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Group Title: Bulletin University of Florida. Agricultural Experiment Station
Title: Effects of irrigation with sewage effluent on the yields and establishment of napier grass and Japanese cane
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 Material Information
Title: Effects of irrigation with sewage effluent on the yields and establishment of napier grass and Japanese cane
Series Title: Bulletin 215 ; University of Florida. Agricultural Experiment Station
Physical Description: 18 p. : ; 23 cm.
Language: English
Creator: Stokes, W. E ( William Eugene ), 1889-1948
Leukel, W. A ( Walter Anthony )
Barnette, R. M
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville, Fla.
Publication Date: May, 1930
Copyright Date: 1930
 Subjects
Subject: Irrigation water -- Florida   ( lcsh )
Sewage as fertilizer   ( lcsh )
Sugarcane -- Fertilizers -- Florida   ( lcsh )
Grasses -- Fertilizers -- Florida   ( lcsh )
Sugarcane -- Irrigation -- Florida   ( lcsh )
Grasses -- Irrigation -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by W.E. Stokes, W.A. Leukel, R.M. Barnette.
General Note: Cover title.
 Record Information
Bibliographic ID: UF00026853
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltuf - AEN4074
oclc - 18175554
alephbibnum - 000923523

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Bulletin 215 May, 1930


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
Wilmon Newell, Director







EFFECTS OF IRRIGATION WITH SEWAGE
EFFLUENT ON THE YIELDS AND
ESTABLISHMENT OF NAPIER
GRASS AND JAPANESE
CANE

BY
W. E. STOKES
W. A. LEUKEL
R. M. BARNETTE



TECHNICAL BULLETIN








Bulletins will be sent free upon application to the
Florida Agricultural Experiment Station
GAINESVILLE, FLORIDA










BOARD OF CONTROL
P. K. YONGE, Chairman, Pensacola RAYMER F. MAGUIRE, Orlando
A. H. BLENDING, Leesburg FRANK J. WIDEMAN, West Palm Beach
W. B. DAVIS, Perry J. T. DIAMOND, Secretary, Tallahassee

STATION EXECUTIVE STAFF
JOHN J. TIGERT, M.A., LIl.D., President IDA KEELING CRESAP, Librarian
WILMON NEWELL, D. Sc., Director RUBY NEWHALL, Secretary**
S. T. FLEMING, A.B., Asst. Director K. H. GRAHAM, Business Manager
J. FRANCIS COOPER, M.S.A., Editor RACHEL McQUARRIE, Accountant
R. M. FULGHUM, B.S.A., Asst. Editor

MAIN STATION-DEPARTMENTS AND INVESTIGATORS
AGRONOMY ECONOMICS, AGRICULTURAL
W. E. STOKES, M.S., Agronomist C. V. NOBLE, Ph.D., Agricultural Economist
W. A. LEUKEL, Ph.D., Associate BRUCE McKINLEY, A.B., B.S.A., Associate
G. E. RITCHEY, M.S.A., Assistant* M. A. BROOKER, M.S.A., Assistant**
FRED H. HULL, M.S., Assistant JOHN L. WANN, B.S.A., Assistant
J. D. WARNER, M.S., Assistant
JOHN P. CAMP, M.S.A., Assistant ECONOMICS, HOME
ANIMAL HUSBANDRY OUIDA DAVIS ABBOTT, Ph.D., Head
A. L. SHEALY, D.V.M., Veterinarian in L. W. GADDUM, Ph.D., Biochemist
Charge C. F. AHMANN, Ph.D., Physiologist
E. F. THOMAS, D.V.M., Asst. Veterinarian ENTO
R. B. BECKER, Ph.D., Associate in Dairy ENTOMOLOGY
Husbandry J. R. WATSON, A.M., Entomologist
W. M. NEAL, Ph.D., Assistant in Animal A. N. TISSOT, M.S., Assistant
Nutrition H. E. BRATLEY, M.S.A., Assistant
C. R. DAWSON, B.S.A., Assistant Dairy
Investigations HORTICULTURE
CHEMISTRY A. F. CAMP, Ph.D., Horticulturist
W. RUPRECHT Ph.D., Chemt M. R. ENSIGN, M.S., Assistant
R. M. BARNETTE, Ph.D., Associate HAROLD MOWRY, B.S.A. Assistant
C. M. BAREL Ph.D., Assistant A. L. STAHL, Ph.D., Assistant
H. E. MARSHALLBELL, M.S., M.SAssistant G. H. BLACKMON, M.S.A., Pecan Culturist

J. B. HESTER, B.S., Assistant PLANT PATHOLOGY
W. B. TISDALE, Ph.D., Plant Pathologist
COTTON INVESTIGATIONS G. F. WEBER. Ph.D., Associate
W. A. CARVER, Ph.D., Assistant A. H. EDDINS, Ph.D., Assistant
E. F. GROSSMAN, M.A., Assistant** K. W. LOUCKS, M.S., Assistant
RAYMOND CROWN, B.S.A., Field Assistant ERDMAN WEST, B.S., Mycologist

BRANCH STATION AND FIELD WORKERS

R. R. KINCAID, M.S., Assistant Plant Pathologist (Quincy)
JESSE REEVES, Foreman, Tobacco Experiment Station (Quincy)
J. H. JEFFERIES, Superintendent, Citrus Experiment Station (Lake Alfred)
W. A. KUNTZ, A.M., Assistant Plant Pathologist (Lake Alfred)**
B. R. FUDGE, Ph.D., Assistant Chemist (Lake Alfred)
W. L. THOMPSON, B.S., Assistant Entomologist (Lake Alfred)
R. V. ALLISON, Ph.D., Soils Specialist in charge Everglades Experiment Station (Belle Glade)
GEO. E. TEDDER, Foreman, Everglades Experiment Station (Belle Glade)
R. N. LOBDELL, M.S., Assistant Entomologist (Belle Glade)
F. D. STEVENS, B.S., Sugarcane Agronomist (Belle Glade)
H. H. WEDGWORTH, M.S., Associate Plant Pathologist (Belle Glade)
FRED YOUNT, Office Assistant (Belle Glade)
E. R. PURVIS, B.S., Laboratory Assistant in Soils (Belle Glade)
L. O. GRATZ, Ph.D., Associate Plant Pathologist (Hastings)
A. N. BROOKS, Ph.D., Associate Plant Pathologist (Plant City)
A. S. RHOADS, Ph.D., Associate Plant Pathologist (Cocoa)
STACY O. HAWKINS, M.A., Field Assistant in Plant Pathology (Homestead)
L. R. TOY, B.S.A., Assistant Horticulturist (Homestead)
D. G. A. KELBERT, Field Assistant in Plant Pathology (Bradenton)
R. E. NOLEN, M.S.A., Field Assistant in Plant Pathology (Monticello)
FRED W. WALKER, Assistant Entomologist (Monticello)**
D. A. SANDERS, D.V.M., Associate Veterinarian (West Palm Beach)
M. N. WALKER, Ph.D., Associate Plant Pathologist (Leesburg)
W. B. SHIPPY, Ph.D., Assistant Plant Pathologist (Leesburg)
C. C. GOFF, M.S., Assistant Entomologist (Leesburg)
J. W. WILSON, Ph.D., Assistant Entomologist (Pierson)
*In cooperation with U. S. Department of Agriculture.
**On leave of absence.



























CONTENTS

PAGE

SEWAGE IRRIGATION EXPERIMENT .................................... 5

COMPARATIVE YIELDS OF SILAGE .................................... 6

SEWAGE ANALYSIS ................................................. 8

SOIL ANALYSIS .................................................. 8

ORGANIC FOOD RESERVES .......................................... 10

RATIO RELATIONS .................................................. 12

D ISCUSSION .................................................... 14

SUMMARY ........................ ............ ................... 15

LITERATURE CITED ............................................... 16

A PPENDIX ........................................................ 17












EFFECTS OF IRRIGATION WITH SEWAGE EFFLUENT ON
THE YIELDS AND ESTABLISHMENT OF NAPIER
GRASS AND JAPANESE CANE

BY
W. E. STOKES
W. A. LEUKEL
R. M. BARNETTE



Due to higher temperature in Florida during the course of the
year and further to the type of soil developed under this climatic
condition, the establishment of a perennial forage crop presents
a different problem in this State from that in the more northern
portions of the country. The limiting factors for the establish-
ment of a perennial forage crop under Florida conditions appear
to be the distribution of rainfall as related to nitrogen utilization.
An experiment using sewage effluent for irrigation purposes
afforded an opportunity to study the establishment of such forage
crops under Florida conditions.

SEWAGE IRRIGATION EXPERIMENT

In February, 1922, a cooperative agreement was entered into
between the Florida Agricultural Experiment Station of the
University of Florida and the Division of Agricultural Engineer-
ing, Bureau of Public Roads, United States Department of Agri-
culture, for the purpose of studying the use of sewage effluent for
the fertilization of forage crops. For this experiment, eight plats
of Japanese cane (Saccharum officinarum) and eight plats of
Napier grass (Pennisetum purpureum) were established in Feb-
ruary, 1922. Each plat consisted of 6 rows, 6 feet apart on a
gradual sloping area of Norfolk fine sandy soil (deep phase).
Four of each of the eight Napier and Japanese cane plats were
used for irrigation purposes, the remaining four plats receiving
no irrigation.
The sewage effluent used for irrigation was obtained from the
septic tanks employed, at the time, for sewage disposal at the
University of Florida. The receiving tank for the effluent was
placed outside the plats at their lower level. The effluent was








6 Florida Agricultural Experiment Station

pumped to the higher border of the plats through a pipe line
and a valve system installed for distribution. The valves were
so arranged that the effluent flowed by gravity down the four
middles of the six rows of Japanese cane or Napier grass in each
irrigated plat. Each irrigated plat received a 24-hour flow of
this effluent every eight days from early spring until late fall or
until the harvest of the crops, except during the vacation periods
of the University. In 1924 and 1925 a three-row plat of unirri-
gated Napier grass was used to study the effect of irrigation with
city water.
The Napier grass and Japanese cane were cultivated during the
early part of the growing season so as to remove all weed growth
and establish a bed for the effective flow of the water and insure
a better utilization of the effluent by the forage plant.
The effluent was used for irrigation purposes from the spring
of 1922 until the fall of 1925, at which time the plant was dis-
mantled. However, the Napier grass was continued in culture
until the fall of 1928 in order to ascertain the effects of the irri-
gation with sewage effluent upon the subsequent growth of the
grass.

COMPARATIVE YIELDS OF SILAGE
A single harvest of the Japanese cane was made in late fall
when the cane was suitable for silage. Two cuttings of the Napier
grass were made during the season, at a stage of growth when
the grass was most suitable for silage purposes. The yields of
Japanese cane and Napier grass were obtained from the four
inner rows of the irrigated and non-irrigated plats. The area of
the inner four rows harvested was adjusted so as to give a repre-
sentative yield for the plat. The yields for each season from 1922
to 1927, inclusive, were calculated in terms of tons of silage per
acre. The results are given in Table I.
During the years 1922-1925, inclusive, when the sewage was
applied, the average tonnage of Napier grass silage from the sew-
age irrigated areas was 40.57 tons per acre as compared with 17.64
tons per acre from the non-irrigated plats. The average silage
tonnage from the plat irrigated with city water during 1924-25,
inclusive, was 18.86 tons per acre as compared with 16.59 tons per
acre from the non-irrigated area during the same period. The
average yield of silage from the plats irrigated with sewage for
this period was 45.78 tons per acre. The yields of Napier grass







Bulletin 215, Effects of Irrigation 7

silage from the irrigated and non-irrigated plats after the sewage
irrigation was discontinued in 1925 (or for the years 1926-27)
show that the irrigation had a distinct after-effect. The yields
from the plats previously irrigated with sewage were on an aver-
age, 3.3 times as large as those obtained from the non-irrigated
areas. No yields were calculated for the 1928 season; however,
the beneficial effects of the previous irrigation with sewage were
apparent from the larger stand on the irrigated plats.
The average tonnage of Japanese cane silage from the irrigated
plats for 1922-25, inclusive, (during the time of irrigation with
sewage effluent), was 25.89 tons per acre as compared with 15.43
tons per acre from the non-irrigated plats. After 1925, the Jap-
anese cane experiment was discontinued.
There was a marked increase in tonnage of silage of Napier
grass and Japanese cane from the plats irrigated with sewage over

TABLE I.-YIELD IN TONS per acre OF NAPIER GRASS AND JAPANESE CANE
SILAGE FROM IRRIGATED AND NON-IRRIGATED AREAS DURING THE SEASONS
1922-1925, INCLUSIVE, AND YIELD OF NAPIER GRASS SILAGE AFTER SEWAGE
IRRIGATION WAS DISCONTINUED.

Napier grass Japanese cane

Year Irrigated Not Irrigated Irrigated Not
with irrigated with city with irrigated
sewage water sewage
Tons Tons Tons Tons Tons

DURING IRRIGATION

1922......... 28.28 15.79 ..... 29.45 19.02
1923........ 42.43 21.61 ..... 34.97 21.78
1924......... 39.54 14.08 20.34 15.86 9.33
1925......... 52.02 19.09 17.37 23.31 11.59
Average...... 40.57 17.64 18.86 25.89 15.43

IRRIGATION DISCONTINUED

1926......... a12.90 4.59 .........
1927......... 55.44 14.56 ... ..... ..

a-Only one cutting made during season.







8 Florida Agricultural Experiment Station

that from those not irrigated during 1922-25, inclusive. There
was no marked increase in yield of silage of Napier grass from
the plat irrigated with city water over that from plats receiving
no irrigation. Since the yields from the plat irrigated with city
water showed only a slight increase over those from the non-irri-
gated plats, then the greatly increased yields from the sewage-
irrigated plats must not be due to an increased water supply alone.
The plant nutrient materials supplied by the sewage effluent to-
gether with the increased water supply were apparently effective
in bringing about the increased yields during the period that the
plants were irrigated with this effluent. A typical analysis of
the sewage effluent is given in Table II.
TABLE II.-TYPICAL ANALYSIS OF SEWAGE EFFLUENT USED FOR IRRIGATION
PURPOSES.

Parts Parts
Compound per Compound per
million million
Total solids
original 266
Nitrates............. none filtered 125
Nitrites............. 1.21 Phosphorous pentoxide 8.2
Free ammonia....... 27.31 Calcium oxide........ 41.9
Albuminoid ammonia. 5.32 Magnesium oxide..... 19.2

SEWAGE ANALYSIS
From the analysis given in Table II it may be seen that the
nitrogen content of the sewage is relatively high, and the efflu-
ent, in addition, contains a number of nutrient elements; i. e., cal-
cium oxide, phosphorus pentoxide, and magnesium oxide in con-
siderable quantities.
SOIL ANALYSIS
After the irrigation with sewage effluent was discontinued in
November, 1925, soil samples were taken from the irrigated and
non-irrigated plats and prepared for analysis. The loss on igni-
tion was used as a measure of the organic matter content of the
soil. Total nitrogen was determined by the Kjeldahl (1) method
and phosphorus pentoxide by the magnesium nitrate method (1).

*Figures in parentheses (italic) refer to "Literature Cited" in the back
of this Bulletin.









TABLE III.-AVERAGED ANALYSIS OF SOILS FROM EFFLUENT-IRRIGATED AND FROM NON-IRRIGATED PLATES OF NAPIER GRASS AND
JAPANESE CANE.

Loss bPhosphorous Replaceable Replaceable
Depth on Nitrogen pentoxide calcium magnesium pH
ignition oxide oxide

ins. % aLbs. % aLbs. % aLbs. %
per acre per acre per acre

NON-IRR IGATED

0-6............ 1.75 35,000 0.0408 816 0.210 4,200 0.049 0.021 6.33
6-12.......... 1.47 29,400 0.0273 546 0.187 3,940 0.046 0.021 6.29 .

12-18......... 1.27 25,400 0.0169 338 0.206 4,120 0.038 0.021 6.33 0

IRRIGATED WITH SEWAGE EFFLUENT

0-6........... 2.03 40,600 0.0444 888 0.220 4,400 0.074 0.027 6.34
612.......... 1.49 29,800 0.0289 578 0.200 4,000 0.057 0.023 6.34
12-18......... 1.29 25,800 0.0203 406 0.193 3,860 0.051 0.021 6.32

a-On basis of 2,000,000 pounds per acre 6 inches.
b-Analysis made on Napier grass plats only.








10 Florida Agricultural Experiment Station

The replaceable calcium oxide and magnesium oxide were deter-
mined by replacing these bases with a normal ammonium chloride
solution. The hydrogen-ion concentration was determined with
a wedge colorimetric outfit using a clear soil extract. Table III
gives the averaged analysis of the samples taken from the efflu-
ent-irrigated and non-irrigated plats of Napier grass and Jap-
anese cane.
An increase of 6,400 pounds of organic matter and 172 pounds
of nitrogen per acre 18 inches was observed for the effluent-ir-
rigated plats over that of those receiving no such irrigation. No
increase in phosphorus pentoxide was noted, while the percent-
ages of replaceable calcium oxide and magnesium oxide were
increased by the irrigation with sewage effluent. The pH value
- of the soil remained the same. Thus, irrigation with sewage efflu-
ent has increased somewhat the total nutrient supply of the soil
for plant growth.

ORGANIC FOOD RESERVES

Although a slight increase is noted in the soil fertility of the
sewage effluent irrigated plats over that of those not irrigated,
this difference in fertility alone does not account for the out-
standing increase in tonnage yields of Napier grass silage from
the irrigated plats after irrigation was discontinued. Thus, an
explanation for this difference in silage yields after irrigation was
discontinued was attempted from the increased accumulation of
plant foods in the subterranean storage organs of the plants them-
selves. It seems reasonable to assume that with an increased
supply of nitrogen and moisture (as was furnished by the sewage
effluent) an increase in the production of top growth (increased
silage yields) would result. The greater leaf area on such top
growth naturally would result in the elaboration of organic foods
far in excess of the growing needs of the plants, which foods are
in turn translocated to the. lower storage organs of the plant.
This would result in an increased growth of these storage organs
and a larger supply of organic foods for future growth stored
therein.
A study was made to determine whether such an increased
elaboration and storage of organic foods in the storage parts of
the plants in the sewage effluent irrigated plats was a factor in
bringing about the increased silage yields. Samples of crowns and







Bulletin 215, Effects of Irrigation 11

roots of Napier grass from the irrigated and non-irrigated plats
were taken some time before top-growth started in the years
1926-1929, inclusive. These samples consisted of the crowns and
roots of such plants from an area of 60 square feet, or 10 feet
of row. These samples were rapidly dried and prepared by meth-
ods described by Leukel (2).
SThe various carbohydrate compounds and total nitrogen in
these materials were determined, according to methods used by
Leukel (2). The averaged results of these determinations on the
crowns and roots of Napier grass from the sewage irrigated and
non-irrigated plats for the years 1926-1929, inclusive, are given
on the percentage basis in Table IV (see appendix, Table IX for
detailed calculations).
In percentage of dry matter, the roots of the plants were con-
siderably higher than the crowns. There was little variation in
the percentage of dry matter in the roots and crowns of plants
from the sewage irrigated and non-irrigated plats for the period
1926-1929, inclusive. On a percentage basis, the various carbo-
hydrate compounds in the roots and crowns of the plants from the
irrigated and non-irrigated plats show slight variations from one
year to another, being slightly higher in the roots and crowns of
the irrigated plats in most instances. In percentage of total car-
bohydrates, the crowns of the plants from the irrigated plats
were higher during this period (1926-1929) than those from the

TABLE IV.-AVERAGE PERCENTAGE OF DRY MATTER, SUGARS, AND HIGHER
CARBOHYDRATES IN CROWNS AND ROOTS OF NAPIER GRASS DUG PREVIOUS
TO THE PRODUCTION OF SPRING TOP GROWTH FOR THE YEARS 1926 TO
1929, INCLUSIVE.
Irrigated with Not
Compound sewage effluent irrigated
Crowns Roots Crowns Roots
% % % %
Dry matter .......................... 27.750 49.600 26.550 49.825
Reducing sugar ......................... 3.513 1.688 3.452 2.067
Total sugar ......... .... ... .. ........ 4.811 4.113 4.639 4.083
Starches, dextrins, hemicelluloses .......... 25.909 21.345 24.142 20.613
Total carbohydrates ...................... 30.708 25.735 28.781 24.958

All percentages calculated on a dry weight basis except percentage of dry
matter. All carbohydrates given in terms of glucose.







12 Florida Agricultural Experiment Station

non-irrigated. In the roots of the plants from the plats differently
treated, less difference was shown in percentage of total carbo-
hydrates during this period (1926-1929, inclusive). In percent-
age of total nitrogen, the roots and crowns of the Napier grass
plants from the effluent irrigated plats were consistently higher,
except those dug in 1929, in which case the roots of the plants
from the non-irrigated plats were slightly higher.
The average percentage of total carbohydrates in the crowns
and roots of the plants for this period (1926-1929, inclusive), was
slightly higher in these plant parts from the irrigated plats. The
average percentage of nitrogen in the plant parts for this same
period showed a more significant difference in favor of the crowns
and roots of the plants from the effluent irrigated plats.
The quantities of dry matter, various carbohydrate compounds,
total carbohydrates, and total nitrogen in the crowns of the plants
from the sewage irrigated plats were approximately 3.5 times that
of similar materials in the crowns of plants from non-irrigated
plats (Table V).

TABLE V.-AVERAGE WEIGHT IN GRAMS OF DRY MATTER, SUGARS, HIGHER
CARBOHYDRATES AND TOTAL NITROGEN IN CROWNS OF SEWAGE IRRIGATED
AND NON-IRRIGATED NAPIER GRASS DUG PREVIOUS TO THE PRODUCTION OF
SPRING TOP GROWTH FROM 10 FEET OF ROW (OR AN AREA OF 60 SQUARE
FEET) FOR YEARS 1926 TO 1929, INCLUSIVE.
Crowns
Compound Irrigated with Not
sewage effluent irrigated
grams grams
Dry matter ............................. 2,064.747 621.460
Reducing sugar........................... 72.535 21.453
Total sugar.............................. 99.335 28.830
Starches, dextrins, hemicellulose ............ 534.955 150.033
Total carbohydrates ................... 634.043 178.862
Total nitrogen ............................ 25.396 6.693

All carbohydrates given in terms of glucose. All compounds calculated
on a dry weight basis except dry matter.

RATIO RELATIONS
The ratio between the Napier grass silage yields of the non-ir-
rigated and irrigated plats in 1922 at the end of the first year's







Bulletin 215, Effects of Irrigation 13

irrigation was 1:1.8, which ratio widened to 1:2.0 in 1923, 1:2.8
in 1924, and 1:2.7 in 1925. After irrigation was discontinued in
the fall of 1925, the average ratio of the silage yields between the
non-irrigated and irrigated plats was 1:2.8 for 1926 and 1:3.8
for 1927, or an average of 1:3.3 for the two-year period (Table
VI).

TABLE VI.-RATIOS BETWEEN SILAGE YIELDS OF NAPIER GRASS FROM NON-
IRRIGATED AND SEWAGE EFFLUENT IRRIGATED PLATS.
During Irrigation After irrigation was discontinued

Year Ratio Year Ratio

1922................. 1:1.791 1926.............. 1:2.810
1924 ................. 1:1.963 1927.............. 1:3.807
1923................. 1:2.808 Average........... 1:3.308
1925..... ........... 1:2.725


As given in Table VII, the ratios of the quantities of dry mat-
ter, total nitrogen, each of the various carbohydrate compounds
and total carbohydrates in the crowns of plants from non-irri-
gated and irrigated plats are approximately constant.

TABLE VII.-RATIOS BETWEEN THE QUANTITIES OF VARIOUS PLANT COM-
POUNDS IN CROWNS OF NAPIER GRASS FROM NON-IRRIGATED AND SEWAGE
IRRIGATED PLATS.

Compounds
Starches, Total
Dry Reducing Total dextrin and carbo- Total
Matter Sugars Sugars hemicellu- hydrates nitrogen
loses

1: 3.322 1:3.381 1:3.446 1:3.559 1:3.545 1:3.694

Ratio, non-irrigated: sewage-irrigated.

The average ratio between the quantities of dry matter, vari-
ous carbohydrate compounds, total carbohydrates and total ni-
trogen of the Napier grass crowns from non-irrigated and efflu-
ent irrigated plats is 3.5 for the four years during which they
were analyzed.
This ratio is very similar to that obtained between the yields







14 Florida Agricultural Experiment Station

of Napier grass silage from the non-irrigated and the irrigated
plats after discontinuing sewage irrigation.

DISCUSSION
It is apparent that the continued large yields of Napier grass
silage from the irrigated plats, after the discontinuation of the ir-
rigation with sewage effluent, cannot be explained alone on the
basis of a greatly increased soil fertility of the irrigated plats
nor to water alone as shown by the yields of the plat irrigated
with city water. Again, the gradual widening ratios between si-
lage yields from the non-irrigated and irrigated plats indicates a
more effective utilization of various plant nutrients, especially
nitrogen furnished by the sewage effluent during the period of
irrigation (1922-1925, inclusive). This more effective utilization
of plant nutrients resulted in the production of a larger plant sys-
tem. This larger plant system with its increased leaf area in
turn was capable of elaborating larger quantities of organic foods.
This condition is reflected in the increased growth of the lower
storage parts of the plants and the large quantities of organic
foods stored therein.
Analyses show that there are only slight increases in percent-
ages of these organic compounds in the crowns of the plants irri-
gated with sewage over those of plants not irrigated. However,
the quantities of carbohydrate and nitrogenous reserves stored in
the crowns of the plants from the irrigated plats were 3.5 times
as great as such food reserves in the crowns of plants from the
non-irrigated plats. Likewise, the silage yields from the sewage
irrigated and non-irrigated plats are in direct proportion to the
quantities of stored organic food reserves, being 3.3 times as high
from the irrigated plats as from the non-irrigated plats. As al-
ready established (1), the quantity of early vegetative top growth
produced is dependent upon the quantity of organic foods previ-
ously deposited in the storage parts of the plants. The subsequent
growth of the plant and the storage of organic food reserves in
the crowns depend upon a continued elaboration of carbohydrate
and nitrogenous materials which must necessarily be attended
with an absorption of nitrogen from the soil. The analyses of the
crowns subsequent to the discontinuation of the irrigation indicate
that this absorption of nitrogen in the irrigated plats has been
more effective despite the very slight increases of nitrogen due to







Bulletin 215, Effects of Irrigation 15

the irrigation. Thus the establishment of a larger plant system
on the sewage irrigated plats brought about by the increased ni-
trogen supplied by the effluent necessarily accounts for the more
effective utilization of soil nitrogen and the elaboration of organic
foods for increased silage production.
To judge from the above results, it is reasonable to assume that
some perennial forage crops may be effectively established by the
use of other nitrogenous fertilizers applied under favorable mois-
ture conditions.

SUMMARY
A study was made of the possible utilization of sewage from
septic tanks for the irrigation of forage crops. Plats of Napier
grass and Japanese cane were established and irrigated with
sewage effluent for four years.
Yields of silage from these plats as compared with silage yields
from non-irrigated plats and plats irrigated with city water were
taken during the period of irrigation, 1922-25, inclusive, and
thereafter (1926-28). Samples of soil for analyses were col-
ected in 1925 immediately after the discontinuance of irrigation.
Samples of crowns and roots of Napier grass were taken for anal-
ysis previous to production of early spring top growth for the
years 1926 to 1929, inclusive.
The following findings are reported:
1. During the period of irrigation, 1922-25, inclusive, the silage
yields of Japanese cane and Napier grass from the sewage efflu-
ent irrigated plats were higher than yields obtained from the
non-irrigated plats and from the plat irrigated with city water.
The ratio of the yields from the non-irrigated to the sewage irri-
gated plats widened during the course of irrigation, 1922 to 1925,
inclusive.
2. The yields of Napier grass silage from the sewage irrigated
plats subsequent to the discontinuance of irrigation continued to
be about 3.3 times as great as the yields from the non-irrigated
plats.
3. Analyses of typical sewage effluent showed the presence of
considerable quantities of nitrogen compounds.
4. Analyses of the soil after the discontinuance of irrigation
showed only slight increases in nitrogen content.
5. Analyses of the crowns and roots of Napier grass after irri-







16 Florida Agricultural Experiment Station

gation was discontinued showed only slight increases in organic
foods on a percentage basis.
6. On a quantity basis, the organic foods stored in the crowns
of Napier grass from the sewage irrigated plats were 3.5 times
that of those in the crowns of similar plants from plats not irri-
gated with sewage effluent.
7. It appears that the early fertilization of the forage crop with
nitrogen (and perhaps watering) established a larger plant sys-
tem which remained more effective for the better utilization of
soil nutrients and the elaboration of organic plant foods for in-
creased silage production.

LITERATURE CITED
(1) Official and tentative methods of analyses.
A. O. O. C. Revised. Washington, 1924.
(2) LEUKEL, W. A. Utilization and Deposition of reserve foods in Alfal-
fa Plants. Jour. Amer. Soc. Agron., 19: 7: 596-623.











APPENDIX

TABLE VIII.-WEIGHT IN GRAMS OF DRY MATTER, VARIOUS EASILY HYDROLYZABLE CARBOHYDRATES AND TOTAL NITROGEN IN
THE CROWNS OF NAPIER GRASS DUG BEFORE THE PRODUCTION OF TOP GROWTH TOOK PLACE DURING 1927 TO 1929, INCLUSIVE.

1927 1928 1929
Crowns Crowns Crowns

Compound Irrigated Not Irrigated Irrigated Not Irrigated Irrigated Not Irrigated I
with irrigated with city with irrigated with city with irrigated with city
sewage water sewage water sewage water.
grams grams grams grams grams grams grams grams grams

Dry matter ...................... 1,607.95 496.08 567.18 2,335.00 638.30 725.40 2,251.29 730.00 293.18
Reducing sugars ................... 22.99 16.02 9.08 124.18 22.23 14.87 82.40 24.45 9.469
Total sugars..................... 51.94 23.61 10.49 136.20 25.36 27.27 121.93 38.44 19.446
Starches, dextrins, hemicelluloses.... 433.67 115.88 146.33 533.15 132.32 227.05 557.56 168.38 78.179
Total carbohydrates............... 485.60 139.50 156.82 669.35 157.68 254.32 678.36 206.82 97.626

All compounds calculated on a dry weight basis except dry matter.' All carbohydrates given in terms of glucose.



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TABLE IX.-PERCENTAGE OF DRY MATTER, VARIOUS EASILY H YDROLYZABLE CARBOHYDRATES, AND TOTAL NITROGEN IN THE
CROWNS AND ROOTS OF NAPIER GRASS DUG BEFORE THE PRODUCTION OF TOP GROWTH TOOK PLACE DURING 1926-1929, IN-
CLUSIVE.

1926 1927
Compound Irrigated Not Irrigated Not Irrigated
with sewage irrigated with sewage irrigated with city water
Crowns Roots Crowns Roots Crowns Roots Crowns Roots Crowns Roots

% % % % % % % % % %
Dry matter............................ 30.000 44.800 27.000 44.000 32.200 50.000 25.800 53.000 25.400 54.400
Reducing sugars.......................... 3.644 2.200 3.745 3.330 1.430 1.330 3.230 1.380 1.600 3.080
Total sugars............................ 4.764 2.940 4.559 5.050 3.230 7.050 4.760 4.490 1.850 4.710
Starches, dextrins, hemicelluloses ............. 29.070 25.230 29.410 23.830 26.970 21.660 23.360 21.760 25.800 23.400
Total carbohydrates....................... 33.834 28.170 33.969 28.880 30.200 28.710 28.120 26.250 27.650 28.110
Total nitrogen ............................ 1.400 0.770 1.150 0.560 1.320 0.730 0.990 0.510 0.940 0.580

1928 1929

Irrigated Not Irrigated Irrigated Not Irrigated
Compound with sewage irrigated wth ct irrigated with city
water sewage water
Crowns Roots Crowns Roots Crowns Roots Crowns Roots Crowns Roots Crowns

% % % % % % % % % % %
Dry matter..................... 24.400 54.000 26.000 52.400 31.200 55.200 24.400 49.600 27.400 49.900 27.400
Reducing sugars.................. 5.316 1.110 3.483 1.050 2.050 1.900 3.660 2.110 3.350 2.510 3.230
Total sugars..................... 5.833 1.900 3.973 1.380 3.760 2.360 5.416 4.560 5.266 5.410 6.633
Starches, dextrins, hemicelluloses.. 22.833 17.660 20.730 18.160 31.300 20.400 24.766 20.830 23.066 18.700 26.666
Total carbohydrates ............. 28.666 20.670 24.703 20.590 25.060 24.660 30.132 25.390 28.332 24.110 33.299
Totalnitrogen ................... 1.060 0.600 0.940 0.560 1.000 0.510 1.140 1.210 1.230 1.080 2.020
All percentages calculated on a dry weight basis. All carbo hydrates given in terms of glucose.





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