The Relationships of Nitrate Concentrations in Young Corn Stalks to Soil Nitrogen Availability and Grain Yields1
- K. V. Iversen,
- R. H. Fox and
- W. P. Piekielek2
The importance of N in crop production makes accurate estimation of the available N in the soil desirable, especially with increasing costs of N fertilizers and concern for environmental hazards associated with excessive fertilization. Although several soil N availability indices have been developed, none of those tested has had wide success in Pennsylvania. A 2-yr study was conducted in central Pennsylvania to determine if nitrate (NO−3) analysis of young corn plants (Zea mays L.) was significantly related to soil N availability. The NO−3 contents of basal stalks were determined weekly for several weeks after emergence in two N fertilizer response experiments in 1982 and 1983. The soil in sites in 1982 and 1983 were Murrill silt loam, a Typic Hapludult, and Hagerstown silt loam, a Typic Hapludalf, respectively. Stalk NO−3 −N increased with increasing N fertilizer rates. The effect of plant age on stalk NO−3 concentration varied between the 2 yr, probably due to hail damage or available water differences. Differences in stalk NO−3 among N fertilizer treatments increased with time in both years. The optimum time for sampling appeared to be approximately 30 days after emergence (DAE). Correlations of stalk NO−3 at this time with relative grain yield and N uptake were significant (r>0.94) both years. Based on regression lines, at approximately 30 DAE, the critical concentration of stalk NO−3−N (for 95% of the plateau yield) was about 11 g NO−3 kg−1 in 1982, and 16 g NO−3−-N kg−1 in 1983. Combined data from both years had a significant but lower correlation (r=0.754) between stalk NO−3 and relative grain yield, with an apparent critical concentration of 15.7 g NO−3−N kg−1. The potential for predicting soil N availability from NO−3 tissue testing appears possible if the environmental factors that affect tissue NO−3 accumulation can be identified and quantified.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © . .