up to 160 L (42.5 gal) of water

per day while a corn plant may only reach about 1.9 L (0.5 gal)

(Viessman et al., 1977. p. 54).

Actual plant transpiration plus the evaporation of water from

soil, rock, free water and vegetative surfaces for a given time

interval is known as evapotranspiration (ET). Potential evapotrans-

piration (ETp) is the amount of water removed, per unit of time, from

the soil and above ground surfaces by transpiration and evaporation if

adequate water is available. Potential evapotranspiration is a

reference for comparison of climatic conditions between different

locations. Van Bavel (1959) listed the following five uses for ET

information: 1) evaluating drought occurrence, 2) flooding, 3) traf-

ficability, 4) current moisture status, and 5) irrigation scheduling.

This research represents a sixth use, that of managing the land

treatment of wastewater.

Viessman et al. (1977) state three basic approaches to deter-

mining ET: 1) theoretical, based on process physics; 2) analytical,

based on energy or water budgets; and 3) empirical. Many methods of

the purely empirical type have been investigated. They have limited











application because of their tendency to be site and crop specific.

Monteith (1985) and Brutsaert (1982) have reviewed the history of ET

research and suggest future research priorities. Hatfield (1988) sees

a trend of moving to newer approaches to ET determination called

evolving methods. Evolving methods attempt to estimate actual ET for

a given set of conditions rather than the potential or reference ET as

earlier methods have done.

A majority of crop water use information being utilized in the

U.S. was developed for arid or semi-arid regions of the country

(Sadler and Camp, 1985). Florida as well as other southeast states

have a much more humid climate. Shih et al. (1983) and Jones et al.

(1984) compared Penman, Thornthwaite, Blaney-Criddle, modified Blaney-

Criddle, and pan evaporation methods to determine their applicability

to the environment of Florida. These procedures incorporate one or

more of the following approaches to ET estimation: empirical formu-

lae, mass transfer, soil moisture budget, energy budget, water budget,

or groundwater fluctuations. This comparison revealed the Penman

method to give the most accurate estimate of ET under humid, Florida

conditions. Penman (1948) incorporated the climatic factors of net

radiation, air temperature, wind speed, and vapor pressure deficit

into a relationship that combined aerodynamic and energy balance equa-

tions to estimate daily ETp.

The Thornthwaite method is based on mean monthly temperature and

day length. In the study by Shih et al. (1983) this method overpre-

dicted ET during the summer months. This is probably due to its lack

of considering increased cloud cover in Florida during these months.

Likewise, the Blaney-Criddle method falls short due to cloud cover











during the summer, being based on average monthly temperature and per-

cent of annual daylight hours in the month. Shih et al. (1977) modi-

fied the Blaney-Criddle method by replacing the daylight component by

a solar radiation component. This modification resulted in estimates

of actual ET second only to Penman under Florida conditions.

Shih (1984) stressed the fact that, for a given time and loca-

tion, climatological data are often not available or are incomplete at

best. Therefore, the method of ETp estimation used may be dictated by

the input data available. The Penman method of ETp determination was

chosen for this research in the light of available climatological

data.

Potential ET as originally derived by Penman estimated the water

transpired by a uniform short green crop, completely shading the

ground and actively growing with an abundant supply of water (Penman,

1948). This described Pivot 11 at the TSESF very well. It was covered

by well established coastal bermudagrass and was irrigated with an

average of 10 cm (3.9 in) of effluent per week plus a weekly average

of 2.3 cm (0.9 in) of rainfall. Under normal conditions, the Penman

ETp is multiplied by a crop coefficient (kc) to determine actual crop

ET, i.e.

ET = (kc)(ETp) [4-1]


where ET estimated crop evapotranspiration

k crop coefficient

ETp potential crop evapotranspiration


The crop coefficient is a function of growth stage, ground cover,

plant species, and frequency of rain or irrigation. Smajstrla et al.











(1984, p. 2) states that during peak water use periods, most crops

with complete vegetative canopies have crop coefficients very near

1.0.

Smajstrla et al. (1984) calculated ETp values for Tallahassee

using 25 years (1952-1976) of hourly weather records provided by the

National Weather Service. Table 4-1 lists these values at the 50%

probability level. The mean monthly ETp values were accumulated and

then normalized by


F Ay [4-2]
n y i- i

where F normalized ETp fraction after month n, n-1,2,3...,12

YT total ETp for the year, mm

Ayi ETp value for month i, mm


When these normalized values, Table 4-2, were plotted as a probability

graph as Figure 4-1 shows, they fit a straight line very well. This,

in turn, suggested a nearly normal distribution of ETp over time.

Since ETp is very sensitive to solar radiation (Smajstrla et al.,

1986), and solar radiation approaches a normal distribution over each

calendar year, one would expect such a relationship. This pointed to

the regression equation

t-t
F 1/2 [1 + erf(J)] [4-3]


where t time, calendar weeks from January 1

t = mean time, calendar weeks from January 1

a time spread, weeks

F normalized fraction











TABLE 4-1. POTENTIAL EVAPOTRANSPIRATION
PENMAN METHOD FOR TALLAHASSEE, FLORIDA.
ETp WILL NOT BE EXCEEDED IS 50%.


Calendar
Time


Mean
Daily
ETp t


(ETp) CALCULATED BY THE
PROBABILITY LEVEL AT WHICH


Mean
Monthly
ETp


week month


4.4
8.6
13.0
17.3
21.7
26.0
30.4
34.9
39.1
43.6
47.9
52.3


mm in


1.6
2.3
3.0
4.0
4.5
4.7
4.3
4.1
3.7
2.9
2.0
1.4


0.06
0.09
0.12
0.16
0.18
0.19
0.17
0.16
0.15
0.11
0.08
0.06


50.3
65.3
94.5
120.6
139.1
140.6
133.8
126.8
109.9
89.2
59.9
44.8


Smajstrla et al. (1984).


mm


in

1.98
2.57
3.72
4.75
5.48
5.54
5.27
4.99
4.33
3.51
2.36
1.76


Annual 1 174.8 46.26


f Source:











TABLE 4-2. CUMULATIVE AND NORMALIZED MONTHLY ETp FOR TALLAHASSEE,
FLORIDA, CALCULATED BY THE PENMAN METHOD USING 25-YEAR AVERAGE DATA.


Time

week month


4.4
8.6
13.0
17.3
21.7
26.0
30.4
34.9
39.1
43.6
47.9
52.3


Accumulated
Monthly
ETp


Normalized
Monthly
ETp


mm


50.3
115.6
210.1
330.7
469.8
610.4
744.2
871.0
980.9
070.1
130.0
174.8


1.98
4.55
8.27
13.02
18.50
24.04
29.31
34.30
38.63
42.14
44.50
46.26


0.043
0.098
0.179
0.281
0.400
0.520
0.633
0.741
0.835
0.911
0.962
1.000










erf(x) error function (Abramowitz & Stegun, 1965, p. 297)


2__ x 2
2= -T exp(-u )du



The derivative of Equation [4-3] is the familiar Gaussian distribu-

tion. The parameters t and a were evaluated by nonlinear regression

using the second order Newton-Raphson method as explained by Adby and

Dempster (1974). This analysis resulted in t 25.9 weeks and a -

13.9 weeks with the sum of the squares of the deviations being

0.001 13. This yielded the following equation to determine accumu-

lated ETp from the 25 year average data for the Tallahassee area:


ETp
HEX t-25.9
ZETp --- [1 + erf( 1-1)]} [4-4]



where t calendar weeks from January 1

ETp adjusted accumulated ETp for the year, 1 194 mm


Equation [4-4] can be used to estimate ETp for any time period in

weeks by taking the difference between ZETp at the end of the time

period and ZETp at the beginning of the time period. Figure 4-2 shows

Equation [4-4] plotted along with the original data. Table 4-3 also

makes this comparison. Figure 4-3 shows the linear regression analy-

sis of ETp data versus ETp estimated by Equation [4-4]. Visher and

Hughes (1975) report a yearly ETp value for Tallahassee that differs

from this method by only 50 mm (2 in) or about 4%.

The second approach used to estimate ETp for the TSESF was to

apply the Penman method directly to the climatological data collected












TABLE 4-3. ESTIMATED ETp USING EQUATION [4-4] COMPARED TO ETp FROM
PENMAN METHOD USING 25-YEAR AVERAGE DATA.


Time

week month


4.4
8.6
13.0
17.3
21.7
26.0
30.4
34.9
39.1
43.6
47.9
52.3


Accumulated
Monthly ETp

Data Est

mm mm


50.3
115.6
210.1
330.7
469.8
610.4
744.2
871.0
980.9
070.1
130.0
174.8


69.8
124.3
208.8
319.7
457.4
604.6
753.3
888.4
989.7
068.4
117.2
146.7


Mean
Monthly ETp

Data Est

mm mm


50.3
65.3
94.5
120.6
139.1
140.6
133.8
126.8
109.9
89.2
59.9
44.8


69.8
54.5
84.5
110.9
137.7
147.2
148.7
135.1
101.3
78.7
48.8
29.5











over the year 1988. Jones et al. (1984) recommended the following

form of the Penman equation:


ETp (ARn/A + yEa)/(A + y) [4-5]


where ETp daily potential evapotranspiration, mm/day
0
A slope of saturated vapor pressure curve of air, mb/ C
2
R net radiation, cal/cm day
n
A latent heat of vaporization of water

59.59 0.055 Tavg cal/cm mm

Ea 0.263 (ea-ed)(0.5 + 0.0062 u2)

e vapor pressure of air (e max-e )/2, mb
a *max min
ed vapor pressure at dewpoint temperature Td (for

practical purposes Td T ), mb
d mm
u2 wind speed at a height of 2 meters, km/day

y psychrometric constant 0.66 mb/ C
0
Tavg (Tm + Tmin)/2, C
avg max min
emax maximum vapor pressure of air during a day, mb

emin minimum vapor pressure of air during a day, mb
0
T maximum daily temperature, C
max
Tmin minimum daily temperature, C


The following relations were used to calculate saturated air

vapor pressure as a function of air temperature and the slope of the

saturated vapor pressure-temperature function (Bosen, 1960):


e(T) 33.863 9 [(0.007 38 T + 0.807 2)8 [4-6]

0.000 019 (1.8 T + 48) + 0.001 316]











S- 33.863 9 [0.059 04 (0.007 38 T + 0.807 2) [4-7]
avg
0.000 034 2]


Net radiation, Rn, was estimated from total incoming solar radia-

tion, Rs, and outgoing thermal radiation, Rb. The following relation-

ships were proposed by Penman (1948):


Rn (1-a) Rs R [4-8]

where R net radiation, cal/cm2day
n
Rs total incoming solar radiation, cal/cm2day

Rb net outgoing thermal radiation, cal/cm2day

a albedo


with Rb oT4 (0.56 0.08 Jed (1.42 Rs/R 0.42) [4-9]
k* d S SO

where a Stefan-Boltzmann constant (11.71x10-8 cal/cm2day/ K)
0 0
TK average air temperature, K ( C+273)

Rso total daily cloudless sky radiation, cal/cm2day


Values of R were not measured directly at the TSESF but were

estimated from a function proposed by Fritz and MacDonald (1949), viz.

R (0.35 + 0.61 S) Rs [4-10]
s so
where S percent sunshine hours as a decimal


Jones et al. (1984) stated that values of R estimated from Equa-
s
tion [4-10] should not be in error more than 5 to 10 % when averaged

over several days.

When Equations [4-6] through [4-10] are substituted into Equation

[4-5], the following working equation for the Penman method of deter-

mining ETp in mm/day evolves:












ETp [(1-a) R -oT (0.56 0.08 ) [4-11]
ETp + s


R
(1.42 R- 0.42)] / A
so

+ [- [0.263 (e e)(0.5 + 0.006 2 u)]
A + y a d 2


Equation [4-11] was employed to calculate ETp for each week of

1988 at the TSESF. As suggested by Jones et al. (1984) a value of a -

0.05 was used and then a multiplier of 0.7 was applied to each value

obtained from Equation [4-11]. This established a reference ETp value

for Florida conditions as displayed in Table 4-4. Raw data for this

calculation are found in Appendix A.

Figure 4-4 and Table 4-5 display the crop coefficient, k values

for corn and soybeans at the TSESF as calculated using the method by

Doorenbos and Pruitt (1977). Table 4-6 shows crop coefficient, kc,

values for various grass crops and management plans (Doorenbos and

Pruitt, 1977, p. 45). The kc (low) value is applied immediately after

cutting; however, kc (peak) will be reached in one week under inten-

sive irrigation.

Another method for estimating ETp of turfgrasses specifically for

Florida climates is discussed by Augustin (1985) and McCloud (1955).

Augustin (1985) states that all actively growing and well watered

turfgrasses produce nearly the same amount of ET regardless of manage-

ment. This suggests that the coastal bermudagrass at the TSESF could

be analyzed by the McCloud method to determine ET. McCloud and

Dunavin (1954) compared ET estimates using Blaney-Criddle (1950),

Tabor (1931), and Thornthwaite (1948) methods to a modified Thornth-











TABLE 4-4. ETp AT TALLAHASSEE, FLORIDA FOR 1988 AND FOR LONG-TERM
AVERAGE DATA USING THE PENMAN AND McCLOUD METHODS.


Calendar
week



1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44


Penman ETp
1988

mm

6.5
6.5
10.8
9.7
12.5
12.3
12.2
13.0
15.4
16.9
16.1
17.4
17.6
23.8
22.4
27.6
29.5
23.8
22.5
22.7
28.2
30.3
26.3
21.3
23.2
27.2
25.1
31.7
30.3
27.0
23.4
30.5
19.2
29.7
23.2
18.5
21.4
21.2
22.5
21.6
18.3
17.3
15.6
16.7


Penman ETp
25 Year Avg.

mm

6.5
7.3
8.3
9.4
10.5
11.7
12.9
14.3
15.7
17.1
18.6
20.0
21.5
23.0
24.5
25.9
27.3
28.5
29.7
30.8
31.8
32.6
33.2
33.7
34.1
34.3
34.2
34.0
33.7
33.1
32.4
31.6
30.6
29.5
28.3
27.0
25.6
24.2
22.7
21.2
19.7
18.3
16.8
15.4


McCloud ETp
1988

mm

4.8
3.5
9.0
3.1
11.9
4.5
4.5
6.5
8.6
11.7
7.3
9.0
17.5
19.8
11.9
19.6
29.3
15.0
22.5
28.9
29.3
30.5
32.4
31.7
46.7
60.0
41.1
44.5
48.0
43.9
49.3
49.3
47.3
48.9
47.0
35.6
42.5
48.6
39.7
23.3
12.7
17.2
14.9
16.4


McCloud ETp
Long Term Avg.

mm

1.7
2.1
2.7
3.3
4.1
5.0
6.1
7.4
8.8
10.5
12.2
14.2
16.4
18.8
21.3
24.0
26.7
29.5
32.3
35.1
37.7
40.3
42.6
44.6
46.4
47.8
48.8
49.4
49.6
49.3
48.6
47.5
46.0
44.2
42.1
39.8
37.2
34.5
31.8
28.9
26.2
23.4
20.8
18.3











TABLE 4-4--continued.


Penman ETp
1988


mm


11.2
13.5
11.1
10.2
9.8
9.6
8.0
8.8


Penman ETp
25 Year Avg.

mm


14.0
12.7
11.4
10.3
9.1
8.1
7.2
6.3


McCloud ETp
1988

mm


8.0
18.0
13.8
10.8
7.0
12.4
5.0
12.7


McCloud ETp
Long Term Avg.

mm


16.0
13.8
11.9
10.1
8.5
7.1
5.9
4.8


Calendar
week


Annual 991.0 1 119.9 1 237.4 1 306.0











TABLE 4-5.
METHOD FOR


Plant
Age

weeks

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19


CROP COEFFICIENT, k FOR ROW CROPS USING THE PENMAN
ET.


Corn t



0.97
0.97
0.97
0.99
1.02
1.06
1.10
1.13
1.15
1.15
1.15
1.15
1.15
1.15
1.09
0.99
0.88
0.76
0.66


Soybeans t



0.92
0.92
0.92
0.94
0.97
1.00
1.03
1.05
1.05
1.05
1.05
1.05
1.05
1.05
1.05
0.95
0.76
0.57


Doorenbos and Pruitt (1977).


t Source:











TABLE 4-6.
FOR ET.


CROP COEFFICIENT, k FOR GRASSES USING THE PENMAN METHOD
c


Clover &
Grass Grass-Legume
Alfalfa t for Hay t Mix t Pasture t


k mean 0.85 0.80 1.0 0.95
c
k peak 1.05 1.05 1.05 1.05

k low 0.40 0.75 0.70 0.70
c


t Source:


Doorenbos and Pruitt (1977).











waite-type evapotranspirometer. All of the above methods underesti-

mated ET at mean temperatures above 210C (700F). McCloud (1955)

derived an empirical relationship between measured ET and temperature

as shown by Equation [4-12] and applied it to long term temperature

averages for the Tallahassee area. This also fit the form of Equation

[4-3] quite well resulting in Equation [4-13].


(T-32)
ETp KW(T32) [4-12]

where ETp = daily potential evapotranspiration, in/day

K 0.01

W 1.07
0
T mean temperature, F


Since there is no upper limit to this relationship, its use is to be

restricted to T < 290C (850F) (McCloud, 1955). Values for ETp as

calculated by the McCloud method for long term averages and for 1988

at the TSESF are shown in Table 4-4.


ZETp 664.6 [1 + erf( 28)] [4-13]



Figure 4-5 shows accumulated ETp for the various methods dis-

cussed while Figures 4-6 through 4-9 depict seasonal ETp per week for

the same methods.

Table 4-7 shows estimated ET for the TSESF on Pivot 5 for 1988

during the crop season applying the crop coefficient, kc, values from

Table 4-5 using Equations [4-1], [4-4], [4-11], and [4-12]. Comparing

Figure 4-10 to Figure 4-7 shows how the crop coefficient, kc, affects

ET throughout the year. One can graphically see where ET began to











TABLE 4-7. ET ESTIMATES AT


week



1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44


k
c



1.15
1.15
1.15
1.15
1.15
1.15
1.15
0.90
0.70
0.97
0.97
0.97
0.99
1.02
1.06
1.10
1.13
1.15
1.15
1.15
1.15
1.15
1.15
1.09
0.99
0.88
0.76
0.66
0.92
0.92
0.92
0.94
0.97
1.00
1.03
1.05
1.05
1.05
1.05
1.05
1.05
1.05
1.05
0.95


Penman ET
1988

mm

7.5
7.5
12.4
11.1
14.4
14.1
14.0
11.7
10.8
16.4
15.6
16.8
17.4
24.3
23.7
30.4
33.3
27.3
25.8
26.2
32.4
34.8
30.2
23.2
22.9
23.9
19.0
21.0
27.9
24.8
21.6
28.6
18.6
29.7
23.8
19.5
22.5
22.3
23.7
22.7
19.2
18.2
16.3
15.8


Penman ET
25 Year
Average

mm

7.5
8.4
9.6
10.8
12.1
12.7
14.8
12.9
11.0
16.6
18.0
19.4
21.3
23.5
26.0
28.5
30.9
32.8
34.2
35.4
36.6
37.5
38.2
36.7
33.8
30.2
26.0
22.4
31.0
30.5
29.8
29.7
29.7
29.5
29.2
28.4
26.9
25.4
23.8
22.3
20.7
19.2
17.6
14.6


McCloud ET
1988

mm

5.5
4.0
10.4
3.6
13.7
5.2
5.2
5.9
6.0
11.3
7.1
8.7
17.3
20.2
12.6
21.6
33.1
17.3
25.9
33.2
33.7
35.1
37.3
34.8
46.2
52.8
31.2
29.4
44.2
40.4
45.4
46.3
45.9
48.9
48.4
37.4
44.6
51.0
41.7
24.5
13.3
18.1
15.6
15.6


McCloud ET
Long Term
Average

mm

2.0
2.4
3.1
3.8
4.7
5.8
7.0
6.7
6.2
10.2
11.8
13.8
16.2
19.2
22.6
26.4
30.2
33.9
37.1
40.4
43.4
46.3
49.0
48.6
45.9
42.1
37.1
32.6
45.6
45.4
44.7
44.7
44.6
44.2
43.4
41.8
39.1
36.2
33.4
30.3
27.5
24.6
21.8
17.4


TSESF, PIVOT-5, 1988.












TABLE 4-7--continued.


McCloud ET
1988

mm


6.1
10.3
11.0
9.9
6.9
12.9
5.5
14.6


McCloud ET
Long Term
Average

mm


12.2
7.9
9.5
9.3
8.3
7.4
6.4
5.5


week


k
c


Penman ET
1988

mm


8.5
7.7
8.9
9.4
9.6
10.0
8.7
10.1


0.76
0.57
0.80
0.92
0.98
1.04
1.09
1.15


Penman ET
25 Year
Average

mm


10.6
7.2
9.1
9.5
8.9
8.4
7.9
7.3


Annual 996.2 1 125.0 1 226.8 1 299.7











decrease around week 7 due to the maturing rye cover and again at week

23 when the corn was near maturity. ET was up at week 29 due to young

rapidly growing soybeans. And lastly, ET began increasing at week 47

as the soybeans were harvested and rye once again began growing.

As was stated previously and shown in Figure 3-1, 1988 was cooler

than normal. This is reflected in Table 4-7 as a decrease in ET for

1988 as compared to long term averages by either the Penman or McCloud

method. Although the McCloud method gives results which are very

appealing to application at land treatment sites, its purely empirical

nature lends it to very cautious and limited use as a design criteria.

The intent of the TSESF is not only to dispose of wastewater effluent

but to do so while preserving groundwater quality. The most environ-

mentally sound method of doing this is to be very conservative in

making ET estimates. Therefore, the Penman method, as presented in

Equations [4-1] and [4-11] was used throughout the remainder of this

dissertation.










99. 8


_ 99.0 -
E 9B.0-
I--.

- 95.0 -

-J 90.0 -

w 80.0 -

S 70.0
60.0 -
S 50.0 -
3 40.0 L
-- 30.0 -,,


I-
0 20.0 -

< 10.0
-J
2 5.

. 2.0
< 1.0 -


.2
0 10 20 30 40 50 60


TIME, CALENDAR WEEKS


FIGURE 4-1. 25-YEAR AVERAGE ETp DISTRIBUTION FOR TALLAHASSEE, FLORIDA, USING
PENMAN METHOD.










1200

o 25 Year Average Data

1000


E
E
800

t--
w

w 600
I--
_J


u 400
u



200


0
0 -- I II*
0 10 20 30 40 50 60

TIME, CALENDAR WEEKS


FIGURE 4-2. ETp FOR TALLAHASSEE, FLORIDA, USING EQUATION [4-3].










1200


E 1000 r- u.=aa
E










ui
I-
< 800


w
o- 600
I-
W


< 400
Z3
-_J


< 200



0 I I I ,

0 200 400 600 800 1000 1200

ACCUMULATED ETp DATA, mm


ESTIMATED ETp (EQUATION [4-3]) COMPARED TO DATA (TABLE 4-2).


FIGURE 4-3.















------------


/
/
'\ ,/I


, I I I I
10 20 30 40 50 E
TIME, CALENDAR WEEKS


FIGURE 4-4. CROP COEFFICIENT, kc, AT TSESF FOR 1988.


1.4


1.2


1.0


.8


.6


.4


0.0


Rye

Corn

Soybeans










1400

- PENMAN 1988 ---

1200 --- PENMAN 25 Year Averog

McCLOUD 1988

E 1000 ---- McCLOUD Long Term Average /


I-
w 800

IIl

- 600


U
u
< 400



200




0 10 20 30 40 50 60

TIME, CALENDAR WEEKS


FIGURE 4-5. ACCUMULATED ETp BY THE McCLOUD AND PENMAN METHODS FOR
TALLAHASSEE, FLORIDA.










60




50




40


E
E
30 0 0 0
LJ 0
a- O


20 0 000 00 0 0 0 0
0 0 0
0000
SO0 0 0
CO 00

10 0

00
00



0 10 20 30 40 50 60


TIME, CALENDAR WEEKS


FIGURE 4-6. WEEKLY ETp USING PENMAN AT TALLAHASSEE, FLORIDA, 1988.

























000000000
0 0
0 1


0
0O0


SI I I


TIME, CALENDAR WEEKS


FIGURE 4-7. WEEKLY ETp USING PENMAN AT TALLAHASSEE, FLORIDA, FOR 25-YEAR
AVERAGE DATA.


50




40


0
0
00


















00 0
0


0 00



0
0 0


00
0


0 0 0 0
o 0
S0 00 0
0 0
I ,I I I I ,I ,


TIME. CALENDAR WEEKS


FIGURE 4-8. WEEKLY ETp USING McCLOUD AT TALLAHASSEE, FLORIDA, 1988.


0 0 0


0 0











60




50 0000000

o 0o
0 0

40 -0 0

E o o
E 0 0

OL O
30 0
OO
020 0

20 0 0
0 0
o o

0 0
10 o
000
0 0
0
0 0
0 0

000000 0
0 i I I, I I
0 10 20 30 40 50 60


TIME, CALENDAR WEEKS


FIGURE 4-9. WEEKLY ETp USING McCLOUD AT TALLAHASSEE, FLORIDA, FOR LONG-TERM
AVERAGE DATA.










60




50



40 rye corn soybeans rye

0 0
0
E 0 0




0 a
2 0



20 0 0 0 0
o o
0 0 00


0 0


00 00

0 0 0
0 0 '



0 10 20 30 40 50 60


TIME, CALENDAR WEEKS


FIGURE 4-10. WEEKLY ET USING PENMAN AT TSESF FOR 25-YEAR AVERAGE APPLIED TO
THE 1988 CROP ON PIVOT-5.


















CHAPTER 5

SOIL CHARACTERISTICS

Physical Properties

A soil sample monitoring program was initiated at the TSESF in

May 1983. At that time soil samples were taken at locations that had

never received irrigated effluent to provide background soil charac-

teristics. Pivots 5 and 11 were analyzed separately. Pivot-5 repre-

sents continuous row crops with a winter cover of rye or ryegrass,

while Pivot-11 reflects conditions of a perennial grass crop. Four to

six sets of samples were taken from each pivot at each sampling time.

Samples were taken from Pivot-5 in May 1984 (Payne and Overman,

1987) and October 1988 when the pivot had been in operation for 42 and

95 months, respectively. Pivot-11 was sampled in May 1984, May 1986

(Payne and Overman, 1987), and August 1988 when pivot age was 26, 50,

and 77 months, respectively. Samples were taken with a Model 2400 SK

Versa-Drill (Southern Iowa Manufacturing Company, Osceola, Iowa) using

a 10 cm (4 in) soil auger to arrive at depth and a Shelby Tube to

obtain samples. Samples taken at depths from 15 cm (0.5 ft) to 760 cm

(25 ft) were transported in plastic bags to the laboratory in Gaines-

ville. Analyses were performed at the Agricultural Engineering

Department and the Soil Analytical Laboratory, both located at the

University of Florida, Gainesville.

Volumetric water content and dry bulk density were checked March

1988, August 1988, November 1988, and January 1989. Dry bulk density

62











averaged 1.6 g/cm3 (99.9 Ib/ft3) while mean soil water field capacity

measured 0.10 cm3/cm3 as shown in Table 5-1. These figures agree with

a study by Payne et al. (1988) at the same site.

Payne and Overman (1987) and Overman (1979) referred to the soil

as Lakeland fine sand, a Quartzipsamment in the Entisol order. Parti-

cle size distribution was reported as 96% sand, 3% clay, and 1% silt.

Over 75% of the sand fraction was classified as either medium or fine

sand. Analysis of physical properties showed little variation with

depth down to 760 cm (25 ft) except in August 1988 when clay lenses

were encountered at 7.6 m (25 ft) mean sea level in two out of six

sampling holes in Pivot-11. These clay lenses are reported to be dis-

continuous by Pruitt et al. (1988) and Elder et al. (1985) with thick-

nesses varying considerably. The natural soils are quite drouthy with.

a native cover of slash pine and turkey oak.











TABLE 5-1. SOIL CHARACTERISTICS OF PIVOT-11 AT TSESF.


Time
Last Since
Date Time Temp Wetting Wetting Depth L L
military C cm hr cm g/cm3 3 3cm H
military C cm hr cm g/cm cm /cm cm H20


3-29-88 1400 26


8-10-88 1300 33


5
15
30
60
90
120
150


0.2


25 15
25
30
45
60
90
120
150


1.64
1.59
1.63
1.57
1.54
1.55



1.55

1.54
1.60


.124
.100
.096
.091
.102
.099


53
49
42
37
43
33


762
.034
118
.051
.061 251
57
48
46


11-16-88 1330 27


15
30
45
60
90
120
150
305
460
610
760


1-10-89 1130 21


1250


1.75
1.66
1.59
1.38
1.49
1.47
1.50
1.56
1.53
1.61
1.52


1.61








1.70


.151
.086
.068
.063
.063
.060
.056
.065
.079
.099
.141


60
.089
57
48
41
38
37

37
.128
57
48
41
38
37











TABLE 5-1--continued.


Date Time
military


1-10-89 1350


1450


Temp
C


Last
Wetting
cm


21 2.1


Time
Since
Wetting
hr


Depth
cm


g/cm3


2.2


1.65


15
18
30
60
90
120
150

15
18
30
60
90
120
150


1545


1.65








1.62


cm 3/m
cm /cm


cm H20


36
.114
57
48
41
38
37

35
.119 -
- 57
48
41
38
37

36
.111 -
- 56
- 50
- 45
40
45











Chemical Properties

pH

Buckman and Brady (1969, p. 398) report that a soil pH range from

6 to 7 presents the most favorable biological regime. Available phos-

phorus, potassium, calcium, and molybdenum begin to decrease below a

pH of 6 until their availability is cut in half at pH 5. Nitrifica-

tion and nitrogen fixation both begin to slow below a pH of 5.5, while

the availability of sulfur also begins to decrease at this pH value.

As the soil pH increases above a value of 7, phosphorus availability

again starts to decrease as well as that of boron.

Tables 5-2 and 5-3 along with Figures 5-1 and 5-2 show how the pH

of the soil profile in Pivots 5 and 11 have changed over the operation

of the TSESF. Conditions have improved in both pivots from a back-

ground soil pH of about 5.2 to a current value near 7.0.

The low pH values in the background profile were due to the

dominance of hydrogen ions on cation exchange sites of the soil

colloid complex. Over time, with the heavy application of wastewater

effluent, calcium, magnesium, and sodium from the effluent replaced

the adsorbed hydrogen ions, increasing the base saturation and thus

raising the pH of the soil.

Pivot-5 appears in Figure 5-1 to be approaching equilibrium at pH

6.7 to 7.2 down to a depth of 300 cm (10 ft). This is approaching the

average wastewater effluent of pH 7.2. Below 460 cm (15 ft) there is

little pH change in the profile even after 95 months of operation.

Pivot-11, on the other hand, is shown in Figure 5-2 to have its

soil pH influenced down to a depth of 760 cm (25 ft). The equilibrium











SOIL pH IN WATER SOLUTION AT TSESF, PIVOT-5.


Background


5.20 + 0.20
5.30 + 0.30


5.26
5.30
5.24
5.24
5.26
5.26
5.28
5.28
5.37


0.15
0.19
0.05
0.05
0.17
0.18
0.26
0.15
0.06


pH
After 42 Monthst


6.50 + 0.36
6.73 + 0.06


6.73
6.63
6.17
6.10
6.00
5.07
5.10
5.10
5.07


0.06
0.21
0.84
0.95
0.89
0.21
0.10
0.10
0.12


After 95 Months


7.1 + 0.1
7.2 + 0.1
7.2 + 0.1
7.1 + 0.1
7.0 + 0.2
6.8 + 0.4
6.8 + 0.4
6.8 + 0.3
6.7 + 0.1
5.5 + 0.9
5.3 + 0.8
5.0 + 0.1


Payne and Overman (1987)


Depth
cm ft


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


45
60
90
120
150
210
300
460
610
760


TABLE 5-2.


t Source:











TABLE 5-3.


Depth
cm ft


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


SOIL pH IN WATER SOLUTION AT TSESF, PIVOT-11.


pH


Background


5.20 + 0.20
5.30 + 0.30


5.26
5.30
5.24
5.24
5.26
5.26
5.28
5.28
5.37


0.15
0.19
0.05
0.05
0.17
0.18
0.26
0.15
0.06


After
26 Months


6.33 + 0.15
6.23 + 0.15


6.03
5.70
5.57
5.37
5.17
5.20
5.10
5.13
5.20


0.40
0.82
0.72
0.47
0.12
0.10
0.20
0.12
0.00


After
50 Months


6.68 + 0.10
6.35 + 0.27


6.23
6.14
6.10
6.11
5.83
5.79
5.62
5.64
5.44


0.20
0.16
0.19
0.27
0.51
0.60
0.67
0.55
0.53


After
77 Months


7.0
7.0
7.0
7.1
7.1
7.1
7.0
6.8
6.6
6.8
6.4
6.0


+ 0.1
+ 0.1
+ 0.2
+ 0.2
+ 0.3
+ 0.4
+ 0.3
+ 0.4
+ 0.4
+ 0.3
+ 0.1
* 0.8


Payne and Overman (1987)


t Source:











pH value of 6.8 to 7.1 reaches down to 460 cm (15 ft) or 160 cm (5 ft)

deeper than for Pivot-5.

This can be explained in part by considering the different

cropping schemes practiced on the two pivots. Since Pivot-11 is in

perennial bermudagrass, it affords a sink for effluent disposal when

the row crop pivots need to be dry such as at planting and harvest

times. This was demonstrated in 1988 when Pivot-5 received a yearly

application of 408 cm (161 in) of effluent while Pivot-11 received 521

cm (205 in) or nearly 30% more. This is true even though Pivot-11

received no effluent for four weeks during the month of August.

Organic Matter

Organic matter is the major agent responsible for soil aggrega-

tion (Buckman and Brady, 1969, p. 60). It binds soil particles

together, decreases bulk density, increases water holding capacity,

binds metals, and increases the cation exchange capacity. The

increase in organic matter over time is recorded in Tables 5-4 and 5-5

and shown in Figures 5-3 and 5-4. The organic matter content in

Pivot-11 has increased almost 130% at 15 cm (6 in) after 77 months of

operation while Pivot-5 has shown over 160% increase in 95 months.

This increase is reported by King et al. (1985) to be a result of

farming practices and not due to the contents of the wastewater

applied. Crop residue incorporated into the upper soil zone by

tillage operations and the decay of plant roots supply the observed

increase in organic matter. This indicates that corn and soybean

roots extend down at least 90 cm (36 in) below the surface, and

Coastal bermudagrass roots reach down possibly only 45 cm (18 in).

This agrees with findings by Robertson et al. (1979, 1980) showing











TABLE 5-4.


Depth
cm ft


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


SOIL ORGANIC MATTER (OM) AT TSESF, PIVOT-5.


Organic Matter


Background
%db

0.410 + 0.070
0.140 + 0.030


0.082
0.089
0.054
0.020
0.008
0.012
0.008
0.010
0.018


0.046
0.110
0.066
0.017
0.006
0.009
0.006
0.004
0.009


After 42 Monthst
%db

0.661 + 0.203
0.171 + 0.075


0.086
0.043
0.022
0.018
0.016
0.016
0.016
0.020
0.021


0.031
0.020
0.010
0.008
0.005
0.012
0.006
0.004
0.003


After 95 Months
%db


1.08
0.34
0.22
0.17
0.17
0.05
0.03
0.02
0.18
0.05
0.08
0.12


0.11
0.14
0.08
0.02
0.08
0.03
0.03
0.03
0.30
0.03
0.06
0.14


t Source: Payne and Overman (1987)
%db Percent dry basis











SOIL ORGANIC MATTER (OM) AT TSESF, PIVOT-11.


Background
%db

0.410 + 0.070
0.140 + 0.030


0.082
0.089
0.054
0.020
0.008
0.012
0.008
0.010
0.018


0.046
0.110
0.066
0.017
0.006
0.009
0.006
0.004
0.009


Organic Matter


After
26 Months
%db


0.785 + 0.128
0.202 + 0.077

0.072 + 0.009
0.040 + 0.004
0.028 + 0.002
0.018 + 0.006
0.012 + 0.005
0.011 + 0.004
0.018 + 0.001


After
50 Months
%db


0.842 + 0.276
0.270 + 0.109


0.140
0.072
0.044
0.048
0.030
0.030
0.030
0.030
0.030


0.059
0.038
0.031
0.035
0.000
0.000
0.000
0.000
0.000


t Source: Payne and Overman (1987)
%db Percent dry basis


Depth
cm ft


After
77 Months
%db


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


0.93
0.31
0.18
0.11
0.08
0.02
0.02
0.02
0.02
0.02
0.02
0.00


0.29
0.15
0.10
0.06
0.03
0.02
0.02
0.04
0.02
0.02
0.03
0.00


TABLE 5-5.











corn root penetration in a Lakeland fine sand under infrequent irriga-

tion to extend down 120 cm (48 in) and soybean roots to exceed 150 cm

(60 in) under the same conditions. These same reports show root depth

to decrease as irrigation amount and frequency increase. This trend

predicts a shallower root depth under heavy irrigation as reflected in

Pivots 5 and 11.

Available Phosphorus

At soil pH values of 6.0 to 7.0, available inorganic phosphorus

-2
is present in both ionic forms, H2PO4 and HP42. As pH decreases

-3
the H2PO4 is the prevalent form while PO4 appears under very alka-

line conditions. Plants absorb primarily H2PO4 but can utilize
-2
HP04 however at a much slower rate. Iron, aluminum, and manganese

become more soluble in a mineral soil as conditions become more

acidic. As pH approaches 5.0, soluble iron, aluminum, and, to a

lesser extent, manganese and their hydrous oxides react with H2PO4 to

form insoluble, and thus unavailable, hydroxy-phosphates which remain

fixed in position in the soil profile preventing the phosphorus from

becoming a water pollutant.

Phosphate ions react with exchangeable calcium and CaCO3 to form

tricalcium phosphate, Ca3(P04)2, at soil pH values of 7.0 and above.

Tricalcium phosphate is insoluble and unavailable to plants (Buckman

and Brady, 1969).

During the initial phases of the TSESF, phosphorus was probably

fixed by Fe and Al at low soil pH levels. Presently, with soil pH

around 7.0 and abundant calcium being supplied by the wastewater,

phosphorus is most likely being rendered unavailable by forming

calcium phosphates. During 1988 calcium and phosphorus were supplied











by the wastewater in a molar ratio of 5:1. This results in over three

times more calcium available than is needed to convert all the phos-

phorus applied to tricalcium phosphate under alkaline conditions.

However, since soil pH lies in the range of 6.0 to 7.0, the maximum

amount of available inorganic phosphorus occurs for plant growth.

Some of the phosphorus is tied up in both phytin and nucleic acids

released by organic decay. Phytin is absorbed directly by plant

roots, while nucleic acids are broken down by enzymes on the root sur-

faces, with the phosphorus then being absorbed. As Tables 5-6 and 5-7

show along with Figures 5-5 and 5-6, available phosphorus has been

moving deeper into the soil profile as time proceeds. Table 5-6 indi-

cates for Pivot-5 that a change in available phosphorus occurred down

to a depth of 15 cm (6 in) after 4 months of operation and down to 90

cm (36 in) after 95 months of wastewater application. The phosphorus

front is apparently moving downward at the rate of about 10 cm/yr (4

in/yr). The same analysis applied to Pivot-11 shows the phosphorus

front moving at the rate of 17 cm/yr (7 in/yr).

The North Carolina Department of Agriculture rates soil fertility

as very high when available phosphorus reaches 45 mg/kg (King et al.,

1985, p. 16). A quick look at Figures 5-5 and 5-6 shows that the

irrigated effluent under the existing conditions provides adequate

available phosphorus for maximum crop needs under this criteria.

Exchangeable Acidity

Exchangeable acidity can be defined as the titratable hydrogen

and aluminum ions that can be replaced from the adsorption complex

(Buckman and Brady, 1969). Most virgin Florida soils have had a

majority of the basic cations (Ca Mg K and Na ) leached out











SOIL AVAILABLE PHOSPHORUS AT TSESF, PIVOT-5.


Available Phosphorus


After 4 Months
mg/kg


After 42 Monthst
mg/kg


After 95 Months
mg/kg


7.1 + 5.1
3.4 + 1.5
2.5 + 1.1
2.1 + 0.7
2.2 + 0.9
2.3 + 0.6
2.8 + 1.1


75.2 + 17.3
25.2 + 12.7


0.7
0.9
1.2
0.5
0.6
2.9
0.8
0.7
0.6


Payne and Overman (1987)


Depth
cm ft


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


72.8
55.9
41.6
26.3
10.1
3.8
2.7
3.1
3.9
4.1
4.7
3.2


17.8
2.7
12.8
15.1
10.7
1.3
0.9
0.4
1.3
1.5
2.5
2.0


TABLE 5-6.


t Source:











SOIL AVAILABLE PHOSPHORUS AT TSESF, PIVOT-11.


Available Phosphor s


After
4 Months
mg/kg

7.1 + 5.1
3.4 + 1.5
2.5 + 1.1
2.1 + 0.7
2.2 + 0.9
2.3 + 0.6
2.8 + 1.1


After
26 Months
mg/kg

43.7 + 12.1
3.9 + 2.4


2.8
3.3
3.3
2.9
2.4
2.4
3.2
3.4


1.1
1.0
1.0
0.6
0.8
0.4
0.7
0.3


After
50 Months
mg/kg


61.6 + 16.6
20.9 + 16.5


11.8
5.8
5.4
4.6
4.0
4.4
4.2
4.4
4.9


9.0
4.6
2.3
2.0
2.5
1.2
0.7
0.3
1.6


After
77 Months
mg/kg


80.9
69.6
41.9
29.1
13.4
9.6
5.4
3.1
5.1
4.1
2.5
2.0


28.8
29.7
13.1
7.7
9.1
8.2
3.5
2.3
3.6
0.8
1.1
1.0


Payne and Overman (1987)


Depth
cm ft


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


f Source:


`~~~^----- -~~--r


TABLE 5-7.












leaving adsorption sites to be filled by H+ and A+3. This results in

acid conditions. The procedure for determining exchangeable acidity

is given in Appendix G.

Increases in organic matter provide additional adsorption sites

thereby increasing exchangeable acidity, provided other conditions

remain constant. However, Tables 5-8 and 5-9 and Figures 5-7 and 5-8

display a decrease in exchangeable acidity in the upper soil layer

with time, even though we saw earlier an organic matter build-up and

an increase or no change in acidity in the lower profile. This

decrease in the upper layer is due to H and A+3 being replaced by

Ca +, Mg and Na from the irrigated effluent. The large increase

in exchangeable acidity in the lower profile of Pivot-5, Figure 5-7,

is possibly caused by the increase in H and A+3 resulting from their

displacement from above. However, Pivot-11, Figure 5-8, does not show

this trend. Additional research and operation time are needed to

determine the steady-state conditions.

Exchangeable Bases

Exchangeable bases are the cations mentioned previously (Ca++,

Mg++, K and Na ) which can "exchange" or replace H and Al+3 held in

the soil by adsorption. These cation quantities were determined for

Pivots 5 and 11 by the Soil Analytical Laboratory at the University of

Florida, Gainesville. Tables 5-10 through 5-17 list those results.

They are shown graphically in Figures. 5-9 through 5-16.

Background data on both pivots for each cation show very little
++ ++
change with depth. This quickly changed for Ca++ and Mg+ however,

with the application of wastewater effluent. It is apparent that

steady-state conditions still have not been reached for calcium.











SOIL EXCHANGEABLE ACIDITY AT TSESF, PIVOT-5.


Background
meq/100g

2.15 + 0.45
1.11 + 0.15


0.96
0.70
0.65
0.37
0.33
0.41
0.42
0.49
0.62


0.18
0.08
0.27
0.08
0.11
0.16
0.29
0.17
0.15


Exchangeable Acidity


After 42 Monthst
meq/100 g


1.67 + 0.19
0.91 + 0.17


0.74
0.52
0.47
0.33
0.28
0.33
0.50


0.14
0.17
0.25
0.14
0.05
0.00
0.12


After 95 Months
meq/100 g


1.34
1.06
0.96
0.84
0.64
0.42
0.27
0.29
0.49
0.87
1.28
2.09


0.18
0.21
0.17
0.05
0.12
0.27
0.17
0.07
0.29
0.56
0.51
1.67


Payne and Overman (1987)


Depth
cm ft


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


TABLE 5-8.


t Source:











SOIL EXCHANGEABLE ACIDITY AT TSESF, PIVOT-11.


Exchangeable Acidity


Background
meq/100 g

2.15 0.45
1.11 + 0.15


0.96
0.70
0.65
0.37
0.33
0.41
0.42
0.49
0.62


0.18
0.08
0.27
0.08
0.11
0.16
0.29
0.17
0.15


After
26 Monthst
meq/100 g

1.95 + 0.17
1.20 + 0.41


0.88
0.90
0.80
0.71
0.60
0.44
0.58
0.50


0.17
0.29
0.31
0.38
0.34
0.21
0.12
0.23


After
50 Monthst
meq/100 g

1.35 + 0.26
1.09 + 0.23


0.21
0.25
0.24
0.25
0.20
0.26
0.35
0.26
0.25


0.95
0.72
0.63
0.52
0.52
0.58
0.61
0.54
0.72


After
77 Months
meq/100 g


1.16
0.85
0.69
0.48
0.52
0.48
0.49
0.37
0.69
0.50
0.48
0.63


0.27
0.25
0.33
0.37
0.23
0.25
0.09
0.15
0.26
0.38
0.31
0.48


Payne and Overman (1987)


Depth
cm ft


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


TABLE 5-9.


t Source:











SOIL CALCIUM CATION CONTENT AT TSESF, PIVOT-5.


Background
meq/100 g

0.06 + 0.04
0.05 + 0.03


0.06
0.07
0.05
0.03
0.05
0.04
0.04
0.05
0.05


0.02
0.02
0.01
0.01
0.02
0.02
0.01
0.01
0.01


Ca++
Ca
After 42 Monthst
meq/100 g


1.62 + 0.30
0.47 + 0.16


0.29
0.16
0.09
0.06
0.06
0.02
0.03


0.08
0.04
0.04
0.03
0.04
0.00
0.01


After 95 Months
meq/100 g


2.59
1.32
0.87
0.63
0.36
0.20
0.14
0.13
0.17
0.19
0.19
0.21


0.17
0.34
0.05
0.07
0.12
0.09
0.06
0.03
0.07
0.10
0.11
0.17


Payne and Overman (1987)


Depth
cm ft


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


TABLE 5-10.


f Source:











SOIL CALCIUM CATION CONTENT AT TSESF, PIVOT-11.


Background
meq/100 g

0.06 + 0.04
0.05 + 0.03


0.06
0.07
0.05
0.03
0.05
0.04
0.04
0.05
0.05


0.02
0.02
0.01
0.01
0.02
0.02
0.01
0.01
0.01


After
26 Months
meq/100 g

1.56 + 0.30
0.35 + 0.08


0.12
0.06
0.06
0.06
0.03
0.02
0.03
0.03


Ca


0.10
0.08
0.07
0.03
0.03
0.02
0.00
0.00


After
50 Months
meq/100 g

2.02 + 0.53
0.67 + 0.11


0.42
0.28
0.21
0.14
0.09
0.11
0.11
0.15
0.16


0.07
0.03
0.03
0.04
0.05
0.05
0.06
0.06
0.06


After
77 Months
meq/100 g


2.40
1.06
0.75
0.57
0.37
0.26
0.19
0.09
0.16
0.23
0.12
0.11


0.75
0.31
0.18
0.14
0.06
0.10
0.10
0.02
0.10
0.10
0.05
0.05


Payne and Overman (1987)


Depth
cm ft


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


TABLE 5-11.


t Source:











SOIL MAGNESIUM CATION CONTENT AT TSESF, PIVOT-5.


Background
meq/100 g

0.01 + 0.01
0.01 + 0.01


0.01
0.02
0.01
0.01
0.01
0.02
0.02
0.03
0.02


0.01
0.01
0.01
0.01
0.01
0.02
0.01
0.01
0.01


++
Mg
After 42 Monthst
meq/100 g


0.25 + 0.02
0.13 + 0.01


0.11
0.08
0.05
0.03
0.04
0.03
0.04


0.02
0.03
0.02
0.00
0.01
0.01
0.02


After 95 Months
meq/100 g


0.46
0.24
0.18
0.16
0.13
0.07
0.05
0.04
0.07
0.10
0.10
0.26


0.04
0.06
0.02
0.01
0.04
0.04
0.03
0.01
0.03
0.03
0.05
0.24


Payne and Overman (1987)


Depth
cm ft


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


TABLE 5-12.


f Source:











SOIL MAGNESIUM CATION CONTENT AT TSESF, PIVOT-11.


MVe


Background
meq/100 g

0.01 + 0.01
0.01 + 0.01


0.01
0.02
0.01
0.01
0.01
0.02
0.02
0.03
0.02


0.01
0.01
0.01
0.01
0.01
0.02
0.01
0.01
0.01


After
26 Months
meq/100 g

0.29 + 0.01
0.14 + 0.06


0.13
0.06
0.08
0.06
0.03
0.03
0.03
0.04


0.09
0.04
0.06
0.04
0.02
0.02
0.02
0.02


After
50 Monthst
meq/100 g

0.34 + 0.08
0.14 + 0.02


0.11
0.09
0.07
0.05
0.03
0.04
0.04
0.05
0.05


0.01
0.02
0.01
0.01
0.01
0.01
0.01
0.01
0.01


After
77 Months
meq/100 g


0.39
0.18
0.15
0.14
0.12
0.09
0.05
0.03
0.06
0.07
0.04
0.06


0.10
0.02
0.03
0.02
0.03
0.04
0.01
0.01
0.04
0.03
0.02
0.04


Payne and Overman (1987)


Depth
cm ft


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


TABLE 5-13.


f Source:











SOIL POTASSIUM CATION CONTENT AT TSESF, PIVOT-5.


Background
meq/100 g

0.01 + 0.00
0.01 + 0.00


0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01


0.00
0.01
0.00
0.00
0.00
0.00
0.00
0.00
0.00


After 42 Monthst
meq/100 g


0.06 + 0.01
0.03 + 0.01


0.02
0.02
0.02
0.01
0.01
0.01
0.01


0.00
0.01
0.00
0.00
0.00
0.00
0.01


After 95 Months
meq/100 g


0.05
0.05
0.03
0.03
0.04
0.02
0.02
0.01
0.02
0.02
0.03
0.05


0.02
0.03
0.01
0.01
0.01
0.00
0.00
0.00
0.01
0.01
0.01
0.03


Payne and Overman (1987)


Depth
cm ft


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


TABLE 5-14.


t Source:











SOIL POTASSIUM CATION CONTENT AT TSESF, PIVOT-11.


Background
meq/100 g

0.01 + 0.00
0.01 + 0.00


0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01


0.00
0.01
0.00
0.00
0.00
0.00
0.00
0.00
0.00


After
26 Months
meq/100 g

0.08 + 0.03
0.02 + 0.01


0.02
0.02
0.02
0.02
0.01
0.01
0.01
0.01


0.01
0.00
0.01
0.01
0.01
0.01
0.00
0.00


After
50 Months
meq/100 g

0.03 + 0.02
0.04 + 0.03


0.03
0.03
0.02
0.01
0.01
0.01
0.01
0.02
0.02


0.02
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01


After
77 Months
meq/100 g


0.04
0.03
0.03
0.03
0.02
0.02
0.01
0.01
0.01
0.02
0.01
0.01


0.01
0.02
0.03
0.03
0.01
0.01
0.01
0.00
0.01
0.00
0.00
0.01


Payne and Overman (1987)


Depth
cm ft


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


TABLE 5-15.


f Source:












SOIL SODIUM CATION CONTENT AT TSESF, PIVOT-5.


Background
meq/100 g


Na+
After 42 Monthst
meq/100 g


After 95 Months
meq/100 g


0.04 + 0.01
0.04 + 0.01


0.04
0.05
0.04
0.04
0.05
0.05
0.05
0.04
0.05


0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.00
0.01


0.13 + 0.03
0.12 + 0.04


0.09
0.09
0.08
0.09
0.09
0.07
0.08


0.02
0.02
0.00
0.01
0.02
0.00
0.01


Payne and Overman (1987)


Depth
cm ft


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


0.08 +
0.06 +
0.05 +
0.04 +
0.04 +
0.03 +
0.03 +
0.02 +
0.02 +
0.04 +
0.04
0.06 +


0.00
0.01
0.00
0.00
0.01
0.01
0.01
0.00
0.00
0.01
0.01
0.04


t Source:


TABLE 5-16.











SOIL SODIUM CATION CONTENT AT TSESF, PIVOT-11.


Background
meq/100 g

0.04 + 0.01
0.04 + 0.01


0.04
0.05
0.04
0.04
0.05
0.05
0.05
0.04
0.05


0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.00
0.01


After
26 Months
meq/100 g

0.13 + 0.01
0.10 + 0.02


0.10
0.09
0.10
0.10
0.07
0.08
0.09
0.10


Na+


0.01
0.01
0.02
0.03
0.02
0.02
0.02
0.02


After
50 Months
meq/100 g

0.14 + 0.02
0.11 + 0.02


0.11
0.09
0.08
0.08
0.08
0.08
0.08
0.08
0.09


0.02
0.01
0.02
0.02
0.01
0.01
0.02
0.02
0.01


After
77 Months
meq/100 g


0.07
0.06
0.05
0.05
0.04
0.03
0.03
0.03
0.03
0.04
0.03
0.04


0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.00
0.01
0.01
0.01
0.01


Payne and Overman (1987)


Depth
cm ft


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


TABLE 5-17.


t Source:











Magnesium on the other hand seems to be approaching steady-state at

Pivot-11, Figure 5-12. Pivot-5 is indeterminant because of the large

span of time between the last two sampling periods.

Potassium and sodium show little change with depth even after 95

months of irrigation, Tables 5-14 through 5-17 and Figures 5-13

through 5-16. The higher charged calcium and magnesium ions take up

most of the exchange sites, even though sodium is the base with the

highest concentration in the irrigated wastewater. As the content of

organic matter becomes stable, the number of adsorption sites will

become fixed and the concentrations of basic cations will reach

steady-state in the root zone.

Cation Exchange Capacity

The cation exchange capacity (CEC), also called "total-exchange

capacity", "base-exchange capacity", or "cation-adsorption capacity",

is the sum total of exchangeable base cations (Ca Mg K and

Na+) and exchangeable acidity (H and Al+3) expressed in milli-

equivalents per 100 grams of soil (meq/100g). A milliequivalent is

one milligram of hydrogen or the amount of any other ion that will

combine with or displace it. Results of this study are given in

Tables 5-18 and 5-19 and Figures 5-17 and 5-18. A very close correla-

tion is seen between organic matter, Figure 5-3, and CEC, Figure 5-17,

from 15 cm (6 in) down to 120 cm (48 in) in Pivot-5. CEC has contin-

ued to increase with time in the upper soil profile. No change has

occurred in 95 months of wastewater irrigation in the profile layer

between 120 cm (48 in) and 210 cm (83 in). Then, below 210 cm (83 in)

there is a 350% increase in CEC after 95 months of operation. Figure

5-1 shows how pH was raised considerably down to 300 cm (120 in),











SOIL CATION EXCHANGE CAPACITY (CEC) AT TSESF, PIVOT-5.


Background
meq/100 g


2.27
1.22

1.08
0.85
0.76
0.46
0.45
0.53
0.54
0.62
0.75


CEC
After 42 Monthst
meq/100 g

3.73
1.66

1.25
0.87
0.71
0.52
0.49
0.46
0.66


After 95 Months
meq/100 g

4.52
2.73
2.09
1.70
1.21
0.74
0.51
0.49
0.77
1.22
1.64
2.67


Payne and Overman (1987)


Depth
cm ft


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


TABLE 5-18.


t Source:











SOIL CATION EXCHANGE CAPACITY (CEC) AT TSESF, PIVOT-11.


CEC


Background
meq/100 g

2.27
1.22

1.08
0.85
0.76
0.46
0.45
0.53
0.54
0.62
0.75


After
26 Months
meq/100 g

4.01
1.81

1.25
1.13
1.06
0.95
0.74
0.58
0.74
0.68


After
50 Monthst
meq/100 g

3.86
2.05

1.62
1.21
1.01
0.80
0.73
0.82
0.85
0.84
1.04


After
77 Months
meq/100 g

4.06
2.18
1.67
1.27
1.07
0.88
0.77
0.53
0.95
0.88
0.68
0.85


Payne and Overman (1987)


Depth
cm ft


15
30
45
60
90
120
150
210
300
460
610
760


0.5
1.0
1.5
2.0
3.0
4.0
5.0
7.0
10.0
15.0
20.0
25.0


TABLE 5-19.


t Source:











which ionized hydrogen not permananently held on inorganic colloids

making them replaceable, and thereby releasing additional exchange

sites on the mineral colloids. This explains some increase in CEC

down to that depth. Calcium and magnesium also showed an increasing

trend with depth below 210 cm (83 in) as seen in Figures 5-9 and 5-11.

The greatest cause for this unusual CEC trend with depth is the large

increase in exchangeable acidity shown in Figure 5-7. An explanation

of this would reveal all. However, existing data are not sufficient

to analyze the subject adequately.

The CEC of Pivot-11, Figure 5-18, follows the trend of organic

matter shown in Figure 5-4 very closely. It appears that this well

behaved pattern is approaching steady-state conditions.

After nearly eight years of continuous wastewater effluent

irrigation, many soil characteristics are still changing. Soil pH

continues to increase deeper and deeper into the profile. Organic

matter content is still on the rise within the root zone, while the

CEC is also improving in row crop fields. There is a tremendous

phosphorus holding capacity still available in the soil profile which

will continue for decades. Changes in soil characteristics have all

been positive for both wastewater treatment and agricultural produc-

tion.











pH

3 4 5 6 7 8
0




100




200




300

E



CL


500

o Background
x 42 Months
600 95 Months




700




800


FIGURE 5-1. SOIL pH IN WATER SOLUTION AT TSESF, PIVOT-5.




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