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Group Title: Bulletin - Agricultural Experiment Station. University of Florida ; 880 (technical)
Title: Estimation of dry matter production and nitrogen uptake by Pensacola Bahiagrass in Florida
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 Material Information
Title: Estimation of dry matter production and nitrogen uptake by Pensacola Bahiagrass in Florida
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: iii, 25 p. : ; 28 cm.
Language: English
Creator: Overman, Allen R., 1937-
Blue, William G
Publisher: Agricultural Experiment Station, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville
Publication Date: 1991
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Subject: Grasses -- Florida   ( lcsh )
Plants -- Effect of nitrogen on -- Florida   ( lcsh )
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bibliography   ( marcgt )
non-fiction   ( marcgt )
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Bibliography: Includes bibliographical references (p. 7-8).
Statement of Responsibility: Allen R. Overman and William G. Blue.
General Note: Cover title.
General Note: "August 1991."
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Table of Contents
    Front Cover
        Front Cover
    Front Matter
        Front Matter
    Table of Contents
        Page i
        Page ii
        Page iii
    Main
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
    Reference
        Page 7
        Page 8
        Page 9
        Page 10
    Appendix
        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
    Back Cover
        Back Cover
Full Text

88o
August 1991
I-


Bulletin 880 (technical)
I9


Estimation of Dry CaIti ,

Production and Nitrogen Uptake

by Pensacola Bahiagrass

in Florida

Allen R. Overman and William G. Blue















Agricultural Experiment Station
Institute of Food and Agricultural Sciences
University of Florida
J.M. Davidson, Dean















































































Allen R. Overman, Professor, Department of Agricultural Engineering and William G. Blue, Professor Emeritus, Department of Soil
Science, University of Florida, Gainesville, 32611.









Table of Contents

Page
Introduction .............................................................................................................................................................1
Experimental System ..............................................................................................................................................1
Seasonal Distribution of Dry M matter ...................................................................................................................... 1
Yield Response to Applied Nitrogen ................................................................................................................. 2
Average Yields ...................................................................................................................................................... 2
Variation in Yields ........................................................................................................................................ 3
Forage Nitrogen Concentration ........................................................................................................................ 3
Forage Nitrogen Removal ................................................................................................................................. 4
Seasonal N Removal............................................................................................................................................4
Example Calculation ..................................................................................................................................... 4
Total Annual N Removal .............................................................................................................................. 4
Effects of Harvest Interval, Applied N and Soil Type on Yields .................................................. .................5
Summary and Conclusions......................................................................................................................................6
Estimation Procedure .................................................................................................................................... 6
Example Calculations ................................................................................................................................... 6
Application to South Florida ......................................................................................................................... 6
References ................................................................................................................................................................ 7
Appendix A ............................................................................................................................................................. 11
Appendix B ................................................................................................................................................................... 16
Appendix C ...................................................................................................................................................................20

List of Tables

Table Page
1. Summary of model parameters for bahiagrass on an Entisol (1979-1983) ................................... .......... 8
2. Summary of model parameters for bahiagrass on a Spodosol (1979-1983)............................................... 8
3. Summary of N response parameters for bahiagrass ............................................................. ................... 9
4. Analysis of variance for bahiagrass on an Entisol ............................................................................................9
5. Analysis of variance for bahiagrass on a Spodosol ......................................... ................ .......................... 9
6. Summary of model parameters by year for bahiagrass................................................. ......................... 10
7. Forage N concentrations for bahiagrass.................................................................................................... 10
8. Total annual yields and forage N for bahiagrass on a Spodosol at Ona, Florida (1976-1979) .................. 10
Al. Yield and nitrogen data for bahiagrass on an Entisol for 1979............................................. .............. 11
A2. Yield and nitrogen data for bahiagrass on an Entisol for 1980............................................ ............... 12
A3. Yield and nitrogen data for bahiagrass on an Entisol for 1981............................................ ............... 12









A4. Yield and nitrogen data for bahiagrass on an Entisol for 1982............................................ ............... 13
A5. Yield and nitrogen data for bahiagrass on an Entisol for 1983............................................ ............... 13
A6. Yield and nitrogen data for bahiagrass on a Spodosol for 1979 .......................................... ................ 14
A7. Yield and nitrogen data for bahiagrass on a Spodosol for 1980 ........................................... ............... 14
A8. Yield and nitrogen data for bahiagrass on a Spodosol for 1981........................................... ............... 15
A9. Yield and nitrogen data for bahiagrass on a Spodosol for 1982 ........................................... ............... 15
A10. Yield and nitrogen data for bahiagrass on a Spodosol for 1983 ......................................... ............... 16
B1. Normalized yield distributions for bahiagrass on an Entisol for 1979 ............................................... 16
B2. Normalized yield distributions for bahiagrass on an Entisol for 1980 ................................................. 17.
B3. Normalized yield distributions for bahiagrass on an Entisol for 1981 ............................................... 17
B4. Normalized yield distributions for bahiagrass on an Entisol for 1982 ................................................ 17
B5. Normalized yield distributions for bahiagrass on an Entisol for 1983 ............................................... 18
B6. Normalized yield distributions for bahiagrass on a Spodosol for 1979................................................ 18
B7. Normalized yield distributions for bahiagrass on a Spodosol for 1980............................................... 18
B8. Normalized yield distributions for bahiagrass on a Spodosol for 1981................................................ 19
B9. Normalized yield distributions for bahiagrass on a Spodosol for 1982............................................... 19
B10. Normalized yield distributions for bahiagrass on a Spodosol for 1983............................................... 19
C1. Normalized yield and normalized nitrogen for bahiagrass on an Entisol (1979) .....................................20
C2. Normalized yield and normalized nitrogen for bahiagrass on a Spodosol (1979) ....................................20

List of Figures

Figure Page
1. Normalized yield distributions at N = 100 kg/ha for 1979 for bahiagrass on an Entisol
and a Spodosol ........................................................................................................................................................21
2. Cumulative yield distributions for bahiagrass on an Entisol at various applied
N levels for 1979 ................................................................................................................................... ............21
3. Cumulative yield distributions for bahiagrass on an Entisol at various applied
N levels for .1980 ............................................ ......... ................................................................... .......................21
4. Cumulative yield distributions for bahiagrass on an Entisol at various applied
N levels for 1981........................................................................ ................................................. ......................21
5. Cumulative yield distributions for bahiagrass on an Entisol at various applied
N levels for 1982 ......................................... .................................... ................................................ ............... 21
6. Cumulative yield distributions for bahiagrass on an Entisol at various applied
N levels for 1983 ........................................ ................................................................. ..................... .........21
7. Cumulative yield distributions for bahiagrass on a Spodosol at various applied
N levels for 1979 ..................................... ....... ................................................................................................. ..22
8. Cumulative yield distributions for bahiagrass on a Spodosol at various applied
N levels for 1980 ........................................................... ............................................................... .....................22
9. Cumulative yield distributions for bahiagrass on a Spodosol at various applied
N levels for 1981 ............................................... ................................................................................................22









10. Cumulative yield distributions for bahiagrass on a Spodosol at various applied
N levels for 1982 ....................................................................................................................................... 22
11. Cumulative yield distributions for bahiagrass on a Spodosol at various applied
N levels for 1983 ....................................................................................................................................... 22
12. Dependence oft and a in Eq. (1) upon applied N for bahiagrass on an Entisol and
a Spodosol .............................................................................................................................................................23
13. Dependence of a upon t in Eq. (1) for bahiagrass on an Entisol and a Spodosol......................................23
14. Variations in total annual yield with year, applied N and soil ...............................................................23
15. Dependence of total annual yield upon applied N and soil......................................................................23
16. Variations in maximum yield with year and soil ......................................... ........................................24
17. Estimated total annual yield with applied N and soil for average, low (1981)
and high (1983) conditions....................................................................................................................... 24
18. Dependence of forage N concentration upon applied N for bahiagrass on an
Entisol and a Spodosol ............................................................................................................................. 24
19. Relationship between N and dry matter accumulations for 1979 at various
applied N levels for an Entisol ................................................................................................................ 24
20. Relationship between N and dry matter accumulations for 1979 at various
applied N levels for a Spodosol ................................................................................................................ 24
21. Estimated normalized yield distributions for bahiagrass at N = 100 kg/ha
and At = 6.6 weeks for an Entisol and a Spodosol................................................................................ 25
22. Estimated cumulative yield for bahiagrass at N = 100 kg/ha and At = 6.6 weeks
for an Entisol and a Spodosol .................................................................................................................. 25
23. Estimated cumulative N removal by bahiagrass at N = 100 kg/ha and At = 6.6
weeks for an Entisol and a Spodosol ....................................................................................................... 25
24. Estimated yield response of bahiagrass to applied N at At = 6.6 weeks on an
Entisol and a Spodosol ............................................................................................................................. 25
25. Estimated cumulative yield of bahiagrass at N = 100 kg/ha and At = 4 weeks
for an Entisol and a Spodosol .................................................................................................................. 25
26. Estimated cumulative N removal by bahiagrass at N = 100 kg/ha and At = 4 weeks
for an Entisol and a Spodosol .................................................................................................................. 25









Introduction
Forage production is a large enterprise in
Florida and throughout the southern United
States. It is estimated that Pensacola bahiagrass
(Paspalum notatum Flugge) is grown on 0.4 million
hectares (ha) in Florida alone (Chambliss and
Jones, 1980). Bahiagrass is used for both pasture
and hay production.
Extensive field studies have been conducted with
bahiagrass. Early work in Florida on response to
applied nitrogen (N) was reported by Leukel and
co-workers (Leukel and Coleman, 1930; Leukel et
al., 1934; Leukel and Barnette, 1935).
Wallace et al. (1955) measured yield response to
N, phosphorus (P) and potassium (K) fertilization.
Doss et al. (1960) reported on response of
bahiagrass to irrigation. Blue and Gammon (1963)
compared nutrient requirements under clipping
and grazing treatments. Blue (1971) studied
seasonal forage production on a Spodosol.
Blue and Graetz (1977) and Beaty et al. (1980)
measured response to applied N, including the
effect of split applications. Baldwin and Gallaher
(1985) reported yields on an Entisol under extreme
drought conditions. Blue (1987) studied N sources
and times of application on a Spodosol, and Blue
(1987) also compared response to N on an Entisol
and a Spodosol. Recently, Overman et al. (1989a)
developed a regression equation which relates plant
N concentration to applied N and harvest interval.
The effects of N rate and split application on
seasonal dry matter distribution, annual dry
matter production, and annual N removal were also
described (Overman et al., 1989b).
Data from several field studies were used to
evaluate simulation models for bahiagrass produc-
tion (Overman et al., 1989c). Overman et al.
(1989d) also summarized effects of various manage-
ment factors on bahiagrass production.
A simulation model for backgrounding feeder
cattle in Florida was published (Spreen et al.,
1985). It incorporated information on forage
grass and cattle growth to evaluate costs and
returns.
The objective of this bulletin is to develop regres-
sion equations for (1) seasonal distribution of dry
matter, (2) yield response to applied N, (3) depen-
dence of forage N concentration on applied N, and
(4) forage N uptake. The analysis is based upon 5
years of data (1979-1983) on two soils (an Entisol
and a Spodosol) in Florida. These results are


relevant to forage production, and also have poten-
tial water quality implications.
All results in this report are given in SI units.
To convert from SI to English units, use the follow-
ing factors:
kg/ha x 0.893 = lb/acre
t/ha x 0.446 = tons/acre.

Experimental system
The field data for this analysis were drawn from
a study reported by Blue (1987). Plant samples
were collected from established plots of Pensacola
bahiagrass on two soils, an Entisol (Astatula sand)
near Williston, Florida, and a Spodosol (Myakka
fine sand) near Gainesville, Florida. The Entisol
was an excessively drained soil (organic matter
- 1.25%), and the Spodosol was a poorly drained
soil (organic matter 2.85%). Soil pH was main-
tained near 6.0 in each case. Fertilizer was applied
in equal amounts during March and in early July
(immediately after the second harvest) to supply
annual N-P-K rates of 0-11-42, 100-11-42, 200-22-
84, 300-33-126, and 400-44-168 kg/ha. The nitro-
gen source was NH4NO,. Grass was harvested on
15 May, 1 July, 10 August, and 1 October, with an
average harvest interval of 6.6 weeks. Clipping
height was 3 cm, and all treatments were repli-
cated 4 times. Forage N was determined by the
micro-Kjeldahl method. Yields were reported as
dry matter in metric tons/ha (t/ha). Other experi-
mental details were described by Blue (1987).

Seasonal distribution of dry
matter
Grass yields on the two soils and for five growing
seasons were tabulated (see Appendix A). Since
Overman et al. (1989c) showed that cumulative
yield vs. time produced a straight line on probabil-
ity paper, the data were rearranged for analysis
(Appendix B), where
t = time since 1 January, weeks
Ay, = yield of ith harvest, t/ha
n
)Ay, = cumulative yield through nth harvest, t/ha
i=l
Fn = yield fraction through nth harvest.
The yield increment for t > 39.1 weeks was
estimated, to include growth after 1 October. A
typical probability plot is shown in Figure 1. The
lines were drawn from the empirical model










F= 1+erf( (1

where t = time to produce mean of yield distri-
bution (F = 50%), weeks
a = time spread of the yield distribution, weeks


erf x =X e- du
0

Values of t and a were obtained by nonlinear
regression to minimize the residual sum of squares
(error) given by


4
E (Fn- Fn)
n= 1


where F = value from data
A
F = estimate from Eq. (1).


For Figure 1, regression analysis obtained (t, a)
of (28.8,7.41) and (26.6, 8.95) for the Entisol and
Spodosol, respectively. This shows that the
Spodosol provided more growth in early spring than
did the Entisol.
Cumulative yield, y, is described by
y = YTF (3)
where yT = total annual yield, t/ha.
A summary of parameters (t, C, yT) is shown in
Table 1 for the Entisol and in Table 2 for the
Spodosol. These values were used in Eq. (3) to
calculate the curves of cumulative yield shown in
Figures 2 through 11. Data points are also shown.
Reasonable agreement between curves and data is
observed.
The next step was to relate i and a to applied N
for each soil. Mean values of t and a from Tables 1
and 2 are plotted in Figure 12. It may be noted
that increased N led to decreased t and increased a
for both soils. Following Overman et al. (1989c),
exponential equations were used to relate t and a
to applied N, viz.


-o N -N/N'
i=e
O0


) e-N/N" (5
(o am

where N = applied N rate, kg/ha
N' = characteristic N for t, kg/ha
N" = characteristic N for C, kg/ha
subscript o = value at N = 0
subscript oo = limiting value at high N.
As will be shown below, it was reasonable to
assume that N' = N" so that Eqs. (4) and (5) may be
equated, which led to


= (+ T- -F a Jo
( 6a T F M T F


(2) Equation (6) describes a linear relationship
between a and t. Figure 13 shows this correlation,
where the line was drawn from
a = 24.3 0.606 t (


with a correlation coefficient of-0.929. The proce-
dure was to relate t to applied N through Eq. (4),
and then to relate a to applied N by way of Eq. (7).
The approximations were:
Entisol: t = 28.0 + 3.0 e-N50 (8,
Spodosol: t = 25.0 + 3.0 e-N50 (9;
Equations (7) through (9) were used to construct
the curves in Figure 12. While there is scatter in
the data points of Figure 12, the curves appear to
give reasonable descriptions of t and a versus
applied N, and supported the assumption that N' =
N".

Yield response to applied
nitrogen
Regression equations were developed to relate
total annual yield (y,) to applied nitrogen rate (N)
for the two soils. Data from Tables 1 and 2 are
graphed in Figure 14 to show dependence of yield
upon year and applied N. It should be noted that
yields were lower and more variable for the Entisol
than for the Spodosol. There appeared to be consis-
tent trends from year to year, suggesting climatic
variation; this point is addressed later in the text.

Average yields
Tables 1 and 2 list means and standard devia-
tions for total annual yield at each applied N level,
for both soils. These data are plotted in Figure 15.









The procedure of Overman et al. (1989c) was used
to fit the logistic function

A (10)
T b-cN (10)
l+e
to the data, where A, b and c were obtained by
nonlinear regression to optimize fit of Eq. (10) to
the data. Curves in Figure 15 are given by

Entisol : y 1. 68 (11)
T + e1. 7-0.0134N

20.27
Spodosol: y 120. 2 (12)
T + el. 25 0. 0108N
l+e

with correlation coefficients of 0.9986 and 0.9998,
respectively. The A parameter determined maxi-
mum yield at high N, and was clearly greater for
the Spodosol than for the Entisol. The ratio b/c
gave the inflection points of the curves in Figure
15. This value was called N,, since it also repre-
sented the N level where yield was A/2, and was
117 kg/ha for the Entisol and 116 kg/ha for the
Spodosol. Furthermore, at N = 2 the slope of the
curve was greatest, meaning that an increment of
N produced the greatest increment in yield. A
summary of parameters for Eqs. (11) and (12) is
given in Table 3.

Variation in yields
Since total annual yields of grass in this study
varied from year to year (Figure 14), particularly
for the Entisol, an analysis of variance was per-
formed on the parameters in Eq. (10) in an attempt
to assign the variation to one of the parameters.
The procedure for a nonlinear model was described
by Overman et al. (1990). Data from Tables 1 and
2 were analyzed separately for each soil. The
procedure was as follows: (1) compute the variance
for all 5 years together with optimum (A,b,c) for
this set, (2) compute the variance for each year
associated with optimum (A,b,c) values for that
year, and (3) compute the variance for all five years
using individual A values for each year but common
(b,c) values for all years. If the variance ratio of (1)
and (2) was significant, then the variance ratio of
(2) and (3) was computed and examined for signifi-
cance. Analysis of variance for the soils is listed in
Tables 4 and 5. The variance ratio, F, comparing
modes (1) and (2) was quite high (F = 42.5) for the
Entisol. It was reduced to F = 4.8 for mode (3)
compared to mode (2); i.e., assigning year-to-year


variation to A while retaining common (b,c) values
reduced F from 42.5 to 4.8. The variance for the
Spodosol was much lower than for the Entisol
(Table 5 compared to Table 4). Variable A reduced
F from 7.4 to 2.4 for the Spodosol. It may be noted
that the critical F value for the 99% confidence
level is F(8,10,99) = 5.06. While this value may not
rigorously apply to a nonlinear model, due to
unknown error distribution, the use of variable A
with common (b,c) values appears reasonable.
Parameter values for bahiagrass on the two soils
are summarized in Table 6. Relative error (stan-
dard error/estimate) was generally within 5%.
Values of A for individual years for each soil are
shown in Figure 16. Several features may be
noted. Maximum yield (A) was considerably lower
for the Entisol compared to the Spodosol, averaging
about 60% of the latter. Yield variation from year
to year was also considerably greater for the
Entisol. This variation may have resulted from
climatic variations (precipitation and temperature),
particularly during early spring. Figure 17 further
illustrates this variation from year to year. Curves
were constructed from Table 6 with A values for
average, driest (1981), and wettest (1983) condi-
tions. Wide variation in response was particularly
noticeable for the Entisol.

Forage nitrogen concentration
It was shown (Overman et al., 1989a) that nitro-
gen concentration in bahiagrass depended upon
applied N rate and harvest interval. Based on five
field studies in Georgia, Florida and Alabama, an
estimation equation was developed, viz.


N+350
Nc=3. 601 14 1- e


(13)


where Nc = forage N concentration, %
At = harvest interval, weeks
N = applied N rate, kg/ha.
Eq. (13) applies only for At 57 weeks. A modified
form of Eq. (13) can be written as


N+ 350
Nc=N ( 1-e 4)
C )


(14)


where Nc is the maximum value of N at high N and
fixed At.
Weighted average NE values for each soil for the
five years are given in Table 7. Values ofN,,
calculated from Eq. (14), are also listed. Harvest










interval may be incorporated into the analysis
using the equation

o At) (15)
N = N 1 --(15)

where No represents the limiting N, at high N and
continuous clipping (At=0). For this study At = 6.6
weeks (average harvest interval) so that, from Eq.
(15) and Table 7,
Entisol: No = 2.17/0.529 = 4.10%
Spodosol: N: = 1.95/0.529 = 3.69%.
Equations (14) and (15) were combined to give
the following estimation equations:
(16)
N+ 350(16)
Entisol: N, =4. 10ol 1- 1 e
C \. 14
(17)
N+ 350
Spodosol: N = 3. 69(- )(1l-e 450

Results are shown in Figure 18, where the
curves were drawn from Eqs. (16) and (17). Agree-
ment between data and curves was rather close.
The value of N0 for data with the Spodosol
(3.69%) was very close to that (3.60%) of Overman
et al. (1989a), while the value (4.10%) for the
Entisol was 14% higher. Since the latter was a
well-drained soil with lower average water content,
fertilizer N dissolved in less water, which led to
higher N concentrations in the soil solution and
higher forage N concentrations.

Forage nitrogen removal
This section focuses on cumulative N removal
over the season and on total annual N removal.
Both relate to applied N level and harvest interval
for a given soil.

Seasonal N removal
Data on N removal by bahiagrass for each
treatment of the experiment were included in
Appendix A. Data for 1979 were then used in
Appendix C to illustrate the procedure. Cumula-
tive yield and N fractions were calculated for each
applied N rate and each soil. Values of N repre-
sent weighted average for the season. These results
are plotted in Figures 19 and 20. It may be seen
that dry matter and N accumulation progressed
together over the season. Therefore, it was ad-
equate to multiply dry matter accumulation by


weighted average N concentration in the forage to
estimate cumulative N removal over the season.
The estimation procedure was as follows:
1. Estimate t from either Eq. (8) or (9) for selected
N levels.
2. Estimate a from Eq. (7).
3. Estimate yield fraction from Eq. (1).
4. Estimate total yield from either Eq. (11) or (12)
for selected N levels.
5. Calculate cumulative dry matter as the product
of step (3) and step (4).
6. Estimate forage N concentration from either
Eq. (16) or (17) for At = 6.6 weeks and selected
N levels.
7. Calculate cumulative N removal as the product
of steps (5) and (6).

Example calculation
The procedures are now illustrated as follows:
For this example assume:
Harvest interval (At) = 6.6 weeks
Applied nitrogen (N) = 100 kg/ha
Soils: Entisol and Spodosol
Model parameters are estimated to be:


Entisol: t= 30.0 weeks
Spodosol: t = 27.0 weeks
Entisol: a = 6.1 weeks
Spodosol: a = 7.9 weeks


Eq. (8)
Eq. (9)
Eq. (7)
Eq. (7)


Yield fractions were estimated from Eq. (1), and
are shown in Figure 21. Total yield is then calcu-
lated as


Entisol: YT = 5.17 t/ha
Spodosol: yT = 9.28 t/ha


Eq. (11)
Eq. (12)


Cumulative yields are shown in Figure 22 for
bahiagrass on the two soils. Earlier growth and
higher overall yields are noted on the Spodosol
compared to the Entisol. Average forage N concen-
tration for the season was estimated as


Entisol: N, = 1.37%
Spodosol: N = 1.23%


Eq. (16)
Eq. (17)


Cumulative N removals are shown in Figure 23
for the two soils. Maximum removal was approxi-
mately 70 kg/ha for the Entisol and 110 kg/ha for
the Spodosol.










Total annual N removal
Total annual N removal was estimated as the
product of total annual dry matter production (y,)
and forage N concentration (N,). Equations (11) and
(16) were appropriate for the Entisol, while Eqs.
(12) and (17) were used for the Spodosol. Equations
(11) and (12) are correct only for At = 6.6 weeks.
Estimation procedures for other harvest intervals
are described in the next section.

Effects of harvest interval,
applied N, and soil type on
yields
Since Eqs. (11) and (12) were only valid for the
harvest interval (At) of 6.6 weeks used in the field
study, a procedure was needed which incorporated
At explicitly. Overman et al. (1989c) discussed a
phenomenological model for bahiagrass which
achieved this purpose. It was calibrated for a field
study at Americus, Georgia. Preliminary analysis
showed good agreement with this study in Florida
at lower N application rates (N < 200 kg/ha), but
increasing discrepancies at higher N rates (N > 200
kg/ha).
The phenomenological model was given by
(Overman et al., 1989c)
2AC
y = 2A + At (18)
T o-
where A = 1st order coefficient, t/ha
AC = 2nd order coefficient, t/ha.
The coefficients were related to applied N by the
logistic equations:

A
A = A (19)
(N- N'12
l+e N


AC= AC_ (20)

l+e

where A = limiting A at high N, t/ha
AC = limiting AC at high N, t/ha
N'm = value of N at AJ2, kg/ha
N"m = value of N at AC J2, kg/ha
N' = characteristic N for A, kg/ha
N" = characteristic N for AC, kg/ha


The six coefficients in Eqs. (19) and (20) must be
evaluated from field data. Several constraints will
simplify evaluation of the coefficients. Overman et
al. (1989c) found that A = AC for the Georgia
data. The same was assumed here. Therefore, for
very high N and At = 6.6 weeks, it follows that

2A At
Y = 2A + At (21)

For grass grown on the two soils, the following
was obtained:


Entisol : 11. 68 2 + 6. 6 2 Aoo
\. 7. 33

A = AA,= 3.50t/ha


Spodosol: 20. 27 2 + 6.9.6 125A

A =A A =6.70t/ha.

Upper limits, ao, on a were obtained from Eqs.
(7) (9). It was also assumed that N'm = N" _= 120
kg/ha to agree with Eqs. (11) and (12), the empiri-
cal model. A trial and error procedure was then
used on N' and N" for each soil to match yT from
Eqs. (11) and (12) at various N levels. The results
of the procedure were:
Entisol: N'= 100 kg/ha
N"=50 kg/ha
Spodosol: N'=140 kg/ha
N"=70 kg/ha.
The resulting equations were:


3. 50
Entisol : A= 3.50-
1+e 0

350
AC= No
(N N120
+ e

6. 70
Spodosol: A= 6
1+ e

AC= 6.70
N 120)
l +e 70


(22)



(23)



(24)



(25)


1









An estimation procedure for the phenomenologi-
cal model is now outlined:
1. Select soil (Entisol, highly drained versus
Spodosol, poorly drained), applied nitrogen rate
(N) and harvest interval (At).
2. Estimate t from either Eq. (8) or (9).
3. Estimate a from Eq. (7).
4. Estimate A from either Eq. (22) or (24).
5. Estimate AC from either Eq. (23) or (25).
6. Estimate total annual yield (yT) from Eq. (18).
Results of this procedure for At = 6.6 weeks are
shown in Figure 24 for the Florida study. These
curves agree closely with average curves in Figure
17. Variations from year to year were accomodated
by changing A and AC_ in Eqs. (22) through (25).

Summary and conclusions
Several equations were developed to describe dry
matter production, forage nitrogen concentration
and forage N uptake by Pensacola bahiagrass on an
Entisol and a Spodosol. A general procedure is
outlined as follows:

Estimation procedure
1. Select soil type, applied nitrogen level (N, kg/ha)
and harvest interval (At, weeks).
2. Estimate mean time (t, weeks) from either Eq.
(8) or (9).
3. Estimate time spread (u, weeks) from Eq. (7).
4. Estimate model coefficients (A, t/ha and AC,
t/ha) from either Eqs. (22) and (23) or Eqs. (24)
and (25).
5. Estimate total annual yield (YT, t/ha) from Eq.
(18).
6. Calculate cumulative yield from Eqs. (1) and
(18).
7. Estimate forage N concentration (Nc, %) from
either Eq. (16) or (17).
8. Calculate cumulative N removal as the product
of steps (6) and (7).
9. Calculate total annual N removal as the product
of steps (5) and (7).

Example calculations
1. For both an Entisol and a Spodosol, choose N =
100 kg/ha and At = 4 weeks.


2. t = 30.0 weeks for Entisol.
t = 27.0 weeks for Spodosol.
3. a = 6.12 weeks for Entisol.
u = 7.94 weeks for Spodosol.
4. A = 1.58 t/ha, AC = 1.40 t/ha for Entisol.
A = 3.11 t/ha, AC = 2.87 t/ha for Spodosol.
5. y, = 4.45 t/ha for Entisol.
y, = 8.26 t/ha for Spodosol.
6. Cumulative yields are shown in Figure 25.
7. N = 1.85% for the Entisol.
N = 1.66% for the Spodosol.
8. Cumulative N removals are shown in Figure 26.
This procedure should be restricted to At <7
weeks, since Eqs. (16) through (18) have not been
shown to hold beyond this range.
Several conclusions may be drawn from Figure
25. The mean times of the yield curves were 30
weeks for bahiagrass on the Entisol compared to 27
weeks on the Spodosol an advance of 3 weeks for
the wetter soil. The maximum rate of dry matter
accumulation (at t = t) was approximately 0.27 t/ha/
week on the Entisol compared to 0.40 t/ha/week on
the Spodosol 50% greater for the wetter soil.
Estimated annual yield was 5.17 t/ha on the
Entisol compared to 9.28 t/ha on the Spodosol 80%
greater for the wetter soil. Lower production on the
Entisol (drier soil) derived from a slower start in
the spring and a slower production rate throughout
the season. Blue (1987) concluded that low produc-
tion on the Entisol during the spring was due to
low rainfall relative to evapotranspiration and from
low water holding capacity of the soil. Overman et
al. (1989d) showed graphically from data in Florida
(Baldwin and Gallaher, 1985) and data in Alabama
(Doss et al., 1960) that yields were only approxi-
mately 5 t/ha under severe drought conditions.

Application to south Florida
Results for bahiagrass on the Spodosol near
Gainesville were also used to estimate annual dry
matter production and average forage N concentra-
tion for south Florida. Both were related to applied
N rate and harvest interval. Blue et al. (1980)
reported a study at Ona, Florida on Eau Gallie fine
sand (a Spodosol). Average harvest interval was 6.6
weeks. Average total annual yields for 1976-1979
are listed in Table 8. Yields were estimated from









Eq. (18), with a estimated from Eqs. (7) and (9).
Values for A and AC were calculated from


A 6.70
1+e ( 10


6. 70
AC-
SN -20)
1+ e (


It was necessary to change N'm and N". from
120 kg/ha in Eqs. (24) and (25) to 200 kg/ha in Eqs.
(26) and (27). Other coefficients remained the
same. This was thought to reflect a lower soil N
reserve in the Eau Gallie soil at Ona compared to
the soil near Gainesville. Agreement between
measured and estimated yield was within 5%.
Also shown in Table 8 are values for forage N
concentration. Estimates were made from Eq. (17).
Measured values were lower than estimated by as
much as 8.5%. This likely resulted from a lower
effective N rate in the soil, as noted above. Agree-
ment was within 10%.

References
Baldwin, J.A., and R.N. Gallaher. 1985. Growth
and chemical composition as influenced by
nitrogen rate, source and application method.
Agronomy Research Report AY-85-09. University
of Florida, Gainesville, FL.
Beaty, E.R., K.H. Tan, R.A. McCreery, and J.D.
Powell. 1980. Yield and N content of closely
clipped bahiagrass as affected by N treatments.
Agronomy J. 72:56-60.
Blue, W.G. 1971. Nitrogen fertilization in relation
to seasonal Pensacola bahiagrass [Paspalum
notatum Flugge] forage nitrogen and production
distribution on Leon fine sand. Soil and Crop
Sci. Soc. Fla. Proc. 31:75-77.
Blue, W.G. 1987. Response of Pensacola bahiagrass
(Paspalum notatum Flugge) to fertilizer nitrogen
on an Entisol and a Spodosol in north Florida.
Soil and Crop Sci. Soc. Fla. Proc. 47:135-139.
Blue, W.G. and N. Gammon, Jr. 1963. Differences
in nutrient requirements of experimental pas-
ture plots managed by grazing and clipping
techniques. Soil and Crop Sci. Soc. Fla. Proc.
23:152-161.


Blue, W.G., and D.A. Graetz. 1977. The effect of
split nitrogen applications on nitrogen uptake by
Pensacola bahiagrass from an Aeric Haplaquod.
Soil Sci. Soc. Am. J. 41:927-930.
Blue, W.G., C.L. Dantzman, and V. Impithuksa.
1980. The response of three perennial warm
season grasses to fertilizer nitrogen on Eau
Gallie fine sand (Alfic Haplaquod) in central
Florida. Soil and Crop Sci. Soc. Fla. Proc.
39:44-47.
Chambliss, C.G., and D.W. Jones. 1980.
Bahiagrass. Circular 32/B. University of Fla..
Gainesville, FL. 10 pp.
Doss, B.D., O.L. Bennett, D.A. Ashley, and L.E.
Ensminger. 1960. Interrelation of nitrogen
fertilization and irrigation of three forage
grasses. 7th International Congress of Soil Sci.
Vol. IV. 63:496-502.
Leukel, W.A., and R.M. Barnette. 1935. Cutting
experiments with bahiagrass grown in lysimeters.
Fla. Agric. Exp. Stn. Bull. 219. Gainesville, FL.
36 pp.
Leukel, W.A., and J.M. Coleman. 1930. Growth
behavior and maintenance of organic foods in
bahiagrass. Fla. Agric. Exp. Stn. Bull. 219.
Gainesville, FL. 56 pp.
Leukel, W.A., J.P. Camp, and J.M. Coleman. 1934.
Effect of frequent cutting and nitrate fertilization
on the growth behavior and relative composition
of pasture grasses. Fla. Agric. Exp. Stn. Bull.
269. Gainesville, FL. 48 pp.
Overman, A.R., D. Downey and S.R. Wilkinson.
1989a. Effect of applied nitrogen and harvest
interval on nitrogen concentration in bahiagrass.
Commun. Soil Sci. and Plant Anal. 20:513-527.
Overman, A.R., D. Downey and S.R. Wilkinson.
1989b. Effect of N rate and split application on
bahiagrass production. Commun. Soil Sci. and
Plant Anal. 20:501-512.
Overman, A.R., D. Downey, and S.R. Wilkinson.
1989c. Application of simulation models to
bahiagrass production. Commun. Soil Sci. Plant
Anal. 20:1231-1246.
Overman, A.R., D. Downey and C.G. Chambliss.
1989d. Effect of management factors on
bahiagrass production. Soil and Crop Sci. Soc.
Fla. Proc. 48:19-21.
Overman, A.R., F.G. Martin and S.R. Wilkinson.
1990. A logistic equation for yield response of











forage grass to nitrogen. Commun. Soil Sci.
Plant Anal. 21:595-609.

Spreen, T.H., J.A. Ross, J.W. Pheasant, J.E. Moore
and W.E. Kunkle. 1985. A simulation model for
backgrounding feeder cattle in Florida. Bulletin
850. Florida Agricultural Experiment Station,
University of Florida, Gainesville, FL. 66 pp.


Wallace, A.T., G.B. Killinger, R.W. Bledsoe, and
D.B. Duncan. 1955. Effect of nitrogen fertiliza-
tion on the production of pangolagrass and
bahiagrass. Soil and Crop Sci. Soc. Fla. Proc.
15:198-207.


Table 1. Summary of model parameters for bahiagrass on an Entisol (1979-1983).'
N ---------------Year-------------- Mean S.D.
kg/ha 1979 1980 1981 1982 1983

t, weeks

0 31.29 30.68 30.89 30.71 31.09 30.93 0.26
100 28.81 29.63 30.36 29.36 29.95 29.62 0.59
200 28.34 29.18 30.76 28.87 29.27 29.28 0.90
300 28.51 28.80 30.89 28.51 28.73 29.09 1.02
400 28.93 29.26 31.68 28.71 28.35 29.39 1.32

a, weeks

0 6.79 4.90 5.07 4.37 6.08 5.44 0.98
100 7.41 4.48 3.59 6.16 5.94 5.52 1.50
200 8.06 5.60 4.75 6.56 6.79 6.35 1.25
300 8.47 6.76 5.66 6.85 7.53 7.05 1.04
400 8.46 6.87 6.17 7.17 7.65 7.26 0.86

YT, t/ha

0 2.03 1.69 1.40 1.56 2.20 1.78 0.33
100 5.57 5.47 4.47 5.62 6.12 5.45 0.60
200 9.44 7.84 6.15 9.82 9.69 8.59 1.58
300 10.63 9.94 7.26 12.41 13.49 10.75 2.40
400 10.99 10.41 7.45 13.09 15.54 11.50 3.03

'Parameters are for Eqs. (1) and (3).

Table 2. Summary of model parameters for bahiagrass on a Spodosol (1979-1983).'
N ---- ----------Year -------------- Mean S.D.
kg/ha 1979 1980 1981 1982 1983

t, weeks

0 27.95 27.27 28.46 26.58 27.97 27.65 0.73
100 26.62 27.03 28.10 27.22 28.11 27.42 0.67
200 26.29 26.44 27.42 26.67 26.74 26.71 0.43
300 26.01 25.81 26.50 26.10 26.02 26.09 0.25
400 25.67 25.06 26.17 25.78 25.30 25.60 0.43

a, weeks

0 8.79 6.75 7.54 7.63 8.10 7.76 0.75
100 8.95 7.24 7.72 7.43 7.54 7.78 0.68
200 8.77 7.60 7.81 8.11 8.21 8.10 0.45
300 8.74 7.96 8.08 8.66 8.56 8.40 0.36
400 8.67 8.35 8.20 8.74 9.11 8.61 0.36

YT, tha

0 4.00 4.15 4.56 5.92 4.57 4.64 0.76
100 8.85 9.50 7.75 9.40 10.31 9.16 0.95
200 14.13 14.94 12.33 14.96 16.12 14.50 1.40
300 17.87 17.95 16.74 18.03 19.26 17.97 0.89
400 19.07 20.39 17.95 18.85 20.13 19.28 0.99

'Parameters are for Eqs. (1) and (3).











Table 3. Summary of N response parameters for bahiagrass.'
Parameter Standard Relative
Soil Parameter Estimate Error Error

Entisol A, t/ha 11.68 0.24 0.021

b 1.57 0.094 0.060

c, ha/kg 0.0134 0.00092 0.069

Spodosol A, t/ha 20.27 0.18 0.009

b 1.25 0.027 0.022

c, ha/kg 0.0108 0.00027 0.025

'Parameters are for Eq. (10).

Table 4. Analysis of variance for bahiagrass on an Entisol.1
Residual Mean
Parameters Degrees Sum Sum
Mode Estimated Freedom Squares Squares F

(1) Common 3 22 72.83 3.310
A,b,c

(2) Individual 15 10 1.40 0.140
A,b,c

(1)-(2) 12 71.43 5.952 42.5

(3) Individual A 7 18 6.78 0.377
Common b,c

(3)-(2) -8 5.38 0.672 4.8

'Parameters are for Eq. (10).

Table 5. Analysis of variance for bahiagrass on a Spodosol.'
Residual Mean
Parameters Degrees Sum Sum
Mode Estimated Freedom Squares Squares F

(1) Common 3 22 21.18 3.105
A,b,c

(2) Individual 15 10 2.14 0.214
A,b,c

(1)-(2) 12 19.04 1.587 7.4

(3) Individual A 7 18 6.23 0.346
Common b,c

(3)-(2) -8 4.09 0.511 2.4

'Parameters are for Eq. (10).











Table 6. Summary of model parameters by year for bahiagrass.'


Soil

Entis


sol


Year


1979

1980

1981

1982

1983


Parameter


A, t/ha


b

c, ha/kg

A, t/ha


Spodosol


b

c, ha/kg


'Parameters are for Eq. (10).


Table 7. Forage N concentrations for bahiagras
N, kg/ha


ss.


N, %
Entisol Spodosol

1.18 1.13
1.37 1.21
1.51 1.34
1.68 1.45
1.76 1.59
Mean
Standard Deviation
Relative Error


N-, %
Entisol Spodosol

2.18 2.09
2.17 1.91
2.14 1.90
2.20 1.90
2.17 1.96
2.17 1.95
0.022 0.081
0.010 0.042


Table 8. Total annual yields and forage N for bahiagrass on a Spodosol at Ona, Florida (1976-1979).'
N, kg/ha YT, t/ha N, %
Meas. Est. Diff., % Meas. Est. Diff., %

0 2.91 3.06 +2.2 1.08 1.05 -2.8
112 6.74 6.41 -4.9 1.17 1.25 +6.8
224 11.23 11.63 +3.6 1.29 1.40 +8.5
336 15.43 16.02 +3.8 1.41 1.52 +7.8

'Data from Blue et al. (1980).


Estimate

11.68

10.88


Standard
Error

0.33

0.33


Relative
Error

0.028

0.030


8.11

13.39

14.80


1.59

0.0131

19.88

20.79

18.37

20.37

21.69

1.24

0.0109


0.037

0.026

0.026

0.053

0.063

0.018

0.017

0.019

0.018

0.017

0.033

0.039


0.085

0.00082

0.36

0.36

0.35

0.36

0.37

0.041

0.00042











Appendix A

Yield and Nitrogen Data for Bahiagrass on Two Florida Soils

Table Al. Yield and nitrogen data for bahiagrass on an Entisol for 1979.
May 15 July 1 Aug 10 Oct 1 Total
N Rate Rep Yield N N Yield N N Yield N N Yield N N Yield N
kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha kg/ha

0 1 110 1.55 1.71 290 0.78 2.26 630 1.24 7.81 630 1.25 7.88 1660 19.65
0 2 140 1.52 2.13 290 0.93 2.70 590 1.26 7.43 750 1.31 9.83 1770 22.08
0 3 130 1.52 1.98 370 0.94 3.48 780 1.32 10.30 680 1.12 7.62 1960 23.37
0 4 110 1.35 1.49 260 0.86 2.24 620 1.17 7.25 780 1.33 10.37 1770 21.35
Avg. 123 1.82 303 2.67 655 8.20 710 8.92 1790 21.61

100 1 740 1.70 12.58 910 0.89 8.10 1880 1.48 27.82 1240 1.32 16.37 4770 64.87
100 2 760 1.51 11.48 890 1.03 9.17 2180 1.45 31.61 1210 1.33 16.09 5040 68.35
100 3 830 1.64 13.61 1090 0.91 9.92 2260 1.60 36.16 1670 1.44 24.05 5850 83.74
100 4 690 1.63 11.25 980 0.90 8.82 1880 1.69 31.77 1030 1.28 13.18 4580 65.02
Avg. 755 12.23 968 9.00 2050 31.84 1288 17.42 5060 70.49

200 1 2030 1.86 37.76 1630 1.10 17.93 3450 1.64 56.58 2390 1.47 35.13 9500 147.40
200 2 1610 1.88 30.27 900 1.40 12.60 3370 1.64 55.27 2210 1.51 33.37 8090 131.51
200 3 1790 1.79 32.04 1420 1.19 16.90 3280 1.55 50.84 2350 1.34 31.49 8840 131.27
200 4 1300 1.66 21.58 1970 1.10 21.67 3040 1.54 46.82 2050 1.52 31.16 8360 121.23
Avg. 1683 30.41 1480 17.27 3285 52.38 2250 32.79 8698 132.85

300 1 1320 2.14 28.25 1230 1.35 16.61 2650 2.02 53.53 2370 1.66 39.34 7570 137.73
300 2 2210 1.97 43.54 1450 1.47 21.32 3860 1.89 72.95 2760 1.45 40.02 10280 177.83
300 3 2310 1.89 43.66 2070 1.37 28.36 3650 1.87 68.26 2890 1.70 49.13 10920 189.40
300 4 2110 2.00 42.20 1550 1.40 21.70 3490 1.75 61.08 2960 1.50 44.40 10110 169.38
Avg. 1988 39.41 1575 21.99 3413 63.95 2745 43.22 9720 168.58

400 1 2370 1.78 42.19 1840 2.19 40.30 3540 2.09 73.99 2940 1.67 49.10 10690 205.57
400 2 1320 2.28 30.10 1210 1.45 17.55 2850 1.78 50.73 2970 1.73 51.38 8350 149.75
400 3 1810 2.04 36.92 1470 1.40 20.58 3870 1.80 69.66 3130 1.81 56.65 10280 183.82
400 4 2260 2.11 47.69 1790 1.50 26.85 3450 1.97 67.97 3100 1.75 54.25 10600 196.75
Avg. 1940 39.22 1578 26.32 3428 65.59 3035 52.85 9980 183.97











Table A2. Yield and nitrogen data for bahiagrass on an Entisol for 1980.


May 15 July 1
N Rate Rep Yield N N Yield N N
kg/ha kg/ha % kg/ha kg/ha % kg/ha

0 1 80 1.74 1.39 100 0.74 0.74
0 2 50 1.45 0.73 220 1.10 2.42
0 3 60 1.27 0.76 210 0.90 1.89
0 4 60 1.58 0.95 190 1.04 1.98
Avg. 63 0.96 180 1.76

100 1 150 1.56 2.34 890 1.07 9.52
100 2 120 1.33 1.60 560 0.99 5.54
100 3 310 1.72 5.33 1000 1.19 11.90
100 4 200 1.65 3.30 970 1.08 10.48
Avg. 195 3.14 855 9.36

200 1 300 2.33 6.99 2430 1.21 29.40
200 2 160 1.44 2.30 1600 1.17 18.72
200 3 320 2.10 6.72 1710 1.52 25.99
200 4 300 2.13 6.39 1950 1.38 26.91
Avg. 270 5.60 1923 25.26

300 1 230 2.38 5.47 1790 1.73 30.97
300 2 1360 2.36 32.10 2910 1.12 32.59
300 3 700 2.42 16.94 3190 1.54 49.13
300 4 600 2.14 12.84 2820 1.45 40.89
Avg. 723 16.84 2678 38.39

400 1 250 2.48 6.20 3060 1.80 55.08
400 2 650 2.22 14.43 2920 1.43 41.76
400 3 470 2.33 10.95 3360 1.39 46.70
400 4 520 2.38 12.38 2820 1.60 45.12
Avg. 473 10.99 3040 47.17


Aug 10
Yield N N
kg/ha % kg/ha

670 0.89 5.96
790 1.01 7.98
900 0.76 6.84
800 1.03 8.24
790 7.26

2560 1.31 33.54
2770 1.32 36.56
2900 1.32 38.28
2690 1.27 34.16
2730 35.64

3230 1.65 53.30
3170 1.63 51.67
3030 1.54 46.66
3320 1.56 51.79
3188 50.86

2620 1.82 47.68
3350 1.80 60.30
3700 1.80 66.60
3420 1.82 62.24
3273 59.21

3290 1.95 64.16
2830 2.00 56.60
3310 2.02 66.86
2990 1.95 58.31
3105 61.48


Oct 1 Total
Yield N N Yield N
kg/ha % kg/ha kg/ha kg/ha

460 1.02 4.69 1310 12.79
580 1.04 6.03 1640 17.16
570 1.23 7.01 1740 16.50
430 1.14 4.90 1480 16.07
510 5.66 1543 15.63

1180 1.19 14.04 4780 59.44
1340 1.37 18.36 4790 62.06
1510 1.30 19.63 5720 75.14
1300 1.33 17.29 5160 65.23
1333 17.33 5113 65.47

1880 1.33 25.00 7840 114.69
1770 1.21 21.42 6700 94.11
2230 1.39 31.00 7290 110.37
1970 1.40 27.58 7540 112.67
1963 26.25 7343 107.96

1980 1.61 31.88 6620 116.00
2750 1.46 40.15 10370 165.14
2650 1.48 39.22 10240 171.89
2700 1.51 40.77 9540 156.74
2520 38.00 9193 152.44

2520 1.52 38.30 9120 163.74
2390 1.62 38.72 8790 151.50
3870 1.53 59.21 11010 183.73
2840 1.64 46.58 9170 162.38
2905 45.70 9523 165.34


Table A3. Yield and nitrogen data for bahiagrass on an Entisol for 1981.
May 15 July 1 Aug 10 Oct 1 Total
N Rate Rep Yield N N Yield N N Yield N N Yield N N Yield N
kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha kg/ha

0 1 60 1.54 0.92 90 1.36 1.22 740 1.32 9.77 310 1.20 3.72 1200 15.64
0 2 70 1.54 1.08 100 1.26 1.26 750 1.33 9.98 500 1.22 6.10 1420 18.41
0 3 60 1.81 1.09 110 1.32 1.45 640 1.36 8.70 490 1.35 6.62 1300 17.86
0 4 60 1.39 0.83 160 1.19 1.90 510 1.20 6.12 350 1.21 4.24 1080 13.09
Avg. 63 0.98 115 1.46 660 8.64 413 5.17 1250 16.25

100 1 150 1.71 2.57 180 1.50 2.70 2570 1.49 38.29 1040 1.34 13.94 3940 57.49
100 2 160 1.47 2.35 340 1.63 5.54 2650 1.63 43.20 1330 1.35 17.96 4480 69.04
100 3 200 1.88 3.76 400 1.48 5.92 2430 1.52 36.94 1310 1.40 18.34 4340 64.96
100 4 160 1.72 2.75 180 1.37 2.47 2250 1.41 31.73 1070 1.28 13.70 3660 50.64
Avg. 168 2.86 275 4.16 2475 37.54 1188 15.98 4105 60.53

200 1 380 2.10 7.98 400 2.03 8.12 2570 2.02 51.91 1840 1.49 27.42 5190 95.43
200 2 200 2.09 4.18 480 1.83 8.78 3010 1.82 54.78 1850 1.45 26.83 5540 94.57
200 3 390 2.16 8.42 670 1.84 12.33 3180 1.75 55.65 2160 1.32 28.51 6400 104.91
200 4 330 2.10 6.93 350 1.89 6.62 2860 1.92 54.91 1960 1.48 29.01 5500 97.47
Avg. 325 6.88 475 8.96 2905 54.31 1953 27.94 5658 98.10

300 1 330 2.18 7.19 340 2.23 7.58 2340 2.06 48.20 1550 1.59 24.65 4560 87.63
300 2 610 2.16 13.18 520 2.05 10.66 3240 1.91 61.88 2410 1.57 37.84 6780 123.56
300 3 770 2.27 17.48 540 1.95 10.53 4070 1.97 80.18 2550 1.54 39.27 7930 147.46
300 4 780 2.17 16.93 450 1.96 8.82 3150 1.88 59.22 2400 1.51 36.24 6780 121.21
Avg. 623 13.69 463 9.40 3200 62.37 2228 34.50 6513 119.96

400 1 360 2.17 7.81 520 2.11 10.97 2270 2.11 47.90 2150 1.86 39.99 5300 106.67
400 2 700 1.95 13.65 400 2.21 8.84 2830 1.98 56.03 2830 1.68 47.54 6760 126.07
400 3 760 2.39 18.16 600 2.10 12.60 2990 2.10 62.79 3080 1.68 51.74 7430 145.30
400 4 700 2.19 15.33 280 2.14 5.99 3040 2.15 65.36 2690 1.42 38.20 6710 124.88
Avg. 630 13.74 450 9.60 2783 58.02 2688 44.37 6550 125.73











Table A4. Yield and nitrogen data for bahlagrass on an Entisol for 1982.
May 15 July 1 Aug 10 Oct 1 Total
N Rate Rep Yield N N Yield N N Yield N N Yield N N Yield N
kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha kg/ha

0 1 0 1.35 0.00 180 1.08 1.94 640 1.24 7.94 370 1.02 3.77 1190 13.65
0 2 0 1.32 0.00 140 1.05 1.47 750 1.38 10.35 440 1.11 4.88 1330 16.70
0 3 0 1.61 0.00 250 1.28 3.20 1040 1.24 12.90 480 1.07 5.14 1770 21.23
0 4 0 1.48 0.00 140 1.11 1.55 680 1.30 8.84 500 1.14 5.70 1320 16.09
Avg. 0 0.00 178 2.04 778 10.01 448 4.87 1403 16.92

100 1 510 1.57 8.01 910 0.94 8.55 2100 1.60 33.60 1330 1.13 15.03 4850 65.19
100 2 590 1.63 9.62 930 1.24 11.53 2610 1.51 39.41 1570 1.08 16.96 5700 77.52
100 3 610 1.64 10.00 1200 1.21 14.52 2430 1.45 35.24 1640 1.18 19.35 5880 79.11
100 4 320 1.63 5.22 740 0.86 6.36 2103 1.40 29.44 1250 1.08 13.50 4413 54.52
Avg. 508 8.21 945 10.24 2311 34.42 1448 16.21 5211 69.08

200 1 930 1.87 17.39 1810 1.27 22.99 3470 1.55 53.79 2080 1.21 25.17 8290 119.33
200 2 980 2.16 21.17 1820 1.17 21.29 3790 1.59 60.26 2460 1.15 28.29 9050 131.01
200 3 1230 1.74 21.40 1990 1.15 22.89 4080 1.43 58.34 2730 1.16 31.67 10030 134.30
200 4 1100 1.90 20.90 1960 1.09 21.36 3710 1.44 53.42 2710 1.15 31.17 9480 126.85
Avg. 1060 20.22 1895 22.13 3763 56.45 2495 29.07 9213 127.87

300 1 1080 2.07 22.36 2340 1.10 25.74 4410 1.56 68.80 2780 1.36 37.81 10610 154.70
300 2 1700 1.61 27.37 2170 1.23 26.69 4420 1.49 65.86 2860 1.22 34.89 11150 154.81
300 3 1730 1.94 33.56 2990 1.10 32.89 5320 1.49 79.27 3030 1.38 41.81 13070 187.53
300 4 1420 2.14 30.39 2740 1.18 32.33 4390 1.82 79.90 2820 1.43 40.33 11370 182.94
Avg. 1483 28.42 2560 29.41 4635 73.46 2873 38.71 11550 170.00

400 1 1300 2.19 28.47 2820 1.24 34.97 4350 1.54 66.99 3210 1.31 42.05 11680 172.48
400 2 1020 2.10 21.42 2950 1.31 38.65 4520 1.92 86.78 3290 1.32 43.43 11780 190.28
400 3 1620 1.93 31.27 3062 1.36 41.64 4660 1.69 78.75 3400 1.46 49.64 12742 201.30
400 4 1820 2.22 40.40 3010 1.18 35.52 4090 1.74 71.17 3260 1.33 43.36 12180 190.45
Avg. 1440 30.39 2961 37.69 4405 75.92 3290 44.62 12096 188.63

Table A5. Yield and nitrogen data for bahiagrass on an Entisol for 1983.
May 15 July 1 Aug 10 Oct 1 Total
NRate Rep Yield N N Yield N N Yield N N Yield N N Yield N
kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha kg/ha

0 1 180 0.94 1.69 180 1.12 2.02 810 1.10 8.91 660 1.21 7.99 1830 20.60
0 2 240 1.30 3.12 160 1.31 2.10 890 1.12 9.97 710 1.29 9.16 2000 24.34
0 3 100 1.05 1.05 220 1.30 2.86 860 1.21 10.41 790 1.31 10.35 1970 24.67
0 4 110 1.56 1.72 250 1.19 2.98 1000 1.10 11.00 620 1.31 8.12 1980 23.81
Avg. 158 1.89 203 2.49 890 10.07 695 8.90 1945 23.36

100 1 600 1.27 7.62 570 1.49 8.49 2920 1.39 40.59 990 1.38 13.66 5080 70.36
100 2 540 1.07 5.78 580 1.53 8.87 2310 1.39 32.11 1540 1.39 21.41 4970 68.17
100 3 810 1.48 11.99 780 1.59 12.40 3030 1.37 41.51 1740 1.37 23.84 6360 89.74
100 4 550 1.22 6.71 660 1.47 9.70 2490 1.35 33.62 2350 1.33 31.26 6050 81.28
Avg. 625 8.02 648 9.87 2688 36.96 1655 22.54 5615 77.39

200 1 1010 1.83 18.48 1290 1.60 20.64 3910 1.54 60.21 2820 1.50 42.30 9030 141.64
200 2 1080 1.70 18.36 1500 1.57 23.55 3370 1.53 51.56 2290 1.52 34.81 8240 128.28
200 3 1000 1.63 16.30 1590 1.62 25.76 4400 1.48 65.12 3000 1.52 45.60 9990 152.78
200 4 1810 1.37 24.80 1150 1.53 17.60 3730 1.49 55.58 1840 1.46 26.86 8530 124.83
Avg. 1225 19.49 1383 21.89 3853 58.12 2488 37.39 8948 136.88

300 1 1990 1.99 39.60 1920 1.57 30.14 5280 1.82 96.10 2920 1.58 46.14 12110 211.98
300 2 2510 1.86 46.69 1760 1.77 31.15 4110 1.83 75.21 4030 1.52 61.26 12410 214.31
300 3 2230 2.25 50.18 2500 1.78 44.50 5240 1.59 83.32 3730 1.72 64.16 13700 242.15
300 4 1960 1.85 36.26 1840 1.93 35.51 4820 1.57 75.67 3560 1.78 63.37 12180 210.81
Avg. 2173 43.18 2005 35.33 4863 82.57 3560 58.73 12600 219.81

400 1 2560 2.16 55.30 2860 1.72 49.19 5270 1.68 88.54 4070 1.74 70.82 14760 263.84
400 2 3110 2.11 65.62 2820 1.76 49.63 5160 1.70 87.72 3990 1.79 71.42 15080 274.39
400 3 2550 2.23 56.87 2130 2.28 48.56 6080 1.52 92.42 3710 1.70 63.07 14470 260.92
400 4 2130 2.27 48.35 2510 1.78 44.68 5380 1.68 90.38 3840 1.67 64.13 13860 247.54
Avg. 2588 56.53 2580 48.02 5473 89.76 3903 67.36 14543 261.67











Table A6. Yield and nitrogen data for bahlagrass on a Spodosol for 1979.
May 15 July 1 Aug 10 Oct 1 Total
N Rate Rep Yield N N Yield N N Yield N N Yield N N Yield N
kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha kg/ha

0 1 940 0.97 9.12 320 1.13 3.62 1130 1.00 11.30 710 1.13 8.02 3100 32.06
0 2 770 1.15 8.86 450 0.97 4.37 1410 1.03 14.52 1390 1.01 14.04 4020 41.78
0 3 1080 1.14 12.31 480 1.00 4.80 1390 1.12 15.57 1140 1.21 13.79 4090 46.47
0 4 930 1.15 10.70 460 1.25 5.75 1420 1.16 16.47 960 1.10 10.56 3770 43.48
Avg. 930 10.25 428 4.63 1338 14.47 1050 11.60 3745 40.95

100 1 2460 1.08 26.57 900 1.08 9.72 3280 1.06 34.77 1430 1.13 16.16 8070 87.22
100 2 2730 1.02 27.85 880 1.05 9.24 3460 1.12 38.75 1450 1.17 16.97 8520 92.80
100 3 2270 1.00 22.70 840 1.06 8.90 3320 1.03 34.20 1550 1.24 19.22 7980 85.02
100 4 2300 1.02 23.46 950 1.01 9.60 3470 1.04 36.09 2120 1.26 26.71 8840 95.86
Avg. 2440 25.14 893 9.36 3383 35.95 1638 19.76 8353 90.22

200 1 4120 1.21 49.85 1850 1.10 20.35 5300 1.26 66.78 2400 1.23 29.52 13670 166.50
200 2 3700 1.24 45.88 2050 1.03 21.12 5640 1.21 68.24 2800 1.16 32.48 14190 167.72
200 3 3700 1.24 45.88 1600 1.10 17.60 4900 1.23 60.27 2380 1.31 31.18 12580 154.93
200 4 3780 1.17 44.23 2040 1.02 20.81 5010 1.13 56.61 2260 1.25 28.25 13090 149.90
Avg. 3825 46.46 1885 19.97 5213 62.98 2460 30.36 13383 159.76

300 1 4820 1.40 67.48 2790 1.11 30.97 6320 1.48 93.54 2870 1.22 35.01 16800 227.00
300 2 4820 1.46 70.37 3100 1.18 36.58 6240 1.37 85.49 3320 1.33 44.16 17480 236.60
300 3 4620 1.27 58.67 3020 1.13 34.13 6060 1.31 79.39 3020 1.31 39.56 16720 211.75
300 4 4890 1.50 73.35 2790 1.23 34.32 6110 1.27 77.60 3090 1.30 40.17 16880 225.43
Avg. 4788 67.47 2925 34.00 6183 84.00 3075 39.73 16970 225.19

400 1 4900 1.59 77.91 3700 1.26 46.62 6560 1.44 94.46 3190 1.49 47.53 18350 266.53
400 2 5920 1.62 95.90 3670 1.20 44.04 6560 1.56 102.34 3310 1.39 46.01 19460 288.29
400 3 4680 1.60 74.88 3130 1.20 37.56 5820 1.58 91.96 2650 1.54 40.81 16280 245.21
400 4 5000 1.70 85.00 3970 1.17 46.45 6390 1.46 93.29 2870 1.48 42.48 18230 267.22
Avg. 5125 83.42 3618 43.67 6333 95.51 3005 44.21 18080 266.81

Table A7. Yield and nitrogen data for bahiagrass on a Spodosol for 1980.
May 15 July 1 Aug 10 Oct 1 Total
N Rate Rep Yield N N Yield N N Yield N N Yield N N Yield N
kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha kg/ha

0 1 330 1.19 3.93 1170 1.03 12.05 1280 0.93 11.90 830 1.11 9.21 3610 37.10
0 2 220 1.20 2.64 1100 0.69 7.59 1420 0.95 13.49 1000 1.03 10.30 3740 34.02
0 3 860 1.23 10.58 1280 0.88 11.26 1570 1.10 17.27 680 1.09 7.41 4390 46.52
0 4 630 1.34 8.44 1360 0.83 11.29 1240 1.20 14.88 820 1.11 9.10 4050 43.71
Avg. 510 6.40 1228 10.55 1378 14.39 833 9.01 3948 40.34

100 1 1390 1.40 19.46 1760 0.88 15.49 3380 1.14 38.53 1540 1.18 18.17 8070 91.65
100 2 2550 1.37 34.94 1840 0.87 16.01 3320 1.12 37.18 1640 1.05 17.22 9350 105.35
100 3 1400 1.63 22.82 2440 0.85 20.74 3420 1.19 40.70 2020 1.07 21.61 9280 105.87
100 4 1350 1.53 20.66 2610 0.80 20.88 3730 1.16 43.27 1830 1.02 18.67 9520 103.47
Avg. 1673 24.47 2163 18.28 3463 39.92 1758 18.92 9055 101.59

200 1 3000 1.46 43.80 3570 0.89 31.77 4620 1.39 64.22 2580 1.35 34.83 13770 174.62
200 2 3070 1.58 48.51 3560 0.89 31.68 4920 1.26 61.99 2490 1.07 26.64 14040 168.83
200 3 2740 1.77 48.50 4170 0.84 35.03 4500 1.43 64.35 2810 1.22 34.28 14220 182.16
200 4 2660 1.74 46.28 4260 0.88 37.49 5080 1.42 72.14 2930 1.14 33.40 14930 189.31
Avg. 2868 46.77 3890 33.99 4780 65.67 2703 32.29 14240 178.73

300 1 3580 1.70 60.86 4840 0.97 46.95 5290 1.39 73.53 2850 1.34 38.19 16560 219.53
300 2 4720 1.70 80.24 4910 0.87 42.72 5330 1.25 66.63 3300 1.35 44.55 18260 234.13
300 3 3860 1.83 70.64 5120 0.99 50.69 5090 1.52 77.37 2840 1.41 40.04 16910 238.74
300 4 3310 1.95 64.55 5170 0.97 50.15 4930 1.33 65.57 3040 1.30 39.52 16450 219.78
Avg. 3868 69.07 5010 47.63 5160 70.77 3008 40.58 17045 228.05

400 1 5490 1.77 97.17 5520 1.07 59.06 5260 1.44 75.74 3000 1.51 45.30 19270 277.28
400 2 5420 1.87 101.35 4860 1.10 53.46 5700 1.35 76.95 3040 1.48 44.99 19020 276.76
400 3 4670 2.25 105.08 6100 1.14 69.54 4950 1.55 76.73 2640 1.52 40.13 18360 291.47
400 4 4970 1.79 88.96 6370 0.97 61.79 5740 1.62 92.99 3830 1.39 53.24 20910 296.98
Avg. 5138 98.14 5713 60.96 5413 80.60 3128 45.91 19390 285.62











Table A8. Yield and nitrogen data for bahiagrass on a Spodosol for 1981.
May 15 July 1 Aug 10 Oct 1 Total
N Rate Rep Yield N N Yield N N Yield N N Yield N N Yield N
kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha kg/ha

0 1 880 1.56 13.73 1230 1.34 16.48 1430 1.21 17.30 1280 1.28 16.38 4820 63.90
0 2 780 1.14 8.89 1280 1.25 16.00 1190 1.12 13.33 1530 1.26 19.28 4780 57.50
0 3 460 1.34 6.16 840 1.41 11.84 1760 1.17 20.59 1090 1.42 15.48 4150 54.08
0 4 230 1.47 3.38 980 1.21 11.86 860 1.17 10.06 1420 1.22 17.32 3490 42.63
Avg. 588 8.04 1083 14.05 1310 15.32 1330 17.12 4310 54.52

100 1 1450 1.61 23.35 1760 1.25 22.00 3030 1.42 43.03 1950 1.28 24.96 8190 113.33
100 2 910 1.44 13.10 1490 1.22 18.18 2150 1.43 30.75 1970 1.24 24.43 6520 86.46
100 3 1360 1.67 22.71 1810 1.15 20.82 2260 1.46 33.00 2150 1.25 26.88 7580 103.40
100 4 910 1.40 12.74 1810 1.10 19.91 2240 1.41 31.58 1710 1.18 20.18 6670 84.41
Avg. 1158 17.98 1718 20.23 2420 34.59 1945 24.11 7240 96.90

200 1 2080 1.81 37.65 2950 1.33 39.24 4070 1.58 64.31 2930 1.35 39.56 12030 180.74
200 2 2240 1.65 36.96 2950 1.11 32.75 3890 1.57 61.07 2840 1.19 33.80 11920 164.57
200 3 2040 1.89 38.56 3190 1.20 38.28 3670 1.75 64.23 2520 1.50 37.80 11420 178.86
200 4 1780 1.72 30.62 3000 1.27 38.10 3410 1.61 54.90 2750 1.38 37.95 10940 161.57
Avg. 2035 35.95 3023 37.09 3760 61.13 2760 37.28 11578 171.44

300 1 3870 2.03 78.56 4050 1.13 45.77 4810 1.71 82.25 3460 1.51 52.25 16190 258.82
300 2 3670 2.05 75.24 4650 1.20 55.80 4960 1.68 83.33 3600 1.40 50.40 16880 264.76
300 3 2840 2.20 62.48 4300 1.22 52.46 4220 1.78 75.12 3370 1.57 52.91 14730 242.97
300 4 2820 2.05 57.81 4730 1.27 60.07 5000 1.71 85.50 3030 1.43 43.33 15580 246.71
Avg. 3300 68.52 4433 53.52 4748 81.55 3365 49.72 15845 253.32

400 1 3970 2.19 86.94 5400 1.37 73.98 4880 1.82 88.82 3470 1.62 56.21 17720 305.95
400 2 4120 2.11 86.93 5430 1.36 73.85 5250 1.87 98.18 3550 1.65 58.58 18350 317.53
400 3 3060 2.34 71.60 4980 1.38 68.72 4320 1.97 85.10 3430 1.66 56.94 15790 282.37
400 4 3400 2.13 72.42 4770 1.47 70.12 4330 1.93 83.57 3430 1.50 51.45 15930 277.56
Avg. 3638 79.47 5145 71.67 4695 88.92 3470 55.79 16948 295.85

Table A9. Yield and nitrogen data for bahiagrass on a Spodosol for 1982.
May 15 July 1 Aug 10 Oct 1 Total
N Rate Rep Yield N N Yield N N Yield N N Yield N N Yield N
kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha kg/ha

0 1 1330 1.72 22.88 1960 1.02 19.99 1970 1.14 22.46 1150 1.14 13.11 6410 78.44
0 2 1700 1.28 21.76 2080 0.87 18.10 2040 1.02 20.81 1510 1.19 17.97 7330 78.63
0 3 810 1.07 8.67 1020 0.97 9.89 1340 1.32 17.69 1040 1.18 12.27 4210 48.52
0 4 620 1.30 8.06 1040 0.95 9.88 2100 1.20 25.20 970 1.15 11.16 4730 54.30
Avg. 1115 15.34 1525 14.47 1863 21.54 1168 13.63 5670 64.97

100 1 1760 1.80 31.68 2500 1.05 26.25 3840 1.48 56.83 2110 1.23 25.95 10210 140.72
100 2 1500 1.55 23.25 1750 0.90 15.75 2980 1.37 40.83 1840 1.11 20.42 8070 100.25
100 3 1580 1.28 20.22 2130 1.02 21.73 3300 1.47 48.51 2050 1.30 26.65 9060 117.11
100 4 1630 1.46 23.80 2200 0.90 19.80 2960 1.48 43.81 1490 1.28 19.07 8280 106.48
Avg. 1618 24.74 2145 20.88 3270 47.49 1873 23.02 8905 116.14

200 1 3400 1.90 64.60 3300 1.12 36.96 5350 1.73 92.56 3070 1.18 36.23 15120 230.34
200 2 3380 1.28 43.26 3350 1.03 34.51 3980 1.42 56.52 2940 1.39 40.87 13650 175.15
200 3 2910 1.60 46.56 3400 1.01 34.34 5530 1.55 85.72 3070 1.38 42.37 14910 208.98
200 4 2920 1.57 45.84 3080 0.92 28.34 4240 1.63 69.11 2930 1.28 37.50 13170 180.80
Avg. 3153 50.07 3283 33.54 4775 75.97 3003 39.24 14213 198.82

300 1 3660 1.80 65.88 3650 1.16 42.34 5350 1.83 97.91 3500 1.29 45.15 16160 251.28
300 2 5460 1.72 93.91 3920 1.12 43.90 5950 1.51 89.85 3670 1.50 55.05 19000 282.71
300 3 4080 1.62 66.10 4160 1.18 49.09 4720 1.67 78.82 3690 1.51 55.72 16650 249.73
300 4 4260 1.58 67.31 4120 1.02 42.02 4970 1.69 83.99 3380 1.26 42.59 16730 235.91
Avg. 4365 73.30 3963 44.34 5248 87.64 3560 49.63 17135 254.91

400 1 4550 2.06 93.73 4100 1.22 50.02 5480 1.39 76.17 3030 1.65 50.00 17160 269.92
400 2 5320 1.88 100.02 4500 1.21 54.45 4490 1.64 73.64 3400 1.57 53.38 17710 281.48
400 3 4170 1.72 71.72 3730 1.28 47.74 6790 2.01 136.48 3500 1.56 54.60 18190 310.55
400 4 5030 1.70 85.51 4440 1.24 55.06 5280 1.82 96.10 3600 1.26 45.36 18350 282.02
Avg. 4768 87.75 4193 51.82 5510 95.60 3383 50.83 17853 285.99











Table A10. Yield and nitrogen data for bahiagrass on a Spodosol for 1983.
May 15 July 1 Aug 10 Oct 1 Total
N Rate Rep Yield N N Yield N N Yield N N Yield N N Yield N
kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha % kg/ha kg/ha kg/ha

0 1 800 1.26 10.08 1080 1.02 11.02 1290 1.16 14.96 1250 0.99 12.38 4420 48.44
0 2 910 1.41 12.83 950 1.00 9.50 1290 1.01 13.03 1220 0.90 10.98 4370 46.34
0 3 800 1.51 12.08 970 1.01 9.80 1190 1.25 14.88 1530 0.93 14.23 4490 50.98
0 4 570 1.26 7.18 1000 1.08 10.80 1340 1.03 13.80 1080 0.97 10.48 3990 42.26
Avg. 770 10.54 1000 10.28 1278 14.17 1270 12.02 4318 47.00

100 1 2170 1.52 32.98 2190 1.08 23.65 3370 1.32 44.48 2290 1.01 23.13 10020 124.25
100 2 1500 1.42 21.30 1760 1.08 19.01 3670 1.29 47.34 2220 1.09 24.20 9150 111.85
100 3 1510 1.42 21.44 1630 1.09 17.77 3900 1.27 49.53 3840 1.02 39.17 10880 127.91
100 4 1780 1.31 23.32 1780 1.02 18.16 3320 1.30 43.16 2340 1.01 23.63 9220 108.27
Avg. 1740 24.76 1840 19.65 3565 46.13 2673 27.53 9818 118.07

200 1 4150 1.57 65.16 3500 1.23 43.05 5600 1.51 84.56 3270 1.16 37.93 16520 230.70
200 2 2900 1.61 46.69 3040 1.12 34.05 5310 1.41 74.87 3340 1.16 38.74 14590 194.35
200 3 3830 1.62 62.05 3300 1.20 39.60 5200 1.71 88.92 3160 1.33 42.03 15490 232.59
200 4 3020 1.67 50.43 3510 1.14 40.01 4470 1.46 65.26 3870 1.27 49.15 14870 204.86
Avg. 3475 56.08 3338 39.18 5145 78.40 3410 41.96 15368 215.63

300 1 4620 1.68 77.62 4190 1.28 53.63 5620 1.83 102.85 3520 1.32 46.46 17950 280.56
300 2 5150 1.68 86.52 4360 1.23 53.63 6320 1.66 104.91 3870 1.24 47.99 19700 293.05
300 3 4670 1.72 80.32 4160 1.27 52.83 5470 1.79 97.91 3580 1.31 46.90 17880 277.97
300 4 4280 1.77 75.76 4240 1.18 50.03 5430 1.69 91.77 3940 1.24 48.86 17890 266.41
Avg. 4680 80.05 4238 52.53 5710 99.36 3728 47.55 18355 279.50

400 1 4820 1.99 95.92 4010 1.44 57.74 4210 1.86 78.31 2890 1.33 38.44 15930 270.41
400 2 5740 2.01 115.37 4970 1.20 59.64 5860 1.88 110.17 3850 1.66 63.91 20420 349.09
400 3 5850 1.88 109.98 4460 1.33 59.32 5720 2.14 122.41 3890 1.46 56.79 19920 348.50
400 4 5940 1.63 96.82 4220 1.31 55.28 6390 1.85 118.22 3680 1.30 47.84 20230 318.16
Avg. 5588 104.52 4415 58.00 5545 107.27 3578 51.75 19125 321.54



Appendix B

Normalized Yield Distributions for Bahiagrass on Two Florida Soils

Table B1. Normalized yield distributions for bahiagrass on an Entisol for 1979.
N kg/ha t,wks 19.3 26.0 31.7 39.1 >39.1

0 Ay,t/ha 0.12 0.30 0.65 0.71 0.25
lAy,t/ha 0.12 0.42 1.07 1.78 2.03
F 0.059 0.207 0.527 0.877 1

100 Ay,t/ha 0.76 0.97 2.05 1.29 0.50
IAy,t/ha 0.76 1.73 3.78 5.07 5.57
F 0.136 0.311 0.679 0.910 1

200 Ay,t/ha 1.68 1.48 3.28 2.25 0.75
,Ay,t/ha 1.68 3.16 6.44 8.69 9.44
F 0.178 0.335 0.682 0.920 1

300 Ay,t/ha 1.99 1.58 3.41 2.75 0.90
IAy,t/ha 1.99 3.57 6.98 9.73 10.63
F 0.187 0.336 0.657 0.915 1

400 Ay,t/ha 1.94 1.58 3.43 3.04 1.00
,Ay,t/ha 1.94 3.52 6.95 9.99 10.99
F 0.177 0.321 0.632 0.909 1











Table B2. Normalized yield distributions for bahiagrass on an Entisol for 1980.
N kg/ha t,wks 19.3 26.0 31.7 39.1 >39.1

0 Ay,t/ha 0.06 0.18 0.79 0.51 0.15
2Ay,t/ha 0.06 0.24 1.03 1.54 1.69
F 0.036 0.142 0.609 0.911 1

100 Ay,t/ha 0.20 0.86 2.73 1.33 0.35
2Ay,t/ha 0.20 1.06 3.79 5.12 5.47
F 0.037 0.194 0.693 0.936 1

200 Ay,t/ha 0.27 1.92 3.19 1.96 0.50
2Ay,t/ha 0.27 2.19 5.38 7.34 7.84
F 0.034 0.279 0.686 0.936 1

300 Ay,t/ha 0.72 2.68 3.27 2.52 0.75
"Ay,t/ha 0.72 3.40 6.67 9.19 9.94
F 0.072 0.342 0.671 0.925 1

400 Ay,t/ha 0.47 3.04 3.10 2.90 0.90
ZAy,t/ha 0.47 3.51 6.61 9.51 10.41
F 0.045 0.337 0.635 0.914 1


Table B3. Normalized yield distributions for bahiagrass on an Entisol for 1981.
N kg/ha t,wks 19.3 26.0 31.7 39.1 >39.1

0 Ay,t/ha 0.06 0.12 0.66 0.41 0.15
2Ay,t/ha 0.06 0.18 0.84 1.25 1.40
F 0.043 0.129 0.600 0.893 1

100 Ay,t/ha 0.17 0.28 2.48 1.19 0.35
IA y,t/ha 0.17 0.45 2.93 4.12 4.47
F 0.038 0.101 0.655 0.922 1

200 Ay,t/ha 0.32 0.48 2.90 1.95 0.50
2Ay,t/ha 0.32 0.80 3.70 5.65 6.15
F 0.052 0.130 0.602 0.919 1

300 Ay,t/ha 0.62 0.46 3.20 2.23 0.75
2Ay,t/ha 0.62 1.08 4.28 6.51 7.26
F 0.085 0.149 0.590 0.897 1

400 Ay,t/ha 0.63 0.45 2.78 2.69 0.90
Aty,t/ha 0.63 1.08 3.86 6.55 7.45
F 0.085 0.145 0.518 0.879 1



Table El4. Normalized yield distributions for bahiagrass on an Entisol for 1982.
N kg/ha t,wks 19.3 26.0 31.7 39.1 >39.1

0 Ay,t/ha 0 0.18 0.78 0.45 0.15
2Ay,t/ha 0 0.18 0.96 1.41 1.56
F 0 0.115 0.615 0.904 1

100 Ay,t/ha 0.51 0.95 2.31 1.45 0.40
2Ay,t/ha 0.51 1.46 3.77 5.22 5.62
F 0.091 0.260 0.671 0.929 1

200 Ay,t/ha 1.06 1.90 3.76 2.50 0.60
2Ay,t/ha 1.06 2.96 6.72 9.22 9.82
F 0.108 0.301 0.684 0.939 1

300 Ay,t/ha 1.48 2.56 4.65 2.87 0.85
2Ay,t/ha 1.48 4.04 8.69 11.56 12.41
F 0.119 0.326 0.700 0.932 1

400 Ay,t/ha 1.44 2.96 4.40 3.29 1.00
.Ay,t/ha 1.44 4.40 8.80 12.09 13.09
F 0.110 0.336 0.672 0.924 1











Table B5. Normalized yield distributions for bahiagrass on an Entisol for 1983.
N kg/ha t,wks 19.3 26.0 31.7 39.1 >39.1

0 Ay,t/ha 0.16 0.20 0.89 0.70 0.25
Ay,t/ha 0.16 0.36 1.25 1.95 2.20
F 0.073 0.164 0.568 0.886 1

100 Ay,t/ha 0.62 0.65 2.69 1.66 0.50
ZAy,t/ha 0.62 1.27 3.96 5.62 6.12
F 0.101 0.208 0.647 0.918 1

200 Ay,t/ha 1.22 1.38 3.85 2.49 0.75
.Ay,t/ha 1.22 2.60 6.45 8.94 9.69
F 0.126 0.268 0.666 0.923 1

300 Ay,t/ha 2.17 2.00 4.86 3.56 0.90
A.y,t/ha 2.17 4.17 9.03 12.59 13.49
F 0.161 0.309 0.669 0.933 1

400 Ay,t/ha 2.59 2.58 5.47 3.90 1.00
2Ay,t/ha 2.59 5.17 10.64 14.54 15.54
F 0.167 0.333 0.685 0.936 1


Table B6. Normalized yield distributions for bahiagrass on a Spodosol for 1979.
N kg/ha t,wks 19.3 26.0 31.7 39.1 >39.1

0 Ay,t/ha 0.93 0.43 1.34 1.05 0.25
lAy,t/ha 0.93 1.36 2.70 3.75 4.00
F 0.233 0.340 0.675 0.938 1

100 Ay,t/ha 2.44 0.89 3.38 1.64 0.50
XAy,t/ha 2.44 3.33 6.71 8.35 8.85
F 0.276 0.376 0.758 0.944 1

200 Ay,t/ha 3.82 1.89 5.21 2.46 0.75
Ay,t/ha 3.82 5.71 10.92 13.38 14.13
F 0.270 0.404 0.773 0.947 1

300 Ay,t/ha 4.79 2.92 6.18 3.08 0.90
A.y,t/ha 4.79 7.71 13.89 16.97 17.87
F 0.268 0.431 0.777 0.950 1

400 Ay,t/ha 5.12 3.62 6.33 3.00 1.00
"Ay,t/ha 5.12 8.74 15.07 18.07 19.07
F 0.268 0.458 0.790 0.948 1



Table B7. Normalized yield distributions for bahiagrass on a Spodosol for 1980.
N kg/ha t,wks 19.3 26.0 31.7 39.1 >39.1

0 Ay,t/ha 0.51 1.23 1.38 0.83 0.20
IAy,t/ha 0.51 1.74 3.12 3.95 4.15
F 0.123 0.419 0.752 0.952 1

100 Ay,t/ha 1.67 2.16 3.46 1.76 0.45
IAy,t/ha 1.67 3.83 7.29 9.05 9.50
F 0.176 0.403 0.767 0.953 1

200 Ay,t/ha 2.87 3.89 4.78 2.70 0.70
ZAy,t/ha 2.87 6.76 11.54 14.24 14.94
F 0.192 0.452 0.772 0.953 1

300 Ay,t/ha 3.87 5.01 5.16 3.01 0.90
YAy,t/ha 3.87 8.88 14.04 17.05 17.95
F 0.216 0.495 0.782 0.950 1

400 Ay,t/ha 5.14 5.71 5.41 3.13 1.00
ZAy,t/ha 5.14 10.85 16.26 19.39 20.39
F 0.252 0.532 0.797 0.951 1











Table B8.
N kg/ha

0



100



200



300



400


Normalized yield distributions for bahiagrass on a Spodosol for 1981.
t,wks 19.3 26.0

Ay,t/ha 0.59 1.08
lAy,t/ha 0.59 1.67
F 0.129 0.366

Ay,t/ha 1.16 1.72
_Ay,t/ha 1.16 2.88
F 0.150 0.372

Ay,t/ha 2.04 3.02
IAy,t/ha 2.04 5.06
F 0.165 0.410

Ay,t/ha 3.30 4.43
2Ay,t/ha 3.30 7.73
F 0.197 0.462

Ay,t/ha 3.64 5.14
2Ay,t/ha 3.64 8.78
F 0.203 0.489


31.7

1.31
2.98
0.654

2.42
5.30
0.684

3.76
8.82
0.715

4.75
12.48
0.746

4.70
13.48
0.751


39.1

1.33
4.31
0.945

1.95
7.25
0.935

2.76
11.58
0.939

3.36
15.84
0.946

3.47
16.95
0.944


Table B9. Normalized yield distributions for bahiagrass on a Spodosol for 1982.
N kg/ha t,wks 19.3 26.0 31.7 39.1 >39.1

0 Ay,t/ha 1.12 1.52 1.86 1.17 0.25
SAy,t/ha 1.12 2.64 4.50 5.67 5.92
F 0.189 0.446 0.760 0.958 1

100 Ay,t/ha 1.62 2.14 3.27 1.87 0.50
lAy,t/ha 1.62 3.76 7.03 8.90 9.40
F 0.172 0.400 0.748 0.947 1

200 Ay,t/ha 3.15 3.28 4.78 3.00 0.75
lAy,t/ha 3.15 6.43 11.21 14.21 14.96
F 0.211 0.430 0.749 0.950 1

300 Ay,t/ha 4.36 3.96 5.25 3.56 0.90
IAy,t/ha 4.36 8.32 13.57 17.13 18.03
F 0.242 0.461 0.753 0.950 1

400 Ay,t/ha 4.77 4.19 5.51 3.38 1.00
,Ay,t/ha 4.77 8.96 14.47 17.85 18.85
F 0.253 0.475 0.768 0.947 1


Table 1E10. Normalized yield distributions for bahiagrass on a Spodosol for 1983.
N kg/ha t,wks 19.3 26.0 31.7 39.1 >39.1

0 Ay,t/ha 0.77 1.00 1.28 1.27 0.25
Ay,t/ha 0.77 1.77 3.05 4.32 4.57
F 0.168 0.387 0.667 0.945 1

100 Ay,t/ha 1.74 1.84 3.56 2.67 0.50
,Ay,t/ha 1.74 3.58 7.14 9.81 10.31
F 0.169 0.347 0.693 0.952 1

200 Ay,t/ha 3.48 3.34 5.14 3.41 0.75
Ayy,t/ha 3.48 6.82 11.96 15.37 16.12
F 0.216 0.423 0.742 0.953 1

300 Ay,t/ha 4.68 4.24 5.71 3.73 0.90
IAy,t/ha 4.68 8.92 14.63 18.36 19.26
F 0.243 0.463 0.760 0.953 1

400 Ay,t/ha 5.59 4.42 5.54 3.58 1.00
IAy,t/ha 5.59 10.01 15.55 19.13 20.13
F 0.278 0.497 0.772 0.950 1


>39.1

0.25
4.56
1

0.50
7.75
1

0.75
12.33
1

0.90
16.74
1

1.00
17.95
1


---











Appendix C

Normalized Yield and Normalized Nitrogen for Bahiagrass on Two Florida Soils

Table C1. Normalized yield and normalized nitrogen for bahiagrass on an Entisol (1979).
N kg/ha t,wks 19.3 26.0 31.7 39.1 >39.1 N ,%

0 Ay,t/ha 0.12 0.30 0.65 0.71 0.25
F 0.059 0.207 0.527 0.877 1
AN,kg/ha 1.8 2.7 8.2 8.9 3.0 1.29
F 0.073 0.183 0.516 0.878 1

100 Ay,t/ha 0.76 0.97 2.05 1.29 0.50
F 0.136 0.311 0.679 0.910 1
AN,kg/ha 12.2 9.0 31.8 17.4 7.0 1.39
F 0.158 0.274 0.685 0.910 1

200 Ay,t/ha 1.68 1.48 3.28 2.25 0.75
F 0.178 0.335 0.682 0.920 1
AN,kg/ha 30.4 17.3 52.4 32.8 12.0 1.54
F 0.210 0.329 0.691 0.917 1

300 Ay,t/ha 1.99 1.58 3.41 2.75 0.90
F 0.187 0.336 0.657 0.915 1
AN,kg/ha 39.4 22.0 64.0 43.2 16.0 1.74
F 0.213 0.333 0.679 0.913 1

400 Ay,t/ha 1.94 1.58 3.43 3.04 1.00
F 0.177 0.321 0.632 0.909 1
AN,kg/ha 39.2 26.3 65.6 52.8 18.0 1.84
F 0.194 0.324 0.649 0.911 1


Table C2. Normalized yield and normalized nitrogen for bahiagrass on a Spodosol (1979).
N kg/ha t,wks 19.3 26.0 31.7 39.1 >39.1 N,%

0 Ay,t/ha 0.93 0.43 1.34 1.05 0.25
F 0.233 0.340 0.675 0.938 1
AN,kg/ha 10.2 4.6 14.5 11.6 3.0 1.10
F 0.232 0.337 0.667 0.932 1

100 Ay,t/ha 2.44 0.89 3.38 1.64 0.50
F 0.276 0.376 0.758 0.944 1
AN,kg/ha 25.1 9.4 36.0 19.8 5.0 1.08
F 0.263 0.362 0.740 0.948 1

200 Ay,t/ha 3.82 1.89 5.21 2.46 0.75
F 0.270 0.404 0.773 0.947 1
AN,kg/ha 46.5 20.0 63.0 30.4 9.0 1.20
F 0.275 0.394 0.767 0.947 1

300 Ay,t/ha 4.79 2.92 6.18 3.08 0.90
F 0.268 0.431 0.777 0.950 1
AN,kg/ha 67.5 34.0 84.0 39.7 12.0 1.33
F 0.285 0.428 0.782 0.949 1

400 Ay,t/ha 5.12 3.62 6.33 3.00 1.00
F 0.268 0.458 0.790 0.948 1
AN,kg/ha 83.4 43.7 95.5 44.2 15.0 1.48
F 0.296 0.451 0.790 0.947 1



































Time. colendor weeks
Figure 1. Normalized yield distributions at N = 100 kg/ha for
1979 for bahiagrass on an Entisol and a Spodosol.


1s -


Time, calendar weeks

Figure 4. Cumulative yield distributions for bahiagrass on an
Entisol at various applied N levels for 1981.


Time. calendar weeks

Figure 2. Cumulative yield distributions for bahiagrass on an
Entisol at various applied N levels for 1979.


Time, calendor weeks

Figure 3. Cumulative yield distributions for bahiagrass on an
Entisol at various applied N levels for 1980.


Time. colendor weeks

Figure 5. Cumulative yield distributions for bahiagrass on an
Entisol at various applied N levels for 1982.


Time, colendor weeks

Figure 6. Cumulative yield distributions for bahiagrass on an
Entisol at various applied N levels for 1983.


Entisol
1981
N. kq/ho
o 0
x 100
@ 200
* 300
S400













10 20 30 40 5


































Time. calendar weeks
Figure 7. Cumulative yield distributions for bahiagrass on a
Spodosol at various applied N levels for 1979.


Time. calendar weeks

Figure 8. Cumulative yield distributions for bahiagrass on a
Spodosol at various applied N levels for 1980.


o x 100
0 200
300
S S 400








5



0
0 10 20 30 40

Time, colendor weeks
Figure 10. Cumulative yield distributions for bahiagrass on a
Spodosol at various applied N levels for 1982.


Time. calendar weeks
Figure 11. Cumulative yield distributions for bahiagrass on a
Spodosol at various applied N levels for 1983.


Time, colendor weeks

Figure 9. Cumulative yield distributions for bahiagrass on a
Spodosol at various applied N levels for 1981.


50












or B -
dx




o Symbol Soil







300













24 --- i
100 200 300 400 500


N Applied, kg/ha

Figure 12. Dependence oftland a in Eq. (1) upon applied N for
bahiagrass on an Entisol and a Spodosol.


t. weeks

Figure 13. Dependence of a uponfin Eq. (1) for bahiagrass on
an Entisol and a Spodosol.


3U

Spodosol
N. kq/ho
20 400
300

200


10 100


20
.C



Entisol

20




10 200

100

0
0
--------________ ------- 0

1979 1980 1981 1982 1983

Year

Figure 14. Variations in total annual yield with year, applied N
and soil.


Spodosol

20





10 -




O-


















0 100 200 300 400 500


N Applied. kg/ho

Figure 15. Dependence of total annual yield upon applied N
and soil.





























1979 190B 1981 1982 1983

Year

Figure 16. Variations in maximum yield with year and soil.


N Applied. kg/ha

Figure 17. Estimated total annual yield with applied N and soil
for average, low (1981) and high (1983) conditions.


% Total Yield

Figure 19. Relationship between N and dry matter accumula-
tions for 1979 at various applied N levels for an
Entisol.


Z Total Yield

Figure 20. Relationship between N and dry matter accumula-
tions for 1979 at various applied N levels for a
Spodosol.


0 100 200 300 400 500

N Applied. kg/ho

Figure 18. Dependence of forage N concentration upon
applied N for bahiagrass on an Entisol and a
Spodosol.


Spodosol







Entjsol


Symbol Soil
o Entiso]
x Spodosal
































Time, calendar weeks

Figure 21. Estimated normalized yield distributions for
bahiagrass at N = 100 kg/ha and At = 6.6 weeks for
an Entisol and a Spodosol.


Time. calendar weeks
Figure 22. Estimated cumulative yield for bahiagrass at N=
100 kg/ha and At = 6.6 weeks for an Entisol and a
Spodosol.


140


120
ro

100


o 80
S:
z
60


'- 40


21


10 20 30 40 50


Time, calendar weeks
Figure 23. Estimated cumulative N removal by bahiagrass at
N = 100 kg/ha and At = 6.6 weeks for an Entisol and
a Spodosol.


N Applied. kg/ho

Figure 24. Estimated yield response of bahiagrass to applied
N at At = 6.6 weeks on an Entisol and a Spodosol.


Time. calendar weeks
Figure 25. Estimated cumulative yield of bahiagrass at N = 100
kg/ha and At = 4 weeks for an Entisol and a
Spodosol.


Time, calendar weeks
Figure 26. Estimated cumulative N removal by bahiagrass at N
= 100 kg/ha and At = 4 weeks for an Entisol and a
Spodosol.
























































































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