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This article in AJ

  1. Vol. 72 No. 4, p. 593-596
    Received: July 13, 1979

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N-Source and Irrigation Effects on Nitrate Leaching1

  1. J. W. Bauder and
  2. B. R. Montgomery2



Efficiency of N fertilizer sources and N leaching below the root zone of irrigated crops are concerns of agronomists and environmentalists alike. Practical data comparing the efficacy and leaching susceptibility of various N sources are necessary for resource management and as input to current nutrient transport models. This study was conducted to evaluate the effects of N fertilizer source and irrigation management on distribution of N and on leaching of NO3-N within the root zone of a small-grain crop.

Undisturbed columns of Maddock fine sandy loam, a well-drained Udorthentic Haploboroll, were ciopped to wheat (Triticum aestivum L. cv. 'Era') in a greenhouse study. Three N source, Ca(N03)2, (NH4)2SO4, and CO(NH3)2, and a check treatment were compared in factorial combination with two irrigation levels. Nitrate and NH4+-N concentrations in leachate were measured throughout the study. Total-N and NO3--N in the soil columns were measured at harvest. Percolation from the columns was the same for all treatments. Essentially, none of the applied N leached below the rooting depth as either NH4+-N or N03--N. Maximum depth of NO2-- N leaching, which was approximately 60 cm, occurred with Ca(N03)2 and high volume-low frequency irrigations. No N03--N accumulated below 20 cm when (NH4)2SO4, and CO(NH2)2 were applied, followed by low volume-high frequency irrigations. Total amount and depth of N03-3-N leached were dependent on irrigation method and N source. High volume-low frequency irrigations leached solutes to a greater depth than did low volume-high frequency irrigations. Contribution of N source to N03--N leaching was generally CO(NH2)2≤ check<(NH4)2S04<Ca(N03)2, although N02--N leaching from urea treatments may have been offset by ammonia volatilization following treatment applications. Nitrate leaching from N fertilizers under irrigation may be minimized by timely applications of ammonia based fertilizers and low volume irrigations to minimize leaching below the crop root zone.

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