Applied and Residual Nitrate-Nitrogen Effects on Irrigated Grain Sorghum Yield1
- Arthur B. Onken and
- Herbert D. Sunderman2
Multirate nitrogen studies were conducted for a 3-year period, on an irrigated clay loam soil at two locations, to determine the influence of applied and residual soil N on the yield of grain sorghum (Sorghum bicolor L. Moench). Soil samples were taken prior to fertilizer application in depth increments of 0–15, 15–30, 30–61, and 61–91 cm and analyzed for nitrate. Applied and residual soil NO3--N were found to influence grain yields. Regression analysis of the data showed highly significant relationships between (i) quantities of soil nitrates measured at upper depths to those measured at lower depths, and (ii) grain yield and applied N + residual NO3--N. Best correlations were obtained when residual NO3--N was included in the regression equation. Results indicated that soil samples taken to 15 or 30 cm would be sufficient for evaluation of residual nitrogen effects.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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