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Residual Nitrate-N in Fine Sand as Influenced By N Fertilizer and Water Management Practices¹

ABSTRACT

A better understanding of the severity of NO³-N movement out of the crop root zone in irrigated sandy soils is needed. The objective of this study was to determine residual NO³-N after the corn (Zea mays L.) growing season from N applied at rates of (i) 112, (ii) 224, and (iii) 336 kg/ha in 1974 and (iv) 168, (v) 250, and (vi) 324 kg/ha in 1975. Nitrogen was applied as a single broadcast (B) application at the beginning of the corn growing season or injected (S) through the irrigation system at five equal increments before tasseling. Water application for both N application methods was attempted to be 0.8 W₂ water application treatment, residual NO₃-N averaged 0.22 kg/during all but the first 6 weeks of corn growth.

When N was broadcast-applied at seeding very little residual NO₃-N remained in the 150-cm sampling depth after the crop growing season, regardless of N application rate or water application amount. When the N was applied through the irrigation system (injected N), only the W₃ water application treatment resulted in leaching all NO³-N below the crop root zone. With injected N and W₂ water application treatment, residual NO₃-N averaged 0.22 kg/ha for each kg/ha of N applied. With injected N and W₁ application treatment NO₃-N increased linearly at 0.43 kg/ha for each kg/ha of applied N above the B₄ rate. At lower N application rates, residual NO₃-N was very low because this amount of N nearly equalled plant uptake. No overwinter NO₃-N was lost with the injected N treatments. These results showed that the injected N application method with proper water application management can greatly reduce the potential for NO₃-N movement below the corn crop rooting zone on fine sand soils.

¹ Contribution from Soil, Water, and Air Sciences, Science & Education Administration, USDA in cooperation with the Univ. of Nebraska, North Platte Station. Published as Journal Paper no. 5395, Nebraska Agric. Expt. Stn.

² Soil Scientist USDA-SEA, Akron, CO 80720 and Agricultural Engineer, Univ. of Nebraska, Lincoln, NE 68583.

Received for publication January 30, 1978. Accepted for publication August 7, 1978.