N-Source and Irrigation Effects on Nitrate Leaching1
- J. W. Bauder and
- 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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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