Nitrogen Management in Zone-Till Corn – Benton County 2000
Jim Fawcett, Greg Brenneman, and Linda Fischer
ISU Extension
The purpose of this demonstration was to show various tools available to corn
producers to aid in nitrogen management. Corn was planted zone-till (fall strip tilled) on
April 28, 2000 on soybean ground. Various rates of nitrogen (ammonium nitrate) were
spread by hand after planting prior to corn emergence on May 3, 2000 and were
sidedressed by hand on May 31. Plots were 4 rows (10 feet) wide by 50 feet long and
were arranged in a randomized complete block design with three replications. Some plots
had received a fall application of 150 lb/A N as anhydrous ammonia and others had
received no fall nitrogen. Soil samples were pulled on May 24 when the corn was at V4
for soil nitrate analysis. A visual analysis of the corn leaves for nitrogen deficiency
symptoms was made on August 15. Stalk samples were collected on September 29 for
stalk nitrate analysis and the corn was hand harvested for yield.
The optimum rate of nitrogen at this site was a spring application of 50 lb/A
(Table 1). No significant yield increases were observed with additional nitrogen. There
also appeared to be a slight yield decrease with the highest nitrogen rate (200 lb/A),
which may have been due to greater lodging of the corn. The soil nitrate test performed
well in anticipating the nitrogen needs of the crop. The stalk test indicated excesses in
nitrogen with the 150 lb/A spring application of nitrogen, but not with the same rate
applied in the fall, suggesting greater nitrogen losses with the fall applied nitrogen.
Nitrogen Management in Zone-Till Corn – Benton County 2000
Results
No.
Treatment
1
2
3
4
5
6
7
8
O lb/A Nitrogen
50 lb/A N Spring PRE
100 lb/A N Spring PRE
100 lb/A N Spring Sidedress
150 lb/A N Spring PRE
200 lb/A N Spring PRE
150 lb/A N Fall
150 lb/A N Fall
+ 50 lb/A N Spring
Spring
Nitrate
Test
(ppm)*
Leaf
Rating**
Stalk
Nitrate
Test
(ppm)#
Yield
(Bu/A)
15
28
39
12
52
57
29
2.3
3.2
3.2
2.9
3.8
4.0
3.3
51
232
1090
1670
2603
3423
817
124.1
133.4
130.8
129.6
136.8
125.9
133.7
48
3.4
2107
137.6
LSD (0.1)
7.5
*Critical concentration approximately 25 ppm.
** Rating is the number of leaves below ear leaf to first leaf with N deficiency symptoms
on more than half of leaf (Average of 10 plants per rep).
# Low = less than 250
Marginal = 250-700
Optimal = 700-2000
Excess = greater than 2000
We wish to thank Dan Van Steenhuyse and B.J. Wayson for providing the land
and assistance, and the Monsanto Company for their cooperation and for providing the
funds for the nitrogen analysis.