NFREC Res. Rpt. 93-14
S TA R TER FER TILIZER:
RESPONSIVE VERSUS NON-RESPONSIVE
F. M. Rhoads*, D. L. Wright and L.D.
NORTH FLORIDA RESEARCH AND
EDUCA TION CENTER,
Florida Agricultural Experiment Stations
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
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Corn (Zea mays L.) hybrids have been shown to differ in
response to starter fertilizer. We conducted two glasshouse
experiments to determine if a responsive and a non-responsive corn
hybrid differed in nutrient uptake and growth characteristics. In
the first experiment, applied phosphorus levels of 0, 10, 20, or 30
mg kg' were mixed with either 25 or 100% of the total soil volume
(1.5 L). Nitrogen was mixed with the total soil volume in all
treatments at a rate of 100 mg pot-'. Phosphorus rates in the
second experiment were 0, 30, or 60 mg kg1' and the N rate was 200
mg pot". Fertilizer N and P were mixed with total soil volume or
banded 5 cm below the soil surface and 5 cm away from seed. The
soil was obtained from the A horizon of Norfolk loamy fine sand
(fine loamy, siliceous, thermic, Typic Kandiudult). Time from
seeding to harvest was 33 days for the first experiment and 41 days
for the second. Root weight was 31% greater in the first
experiment and 48% greater in the second for the non-responsive
hybrid than the responsive one, averaged over treatments. This
indicates that the non-responsive hybrid was able to tap a larger
N and P supply than the responsive hybrid. The responsive hybrid
produced a significant (0.05) increase in top and root weight due
to banding N only, but the non-responsive hybrid did not respond to
N placement. We conclude that the difference in hybrid response to
starter fertilizer was due to a difference in root growth. The
dry-matter ratio between two P rates (60 mg P kg-/30 mg P kg'')
increased due to band placement and the dry-matter ratio
band/broadcast increased due to higher P rate in the responsive
hybrid, but these ratios did not change in the non-responsive
hybrid. We plan to use this information in future research to
develop a procedure for screening corn hybrids in the greenhouse to
test potential response to starter fertilizer.
Abbreviations: RH, responsive hybrid; NH, non-responsive hybrid;
BC, broadcast; BD, banded; WB, wide band.
Environmental factors that influence response to starter
fertilizer are soil temperature, phosphorus (P) immobilization, and
low fertility soils. Low soil temperatures reduce root growth
(Mackay and Barber, 1984) which in turn reduces nutrient uptake of
plants with limited root systems. Early planting dates, to
maximize corn yield potential (Wright et al.,1988) often result in
exposure of young seedlings to low soil temperatures. Starter
fertilizer increased corn yield in every case when either air or
soil temperature was below normal in a Canadian study (Ketcheson,
1968). Poor seedling growth resulting from low nutrient
availability of N and P in cold soils can occur irrespective of
residual soil fertility levels (Touchton and Hargrove, 1983). Both
N and P are considered essential ingredients in starter fertilizers
(Ketcheson, 1957) to offset low N and P availability in cold soils
(Cassman and Munns, 1980; and Wallingford, 1978).
Some soils have a high capacity to fix or immobilize
fertilizer P, thereby reducing its availability to plants with
limited root systems. Research has shown that there is an optimum
fraction of soil with which to mix a given amount of fertilizer P
in order to obtain maximum P uptake in a given soil (Anghinoni and
Barber, 1980). Where one rate of P was applied to three soils, the
greater the adsorption of P by the soil, the lower the fraction of
P-treated soil necessary to maximize P-uptake. Response to starter
fertilizer in soils with high P adsorption (as in the Southeast)
will be due to added P. Low fertility soils provide a more
favorable environment for plant response to starter fertilizer than
high fertility soils. Placing starter fertilizer in a band near
the seed in a low fertility soil gives a dramatic increase of
nutrient concentration in the limited root zone of young seedlings
and promotes more rapid growth.
All corn hybrids did not show a positive grain yield response
to starter fertilizer ( a small amount of N and P fertilizer
applied at planting) in a 3 yr field plot experiment at Quincy,
Florida (Teare and Wright, 1990). Some were consistent positive
responders, some were consistently negative, while others were
inconsistent, responding positive sometimes and negative sometimes.
Hybrid characteristics that influence response to starter
fertilizer include rate of root growth, P-uptake efficiency, N-
uptake efficiency, rate of top growth, and growth response to
temperature. Hybrids that are highly sensitive to temperature are
expected to be inconsistent in response to starter fertilizers
because when temperature is higher than normal a positive response
is not likely to occur while below normal temperatures would
probably result in a positive response. A hybrid having a high
rate of root growth and a high efficiency of N and P uptake is not
expected to have a positive response to starter fertilizer. A
positive response to starter fertilizer is expected of a hybrid
having a slow rate of root growth and/or low nutrient uptake
We conducted two experiments to compare rate of root and top
growth and N and P uptake efficiency of pre-selected responsive and
non-responsive corn hybrids to starter fertilizer application. Our
hypothesis was that a corn hybrid not responding positively to
starter fertilizer has a more rapid rate of root growth and/or a
higher N and P uptake efficiency than one that consistently
responds positively. Since application of starter fertilizer
increases time required for planting, we hope to develop an
inexpensive screening test in future research to identify hybrids
that respond positively to starter fertilizer. A greenhouse test
should be less expensive and consume less time than field trials.
The most convenient and time saving measurement is dry-matter yield
of plant tops (shoots).
METHODS AND MATERIALS
'Deltapine G4733' and 'Northrup King 508' were selected because
Deltapine G4733 consistently gave a positive grain yield response
to starter fertilizer and NK508 consistently failed to respond
positively in a starter fertilizer field experiment at Quincy,
Florida in 1985-87 (Teare and Wright, 1990). The corn hybrids were
seeded in pots containing 2 kg of soil ( with low P) from the A
horizon of Norfolk loamy fine sand (fine loamy, siliceous, thermic,
Typic Kandiudult) on 15 August 1991 and 17 March 1992 in a
glasshouse at Quincy, Florida. Six seeds were planted in each pot
and plants were thinned to two per pot at the two-leaf stage.
Triple superphosphate was used as a source of P in both
experiments. The P rates for the first experiment were 0, 10, 20,
and 30 mg kg-1 (2mg kg"' is approximately equal to 1 kg ha-1).
Placement of P was either mixed with total soil volume (broadcast
or BC) or mixed with 25% of total soil volume located in the top
center of each pot (wide band or WB). There were seven treatments
consisting of a check, three P rates and two placement methods for
each hybrid. The N at 100 mg N pot-1 (mg pot1 is approximately
equal to kg ha-) as potassium nitrate (KNO3) was mixed with total
soil volume in all treatments (281 mg K pot'1). Both experiments
were limed with 2000 mg CaO pot1.
The second experiment contained P rates of 0, 30, and 60 mg kg-
either mixed with total soil volume (BC) or banded (BD) 5 cm below
the surface and 5 cm horizontally from seed. Rate of N as NH4NO3
was 200 mg pot-1 for all treatments and N was banded with P,
broadcast with P, and banded alone at the 60 mg kg-' broadcast P
rate. There were six treatments for each hybrid. The source of K
for the second experiment was K2SO4 at 415 mg K pot'.
The first experiment was harvested 33 days after seeding and
the second was harvested 41 days after seeding. Temperatures and
day length were greater in the first experiment than in the second.
Average minimum temperatures were 21' C in experiment-1 and 11' C
in experiment-2, while average maximum temperatures were 32' C in
experiment-1 and 24' C in experiment-2. Roots were separated from
the soil by screening and washing with tap water. Dry-matter yield
of both tops and roots was determined after drying to constant
weight at 700C.
Tissue P was determined separately for roots and tops on a
colorimeter by the molybdenum-blue method after ashing plant
samples at 500 C. These values were multiplied by the grams of root
and top dry-matter to determine total P uptake of roots and tops.
Tissue N was determined by micro-kjeldahl procedures and total N
uptake was calculated in the same manner as was P. Soil-test P (in
samples at harvest) was determined in Mehlich-1 extract (Hanlon and
Devore, 1989), also using the molybdenum-blue method. Mehlich-1
extractable soil P at harvest was increased about 7 or 8 mg kg'1 by
each 30 mg kg-' fertilizer P in each experiment. Soil pH was
determined with a pH meter in a 1:1 v/v soil:water slurry for each
experiment. Soil for the first experiment averaged pH 6.1 with a
range of 0.7 and a standard deviation of 0.2. For the second
experiment, soil average was pH 6.7 with a range of 1.2 and a
standard deviation of 0.3.
The experimental design for each experiment was a randomized
complete block containing four replicates. Statistical analysis
consisted of analysis of variance, regression analysis, and single
degree-of-freedom contrasts (Steel and Torrie, 1960).
RESULTS AND DISCUSSION
In the first experiment top growth, root growth, and total P
uptake increased with increased P rate (Table 1). Mixing P with
25% of soil volume did not increase total P uptake or top growth of
either hybrid. This indicates that availability of P was not
increased by mixing fertilizer P with 25% of soil volume because P
was in contact with enough soil to reduce P solubility by the
maximum amount while a smaller portion of the root system was in
contact with fertilizer P. This conclusion is supported by the
reduced P uptake efficiency in terms of P uptake g-1 roots for both
hybrids. However, root growth increased in both hybrids as a
result of mixing P with 25% of soil volume. This may have been due
to the initial root system being in contact with four times as much
P as where it was mixed with the total soil volume.
Root weight was 31% greater in the non-responsive hybrid (NH)
than in the responsive hybrid (RH). Phosphorus uptake was 22%
greater in the NH than in the RH. Since there was no difference
between hybrids in P uptake efficiency or dry-weight of tops the
increased P uptake by the NH was due to increased root growth which
occurred during long hot days. Results of the first experiment
suggest that the main difference between hybrids was in rate of
root growth which increased P uptake in the NH. Therefore, the NH
was able to obtain sufficient P for maximum yield without starter
Since none of the plants appeared to have adequate P in the
first experiment we modified our second experiment by adding the 60
mg P kg- rate and deleting the 10 and 20 mg P kg-1 rates. Our
hypothesis was that band placement would increase root and top
growth by minimizing P and soil contact to a much greater extent
than mixing P with 25% of the soil volume. In the second
experiment dry-matter yield of tops and roots of both hybrids were
increased by band placement with each fertilizer rate (Table 2).
Top growth was 37% greater and root growth was 48% greater for NH
than RH. Total P uptake was 25% greater and total N uptake was 16%
greater for NH than RH. However, P uptake efficiency was 17%
greater and N uptake efficiency was 30% greater for RH than NH.
But increased uptake efficiencies were not great enough to offset
the difference in root growth.
Band placement of N ( 5 cm below soil surface and 5 cm
horizontal from row) increased top and root dry-matter yield of the
RH but the increase of the NH was not significant (P>0.05). The N
uptake of the NH was influenced more by P rate than by N placement.
The opposite was true for the RH because it did not show a
significant increase of broadcast N uptake between 30 and 60 mg kg'1
broadcast P as was shown by the NH. Nitrogen uptake was increased
(P<0.05) in the RH by band applied N, but not in the NH.
Although, there was a difference between hybrids in top dry-
matter yield in the second experiment, there is no conflict between
results of the first and second experiment. The highest P rate in
the first experiment was 30 mg kg-1 and there was no significant
difference in top dry-matter yield between hybrids with 30 mg kg"
P broadcast in the second experiment. The first experiment did not
contain a narrow band treatment.
Both experiments are in agreement that the NH had the largest
root system in terms of dry-matter yield and also took up the most
P. The RH was most efficient in taking up N and P per g of roots
but this was more than offset by the larger root system of the NH.
We conclude that the difference in response between the two hybrids
to starter fertilizer was due to a difference in growth of root
systems. It should be pointed out that both hybrids responded to
band placement of P in the pot experiments but this was a low P
soil. Soil in the field experiment in which these hybrids were
compared contained high Mehlich-1 P (>31 mg kg-) each year (Teare
and Wright, 1990).
Results from both field (Teare and Wright, 1990) and
greenhouse (Table 2) suggest that a positive response to starter
fertilizer in the field was primarily due to N, since both hybrids
responded to band placement of P in the greenhouse with a low P
soil while the field soil was only low in residual N. The
difference between these hybrids in response to N placement may
explain why conflicting results have been obtained with starter
fertilizers containing N (Teare and Wright, 1990).
Future research is planned in which information from this
report will be used to develop a greenhouse screening test to
determine the potential response of corn hybrids to starter
fertilizer. Since recovering the root system is a time consuming
task for use in a screening test, we considered only top dry-weight
data to reveal differences between these two hybrids with
different grain yield responses to starter fertilizer. Using two
placement methods (BD and BC) we compared shoot dry-matter ratio
(60 mg P kg"/30 mg P kg-) of each hybrid to determine the influence
of placement on the ratio (Fig. 1). Shoot dry-matter increase due
to an additional 30 mg kg-1 P was about 67% for the NH regardless of
placement, however, for the RH the increase was 28% broadcast and
101% banded. This suggests that response of corn hybrids to
starter fertilizer may be proportional to the difference between
broadcast and band placement effects on shoot dry-matter ratio of
two P rates. Another comparison of top dry-matter ratio
(band/broadcast) of each hybrid showed that an additional 30 mg P
kg1' increased the ratio from 1.98 to 3.12 for the RH while the
ratio did not change between P rates for the NH (Fig. 2).
A possible protocol for screening corn hybrids to determine
potential response to starter fertilizer is a two by two factorial
fertilizer treatment arrangement having four replications with a
low P soil for each hybrid. One factor could be P rate and the
other placement. The P rates of 30 and 60 mg kg1' and placement of
broadcast (mixing fertilizer with total soil volume) and the
narrowest possible band 5 cm below the soil surface and 5 cm to the
side of the seed were successful in identifying hybrid differences
in this report. The N rate of 200 mg pot-' and plants harvested
after 6 wk of growth appear to be satisfactory. Finally, determine
dry-matter yield of tops and calculate ratios as shown in figures
1 and 2. Hybrids with the largest change in each ratio may have
the greatest potential for a positive response to starter
Anghinoni, I., and S.A. Barber. 1980. Predicting the most
efficient phosphorus placement for corn. Soil Sci. Soc. Am.
Cassman, K.G., and D.N. Munns. 1980. Nitrogen mineralization as
affected by soil moisture, temperature, and depth. Soil Sci
Soc. Am. J. 44:1233-1237.
Hanlon, E.A., and J.M. Devore. 1989. IFAS extension soil testing
laboratory chemical procedures and training manual. Florida
Cooperative Extension Service. Circular 812.
Ketcheson, J.W. 1957. Some effects of soil temperature on
phosphorus requirements of young corn plants in the
greenhouse. J. Soil Sci. 37:41-47.
Ketcheson, J.W. 1968. Effect of controlled air and soil
temperature and starter fertilizer on growth and nutrient
composition of corn (Zea mays L.) Soil Sci. Soc. Amer. Proc.
MacKay, A.D., and S.A. Barber. 1984. Soil temperature effects on
root growth and phosphorus uptake by corn. Soil Sci. Soc. Am.
Steel, R.G.D., and J.H. Torrie. 1960. Principles and procedures
of statistics. McGraw-Hill, NY.
Teare, I.D., and D.L. Wright. 1990. Corn hybrid-starter
fertilizer interaction for yield and lodging. Crop Science.
Touchton, J.T., and W.L. Hargrove. 1983. Grain sorghum response
to starter fertilizers. Better Crops Plant Food 67:1-3.
Wallingford, W. 1978. Phosphorus in starter fertilizer. p. 62-79.
In C. P. Ellington (ed.) Phosphorus for agriculture. Potash
& Phosphate Inst., Atlanta, GA.
Wright, D.L., I.D. Teare and B.T. Kidd.. 1988. Ontogeny of maize
in relation to sequential cropping. Trop. Agric. (Trinidad)
Table 1. Dry matter yield, total P uptake and P uptake per gram of
roots of two corn hybrids. Single degree-of-freedom
comparisons for effect of hybrid are shown at the bottom.
Experiment-i. (33 days after seeding).
P treatment Dry-matter yield Total P uptake
Rate Placementt Tops Roots P uptake per gram of roots
----g pot- ----- mg pot-'
0 -- 2.54 0.95
10 BC 3.16 1.14
20 BC 4.21 1.68
30 BC 4.89 1.85
10 WB 2.89 1.13
20 WB 3.56 1.51
30 WB 4.52 2.40
Non-responsivehybrid (NK 508)------------
0 -- 2.69 1.31 3.16 2.41
10 BC 3.49 1.68 3.56 2.05
20 BC 4.15 1.92 5.19 2.71
30 BC 4.58 2.28 6.74 2.99
10 WB 3.11 1.49 3.50 2.29
20 WB 3.87 2.14 5.10 2.31
30 WB 4.74 3.12 4.34 1.39
Isd (0.05) 0.64 0.45 1.15 0.87
Comparison Tops Roots Total-P Pg-1 roots
G4733 vs NK508 N.S. 31.02** 8.42** N.S.
tBC = P mixed with total soil volume, WB = P mixed with 25% of soil
volume. N was mixed with total soil volume in all treatments.
'**denotes significance at 1% probability. N.S. = not significant.
Table 2. Dry matter yield, total P and N uptake, P uptake per gram
of roots, and N uptake per gram of roots of two corn
hybrids. Single degree-of-freedom comparisons for effect
of hybrid are shown at the bottom. Experiment-2. (41 days
Dry-matter Uptake per
P treatment Nitrogen yield Total Uptake gram roots
Rate Placementt placement Tops Roots P N P N
---g pot-'--- --mg pot-1--
0 BC 1.16 1.15
30 BC BC 2.33 1.57
60 BC BC 2.98 2.03
60 BC BD 5.73 3.58
30 BD BD 4.62 3.19
60 BD BD 9.30 4.75
0 BC 1.95 1.91
30 BC BC 3.19 2.60
60 BC BC 5.39 3.81
60 BC BD 6.52 4.45
30 BD BD 6.99 4.68
60 BD BD 11.62 6.56 3
Isd (0.05) 1.34' 0.85
1.59 54 1.42 48
2.77 104 1.82 67
4.74 124 2.36 62
9.05 181 2.53 51
5.63 165 1.81 52
11.22 179 2.44 41
2.08 81 1.09 42
4.46 132 1.74 51
7.72 175 2.03 46
9.65 177 2.18 40
7.39 176 1.60 38
.2.43 192 1.92 29
1.64 23 0.47 9.9
Dry-matter Total uptake Uptake mcf g' roots
Comparison Tops Roots P N P N
G4733 vs NK 508 35.12**0 58.09** 19.70** 20.97** 10.28** 37.63*
tBC = N and P mixed with total soil volume, BD = band placement of
N and P 5 cm below soil surface and 5 cm horizontal from seed.
1**denotes significance at 0.01 probability.
Fig. 1 Effect of fertilizer placement on top
2 ... ......
Fig. 2 Effect of phosphorus on top dry-matter
2 -- .- ...-.......... ........
1 .5 --..............................
1 --.... -...---........ mg P/kg soil
0 .5 -................................... 0
NK 508 G4733
. I .