OCTOBER 27, 1988
Florid. Cooperative E,.xtension Servics Institute of Food and Agricultural Sciencs I Uiivuority f Floria J. T. ot
JUL 2,0 198, G
FUR TRIAL AND WINTER ANNUAL Flori,
.PLA.-.iNT G DM Florida
SULFUR TRIAL AND WINTER ANNUAL
THURSDAY, OCTOBER 27, 1988
WELCOME AND INTRODUCTION ......................JIM SELPH
THE SULFUR STORY............................. TERRY WISEMAN
SULFUR FERTILIZATION OF BAHIAGRASS............JACK RECHCIGL
WINTER ANNUAL PLANTING DEMONSTRATION.........JIM SELPH
SPECIAL THANKS GOES TO:
ALLIED SIGNAL INC.
DR. AND MR. ALBERT CARLTON
BRADY AND PAT PHYLE
SULFUR FERTILIZATION OF BAHIAGRASS
Bahiagrass is an important forage crop grown in Florida, with nearly 2.5
million acres grown annually. Bahiagrass is found on more acres than all
other improved grass pastures combined. Average annual dry matter yields for
bahiagrass range from 8,000 14,000 lb/acre. Bahiagrass is adapted to most
climatic conditions throughout the state and can be grown on upland well
drained sands as well as poorly drained "flatwoods" soils.
Until recently, little attention has been focused on the need for sulfur
fertilization for plant growth. This is understandable since, in the past
fertilizers were contaminated with sulfur, thus farmers did not need to be
concerned with sulfur fertilization. However, today in the age of modern
technology, fertilizer manufacturing processes have become highly advanced and
as a consequence fertilizers are free of sulfur.impurities. As a result,
sulfur deficiencies are becoming more pronounced throughout the world. When
soils are low in sulfur, forage yields, protein quality and digestibility may
This study was designed to evaluate the influence of sulfur and nitrogen
application on the yield and protein quality of bahiagrass grown on sandy
soils in Florida.
RESULTS AND DISCUSSION
Bahiagrass yields increased with increasing rates of nitrogen regardless
of the nitrogen source (Figures 1 and 2). Comparing nitrogen sources, highest
yields were obtained with ammonium sulfate as compared to ammonium nitrate or
urea. This is most likely due to the sulfur being supplied by ammonium
sulfate. In addition, it is interesting to note that regardless of nitrogen
source the addition of sulfur increased yields as well. Thus, the results
appear to indicate that the addition of sulfur, either applied as potassium
sulfate or the application of ammonium sulfate, does indeed increase yields of
bahiagrass by as much as 0.5 tons/acre/yr.
For the May harvest, the concentration of crude protein increased as the
rate of nitrogen fertilization increased (Figures 3 and 4). There were also
trends showing that crude protein increased as a result of sulfur application.
Generally, addition of sulfur increased crude protein concentration in the
tissue by an average of 1.2 percentage units. In comparing forms of nitrogen,
the ammonium sulfate increased tissue crude protein more than the other forms
of nitrogen. This is to be expected since the ammonium sulfate supplied
needed sulfur which is required for protein production.
Nitrogen content across cuttings dropped dramatically from the May
harvest to the June harvest (data not shown). This is most likely due to the
large amount of rainfall that occurred in May and June resulting in extensive
loss of the nitrogen fertilizer by leaching. Based on the yield and protein
data, it may be necessary to apply nitrogen fertilizer more frequently than
twice a year, in order to provide adequate nitrogen for the plants throughout
the growing season.
In vitro digestibility was also increased as the rate of nitrogen
fertilization increased (Figures 5 and 6). In addition sulfur increased
percent digestibility of the forage. Percent digestibility was increased with
the ammonium sulfate as compared to the ammonium nitrate treatment due to the
addition of sulfur.
As one would expect, addition of sulfur increased plant uptake of sulfur
by as much as 2 fold compared to the control (Figures 7 and 8). Comparing
nitrogen sources, ammonium sulfate treatments had the highest percentage of
sulfur compared to the other nitrogen sources. This is to be expected since
ammonium sulfate contains sulfur.
These findings should be helpful to growers in Florida, particularly
since ammonium sulfate is currently cheaper than ammonium nitrate or urea per
unit of nitrogen. Therefore, growers can increase forage yields and quality
and save money in fertilizer .costs at the same time.
The effect of nitrogen and sulfur treatments on soil pH is shown in
Figure 9. The addition of ammonium sulfate resulted in a decrease in soil pH
by 0.5 of a unit in one year. Whereas, addition of ammonium nitrate decreased
soil pH by only 0.1 of a unit. Thus, farmers may need to apply lime if the
initial soil pH is 5.5 or less in order to maintain the soil pH in the optimum
range for bahiagrass production.
Based on the 1987 preliminary data, sulfur addition appears to increase
both yields and quality of bahiagrass. Under certain conditions it would be
advantageous for growers to use ammonium sulfate over other nitrogen sources,
particularly since ammonium sulfate is currently cheaper than urea and
ammonium nitrate per unit of nitrogen. However, it should be noted that if
the soil pH is less than 5.5, it will probably be necessary to also apply lime
along with ammonium sulfate since the later appears to reduce soil pHl more
rapidly than ammonium nitrate.
1221 0 lb S/A
:IIB= 77 lb S/A
-a21 155 lb S/A
Influence of nitrogen and sulfur rates on bahiagrass yields
(summation of 5 harvests in 1987).
4 :.0 I Ammonium Nitrate
: GMZ Ammonium Sulfate
67 Ib N/A
134 lb N/A
Effect of ammonium nitrate and ammonium sulfate rates
on bahiagrass yields (summation of 5 harvests in 1987).
Ma o b S/A
ID 77 Ib S/A
21 155 Ib S/A
Influece of sulfur and nitrogen rates on percent crude
protein in bahiagrass May, 1987.
67 Ib N/A
134 Ib N/A
Effect of ammonium nitrate and ammonium sulfate rates on
percent crude protein in bahiagrass May, 1987.
o122 0 Ib S/A
nnD 77 Ib S/A
1ZZa 155 Ib S/A
F-1 Ammonium Nitrate
12221 Ammonium Sulfate
67 lb N/A 134 Ib N/A
0 lb N/A 67 Ib N/A 134 Ib N/A
Influence of nitrogen and sulfur rates on percent
digestibility in bahiagrass May, 1987.
0 Ib S/A
77 lb S/A
155 lb S/A
0 Ib N/A 67 lb N/A 134 lb N/A
Effect of nitrogen and sulfur rates on percent sulfur in
bahiagrass tissue May, 1987.
E: 3 Ammonium Nitrate
0.35 *-R3 Ammonium Sulfate
67 Ib N/A 134 lb N/A
Influence of ammonium nitrate and ammonium sulfate rates
on percent sulfur in bahiagrass tissue May, 1987.
6.0 O Control (no N)
6.80- iurm Ammonium Nitrate
6.60 21 Ammonium Sulfate
soil pH Oct., 1987.
The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
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site maintained by the Florida
Cooperative Extension Service.
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