NFREC Res. Report 92-6
SG 12 1982
Univ:rsity of Florida
Response of 'Florida 301' and 'Florida 302'
Wheat Cultivars to N, P, and K Fertilization
F. M. Rhoads and R. D. Barnett
North Florida Research and Education Center
I FAS Florida Agricultural Experiment Stations
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
Yield potential of wheat varies with cultivar, therefore,
nutrient uptake and response to fertilization may also vary between
cultivars. The release of two wheat cultivars (Florida 301 and
Florida 302) by the University of Florida and their wide acceptance
by growers created a need for data showing cultivar response to
"Florida 301 matures very early and normally produces grain
with high test weights. It is medium in height and has relatively
weak straw. It is resistant to prevalent races of leaf rust and
powdery mildew common to the North Florida area, but is susceptible
to Septoria glume blotch and Hessian fly. Damage from Septoria and
Hessian fly can be reduced somewhat by planting late (about
December 1-15). This cultivar performs well in late plantings and
in double cropping systems." (Barnett and Luke, 1980).
Florida 302 is not related to Florida 301. It is medium in
maturity and normally heads out about 10 days later than Florida
301 in Florida. It is several inches shorter than Florida 301 and
has better lodging resistance. It has excellent resistance to
powdery mildew, good resistance to leaf rust, but is susceptible to
soil-borne mosaic virus, stem rust, and Hessian fly. Florida 302
has large seed but the seed have a rather deep crease which causes
it to have a test weight about 2 lbs. lighter than Florida 301.
The objective of this research was to determine yield response
of Florida 301 and Florida 302 wheat cultivars to nitrogen (N),
phosphorus (P), and potassium (K) fertilization on an ultisol.
MATERIALS AND METHODS
Two wheat cultivars (Florida 301 and 302) were planted 18 Nov
1983 and 12 Dec 1984 in plots with various levels of N, P, and K on
Norfolk loamy fine sand (fine-loamy, siliceous, thermic, Typic
Kandiudult). Row spacing was eight inches with six rows between
tractor tracks spaced five feet apart. Irrigation was applied at
one inch per week as needed to reduce plant water stress. Harvest
dates were 31 May 1984 and 3 June 1985.
Fertilizer treatments are shown in Table 1. Preplant
fertilizer consisted of 46% triple superphosphate and muriate of
potash applied broadcast to supply P and K rates shown for each
treatment. These rates were the same each year. Nitrogen was
applied in two equal applications to the 1984 wheat crop on 21 Dec
1983 and 31 Jan 1984. There were four application dates for the
1985 wheat crop on 8 Jan, 6 Feb, 18 Feb and 5 Mar 1985. Only three
N applications were applied to Florida 301 because of severe
lodging. All N was applied broadcast as a topdressing.
Ten 1-inch by 6-inch soil cores were composite from each plot
in March and December of 1984 and January and July of 1985. Soil
samples were air-dried and ground before extracting with Mehlich-I
(double acid) extractant. Soil analyses were carried out according
to University of Florida Extension Soil-testing Laboratory
procedures (Hanlon and DeVore, 1989).
The experimental design was a randomized complete block with
four replications. Regression analysis and single degree-of-
freedom F-tests were used to relate crop response to fertilizer
rate (Steel and Torrie, 1960).
Table 1. Fertilizer nitrogen (N), phosphorus (P) and potassium
levels for each treatment applied to 'Florida 301' and
'Florida 302' wheat cultivars in 1984 and 1985.
Treatment 301 302 301 302 Pt Kt
1 50 50 150 200 0 0
2 50 50 150 200 0 375
3 50 50 150 200 26 375
4 50 50 150 200 52 375
5 50 50 150 200 104 375
6 50 50 150' 200 52 0
7 50 50 150 200 52 188
8 0 0 0 0 52 375
9 100 100 100 100 52 375
tApplication of P and K were thesame for both cultivars each year.
RESULTS AND DISCUSSION
Yield response of wheat to N in 1984 was linear for both
cultivars (Table 2). About 0.28 bushel of grain yield increase per
pound of fertilizer N was predicted for each cultivar. The
reduction in sum of squares due to regression was about 70% in each
case. The yield increase with zero fertilizer N between years was
attributed to residual N left from soybeans that grew during the
summer of 1984. Failure of Florida 302 to respond to N
fertilization in 1985 may have been due to Hessian fly infestation.
The earlier maturing Florida 301 was not affected by Hessian fly
infestation. A quadratic response to N fertilizer was produced in
1985 by Florida 301 as indicated by the 71% reduction in sum of
squares due to regression. Maximum predicted yield occurred with
120 lb of N per acre. This is well above the University of Florida
Extension Service recommendation of 80 lb of N/acre for wheat
(Hanlon et al., 1990).
Test weight of Florida 302 was reduced from 57 to 52 lb/bushel
with excessive N (data not shown). Number of seed heads appeared
to be the most important yield component in response to N
fertilization for both cultivars. Number of seeds per head was
more important than seed size. The increase in number of seed
heads in response to N fertilizer was 66% for Florida 301 and 63%
for Florida 302 in 1984 and 118% for Florida 301 and 47% for
Florida 302 in 1985. Grain yield response to N was about 200% in
1984 and up to 68% in 1985.
Table 2. Yield'of two wheat cultivars in response to fertilizer
nitrogen rates in 1984-85.
Fertilizer 301 302
Nitrogen 1984 1985 1984 1985
0 14.3 25.9 16.1 32.3
50 35.6 -- 26.9 --
100 41.8 43.6 44.3 31.4
150 -- 42.4 -- -
200 -- -- 28.3
Regression equations: 301(1984) Y = 16.8+0.28 FN, r2 = 0.712**;
301(1985) Y = 25.9+0.31(FN)-0.0013(FN)2, R2 = 0.710**; 302(1984)
Y = 14.9+0.28(FN), r2 = 0.700**. FN = fertilizer nitrogen; ** =
significant regression (P < 0.01).
Regression of grain yield of Florida 301 wheat on fertilizer
P was not significant in 1984 or 1985. However, there were
significant yield increases of Florida 301 between 0 and 26 and
between 26 and 52 lb of P/acre in 1984 but only the first 26 lb
increment of P/acre increased yield in 1985 (Table 3). Grain yield
response of Florida 302 wheat to P fertilizer was linear in 1984
and quadratic in 1985. Maximum predicted yield occurred with 66 lb
of P/acre. This is above the maximum of 44 lb of P/acre
recommended by the University of Florida Extension Service (Hanlon
et al., 1990). However, 52 lb of P/acre were required to maintain
soil-test P in the high (31-60 ppm) range in this experiment.
Table 3. Yield response of two wheat cultivars to fertilizer
phosphorus rates in 1984-85. Single degree of freedom
comparisons of P rates and regression equations are shown
at the bottom.
Fertilizer 301 302
Phosphorus 1984 1985 1984 1985
0 24.3 29.0 17.1 8.5
26 27.4 39.3 27.2 35.3
52 35.6 42.4 26.9 28.3
104 35.6 42.0 33.9 27.2
Comparison 1984 1985 Regression equations 302
P0 vs others 6.42* 12.63** 1984-Y = 19.6 + 0.14(FP)
r2 = 0.261*
P26 vs P52 5.30* N.S. 1985-Y = 11.54+0.71(FP) -
and P14 0.00536(FP)2 R2 = 0.655**
*, ** denote significance at probability of 5 and 1%, respectively.
N.S. = not significant and FP = fertilizer phosphorus.
Excessive P reduced test weight of Florida 302 wheat in 1984
and 1985 (data not shown). Number of seed heads were increased by
P fertilization in most cases and number of seed heads was more
important than seed size and seed per head as a component of yield
response to P.
Grain yield of the wheat cultivars did not respond to K
fertilization. However, test weight of Florida 301 was increased
from 54.7 to 57.4 Ib per bushel by 188 lb of K/acre and test weight
of Florida 302 was increased from 48.6 to 53.2 lb per bushel by 375
lb of K/acre in 1985. There was no test weight response to K in
Soil-test P in the zero P treatment remained in the very low
range (Hanlon et al., 1990) for the duration of the experiment
(Table 4). Annual P application of 26 lb/acre resulted in growing
season soil-test P levels in the high range in 1984 and medium
range in 1985. Adequate P to maintain a high soil-test level of P
was supplied by an annual application 52 lb/acre. Annual P
application of 104 lb/acre maintained soil-test P at excessive
Table 4. Soil-test phosphorus (P) and potassium (K) from wheat
production plots at four sampling dates. Values shown
are means of four replications.
Rate Mar-84(b)t Dec-84(d)t Jan-85(a)t Jul-85(c)t
0 9 3 4 4
26 39 11 19 14
52 60 36 56 32
104 115 73 112 68
0 35 44 40 24
188 69 67 177 69
375 96 75 282 103
tSampling dates occurred after fertilizer application as follows:
(a) one month, (b) three months, (c) six months, and (d) 12 months.
Soil-test K in the zero K treatment was in the medium range
(36-60 ppm) during each growing season (Table 4). This explains
the absence of grain yield response to K fertilization by the two
wheat cultivars since 75 to 100% of maximum yield potential is
expected when soil-test K is in the medium range (Johnson et al.,
1984). Annual application of 188 lb K/acre was adequate to
maintain soil-test K in the high range (61-125 ppm). Since 188 lb
K/acre raised soil-test K from 67 to 177 mg/kg (ppm), 40 lb of K
(48 lb K20) should raise soil-test K from the medium to high range.
This compares favorably with 33 lb K/acre (40 lb K20) recommended
for wheat at a medium soil-test K level by the University of
Florida Extension Service (Hanlon, et al., 1990).
Maximum yield of wheat was produced with 100 lb of N/acre,
while the University of Florida Extension Service recommendation is
80 lb of N/acre. Wheat did not respond to additional P when soil-
test P was in the high range (31-60 ppm). The range of soil-test
P extended from very low (<10 ppm) to very high (>60 ppm). Soil-
test K ranged from medium (36-60 ppm) to very high (>125 ppm),
however, there was no wheat grain yield response to K. An increase
in test weight in response to added K suggests that the medium
range of soil-test K is marginal for successful wheat production.
Excessive N and P reduced test weight of wheat in this experiment.
This research was supported by the University of Florida,
Institute of Food and Agricultural Sciences, Experiment Stations
and the Potash and Phosphate Institute.
1 Barnett, R. D. and H. H. Luke. 1980. Florida 301 a new wheat
for multiple cropping systems in North Florida. Agric. Exp.
Sta. IFAS. Univ. of Fla. Cir. S-273.
2 Hanlon, E. A. and J. M. DeVore. 1989. IFAS extension soil
testing laboratory chemical procedures and training manual.
Fla. Coop. Ext. Serv. IFAS. Univ. of Fla. Cir. 812.
3 Hanlon, E. A., G. Kidder, and B. L. McNeal. 1990. Soil,
container media, and water testing interpretations and IFAS
standardized fertilization recommendations. Fla. Coop. Ext.
Serv. IFAS. Univ. of Fla. Cir. 817.
4 Johnson, G. V., R. A. Isaac, S. J. Donohue, M. R. Tucker, and
J. R. Woodruff. 1984. Procedures used by state soil testing
laboratories in the southern region of the United States.
Southern Cooperative Series Bulletin 190.
5 Steel, R. G. D. and J. H. Torrie. 1960. Principles and
procedures of statistics. McGraw-Hill, New York.