Nitrogen Management in Zone-Till Corn Benton County 2000

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

Spring Stalk Nitrate Nitrate Test Leaf Test Yield No. Treatment (ppm)* Rating** (ppm)# (Bu/A)

1 O lb/A Nitrogen 15 2.3 51 124.1 2 50 lb/A N Spring PRE 28 3.2 232 133.4 3 100 lb/A N Spring PRE 39 3.2 1090 130.8 4 100 lb/A N Spring Sidedress 12 2.9 1670 129.6 5 150 lb/A N Spring PRE 52 3.8 2603 136.8 6 200 lb/A N Spring PRE 57 4.0 3423 125.9 7 150 lb/A N Fall 29 3.3 817 133.7 8 150 lb/A N Fall + 50 lb/A N Spring 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.