Nitrate leaching using two potato-corn N-fertilizer plans on sandy soil

Abstract

Intensive use of inputs characteristic of irrigated potato ( Solanum tuberosum L.) production presents the risk of contaminating groundwater with fertilizer nitrate. Our research objectives were to compare two N fertilizer management plans with respect to: (1) crop production; (2) nitrate accrual to groundwater; and (3) N mass balance components. The two plans for a potato-corn ( Zea mays L.) crop sequence were: (1) ‘standard’ management using N fertilizer input rate and application timing typifying producer practices (46°N, 98°W); and (2) ‘conserving’ management using lower N fertilizer rates, more frequent and later N applications, and a rye ( Secale cereale L.) cover crop to scavenge N. The first crop (potato) was planted in 1992 and measurements continued through September 1996. Lysimeters measured soil water N flux and concentration passing a 2.3 m deep water-table interface. Higher N fertilizer rates of the standard plan did not result in statistically higher yields (α = 0.05). After two cycles of the potato-corn sequence standard and conserving plans had, 934 and 628 kg ha −1 applied N fertilizer; 519 and 478 kg ha −1 N removed in harvested crops; 244 and 92 kg ha −1 N lost in soil water effluent; and 14 and 7 mg l −1 nitrate N concentration in soil water effluent at the end of the study, respectively. Increases in nitrate concentration in lysimeter effluent were delayed by approximately one year from when higher N fertilizer rates were applied, consistent with our previous studies. Nitrate concentrations in lysimeter effluent were surprisingly low considering total N applied during the entire study.