• TABLE OF CONTENTS
HIDE
 Front Cover
 Table of Contents
 Introduction
 Getting started
 Operating conventions
 Introductory information
 Description of model
 Assumptions in model
 Reference
 Appendix
 Errata
 Back Cover






Group Title: Circular Florida Cooperative Extension Service
Title: Chemical movement in soil
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00094903/00001
 Material Information
Title: Chemical movement in soil IBM PC user's guide
Series Title: Computer series - Florida Cooperative Extension Service ; 654
Physical Description: Book
Language: English
Creator: Nofziger, D. L.
Hornsby, Arthur G.
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 1985
Copyright Date: 1985
 Subjects
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Record Information
Bibliographic ID: UF00094903
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: alephbibnum - 001745139
notis - AJF7913

Table of Contents
    Front Cover
        Page 1
    Table of Contents
        Page 2
    Introduction
        Page 3
    Getting started
        Page 4
    Operating conventions
        Page 5
        Page 6
    Introductory information
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
        Page 51
        Page 52
        Page 53
    Description of model
        Page 54
        Page 55
    Assumptions in model
        Page 56
        Page 57
    Reference
        Page 58
    Appendix
        Page 59
    Errata
        Page i
        Page ii
        Page iii
        Page iv
    Back Cover
        Page 60
Full Text


. ins.. : -


Chemical

IBM
D. L


Movement in Soil:


PC
. Nofziger


Ico


User's Guide. : ..
and A. C. Homby Q e jRie


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CONTETS



SI'.. :ntroduction........: **** ********************.******.** ***

2. Hardware and Soft areS eq irement:.......... ... ........
.3. Getting St arted ..... .... .. ............*** ..0

Operating Convention................... ... ....... ....

5. Illustrations of Software
Sn :troductory Information.. ............. .........
Option As Calculate Chemical Movement in Soil..........
.Option B: Eater, Modify, or Print Soil Data File......
Option C: Enter. Modify, or Print Chemical Data File...
Option D: Enter, Modify, or Print Rainfall Data File...
Option I: Eater. Modify, or Print Evapotranspiration
Data File ...............*... **.....*.......,

60. e-.scription Model ......... ....................... ...

S Ar efeirelce s....*******************************


*9. Appendi .............. ...... ... **** *********















0 IFAS, Unhiaty of PFlrods e9I


3

3

4
5


7
10
20
29
39

45
54

56

58

59









CHEMICAL MOVEMENT IN SOIL: IBM PC USER'S GUIDE


D. L. Nofziger and A. G. Hornsby*



INTRODUCTION

A model describing chemical movement in soils is presented. The model estimates the
location of the leading edge of a non-polar organic chemical as it moves downward in
the soil. The model also determines the relative amount of the applied organic
chemical remaining in the soil as a function of time.

This software is based on water and solute transport principles presented by Rao,
Davidson, and Hammond (1976). It also incorporates the work of Hamaker and Thompson
(1972) and Karickhoff (1981, 1984) who have shown that the partition coefficient for
a particular organic chemical in a soil divided by the organic carbon content of
that soil is nearly constant for a wide range of soils. A fact sheet ("Pesticides
and Their Behavior in Soil and Water") included in the Appendix describes the
relationships between sorption, degradation, and loss of pesticides in soil water
systems.

The model is intended to illustrate chemical transport principles and to serve as an
educational tool. It was written for use by individuals interested in learning the
principles of chemical movement in soils. It is also useful for group instruction
in the classroom and in extension. It is interactive with graphical and tabular
output. The software was written to allow the user to make repeated simulations of
different soil-chemical systems with a minimum of effort. The model is fast. Most
simulations require less than 10 seconds to complete once the system has been
defined.

HARDWARE AND SOFTWARE REQUIREMENTS

This software requires an IBM PC or XT (or a comparable) computer with at least
192K bytes of random access memory. The computer is assumed to have the IBM
color/graphics board, but machines without the graphics board can be used for
tabular output by specifying the monochrome (m) option when the program is loaded
(see GETTING STARTED). A printer is useful, but not essential. A version of the
software is included which uses the 8087 numeric coprocessor for enhanced speed if
it is available.

The operating system must be PC-DOS 2.0 or MS-DOS 2.0 (or a more recent version).
The GRAPHICS.COM file from your DOS diskette must be executed to obtain copies of
graphics on the printer.



*, L. Nofitzjer is a Visiting Associate ProfePr. .on leave from tLgp.nartment oAgromprny, OklahimoattaleoUniyvrsity.StiltwaeLanALd.A.L
Hornsby is an Associate Professor, Soil Science Department, IFAS, University of Florida, Gainesville.
1. IBM is a registered trademark of International Business Machines, Inc.









GETTING STARTED

Making a Working Diskette: The software is distributed on a single diskette. The
first step is to make a working diskette from the original. The following steps can
be used to make a working diskette:

1. FORMAT a diskette with the /S option.

2. COPY the file GRAPHICS.COM from your DOS diskette to the new diskette.

3. COPY the entire software distribution diskette to the new diskette.

4. Place the distribution diskette in a safe place.

Details on the use of the FORMAT and COPY commands are given in your DOS manual.

Program Execution Options: Below is a list of ways in which the program can be
executed on different computer systems and for different levels of introductory
material. Identify the options which match the computer hardware in your system and
enter the desired associated command. The working diskette is assumed to be in the
default disk drive.

1. Computer with IBM comparable color/graphics board but without 8087
coprocessor: Enter

1. CMIS for the complete program with introductory material.

2. CMS S for the program without introductory material.

2. Computer with IBM comparable color/graphics board and 8087 coprocessor: Enter

1. CMIS87 for the complete program with introductory material.

2. CMS87 S for the program without introductory material.

3. Computer without IBM comparable color/graphics board and without 8087
coprocessor: Enter

1. CMS M for the complete program with introductory material.

2. CMS M S for the program without introductory,material.

4. Computer without IBM comparable color/graphics board but with 8087
coprocessor: Enter

1. CMS87 M for the complete program with introductory material.

2. CMS87 M S for the program without introductory material.







OPERATING CONVENTIONS


The following conventions are used throughout this software.

1. Program Interruption: The user can interrupt the program and return to the
most recent menu by pressing the escape key.

2. Keyboard Inputs: Single character entries such as menu selections and
responses to yes/no questions are made by pressing only the desired key. The
key is not required. All other inputs require that the key be
depressed.

3. Default Values: The software makes use of default values to reduce the amount
of typing required. These values are displayed in square brackets when inputs
are requested. If the default value is the desired input, the user can press
only the key. If another value is desired, that value may be
entered. The value selected becomes the default for that parameter until it
is changed or the program is terminated.

4. File Names: File names can be any legal MS-DOS file name. File extensions are
not needed. Meaningful file extensions for the different types of files will
be assigned by the software.

5. Cursor Control Keys: Parameters stored in data files can be edited at several
places in the program using a full screen editor. The arrow keys in the
numeric keypad can be used to position the cursor as desired for editing.
Characters can be deleted by pressing the key. When finished editing
data on the screen, the key should be pressed.

6. Help: When using option A to define the problem to be simulated, the user must
enter the desired chemical, soil identifier, and file names for rainfall and
evapotranspiration files. If the user enters the word "HELP" in response to
any of these questions, the computer will display a list of possible
responses. Then the question will be repeated.

7. Parameter Limits: Numeric data entered into the computer is compared with
specified limits for each parameter. If the value entered is out of the
accepted range, a message is displayed for the user. This message includes
the accepted range of values. The range of values is surrounded by square
brackets if the range includes the end points specified. It is surrounded by
parentheses if it does not include the end points. For example:

[0 to 100] means the parameter must be greater than or equal to 0
and less than or equal to 100.

(0 to 100) means the parameter must be greater than 0 and less
than 100.

(0 to 100] means the parameter must be greater than 0 and less
than or equal to 100.







[0 to ??] means the parameter must be greater than or equal to 0.
No upper limit exists.

The following pages contain selected screen images and underlined user responses for
different program options. Comments have been inserted to explain the operational
details of the software.













INTRODUCTORY INFORMATION


f-----------~-----------------------_----__---_

CHEMICAL MOVEMENT IN SOILS

by

D. L. Nofziger and A. G. Hornsby

Soil Science Department
Institute of Food and Agricultural Sciences
University of Florida
Gainesville, Florida
(904) 392-1951

Copyright 1984 by IFAS, UF

This program was written to illustrate the influence of soil properties,
chemical properties, rooting depth, precipitation, and evapotranspiration
upon the movement and persistence of surface-applied organic chemicals
(pesticides) in well-drained soils.


Press Space Bar to Continue:


Screen 1. Purpose of the program.











The program requires the following inputs:

Soil:
1. Percent Organic Carbon
2. Water Content at matric potential of -0.1 bar
3. Water Content at matric potential of -15 bars
4. Bulk Density


Chemical:
1. Partition Coefficient Normalized for
2. Half-Life


Organic Carbon


Root Depth of Plant

Daily Precipitation Records

Daily Evapotranspiration Records


Soil, chemical, and climatic data can be stored in data files
for repeated use.

Press Space Bar to Continue:


Screen 2. Required inputs for the model.


Screen 3. Types of output available from the model.





8


Outputs from the program include:

Graphs:
1. Precipitation and depth of selected chemical as
a function of time since application of chemical.
2. Precipitation and depth of selected chemical and
a non-adsorbed chemical as a function of time.

Tables:
Precipitation, depth of selected chemical, and
relative mass of chemical remaining in soil as
a function of time since application of chemical.
(Tables may be output to screen, printer, or disk.)

Press Space Bar to Continue:










ACKNOWLEDGEMENTS


Screen 4. Special acknowledgements.


Screen 5. Disclaimer and condition of release.


This software is based on the procedure presented by P. S. C. Rao, J. M.
Davidson, and L. C. Hammond, 1976, in "Estimation of Nonreactive and
Reactive Solute Front Locations in Soils" (EPA-600/9-76-015, July, 1976).

The authors wish to express appreciation to Mr. Ron Jessup and Dr. P. S. C.
Rao for their helpful suggestions during the development of the software
and for their review of the software. Special appreciation is expressed to
Mr. Jessup for providing the program for the IFAS logo.


Press Space Bar to Continue:


DISCLAIMER

The University of Florida (UF), Institute of Food and Agricultural
Sciences (IFAS), and Florida Cooperative Extension Service (FCES) shall
have no liability or responsibility to cooperator or any other person
or entity with respect to any liability, loss, or damage caused
or alleged to be caused directly or indirectly by programs released by
IFAS for sale or cooperative use including but not limited to any
interruption of service, loss of business, or anticipatory profits or
consequential damages resulting from use or operation. And in no event
shall FCES be liable for loss of profits, indirect, special, or
consequential damages arising out of any breach of the agreement or
obligations of this contract.

CONDITION OF RELEASE OR SALE
All computer software distributed by IFAS or FCES are on an 'AS IS'
basis without warranty. Distribution or resale without written
permission of the department of origin is not permitted.


Press Space Bar to Continue:













OPTION A: CALCULATE CHEMICAL MOVEMENT IN SOIL


CHEMICAL MOVEMENT IN SOILS

by

D. L. Nofziger and A. G. Hornsby
Copyright 1984

OPTIONS :

A. Calculate Chemical Movement in Soil
B. Enter, Modify, or Print Soil Data File
C. Enter, Modify, or Print Chemical Data File
D. Enter, Modify, or Print Rainfall Data File
E. Enter, Modify, or Print Evapotranspiration Data File
F. Display File Directory
Q. Quit. Terminate Program and Return to DOS

Desired Option ? a


Screen 6. The main menu.

Option A in this menu is used to simulate chemical movement. Options B to E are
used to store and manipulate data files. Option F is used to display the directory
of a disk and option Q is used to terminate the program and to return to the disk
operating system (DOS). In this case, option A was selected. The following pages
illustrate option A.

NOTE: Throughout the program the selection of menu options and answers to questions
which can be answered uniquely with one character do not require the user to press
the key. In the above example, only the letter was entered.











Distances or lengths can be expressed in the following units:


E. English inches
M. Metric centimeters

Enter or for desired units [Default is E] :

Enter Rooting Depth in inches [30.0] : 25


Screen A-i. Selection of desired units of length and depth of plant roots.

The user may choose English or metric units of length. The rooting depth of the
plant determines the depth to which the plant can take up water.

NOTE: Information in brackets are default values. Those values can be selected by
simply pressing the key. In the example above, the user selected the
default (English) units by pressing the key. In the case of rooting depth,
30 was the default value but 25 was entered as the desired value. When repetitive
simulations are made (without return to the DOS) the last value entered for a given
parameter becomes the default value. For example, the default rooting depth will be
25 for the next run.



Selection of Chemical for Simulation:
Name of Chemical : diuron

Chemical Data:
Common Name : DIURON
Trade Name : KARMEX
Partition Coefficient (ml/g OC) : 383
Half-Life (days) : 328


Screen A-2. Selection of the chemical of interest.

Chemicals can be selected by common name or by trade name. Upper or lower case
letters may be used. If the word "HELP" is entered instead of a chemical name, the
names of all the chemicals in the file will be displayed. The user will then be
asked again for the chemical of interest. If the chemical specified is not found in
the file, the user will be given the opportunity to enter its properties manually or
to select another chemical. (Manually entered data for new chemicals will not be
stored in the disk file. Option C in the main menu can be used to add a chemical to
the disk file.)











Selection of Soil for Simulation:
Identification Code for Soil : s27-8-(1-6)


Soil Data:
Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density, (g/cc)
Maximum Soil Depth Represented (in)


: TAVARES FINE SAND
: S27-8-(1-6)
: 0.09
:8.2
: 0.9
: 1.55
: 80.0


Screen A-3. Selection of the soil of interest.

Soils can be selected from the soil file on disk by entering their identification
code. Users may define any convention they choose for these codes although they
must be unique and should be relatively easy to enter. The code in the example
above was used because it is being used in a large soil data base at the University
of Florida. If the word "HELP" is entered, all the soil map unit names and their
identifiers will be displayed. The user will then be asked to enter the soil
identifier of interest. If the specified identifier is not found in the permanent
file, the user is given the choice of entering its properties manually or of
entering another soil identifier. Manually entered data is not saved on disk.
Option B of the main menu must be used to add soils to the disk file.



Rainfall data must be read from file.

Enter Name of File to be Used : local83

Evapotranspiration data must also be read from file.

Enter Name of File to be Used : local83


Screen A-4. Selection of rainfall and evapotranspiration files.

Rainfall and evapotranspiration data are entered and stored in files using main menu
options D and E, respectively. The file name (and disk drive unit if the file is
not on the default drive) must be entered by the user. Since all rainfall files
have an extension of R and all evapotranspiration files have an extension of ET, the
user need not enter the extension. If the user enters the word "HELP" the files
available on the default disk drive will be displayed. If a specified file is not
found, a message is given and another file name is requested.










Rain data are now being read.
First Date is : 1 2 83
Last Date is :12 29 83

ET data are now being read.
First Date is : 1 1 83
Last Date is :12 23 83


Starting Date
Month [1]:5
Day [2]:10
Year [83]:


Stopping Date:
Month [12]:
Day [29]:
Year [83]:


Screen A-5. Reading climatic data and specification of time to be simulated.

As rainfall and evapotranspiration data are being read, the first and last dates
included in the file are displayed. The user then specifies the starting and
stopping dates for the simulation. The starting date represents the date at which
the chemical was applied to the soil surface. The stopping date is the desired date
for terminating the simulation. In this example, the chemical was applied on
5-10-83 and movement was simulated to 12-29-83.










Simulation of Chemical Movement in Soil

Chemical Data:
Common Name : DIURON
Trade Name : KARMEX
Partition Coefficient (ml/g OC) : 383
Half-Life (days) : 328


Soil Data:
Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar
Water Content at -15 bars
Bulk Density, (g/cc)


(% by vol.)
(% by vol.)


TAVARES FINE SAND
S27-8-(1-6)
0.09
8.2
0.9
1.55


Root Depth: 25.0 inches

Rainfall File : LOCAL83.R
Evapotranspiration File: LOCAL83.ET


Starting Date
Stopping Date


: 5 10 -
: 12 29 -


Press Space Bar to Continue:


Screen A-6. Summary of defined problem.

At this point the problem to be simulated has been fully defined. This screen
provides a concise summary of the user inputs. After any key is pressed, the
rainfall data and the results of the simulation are displayed in graphical form (see
Fig. 1). A printed copy of the figure can be obtained by pressing the and
keys. Pressing any other key will display the menu shown in screen A-7.










1,5 -


""

-.+- H d ii i 4l -

S50 100 150 200 2
ELAPSED TIME, daus


-- 1 1 I r ---


0 -*I -

E 10 -___
-~-
P
T 20 "
-------------- - --
H
30 --
i
n 40
50 --
Rainfall and Depth of CheMical as a Function of TiMe After Ap]
Figure 1. Copy of video screen obtained by pressing 'Shift' anc


3,0


-5
50


Simulation
From
5 10 83
To
12 29 83

Soil
TAUARES FINE SAND
S27-8-(1-6)

CheMical
DIURON
mARMEX



Root Depth




plication.
d 'PrtSc' keys.











Output Options:

S. Output Table to Screen
P. Output Table to Printer
F. Output Table to File

G. Output Graphs for DIURON
N. Output Graphs for DIURON and
for a Non-Adsorbed Chemical such as Nitrate

M. Return to Main Menu

Desired Option:P


Screen A-7. Output option menu.

This menu allows the user to select tabular and graphic outputs of calculated
results.

Options S, P, and F result in tabular output to the video screen, printer, and disk
file, respectively. An example of this output is shown in Table 1. If the table is
stored output to a file, the table is stored as a text file which can be displayed
later using the DOS commands "TYPE" or "COPY". (Consult the DOS manual for further
information on these commands.) The file can also be edited with most word
processors. The user will need to provide a file name. The file name must be
unique to avoid erasing existing information.

Options G and N provide graphical outputs of the results. (To obtain graphical
output, the computer must be contain a graphics card compatible with the IBM color
graphics card.) Selecting option G displays the graphics shown in Fig. 1.
Selecting option N displays the results shown in Fig. 2. This figure shows the
simulated movement of the selected chemical and the simulated movement of a
non-adsorbed chemical, such as nitrate.

Option M returns program control to the main menu.








TABLE 1.


Simulation of Chemical Movement in Soil


Chemical Data:
Common Name
Trade Name
Partition Coefficient
Half-Life (days)


(ml/g OC)


DIURON
KARMEX
383
328


Soil Data:
Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density (g/cc)

Root Depth: 25 inches

Rainfall File : LOCAL83.R
Evapotranspiration File: LOCAL83.ET


Starting Date
Stopping Date


TAVARES FINE SAND
S27-8-(1-6)
0.09
8.2
0.9
1.55


: 5 10 -
: 12 29 -


Total Rainfall:
Total Evapotranspiration:
Potential Evapotranspiration:


35.97 inches
22.19 inches
37.45 inches


Month Day Year


Rainfall Solute Depth


0.60
1.35
2.43
0.39
2.05
1.67
1.03
0.41
0.33
0.43
0.26
0.13
0.25
0.35
0.40


inches
1.0
3.1
6.8
6.8
9.4
12.0
12.2
12.2
12.2
12.2
12.2
12.2
12.2
12.2
12.2


Relative Mass

0.99
0.99
0.97
0.95
0.94
0.94
0.91
0.90
0.90
0.86
0.86
0.85
0.85
0.85
0.84


Elapsed Time
Days
4
7
14
26
28
29
43
50
52
71
72
75
77
78
82









TABLE 1. Continued


Month Day Year


Chemical Movement Bel
11 25 83
11 28 83
11 29 83
12 4 83
12 7 83
12 12 83
12 14 83
12 15 83
12 17 83
12 18 83
12 19 83
12 29 83


Rainfall Solute Depth


--- inches
1.32
1.32
1.72
0.10
0.18
1.68
0.17
0.10
0.17
0.12
0.15
0.29
1.95
0.14
0.38
0.35
0.38
0.33
0.12
0.11
0.55
0.17
0.17
0.10
0.24
0.14
2.17
ow Root Zone
2.30
0.49
0.36
0.38
0.22
2.04
0.41
0.11
0.70
0.68
0.19
1.39


13.1
15.1
17.7
17.8
17.8
20.4
20.4
20.4
20.4
20.4
20.4
20.4
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
22.2

25.5
25.9
26.4
26.4
?6.4
29.0
29.5
29.7
30.4
31.4
31.5
32.2


Relative Mass

0.84
0.84
0.83
0.83
0.83
0.83
0.82
0.82
0.79
0.78
0.78
0.78
0.77
0.75
0.75
0.73
0.72
0.72
0.72
0.72
0.72
0.72
0.71
0.69
0.67
0.66
0.66

0.66
0.65
0.65
0.64
0.64
0.63
0.63
0.63
0.63
0.63
0.62
0.61


Elapsed Time
Days
84
85
86
87
89
90
95
96
113
115
116
118
126
133
135
152
153
154
155
156
157
158
161
179
190
194
195

199
202
203
208
211
216
218
219
221
222
223
233






3.0


1,5 -


0
D
E 10
P
T 20
H
30
i
n 40

50
Rainfall
Figure 2.


' i . I .. .... .. I 'J I.I. .. I . .
0 50 100 150 200 250
ELAPSED TIME, days
I I I I

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


-i


I I I


I I I I
and Depth of CheMical as a Function of TiMe After Application,
Printed copy of video screen produced by output option N.


I


'


S SiMulation
FroM
5 10- 83
To
12 29 83

Soil
- TAVARES FINE SAND
27-8-(1-6)

Chemical
DIURON
E ARMEX

Non-Adsorbed
Solute ..........

Root Depth


i ,













OPTION B: ENTER, MODIFY, OR PRINT SOIL DATA FILE


CHEMICAL MOVEMENT IN SOILS

by

D. L. Nofziger and A. G. Hornsby
Copyright 1984


OPTIONS :
A.
B.
C.
D.
E.
F.
Q.


Calculate Chemical Movement in Soil
Enter, Modify, or Print Soil Data File
Enter, Modify, or Print Chemical Data File
Enter, Modify, or Print Rainfall Data File
Enter, Modify, or Print Evapotranspiration Data File
Display File Directory
Quit. Terminate Program and Return to DOS


Desired Option ? b


Screen 6. Selection of option B in main menu.









Enter or Modify Soil Data Files:


This simulation of organic chemical movement in soils requires the
following information about the soil:
A. Soil Name
B. Soil Identification Code
C. Percent Organic Carbon
D. Soil Water Content (percent by volume)
at Matric Potential of -0.1 bar
E. Soil Water Content (percent by volume)
at Matric Potential of -15 bars
F. Soil Bulk Density (grams per cubic centimeter)
G. Maximum Depth of Soil Represented by Values Above

The information can be entered into a data file and stored for
future use. This option is used to enter or modify this data.

NOTE: The soil properties are assumed to be uniform over depth in this
model. The data entry option calculates a weighted average for
the entire profile from data for each horizon.

Press Space Bar to Continue:


Screen B-1. Introduction to soil data management option.

Percent organic carbon is used to determine the chemical partition coefficient for
this soil from the normalized partition coefficient for each chemical. If only the
organic matter of the soil is known, the percent organic carbon can be estimated by
multiplying the percent organic matter by a factor in the range of 0.5 to 0.6.

Water contents at -0.1 bars and -15 bars are used to estimate the "field capacity"
and the "permanent wilting point" of the soil. The user may insert water contents
at other matric potentials if they provide better estimates of these quantities.

The maximum depth should be entered in inches or in centimeters depending upon the
units chosen in the next screen.

The depth weighted average soil property, X, for a soil with n horizons is given by

X = (dlx1 + d2x2 + d3x3 + ... + dnx ) / D

where xl, x2, x3, ..., xn represent the values of the soil property for each of the
n horizons, dI, d2, d3, ..., dn represent the thicknesses of the respective
horizons, and D represents the depth of the entire profile (D=dl+d2+d3+...+d ).











Distances or lengths can be expressed in the following units:


E. English inches
M. Metric centimeters

Enter or for desired units [Default is E] :


Enter Name of File to be Used [Default is MAIN.S]:

OPTIONS:
E. Enter new information
M. Modify existing data
P. Print data in file

Desired Option:e


Screen B-2. Selection of units, soil file, and desired function.

The selection of units here determines whether English or metric units
entering the maximum depth. Information entered with one type of units
later with other units.


In most situations, the user
The program looks for that
should not be on the default


are used in
can be used


will want to use the default soil file called MAIN.S.
file automatically. If another file is used, MAIN.S
disk drive.


Option E in the above menu is used to enter information for a new soil and to store
the depth-weighted average values on the disk file. Option M is used to edit and
modify information already in the file. Option P is used to display stored
information on the printer or the screen.

Option E is illustrated on the following pages.



Enter Soil Data (Enter the word END to stop data entry)


Enter Number of Horizons to be Averaged:6


Screen B-E-1. Beginning of soil entry.


:tavares fine sand


Soil Name


:s27-8-(1-6)


Soil Identifier










Data for Horizon 1


Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by.vol.)
Bulk Density, (g/cc)
Maximum Soil Depth Represented (in)


:.55
:6.5
:1.3
:1.42
:4.0


Screen B-E-2. Data entry for horizon 1.

After entering this information, the user can inspect the data and make any
necessary changes. The editing screen is shown below.


Edit Record


Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density, (g/cc)
Maximum Soil Depth Represented (in)


: TAVARES FINE SAND
: S27-8-(1-6)
: .55
: 6.5
: 1.3
: 1.42
: 4.0


Use cursor control keys to position cursor as needed.
Then make the desired changes.

Press key when finished editing record on screen.


Screen B-E-3. Edit data for horizon 1.

The data shown were entered on the previous screen. If any errors are detected, the
cursor is moved to the error using the arrow keys at the right of the keyboard. The
modifications are then made. After making all corrections, press the key to
proceed with the next horizon.

In this case, no corrections were needed so was pressed.










Data for Horizon 2


Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density, (g/cc)
Maximum Soil Depth Represented (in)


:.42
:7.2
:1.5
:1.44
:8.0


Screen B-E-4. Data entry for horizon 2.

At this point the user would be given opportunity to edit the data for this horizon
as in Screen B-E-3. Data would then be entered for horizons 3 to 6 as in the
following screens. The user would. be given opportunity to edit data for each
horizon as described for horizon 1.


Data for Horizon 3


Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density, (g/cc)
Maximum Soil Depth Represented (in)


:.09
:5.2
:0.8
:1.50
:21.0


Screen B-E-6. Data entry for horizon 3.


Data for Horizon 4


Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density, (g/cc)
Maximum Soil Depth Represented (in)


:.06
:5.4
:0.7
:1.56
:42.0


Screen B-E-8. Data entry for horizon 4.











Data for Horizon 5


Percent Organic Carbon
Water Content at -0.1 bar b\ vol.)
Water Content at -15 bars (% by vol.)
Bulk Density, (g/cc)
Maximum Soil Depth Represented (in)


:.04
:6.1
:0.8
:1.56
:48.0


Screen B-E-10. Data entry for horizon 5.


Data for Horizon 6


Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density, (g/cc)
Maximum Soil Depth Represented (in)


:.02
:11.9
:1.O0ENTER>
:1.58
:80.0


Screen B-E-12. Data entry for horizon 6.

After editing information for this horizon, the computer would proceed to calculate
the depth-weighted average values for the parameters and would store the weighted
averages in the soil file. (Data for each horizon are not stored in the file.) In
this case, the information stored was


Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density, (g/cc)
Maximum Soil Depth Represented (in)


:TAVARES FINE SAND
:S27-8-(1-6)
:0.09
:8.2
:0.9
:1.55
:80.0








The user would then be asked to enter information as shown below.


Enter Soil Data (Enter the word END to stop data entry)

Soil Name :end


Screen B-E-7. Termination of data entry.

The word "end" was entered here instead of a soil name because the user did not want
to enter more soil data. The program then returned to the main menu.

NOTE: The word "end" must be typed. Do not use the key.

Data stored in the file can be modified using option M (Screen B-2). This editing
process would be similar to that shown in Screen B-E-3. The editing process simply
replaces information in the file with new information entered by the user. No
averaging is done. If averaging is desired for a soil already in the disk file, the
user must first DELETE the present entry in the file (using the Modify option) and
then enter a new set of information (using the Enter option).

Table 2 is an example of output from option P. It includes the averaged values for
the Tavares soil entered above.








TABLE 2.


File : MAIN.S


Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density (g/cc)
Maximum Soil Depth Represented (in)

Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density (g/cc)
Maximum Soil Depth Represented (in)

Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density (g/cc)
Maximum Soil Depth Represented (in)

Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density (g/cc)
Maximum Soil Depth Represented (in)

Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density (g/cc)
Maximum Soil Depth Represented (in)

Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density (g/cc)
Maximum Soil Depth Represented (in)


:LAUDERHILL MUCK
:S50-27-(1-3)
:43.57
:62.3
:17.3
:0.22
:26.0

:SPARR FINE SAND
:S1-58-(1-9)
:0.27
:21.6
:9.5
:1.61
:79.9

:ARREDONDO FINE SAND
:S1-66-(1-7)
:0.14
:20.4
:9.1
:1.58
:85.8

:GAINESVILLE SAND
:S1-73-(1-5)
:0.21
:14.8
:5.8
:1.47
:81.9

:ORANGEBURG FINE SANDY LOAM
:S37-8-(1-6)
:0.31
:30.3
:15.8
:1.61
:79.9

CHAIRSS FINE SAND
:S37-20-(1-10)
:0.48
:25.9
:8.7
:1.57
:79.9








TABLE 2. Continued


Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density (g/cc)
Maximum Soil Depth Represented (in)

Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density (g/cc)
Maximum Soil Depth Represented (in)

Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density (g/cc)
Maximum Soil Depth Represented (in)

Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density (g/cc)
Maximum Soil Depth Represented (in)

Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density (g/cc)
Maximum Soil Depth Represented (in)

Soil Name
Soil Identifier
Percent Organic Carbon
Water Content at -0.1 bar (% by vol.)
Water Content at -15 bars (% by vol.)
Bulk Density (g/cc)
Maximum Soil Depth Represented (in)


:TROUP FINE SAND
:S37-5-(1-7)
:0.19
:25.1
:11.8
:1.63
:100.0

:FUQUAY FINE SAND
:S37-25-(1-7)
:0.34
:23.5
:12.9
:1.52
:79.9

:MYAKKA FINE SAND
:S49-10-(1-8)
:1.00
:13.2
:2.5
:1.51
:70.1

:LAKELAND FINE SAND
:S61-29-(1-7)
:0.14
:7.7
:1.5
:1.53
:100.0

:BLANTON FINE SAND
:S16-14-(1-8)
:0.18
:16.4
:6.3
:1.45
:90.2

:TAVARES FINE SAND
:S27-8-(1-6)
:0.09
:8.2
:0.9
:1.55
:80.0













OPTION C: ENTER, MODIFY, OR PRINT CHEMICAL DATA FILE


CHEMICAL MOVEMENT IN SOILS

by

D. L. Nofziger and A. G. Hornsby
Copyright 1984


OPTIONS :
A.
B.
C.
D.
E.
F.
Q.


Calculate Chemical Movement in Soil
Enter, Modify, or Print Soil Data File
Enter, Modify, or Print Chemical Data File
Enter, Modify, or Print Rainfall Data File
Enter, Modify, or Print Evapotranspiration Data File
Display File Directory
Quit. Terminate Program and Return to DOS


Desired Option ? c


Screen 6. Selection of option C in main menu.











Enter or Modify Chemical Data Files:

This simulation of organic chemical movement in soils requires the
following information about the chemicals:
A. Common Name
B. Trade Names (Up to 4 may be used)
C. Partition Coefficient (ml/gram of Organic Carbon)
D. Half-Life (days)

NOTE: This model is restricted to non-polar organic chemicals and
non-adsorbed chemicals.

The information can be entered into a data file and stored for
future use. This option is used to enter or modify this data.


Screen C-1. Introduction to chemical data management option.

This option is similar to option B for soil data except that no averaging is done.

The partition coefficient, KOC, required in part C above is the linear sorption
coefficient normalized by the organic carbon content of the soil. That is

KOC = KD / OC

where K is the linear sorption coefficient (ml/g soil) of a particular chemical on
a soil with organic carbon content OC (g organic carbon/g soil). NOTE: OC in the
above equation is the fractional organic carbon content rather than the percent
organic carbon content.

The half-life is the length of time (days) required for one-half of the present
concentration of the chemical to be degraded.

An illustration of the use of this option follows.










Enter Name of File to be Used [Default is MAIN.CHM]:


OPTIONS:
E. Enter new information
M. Modify existing data
P. Print data in file

Desired Option: e


Screen C-2. Selection of chemical file and option.

In most cases the default file, MAIN.CHM, should be used here since this file is
searched automatically in the simulation option A. If another file name is used,
MAIN.CHM should not be on the default disk drive. The following screens illustrate
option E.


Enter the word END to stop data entry


Commom Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)


:diuron
:karmex
:
:
:
:383
:328


Screen C-E-1. Entry of chemical data.

As each line appears on the screen, the user enters the desired information. If
less than 4 trade names are wanted, the user can simply push the key at that
line. If mistakes are made in this data entry process, option M above can be used
to modify or correct the information.


Enter the word END to stop data entry


Commom Name


:end


Screen C-E-2. Termination of data entry.

In this case the user did not want to enter more chemicals. By typing "end" instead
of another common name, the program returns to the main menu.

Table 3 is an illustration of option P for chemical data. It includes diuron as
entered above. The information in the table was obtained from publications of Rao
and Davidson (1980) and Laskowski et.al. (1982).









TABLE 3.


File : MAIN.CHM


Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)


:ALDICARB
:TEMIK
:TEMIK15G
:OMS 771
:UC21149
:12
:28

:FENAMIPHOS
:NEMACUR
:BAY 68138
:BAY SRA3886

:171
:10

:OXAMYL
:VYDATE
:VYDATE L
:VYDATE G
:HA-2214
:9
:6

CAPTAINN
CAPTAINN
:ORTHOCIDE
:PILLARCAP
:VONDCAPTAN
:33
:3

:PENTACHLOROPHENOL
:PCP
:PENTA
PENTAGONN
:PENWAR
:14290
:48








TABLE 3 Continued


Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)


:DIURON
:KARMEX
:UROX D
:DIREX 4L
:DIUROL
:383
:328

:PICLORAM
:TORDON
:TORDON 22K
:AMDON
:GRAZON
:26
:138

:BROMOCIL
:HYVAR XL
:BOROCIL
:UREABOR
:HYVAR X
:72
:106

:TERBACIL
:SINBAR



:46
:50

:TRIDIPHANE
:DOWCO 356
:TANDEM


:5600
:28

:HALOXYFOPMETHYL
:XRM-4570
:DOWCO 453 ME


:75
:1








TABLE 3 Continued


Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)


:LINURON
:AFALON
:HOE 2810
:LOROX L
:LINUREX
:863
:75

:DICAMBA
:BANVEL D
:BANEX
:DIANAT
:WEEDMASTER
:2
:14

:ATRAZINE
:AATREX
:GRIFFEX
:ATRANEX
:VECTAL SC
:163
:48

:SIMAZINE
:AQUAZINE
:PRINCEP
:SIMADEX
:SIM-TROL
:138
:75

PARATHIONN
:THIOPHOS
:BLADAN
:ORTHOPHOS
:PANTHION
:10650
:35

:METHYL PARATHION
:METAFOS
:PARATHION-METHYL
:DEVITHION
:NITROX 80
:5102
:4








TABLE 3 Continued


Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)


:MALATHION
:MERCAPTOTHION
:CALMATHION
:CARBOFOS
:CYTHION
:1797
:1

:LINDANE
:GAMMA BHC
:ISOTOX
:LINTOX
:SILVANOL
:1081
:266

:FONOFOS
:DYFONATE
:N-2790


:846
:60

:CARBOFURAN
:FURADAN
:BAY 70143
:YALTOX
:CURATERR
:29
:37

:DISULFOTON
:DISYSTON
:DITHIOSYSTOX
:THIODEMETON
:DITHIODEMETON
:1603
:5

:CHLORPYRIFOS
:LORSBAN
:BRODAN
:DURSBAN
:ERADEX
:6070
:63









TABLE 3 Continued


Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)


CYANAZINEE
:BLADEX
:FORTROL
:SD 15418
:WL 19805
:168
:108

:NAPROPAMIDE
:DEVRINOL
:R-7465


:900
:70

:DBCP
:NEMAGON
:FUMAZONE
:NEMANAX
:NEMAFUME
:70
:180

:ALACHLOR
:ALANEX
:PILLARZO
:LASSO

:190
:7

:CHLORDANE
:CHLORDAN
:ORTHO-KLOR
:BELT

:38000
:3500

:DIAZINON
:BASUDIN
:DIANON
:SPECTRACIDE

:580
:30








TABLE 3 Continued


Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)


:1,3-D
:TELONE II
:DICHLOROPROPENE


:26
:10

:DIELDRIN
:ALVIT
:DIELDREX
:DIELDRITE
:OCTALOX
:8400
:1000

:DINOSEB
:DNBP
:BASANITE
:KILOSEB
:CHEMOX
:120
:30

:ENDRIN
:ENDREX
:HEXADRIN


:8100
:4300

:HEPTACHLOR
:DRINOX
:HEPTOX
:HEPTAMUL

:24000
:2000

:PHORATE
:THIMET
:RAMPART
:AGRIMET
:CEOMET
:3200
:14








TABLE 3 Continued


Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)

Common Name
Trade Name
Trade Name
Trade Name
Trade Name
Partition Coefficient (ml/g OC)
Half-Life (days)


:PROPACHLOR
:RAMROD
:BEXTON


:420
:7

:TRIFLURALIN
:ELANCOLAN
:TREFANOCIDE
:TREFLAN
:TRIM
:14000
:70













OPTION D: ENTER, MODIFY, OR PRINT RAINFALL DATA FILE


CHEMICAL MOVEMENT IN SOILS

by

D. L. Nofziger and A. G. Hornsby
Copyright 1984


OPTIONS :
A.
B.
C.
D.
E.
F.
Q.


Desired Option ? d


Calculate Chemical Movement in Soil
Enter, Modify, or Print Soil Data File
Enter, Modify, or Print Chemical Data File
Enter, Modify, or Print Rainfall Data File
Enter, Modify, or Print Evapotranspiration Data File
Display File Directory
Quit. Terminate Program and Return to DOS


Screen 6. Selection of option D in main menu.











Enter or Modify Rainfall Data Files:


This simulation of organic chemical movement in soils requires the
following rainfall information:
A. Month
B. Day
C. Year
D. Effective Rainfall

NOTE: Effective Rainfall is approximately the difference
between the amount of precipitation and runoff.

The information for each day with a rainfall event must be
entered into a data file. This option is used to enter or
modify this data.


Press Space Bar to Continue:


Screen D-1. Introduction to rainfall data management option.

This option is similar to option C for chemical data. In this case the user must
select the units for entering effective rainfall amounts. Note that the effective
rainfall is the quantity of water entering the soil. Only dates with effective
rainfall need to be entered in the file. Missing dates are assumed to have no
rainfall.

The following frames illustrate the process of storing such data.










Distances or lengths can be expressed in the following units:

E. English inches
M. Metric centimeters

Enter or for desired units [Default is E] :

Enter Name of File to be Used : local83

File LOCAL83.R does not exist.
Do you want to create it (Y,N)? v


Screen D-2. Selection of units and file for rainfall data.

The units must be selected to match with the units of rainfall data being entered.
Since the rainfall data to be entered were in inches, the English units were
selected.

The file specified for this data was LOCAL83. Any legal file name may be used.
(See the DOS manual for more information on file names). NOTE: No file extension
was entered by the user. The computer assigned a extension of .R to represent a
rainfall file. The computer then checked the disk drive for this file. Since it
was not found on the default drive, the user was asked if the file should be
created. In this case the user responded affirmatively so the file was created.
Since the file was new, the program branched immediately to the data entry part of
the data manager. If an existing file had been specified, the user would have been
given the usual E (Enter), M (Modify), and P (Print) options (as in screen C-2).










Enter the word END to stop data entry


Month: 1
Day : CENTER>
Year : 83
Effective Rainfall (in): .33


Screen D-E-1. Entering rainfall data.

When this information is entered it is stored in the disk file. The user is then
prompted for more data as shown below. The data can be modified later using the M
(Modify) option for rainfall data.



Enter the word END to stop data entry

Month: 1
Day : 3
Year : 83
Effective Rainfall (in): .68
J^____________-----------------


Screen D-E-2. Entering more rainfall data.


Screen D-E-3. Terminating data entry.


The steps shown in screens D-E-1 and D-E-2 may be continued until all data for this
file have been entered. At that time, the data entry process is terminated as shown
here. Control is transferred back to the main menu.

All the information in file LOCAL83.R is shown in Table 4.








TABLE 4.


File : LOCAL83.R

Month Day Year Effective Rainfall (in)

1 2 83 0.33
1 3 83 0.68
1 20 83 0.28
1 21 83 1.48
1 23 83 0.23
1 27 83 0.20
1 28 83 0.70
1 30 83 0.12
2 2 83 2.00
2 6 83 0.40
2 13 83 0.44
2 14 83 2.27
2 17 83 0.10
2 23 83 0.57
2 28 83 0.17
3 1 83 0.70
3 6 83 2.33
3 7 83 2.97
3 16 83 0.43
3 17 83 1.63
3 18 83 0.83
3 21 83 0.83
3 24 83 0.33
3 27 83 1.53
3 31 83 0.50
4 3 83 0.28
4 8 83 1.07
4 9 83 2.56
4 10 83 0.16
4 15 83 2.56
4 16 83 0.25
4 19 83 0.61
4 23 83 1.50
5 4 83 0.26
5 14 83 0.60
5 17 83 1.35
5 24 83 2.43
6 5 83 0.39
6 7 83 2.05
6 8 83 1.67
6 22 83 1.03
6 29 83 0.41








TABLE 4. Continued


Month Day Year Effective Rainfall (in)

7 1 83 0.33
7 20 83 0.43
7 21 83 0.26
7 24 83 0.13
7 26 83 0.25
7 27 83 0.35
7 31 83 0.40
8 2 83 1.32
8 3 83 1.32
8 4 83 1.72
8 5 83 0.10
8 7 83 0.18
8 8 83 1.68
8 13 83 0.17
8 14 83 0.10
8 31 83 0.17
9 2 83 0.12
9 3 83 0.15
9 5 83 0.29
9 13 83 1.95
9 20 83 0.14
9 22 83 0.38
10 9 83 0.35
10 10 83 0.38
10 11 83 0.33
10 12 83 0.12
10 13 83 0.11
10 14 83 0.55
10 15 83 0.17
10 18 83 0.17
11 5 83 0.10
11 16 83 0.24
11 20 83 0.14
11 21 83 2.17
11 25 83 2.30
11 28 83 0.49
11 29 83 0.36
12 4 83 0.38
12 7 83 0.22
12 12 83 2.04
12 14 83 0.41
12 15 83 0.11
12 17 83 0.70
12 18 83 0.68
12 19 83 0.19
12 29 83 1.39













OPTION E: ENTER, MODIFY, OR PRINT EVAPOTRANSPIRATION DATA FILE


CHEMICAL MOVEMENT IN SOILS

by

D. L. Nofziger and A. G. Hornsby
Copyright 1984


OPTIONS :
A.
B.
C.
D.
E.
F.
Q.


Desired Option ? e


Calculate Chemical Movement in Soil
Enter, Modify, or Print Soil Data File
Enter, Modify, or Print Chemical Data File
Enter, Modify, or Print Rainfall Data File
Enter, Modify, or Print Evapotranspiration Data File
Display File Directory
Quit. Terminate Program and Return to DOS


Screen 6. Selection of option E in main menu.










Enter or Modify Evapotranspiration Data Files:

This simulation of organic chemical movement in soils requires the
following evapotranspiration information:
A. Month
B. Day
C. Year
D. Evapotranspiration

NOTE: The model requires evapotranspiration data for each
day during which movement will be simulated. If
any days are missing in the file, the ET rate for
the proceeding day is used. Therefore, consecutive
days with the same ET need to be entered only for
the first day.

The information for each day must be entered into a data
file. This option is used to enter or modify this data.

Press Space Bar to Continue:


Screen E-1. Introduction to evapotranspiration data management option.

NOTE: Evapotranspiration data is needed for each day simulated. If days are missing
in this file, the value for the proceeding day is assumed to apply.


Distances or lengths can be expressed in the following units:

E. English inches
M. Metric centimeters

Enter or for desired units [Default is E] :

Enter Name of File to be Used : local83

File LOCAL83.ET does not exist.
Do you want to create it (Y,N)? _


Screen E-2. Selection of units and file for evapotranspiration data.


The units must be selected to match with the units of evapotranspiration
entered. Here English units were selected.


data being


The file name entered in this case was again LOCAL83 since it was to be used with
the rain file entered above. In this case the computer put the extension .ET on the
file to designate its contents. After the user entered to the final question,
the following screen was displayed.











Enter the word END to stop data entry


Month: 1
Day : 2
Year : 83
Evapotranspiration (in): .06
s^ _____ __ _- -- --- - - - - - - - ^ -- *


Screen E-E-1. Entering evapotranspiration data.


As this
prompted
(Modify)


information is entered it is stored in the disk file. The user is then
for more data as shown below. The data can be modified using the M
option for evapotranspiration data.


Screen E-E-2.


Entering more evapotranspiration data.


Screen E-E-3. Terminating data entry.


The steps shown in screens E-E-1 and E-E-2 may be continued until all data for this
file have been entered. At that time, the data entry process is terminated as shown
here. Control is transferred back to the main menu.

Table 5 shows all the information stored in file LOCAL83.ET.


Enter the word END to stop data entry

Month: 1
Day : 5
Year : 83
Evapotranspiration (in): .09








TABLE 5.


File : LOCAL83.ET

Month Day Year Evapotranspiration (in)

1 1 83 0.06
1 5 83 0.09
1 6 83 0.06
1 9 83 0.07
1 11 83 0.04
1 12 83 0.12
1 13 83 0.08
1 15 83 0.16
1 16 83 0.08
1 17 83 0.10
1 19 83 0.09
1 22 83 0.08
1 25 83 0.07
1 26 83 0.06
1 31 83 0.14
2 1 83 0.06
2 3 83 0.20
2 4 83 0.14
2 5 83 0.12
2 6 83 0.08
2 7 83 0.05
2 8 83 0.10
2 9 83 0.12
2 11 83 0.08
2 12 83 0.06
2 13 83 0.09
2 14 83 0.10
2 15 83 0.13
2 16 83 0.12
2 17 83 0.13
2 18 83 0.14
2 20 83 0.12
2 21 83 0.18
2 22 83 0.14
2 26 83 0.23
2 27 83 0.13
2 28 83 0.08








TABLE 5. Continued


Month Day Year Evapotranspiration (in)

3 1 83 0.16
3 3 83 0.18
3 4 83 0.14
3 7 83 0.10
3 8 83 0.06
3 9 83 0.19
3 10 83 0.25
3 11 83 0.14
3 12 83 0.12
3 13 83 0.14
3 17 83 0.13
3 18 83 0.12
3 19 83 0.10
3 20 83 0.14
3 21 83 0.15
3 22 83 0.17
3 23 83 0.18
3 24 83 0.17
3 25 83 0.16
3 26 83 0.14
3 28 83 0.27
3 29 83 0.25
3 30 83 0.14
4 1 83 0.11
4 2 83 0.09
4 4 83 0.21
4 5 83 0.14
4 6 83 0.24
4 7 83 0.26
4 13 83 0.20
4 14 83 0.22
4 15 83 0.28
4 16 83 0.08
4 17 83 0.28
4 18 83 0.14
4 20 83 0.21
4 21 83 0.14
4 22 83 0.24
4 23 83 0.26
4 24 83 0.36
4 25 83 0.28
4 26 83 0.25
4 27 83 0.19
4 28 83 0.28
4 29 83 0.16
4 30 83 0.28








TABLE 5. Continued


Month Day Year Evapotranspiration (in)

5 1 83 0.24
5 2 83 0.18
5 3 83 0.28
5 6 83 0.24
5 8 83 0.27
5 9 83 0.14
5 12 83 0.16
5 13 83 0.19
5 14 83 0.24
5 15 83 0.28
5 16 83 0.16
5 17 83 0.20
5 18 83 0.28
5 19 83 0.20
5 20 83 0.07
5 21 83 0.18
5 22 83 0.24
5 23 83 0.23
5 27 83 0.28
5 28 83 0.25
5 29 83 0.23
5 30 83 0.26
5 31 83 0.20
6 1 83 0.14
6 2 83 0.22
6 5 83 0.19
6 6 83 0.14
6 7 83 0.18
6 8 83 0.20
6 9 83 0.27
6 10 83 0.25
6 11 83 0.28
6 12 83 0.23
6 13 83 0.20
6 15 83 0.24
6 17 83 0.22
6 18 83 0.27
6 19 83 0.23
6 21 83 0.14
6 24 83 0.07
6 25 83 0.12
6 26 83 0.26
6 27 83 0.16
6 28 83 0.21








TABLE 5. Continued


Month Day Year Evapotranspiration (in)

7 1 83 0.20
7 4 83 0.14
7 5 83 0.09
7 6 83 0.23
7 8 83 0.28
7 9 83 0.26
7 10 83 0.28
7 12 83 0.23
7 13 83 0.27
7 15 83 0.23
7 16 83 0.28
7 19 83 0.29
7 20 83 0.28
7 22 83 0.27
7 23 83 0.30
7 24 83 0.20
7 25 83 0.23
7 26 83 0.11
7 28 83 0.28
7 29 83 0.27
7 30 83 0.18
8 1 83 0.14
8 3 83 0.13
8 4 83 0.12
8 5 83 0.10
8 6 83 0.20
8 7 83 0.07
8 9 83 0.20
8 12 83 0.14
8 13 83 0.13
8 15 83 0.14
8 16 83 0.28
8 17 83 0.23
8 18 83 0.21
8 20 83 0.26
8 21 83 0.25
8 22 83 0.19
8 23 83 0.28
8 24 83 0.21
8 25 83 0.25
8 26 83 0.28
8 28 83 0.17
8 29 83 0.21
8 30 83 0.19
8 31 83 0.10









TABLE 5. Continued


Month Day Year Evapotranspiration (in)

9 1 83 0.19
9 3 83 0.14
9 4 83 0.11
9 6 83 0.22
9 7 83 0.24
9 9 83 0.14
9 12 83 0.21
9 13 83 0.15
9 14 83 0.18
9 15 83 0.12
9 16 83 0.10
9 17 83 0.12
9 19 83 0.19
9 20 83 0.13
9 21 83 0.16
9 24 83 0.22
9 25 83 0.20
9 26 83 0.19
9 27 83 0.23
9 28 83 0.18
9 29 83 0.16
9 30 83 0.19
10 1 83 0.13
10 2 83 0.09
10 3 83 0.19
10 4 83 0.14
10 5 83 0.12
10 6 83 0.10
10 7 83 0.20
10 8 83 0.18
10 9 83 0.10
10 10 83 0.12
10 11 83 0.15
10 12 83 0.10
10 13 83 0.11
10 17 83 0.17
10 18 83 0.05
10 19 83 0.14
10 22 83 0.09
10 23 83 0.07
10 24 83 0.12
10 25 83 0.05
10 26 83 0.13
10 27 83 0.14
10 28 83 0.11
10 29 83 0.13
10 30 83 0.12








TABLE 5. Continued


Month Day Year Evapotranspiration (in)

10 31 83 0.14
11 1 83 0.10
11 2 83 0.12
11 3 83 0.13
11 4 83 0.14
11 5 83 0.04
11 6 83 0.14
11 7 83 0.07
11 8 83 0.04
11 11 83 0.12
11 12 83 0.09
11 13 83 0.10
11 14 83 0.09
11 15 83 0.08
11 16 83 0.10
11 17 83 0.14
11 18 83 0.05
11 19 83 0.09
11 20 83 0.10
11 22 83 0.08
11 23 83 0.11
11 24 83 0.05
11 25 83 0.06
11 26 83 0.11
11 27 83 0.04
11 28 83 0.07
11 30 83 0.11
12 2 83 0.10
12 3 83 0.08
12 5 83 0.12
12 6 83 0.06
12 7 83 0.02
12 8 83 0.09
12 9 83 0.10
12 10 83 0.05
12 11 83 0.08
12 12 83 0.06
12 13 83 0.04
12 14 83 0.02
12 16 83 0.15
12 17 83 0.10
12 18 83 0.10
12 20 83 0.11
12 21 83 0.09
12 22 83 0.05
12 23 83 0.10










DESCRIPTION OF MODEL


Let d. represent the depth of the solute front i days after the chemical was applied

to the soil surface. Let I. and ET. represent the amount of water infiltrating the
1 1
soil surface and the potential evapotranspiration, respectively, on day i. The

depth of the solute front at the beginning of day i+1 is given by

di+1 = di + i/(Re FC) if qi > 0
or (1)
di = di if qi < 0


where qi is the amount of water passing the depth di, eFC is the soil-water content

on a volume basis at "field capacity", and R is the retardation factor for the

chemical in this soil. Assuming a linear and reversible equilibrium adsorption

model, the retardation factor R is given by

R = 1 + (PKD)/6FC (2)


where p is the soil bulk density and KD is the linear sorption coefficient or the

partition coefficient of the chemical in this soil. The partition coefficient is

given by

KD = KOC OC (3)


where KOC is the linear sorption coefficient normalized by the organic carbon

content (OC) of the soil. (Note: The use of KOC as defined in equation 3 is

applicable only to non-ionic organic solutes). The majority of computation in the

model is directed to the determination of qi in equation 1 from known values of Ii

and ET.. This process is described below.


Consider a soil with the solute front at depth d.. Due to evapotranspiration, the








soil-water content in the root zone may be less than e FC When an infiltration

event occurs, some water is needed to increase the soil-water content above the

solute front to a FC. The excess water (if any) contributes to downward movement of

the solute front. That is,

q. = I. swd (4)


where swd is the soil water deficit above the depth of the solute front, d.. The
1

soil water deficit is given by

swd = [6FC 6 ] d. if d. < d
FC a 1 1i root (
or (5)
swd = [6F e ] droot if d. > d
FC a root i root


where droot is the depth of the root zone and a is the average volumetric
root a
soil-water content above depth d. if d. < droot or above droot if d. > d If q
1 1 root root i root i
in equation 4 is greater than zero, a is increased to FC. If qi is less than or
a FC 1

equal to zero, the solute depth does not change (di+I = di). Instead, the inflowing

water just increases the water content 6 as given by
a
e = 6 + I./d. if d. < d
or (6)
6 = 9 + I./d if d. > d
a a i root i root

To deal with evapotranspiration in the model, the average water content, defined

above is calculated for each day. In addition, during the time in which the solute

front is in the root zone (i.e. d. < d ), a second average water content, 6b, is

calculated for the soil between the solute depth and the maximum rooting depth. If

6 = 6 both water contents decrease together to meet the evapotranspiration
a b
demand. In this case

6 = 6 ET./d
and a a (7)
S 6 ET./droot
b b i root









If 0a is greater than b, then e is decreased to meet all of the ET demand until ea

= eb at which point the remaining ET is removed uniformly from the entire root

zone. The water contents in the root zone are not permitted to decrease below the

water content corresponding to the "permanent wilting point" of the soil.

ASSUMPTIONS IN MODEL

The following assumptions are used in this model:

1. The soil is homogeneous. This assumption is reasonable for a model intended
for instructional purposes. This model will not describe movement in soils
containing layers with different organic carbon contents, textures, or pore
size distributions precisely.

2. All soil water residing in pore spaces participates in the transport process.
Soil water initially present in the profile is completely displaced ahead of
water entering at the soil surface. Rao et.al.(1976) present data from
different researchers which indicate that these assumptions are valid for many
soils. If they are not valid and a portion of the soil water is bypassed
during flow, this model would tend to underestimate the depth of the
chemical.

3. Water entering the soil redistributes instantaneously to "field capacity".
This assumption is approached for coarse textured soils. If the water
redistributes more slowly as in fine textured soils, the depths predicted here
would need to be associated with an ellapsed time a few days later than that
specified.

4. Water is removed by evapotranspiration from the wettest part of the root zone
first. When the water content in the root zone is uniform, water is lost
uniformly at all depths. The validity of this assumption will depend upon the
root distribution in the soil. It will not be strictly valid for many
situations. It is a reasonable assumption for an instructional model.

5. Upward movement of water does not occur anywhere in the soil profile. Water
is lost from the root zone by evapotranspiration, but soil-water in the root
zone is not replenished from below. This assumption seems reasonable for
homogeneous well-drained soils.

6. The adsorption process can be described by a linear, reversible equilibrium
model. If the sorption coefficient is described by a nonlinear isotherm, the
partition coefficient decreases with increasing concentration of the
chemical. Thus, the depth to which the chemical will be leached will depend
upon the concentration. This aspect is probably not significant for the
concentration range of interest in most agricultural applications( Rao and
Davidson, 1980). When adsorption equilibrium is not instantaneous, the
chemical will be leached to a greater depth than predicted here. Irreversible
sorption would result in less leaching.







7. The half-life for degradation of the chemical is a constant with time and soil
depth. Degradation rate coefficients are dependent upon a variety of
environmental factors, primarily temperature and soil-water content. Hence,
seasonal changes in rate coefficient can be expected. Also, with decreasing
microbial activity at greater soil depths, the degradation rate coefficient
may decrease with depth. Sufficient data are not available to formulate
mathematical relationships to describe these effects. For instructional
purposes, this additional complication was not considered important, but it
would need to be modeled for actual prediction of pesticide fate under field
conditions.









REFERENCES


1. Hamaker, J. W., and J. M. Thompson. 1972. Adsorption. Vol. 1, p. 49-143.
In C. A. I. Goring and J. W. Hamaker (ed.) Organic chemicals in the
environment. Marcel Dekker Inc., NY.

2. Karickhoff, S. W. 1981. Semi-empirical estimation of sorption of hydrophobic
pollutants on natural sediments and soils. Chemosphere 10:833-846.

3. Karickhoff, S. W. 1984. Organic pollutant sorption in aquatic systems. J.
Hydraulic Engineering 110:707-735.

4. Laskowski, D. A., C. A. I. Goring, P. J. McCall, and R. L. Swann. 1982.
Terrestrial environment. p. 198-240. In R. A. Conway (ed.) Environmental
risk analysis for chemicals. Van Nostrand Reinhold Co., NY.

5. Rao, P. S. C., and J. M. Davidson. 1980. Estimation of pesticide retention
and transformation parameters required in nonpoint source pollution models.
p.23-67. In M. R. Overcash and J. M. Davidson(ed.) Environmental impact of
nonpoint source pollution. Ann Arbor Science Publishing Inc., Ann Arbor,
Mich.

6. Rao, P. S. C., J. M. Davidson, and L. C. Hammond, 1976. Estimation of
nonreactive and reactive solute front locations in soils, p. 235-241. In
Proc. Hazardous Wastes Research Symp., EPA-600/9-76-015, Tucson, Ariz.










APPENDIX









Soil Science Fact Sheet
Sept. 1983


SL 40 (Revised)


Pesticides and Their Behavior in Soil and Water

P.S.C. Rao, R.S. Mansell, L.B. Baldwin and M.F. Laurent*

Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / J. T. Woeste, Dean


Concern for man himself and his fate must always form the
chief interest of all technical endeavor.
Albert Einstein
Pesticides stand out as one of the major
developments of the twentieth century. During the
past twenty years, however, concern has arisen as
to the extent their presence in the environment
poses a threat to wildlife and mankind.
Certainly, pesticides have improved longevity
and the quality of life, chiefly in the area of public
health. Insect control programs have saved
millions of lives by combatting diseases such as
malaria, yellow fever and typhus. The use of
pesticides also constitutes an important aspect


of modern agriculture, for without chemicals to
control various pests like insects, weeds, plant
diseases, worms and rodents, our food supply
would decrease and prices would increase.
Florida's temperate to subtropical climate favors
growth of many harmful insects, weeds and
diseases, thus making this state particularly
dependent on pesticides for economical crop
management.
Unfortunately, pesticides are poisons and can
be particularly dangerous when misused. Fish-
kills, reproductive failure in birds, and acute ill-
nesses in people have all been attributed to
exposure to or ingestion of pesticides usually


Figure 1: Pathways of pesticide loss. P=pesticide.
Adapted from Herbicide Iniury. Svmotoms and Diaonosis
Service, AG-85, Dec. 1981.


Skroch, W. A. and Sheets, T. J. (eds.), North Carolina Agricultural Extension


*Associate Professor of Soil Science, Professor of Soil Science, Associate Professor of Agricultural Engineering and Assistant in Editorial,
respectively.






as a result of misapplication or careless disposal
of unused pesticides and pesticide containers.
Pesticide losses from areas of application and
contamination of non-target sites such as surface
and ground water represent a monetary loss to
the farmer as well as a threat to the environment.
Thus careful management of pesticides in order
to avoid environmental contamination is desired
by both farmers and the general public.
The purpose of this fact sheet is to explain how
pesticides can move from the area in which they
are applied, and to show how this information can
be used, along with other factors, to select the
proper pesticide.

PATHWAYS OF PESTICIDE LOSS
There are basically two ways properly-applied
pesticides may reach surface and underground
waters through runoff and leaching.1 Runoff is
the physical transport of pollutants over the
ground surface by rainwater which does not
penetrate the soil. Leaching is a process whereby
pollutants are flushed through the soil by rain or
irrigation water as it moves downward. In many
areas of Florida soils are sandy and permeable
and leaching is likely to be a more serious prob-
lem than runoff. We now have technology to help
estimate the potential contamination of water
from a given pesticide. To understand this
technology, it is necessary to know how a
pesticide behaves in soil and water.
Once applied to cropland, a number of things
may happen to a pesticide (Fig. 1). It may be taken
up by plants or ingested by animals, insects,
worms, or microorganisms in the soil. It may move
downward in the soil and either adhere to par-
ticles or dissolve. The pesticide may vaporize and
enter the atmosphere, or break down via microbial
and chemical pathways into other, less toxic com-
pounds. Pesticides may be leached out of the root
zone by rain or irrigation water, or wash off the
surface of land. The fate of a pesticide applied to
soil depends largely on two of its properties: per-
sistence and solubility.

PERSISTENCE
Persistence defines the "lasting-power" of a
pesticide. Most pesticides break down or "de-
grade" over time as a result of several chemical
and micro-biological reactions in soils. Sunlight
breaks down some pesticides. Generally,
chemical pathways result in only partial deactiva-
tion of pesticides, whereas soil microorganisms
can completely break down many pesticides to


carbon dioxide, water and other inorganic consti-
tuents. Some pesticides produce intermediate
substances, called metabolitess" as they
degrade. The biological activity of these
substances may also have environmental signifi-
cance. Because populations of microbes
decrease rapidly below the root zone, pesticides
leached beyond this depth are less likely to be
degraded. However, some pesticides will con-
tinue to degrade by chemical reactions after they
have left the root zone.
Degradation time is measured in "half-life."
Each half-life unit measures the amount of time it
takes for one-half the original amount of a
pesticide in soil to be deactivated. Half-life is
sometimes defined as the time required for half
the amount of applied pesticide to be completely
degraded and released as carbon dioxide. Usu-
ally, the half-life of a pesticide measured by the
latter basis is longer than that based on deactiva-
tion only. This is especially true if toxic or non-
toxic metabolites accumulate in the soil during
the degradation. Table 1 groups some of the
pesticides used in Florida by persistency, or
length of half-life, on the basis of their deactiva-
tion in soils.
Table 1: Grouping of pesticides based on persistence in soils.
Persistent
Non-Persistent Moderately Persistent (half-life
(half-life less (half-life greater than greater than
than 30 days) 30 days, less than 100) 100 days)
Aldicarb Aldrin Heptachlor Bromacil
Captan Atrazine Linuron Chlordane
Dalapon Carbaryl Parathion Lindane
Dicamba Carbofuran Phorate Paraquat
Malathion Diazinon Simazine Picloram
Methyl para- Endrin Terbacil Trifluralin
thion
Oxamyl Fonofos TCA
2, 4-D Glyphosate
2, 4, 5-T


SOLUBILITY AND SORPTION
Probably the single most important property in-
fluencing a pesticide's movement with water is its
solubility. Soil is a complex mixture of solids, li-
quids and gases that provides the life support
system for roots of growing plants and micro-
organisms such as bacteria. When a pesticide
enters soil, some of it will stick to soil particles,
particularly organic matter, through a process
called adsorption and some will dissolve and mix
with the water between soil particles, called "soil-
water." As more water enters the soil through rain
or irrigation, the adsorbed pesticide molecules
may be detached from soil particles through a
process called desorption. The solubility of a


1Two other pathways of pesticide loss are through removal in the harvested plant and by vaporization volatilizationn) into the atmosphere.
Occurrence of pesticide residues in edible parts of plants is significant in terms of human exposure, while pesticides released into the atmos-
phere have an impact on air quality and create problems when agricultural workers enter the treated areas. While these two pathways are
important, they will not be considered further in this factsheet, which is devoted to pesticide behavior in soil and water.






pesticide and its sorption on soil are inversely
related; that is, increased solubility results in less
sorption.
One of the most useful indices for quantifying
pesticide adsorption on soils is the "partition
coefficient" (PC). The PC value is defined as the
ratio of pesticide concentration in the adsorbed-
state (that is, bound to soil particles) and the
solution-phase (that is, dissolved in the
soil-water). Thus, for a given amount of pesticide
applied, the smaller the PC value, the greater the
concentration of pesticide in solution. Pesticides
with small PC values are more likely to be leached
compared to those with large PC values.
Partition coefficients of several chemicals are
shown in Table 2. Note the wide range of partition
coefficients. Values of partition coefficients
listed in Table 2 are independent of soil type and
are characteristic of each pesticide. The partition
coefficient is determined by a pesticide's
chemical properties such as solubility and
melting point.


Table 2: Partition coefficients (PC) for selected pesticides
(generic name only)


Pesticide
Aldicarb
Chloramben
Carbofuran
2,4-D
Fenuron
Terbacil
Propham
Bromacil
Monuron
Simazine
Dichlobenil
Atrazine
Fluometuron
Cynazine
Propazine


Pesticide PC
Carbaryl 229
Monolinuron 237
Prometone 300
Ametryn 380
Diuron 389
Prometryn 513
Trietazine 549
Chlorpropham 589
Linuron 841
Ipazine 1,161
Malathion 1,778
Chloroxuron 4,986
Methyl parathion 7,079
Parathion 7,161
Chloropyrifos 13,490
DDT 243,000


The partition coefficient makes it possible to
put a value on a particular pesticide's chance of
being lost via runoff or leaching in a specific soil,
via the formula:
K= (PC)(%OM)(0.0058)

where K is an index for sorption of a given
pesticide on a particular soil, %OM is the percent
of organic matter in the soil, as determined by
chemical analysis of the soil, and where PC is the


partition coeffcient of the pesticide, as listed in
Table 2. Note that for pesticides that are not ad-
sorbed on soil, PC is equal to zero; hence, K = O.
In rhost soils, inorganic ions such as nitrate and
chloride are not adsorbed by soils. Thus,
pesticides with PC or K = O will leach in a man-
ner similar to nitrate or chloride.


ESTIMATING PESTICIDE LOSS
In evaluating the contamination potential of a
particular pesticide, it is essential to consider its
partition coefficient and half-life jointly. For ex-
ample, a pesticide with a small PC, say less than
100, and a long half-life, say more than 100 days,
poses considerable threat to ground water
through leaching. On the other hand, a nonvolatile
pesticide with a large PC, say 1000 or more, and a
long half-life (e.g., more than 100 days) is likely to
remain on or near the surface of soil, increasing
its chances of being carried to a lake or stream in
runoff. For pesticides with short half-lives, (less
than 30 days), the possibility of surface or ground
water pollution depends primarily on whether
heavy rains or irrigations occur soon after applica-
tion. Without water to move, pesticides with short
half-lives remain in the biologically active root
zone of soil and may degrade rapidly. In terms of
water quality, pesticides with intermediate PCs
and short half-lives may be considered "safest."
They are not readily leached and degrade fairly
rapidly.
From the foregoing discussion and Table 3, a
qualitative assessment of a pesticide's potential
Table 3: Combination of sorption and persistence of a
pesticide for determining its contamination potential.

Partition Half-life Pathway Has potential
coefficient of loss for
(PC) contam-
inating

small long leaching ground water
small short leaching ground water
large long runoff surface water
large short runoff surface water
aOnly if heavy rains or irrigations occur soon after pesticide application.

to pollute surface or ground water is possible.
Quantitative prediction of pesticide loss via
runoff and leaching requires complex computer
models which utilize site-specific soil, crop, and
climatological information. This would include
the soil type, the date, amount and method of ap-
plication, and the amount, frequency and duration
of rain or irrigation following application.








PESTICIDE SELECTION AND USE
Agricultural use of pesticides should be part of
an overall pest management strategy which in-
cludes biological controls, cultural methods, pest
monitoring and other applicable practices, re-
ferred to altogether as Integrated Pest Manage-
ment or IPM. When a pesticide is needed its selec-
tion should be based on effectiveness, toxicity to
non-target species, cost, and site characteristics,
as well as its solubility and persistence.
Half-lives and partition coefficients are par-
ticularly important when the application site of a
pesticide is near surface waters or is underlain
with permeable subsoil and a shallow aquifer.
Short half-lives and intermediate to large PC's are
best in this situation.
Many areas of Florida have impermeable sub-
soils which impede deep leaching of soluble
pesticides. On such land, soluble pesticides with
low PCs and moderate-to-long half-lives require
cautious application to prevent rapid transport in
drainage water to a nearby lake or stream. Non-
erosive soils are common to much of Florida and
pesticides with large PCs remain on the applica-
tion site for a long time. However, the user should
be cautious of pesticides with long half-lives as
they are likely to build up in the soil.
In addition to the pesticide solubility and soil
permeability it is important that the pesticide's
toxicity to non-target species be considered.
Some of the pesticides listed in Tables 1 and 2
have severely restricted use due to acute toxicity
or long half-life. An important purpose of the
pesticide container's label is to instruct users to
apply the pesticide safely and with minimum
threat to non-target species, both on and off the
application site. Pesticide users assume respon-


sibility to follow label instructions. It is unsafe
and unlawful not to do so.


NEED MORE INFORMATION?
Pesticide recommendations for various crops
and pests may be obtained from the Florida Co-
operative Extension Service. Contact your county
Extension office for this information. For more
discussion of some of the ideas presented here,
consult these Extension publications.
IFAS 16 A Clean Water Refresher... answers
frequently asked questions about water quality in
Florida and describes Florida's agricultural water
quality program.
SP-19 Pollution Solutions for Florida Farmers
... discusses agricultural water quality problems
in Florida and presents prevention measures.
SL-14 The Soil: Our Number One Waste
Disposal System ... discusses 14 types of
pollutants related to agriculture and explains soil
as a recycling system for treatment.
SL-37 Soil as a Porous Medium ... part one in
Basics of Soil and Water Relationships series; ex-
plains fundamentals of soil structure, particularly
particle and pore size, total porosity and soil bulk
density.
SL-38 Retention of Water... part two in above
series; explores the influence of soil structure on
retention of water.
SL-39 Movement of Water... part three in
above series; deals with fundamental principles
of water flow in soil.
IPM-1 Integrated Pest Management Primer...
goals, benefits and implementation of IPM as an
alternative to heavy use of pesticides.


MBest
Management
Practices
PRODUCING GOOD FOOD WHILE PROTECTING FLORIDA'S WATER

This public document was promulgated at a cost of $304.05, or 10.1 cents per copy, to help implement the agricultural
element of the Florida water quality plan. 10-3.0M-83

COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOOD AND AGRICULTURAL
SCIENCES, K. R. Tefertller, director, In cooperation with the United States Department of Agriculture, publishes this infor-
mation to further the purpose of the May 8 and June 30, 1914 Acts of Congress; and is authorized to provide research, educa-
tional Information and other services only to Individuals and Institutions that function without regard to race, color, sex or
national origin. Single copies of Extension publications (excluding 4-H and Youth publications) are available free to Florida
residents from County Extension Offices. Information on bulk rates or copies for out-of-state purchasers is available from
C. M. Hinton, Publications Distribution Center, IFAS Building 664, University of Florida, Gainesville, Florida 32611. Before publicizing this
publication, editors should contact this address to determine availability.















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