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NFREC, Quincy Research Report 899
Coastal Bermudagrass
Yield, SoilpH, and
Ammonium SulfateNitrate Rates
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F. M. Rhoadrgi C.
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Stanley, Jr.
JAN 11 1990
University of Florida
Florida Agricultural Experiment Stations
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
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Coastal Bermudagrass Yield, SoilpH,
and
Ammonium SulfateNitrate Rates
by
F. M. Rhoads and R. L. Stanley, Jr.
North Florida Research and Education Center
Route 3 Box 4370, Quincy, FL 32351
Institute of Food and Agricultural Sciences
University of Florida
Research Report 899
INTRODUCTION
High rates of nitrogen (N) applied to acid soils increase the requirement
for lime application to maintain soil pH at levels favorable for production of
most crops. Coastal bermudagrass responded positively to Nrates up to 400
lb/acre with no lime added for a period of three years (Adams et al., 1967).
However, yields declined each year without lime at Nrates of 800 and 1600
lb/acre. A positive response to Nrates up to 1600 lb/acre was observed with
adequate lime applied. Nitrogen recovery dropped rapidly when N fertilizer
rates increased from 600 to 1200 lb of N/acre in Alabama (Doss et al., 1966).
Anhydrous ammonia produced lower bermudagrass yield than ammonium nitrate and
urea at Nrates greater than 100 lb/acre (Hill and Tucker, 1968). Near maxi
mum coastal bermudagrass yield occurred with 800 lb of N/acre in North Georgia
(Wilkinson and Langdale, 1974).
A reduction in sulfur oxides entering the atmosphere, as well as the
increasing use of sulfurfree fertilizers have the potential to cause sulfur
(S) deficiency problems under the soil and climatic conditions of the South
eastern United States. Ammonium sulfate contains both N (21%) and S(24%), but
research on its use as a source of sulfur for coastal bermudagrass is limited
(Burton and Jackson, 1962, and Matocha, 1971). Ammonium sulfate produces
twice as much acidity per unit of N as ammonium nitrate.
Objectives of this report were to determine: (1) coastal bermudagrass
response to Nrates, (2) minimum and maximum Nrates for coastal bermudagrass,
and (3) expected soil pH reduction due to application of ammonium nitrate and
ammonium sulfate.
METHODS
Coastal bermudagrass sprigs were planted in July of 1984 at the North
Florida Research and Education Center, Quincy on a Dothan loamy sand (Plinthic
Kandiudult). A full season harvest was not made until 1986 when the stand was
well established.
Annual applications of 500 lb/acre of triple superphosphate (46%) and 700
lb/acre of muriate of potash were made in early March of each year following
establishment of the coastal bermudagrass sod. Zinc sulfate (36% Zn) and
solubor (20% B) were applied at the beginning of the study at 28 and 25
lb/acre, respectively.
Two tons/acre of dolomite were incorporated into the soil before planting
the bermudagrass sprigs in 1984. Dolomite was applied over the top of
bermudagrass in the fall of 1987 at the rate of 1ton/acre.
Nitrogen rates were 0, 200, 400, 600, and 800 lb/acre, with each rate
supplied separately by ammonium nitrate and ammonium sulfate for a total of
nine treatments. Onehalf of the N for each treatment was applied in the
spring when plant growth resumed and onehalf was applied following the second
harvest. Soil samples (10 cores per plot, 1inch x 6inches, composite) were
collected from each plot in June, 1986 and December 1988 for soilpH
determination with a glass electrode pH meter.
Plot size was 6' x 15' with 6ft alleys between plots within blocks and
10ft alleys between blocks. The experimental design was a randomized
complete block with four replicates. Yield was estimated from the harvest of
a 30inch by 15ft strip in each plot. Total green weight of forage from each
plot was determined and moisture content was determined from a dried 400 gram
sample of green forage. Dry matter yield and hay yield (16% moisture) were
calculated using appropriate conversion factors. Nitrogen concentration of
bermudagrass tissue was determined by microKjeldahl procedures. Clipping
frequency was about every four weeks.
Maximum and minimum Nrates were determined by a twostep process: (1)
least significant differences (Isd) for yield at P (probability) = 0.05 and P
= 0.50 were calculated from the analysis of variance (AOV) error mean square
and student's t (Steel and Torrie, 1960), (2) nitrogen fertilizer levels
with 5 and 50% probabilities of no response (PNR) to additional fertilizerN
were determined from graphs of regression models (yield versus fertilizerN)
by subtracting Isd (0.05) and Isd (0.50) from maximum predicted yield,
plotting horizontal lines from these points on the Yaxis to the regression
line and vertical lines from the resulting points on the regression line to
the Xaxis, respectively. Minimum fertilizerN corresponds to PNR (0.05) and
maximum fertilizerN corresponds to PNR (0.50).
Regression equations for soilpH versus rates of ammonium sulfate and
ammonium nitrate were calculated using the minitab data analysis system
(Minitab, Inc. 1985). Predicted soilpH changes were calculated from
regression equations for annual application of 450 lb of N/acre and 48 lb of
S/acre with specified applications of dolomite.
RESULTS AND DISCUSSION
Yields of bermudagrass hay were above 14 tons/acre in 1986 (Fig. 1.).
Lower yields in 1987 and 1988 were due to lower rainfall amounts during the
growing season each year, compared to 1986. Highest yield in 1987 was about
13 tons/acre and it was near 11.6 tons/acre in 1988. Residual soil nitrogen
was higher in 1986 than in the following years as indicated by a yield of 9.5
tons/acre in 1986 with zero fertilizerN and near 6 tons/acre with zero N in
198687.
A linear yield response of bermudagrass to nitrogen was observed in 1986
(regression not shown). However, mean yields for 600 and 800 lb of N/acre
were about the same. Maximum and minimum Nrates were calculated for 1987 and
1988 (Fig. 2.). The minimum Nrate was 350 lb/acre each year, because the
probability of no response (PNR) to additional fertilizer N was only 5%.
Therefore, the risk of not getting a response to 350 Ib of N per acre was very
low. Maximum Nrate was 500 lb/acre in 1987 and 450 lb/acre in 1988, because
the PNR to additional N was 50%. These data suggest that 350 lb of N/acre be
applied to unirrigated coastal bermudagrass and no more than 500 lb of N/acre
be applied to irrigated coastal bermudagrass for maximum N recovery efficiency
and minimum environmental impact.
Nitrogen content of the third harvest of coastal bermudagrass ranged from
1.74% with no applied N to 2.36% with 800 lb of N/acre (Fig. 3.). However,
the 200 lb of N/acre treatment contained 2.33% N, indicating that protein
concentration was not increased by high Nrates. Nitrogen concentration of
16
14
12
10o
8
6
4
2
Hay (16% moisture) Yield (tons/acre)
Nitrogen Source
I Ammonium Nitrate
0 200 400 600 800
0 200 400 600 800
0 200 400 600 800
Figure 1.
Nitrogen Rate (Ibs/acre)
Hay yield of coastal bermudagrass in response to Nrates supplied from
ammonium nitrate and ammonium sulfate in 1986, 1987, and 1988.
t~rae
Yield (tons/acre) Coastal Bermuda
0 200
400
N Rate
600
(Ibs/acre)
800
1000
0 200
400
N Rate
600
(Ibs/acre)
Figure 2.
Regression analysis of coastal bermudagrass drymatter yield versus fertilizer
Nrates in 1987 and 1988, showing Nrates for probability of no response (PNR)
at 5% and 50% probability.
800
1000
Yield (tons/acre) Coastal Bermuda
% N in Coastal Bermuda
Harvest #3
1.5 h
0.5
200
Figure 3.
400
600
Nitrogen Rate (Ibs/acre)
Nitrogen concentration of coastal bermudagrass tissue as a
Nrate for the third clipping date.
800
function of
3; 2, ?7
2.5
2
SoilpH
June, 1986
S Amm. Nitrate M Amm. Sulfate
Dec, 1988
200 400 600
800
0 200
Figure 5.
Soil pH
in 1986
Nitrogen Rate (Ibs/acre)
of coastal bermudagrass plots as a function of Nrate and Nsource
and 1988.
I
0
400
600
800
coastal bermudagrass was highest in cuttings immediately following N
application (Fig. 4.). Fertilizer N was applied in the spring when growth
resumed and again following the second cutting, with each application
supplying onehalf of the total amount. We suggest that N be applied to
coastal bermudagrass in four equal applications, with one application in
spring when growth resumes and one application following each of the first
three cuttings.
Ammonium nitrogen is oxidized to nitrate nitrogen by microbial activity
when applied to the soil. The resulting chemical reaction increases soil
acidity, thereby lowering soil pH. Since ammonium nitrate contains only half
as much ammonium N per unit of N applied as does ammonium sulfate, we expect
ammonium sulfate to produce twice as much soil acidity per unit of N as
ammonium nitrate. Soil pH in coastal bermudagrass plots ranged from 5.7 with
200 Ib of N/acre as ammonium nitrate to 5.4 with 800 lb of N/acre as ammonium
nitrate in December of 1988 after four annual applications of N, and three
tons of dolomite/acre. However, soil pH ranged from 5.7 to 4.9 with the same
N rates applied as ammonium sulfate (Fig. 5.). Obviously, more lime would be
required if all nitrogen is supplied by ammonium sulfate rather than ammonium
nitrate. But, when ammonium sulfate is used only in amounts to supply sulfur
for coastal bermudagrass soil acidity can be kept in the favorable range with
a nominal liming program. The use of equations in table 1 to calculate the pH
change resulting from the use of 200 Ib of ammonium sulfate per acre and 1200
Ib of ammonium nitrate per acre reveals that soil pH would be reduced by about
0.4 units and most of the reduction would be due to ammonium nitrate (Table
2.). Ammonium sulfate is an excellent source of sulfur for coastal
bermudagrass and it supplies part of the nitrogen.
Table 1. Regression equations for soilpH versus rate of ammonium sulfate and
ammonium nitrate on two sampling dates.
Sample Fertilizer
date source Equation C.D.+
June, 1986 I Ammonium Sulfate Y = 5.710.00022X 0.508
Dec, 1988++ Ammonium Sulfate Y = 6.010.000533X+(7x10 )X2 0.854
June, 19864 Ammonium Nitrate Y = 6.220.000285X 0.377
Dec, 1988++ Ammonium Nitrate Y = 5.920.000217X 0.724
C.D. = Coefficient of determination.
#Sampled after 2 tons of dolomite/acre in 1984 and 2 annual applications of S
and N.
"Sampled after 2 tons of dolomite/acre in 1984, 1 ton of dolomite/acre in
1987 and 4 annual applications of S and N.
Table 2. Predicted soilpH changes for annual applications of 48 lb of S/acre
and 450 lb of N/acre with a liming program.
Sample Ammonium Sulfate Ammonium Nitrate
date 200 lb/acre 1200 lb/acre Total
SoilpH change
June, 1986+ 0.04 0.34 0.38
Dec, 19884 0.10 0.26 0.36
+Sampled after 2 tons of dolomite/acre in 1984 and 2 annual applications of S
and N.
+Sampled after 2 tons of dolomite/acre in 1984, 1 ton of dolomite/acre in 1987
and 4 annual applications of S and N.
ACKNOWLEDGEMENT
We are grateful to AlliedSignal, Inc. for financial support of the
research presented in this report.
UNIVERSITY OF FLORIDA
3 1262074684555
LITERATURE CITED
1 Adams, W. E., R. W. Pearson, W. A. Jackson, and R. A. McCreery. 1967.
Influence of limestone and nitrogen on soil pH and coastal bermudagrass
yield. Agron. J. 59:450453.
2 Burton, Glenn W. and James E. Jackson. 1962. Effect of rate and
frequency of applying six nitrogen sources on coastal bermudagrass.
Agron. J. 54:4043.
3 Doss, B. D., D. A. Ashely, 0. L. Bennett, and R. M. Patterson. 1966.
Interactions of soil moisture, nitrogen, and clipping frequency on yield
and nitrogen content of coastal bermudagrass. Agron. J. 58:510512.
4 Hill, W. E. and B. B. Tucker. 1968. A comparison of injected anhydrous
ammonia into bermudagrass sod compared to topdressed applications of urea
and ammonium nitrate. Soil Sci. Soc. Amer. Proc. 32:257261.
5 Matocha, J. E. 1971. Influence of sulfur sources and magnesia on forage
yields of coastal bermudagrass (Cynodon dactylon (L.) Pers.). Agron. J.
63:493496.
6 Minitab, Inc. 1985. Minitab reference manual. University Park, PA.
7 Wilkinson, S. R., and G. W. Langdale. 1974. Fertility needs of the
warmseason grasses. In: D. A. Mays (ED.). Forage fertilization. Amer.
Soc. of Agron., Crop Sci. Soc. of Amer., and Soil Sci. Soc. of Amer.
Madison, Wis. p. 119145.
8 Steel, R. G. D., and J. H. Torrie. 1960. Principles and procedures of
statistics. McGrawHill, New York.
