Nitrate Leaching Through Sandy Soil as Affected by Sprinkler Irrigation Management

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Abstract
Nitrate‐N (NO3) leaching losses were quantified for irrigated corn (Zea mays L.) grown on a Valentine sand using a ceramic candle extraction system buried at 1.5‐m depth. Irrigation rates were 85% and 130% of evapotranspiration (ET). Total dry matter, grain yield and crop N uptake were not significantly affected by irrigation level. During the two year study average annual flow‐weighted NO3‐N concentrations in extracted soil water ranged from 28.3 to 75.2 mg NO3‐N L−1 for 0.85 and 1.3 ET irrigation levels, respectively. In 1976 the 0.85 ET treatment had 37 ha‐mm of soil water percolation and leaching of 12 kg NO3‐N. The 1.3 ET treatment lost 191 ha‐mm of percolation and 75 kg NO3‐N. In 1977 132 ha‐mm of soil water was lost by percolation and 109 kg NO3‐N ha−1 for 0.85 ET and 182 ha‐mm and 146 kg NO3‐N ha−1 for the 1.3 ET irrigation level. The higher soil water percolation and NO3‐N losses in 1977 resulted from over‐winter precipitation and early spring leaching of the previous year's residual nitrate. In‐season NO3‐N leaching was reduced by matching irrigation to ET. To effectively reduce NO3‐N leaching N fertilizer rates must match crop yield requirements to reduce soil NO3‐N carryover and irrigation scheduling must be used on sands.