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This article in AJ

  1. Vol. 77 No. 6, p. 927-932
    Received: Oct 12, 1984

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The Relationships of Nitrate Concentrations in Young Corn Stalks to Soil Nitrogen Availability and Grain Yields1

  1. K. V. Iversen,
  2. R. H. Fox and
  3. 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 (NO3) analysis of young corn plants (Zea mays L.) was significantly related to soil N availability. The NO3 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 NO3 −N increased with increasing N fertilizer rates. The effect of plant age on stalk NO3 concentration varied between the 2 yr, probably due to hail damage or available water differences. Differences in stalk NO3 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 NO3 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 NO3−N (for 95% of the plateau yield) was about 11 g NO3 kg−1 in 1982, and 16 g NO3−-N kg−1 in 1983. Combined data from both years had a significant but lower correlation (r=0.754) between stalk NO3 and relative grain yield, with an apparent critical concentration of 15.7 g NO3−N kg−1. The potential for predicting soil N availability from NO3 tissue testing appears possible if the environmental factors that affect tissue NO3 accumulation can be identified and quantified.

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