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

摘要

Two N fertilizer management plans were compared with respect to: (i) crop production; (ii) nitrate accrual to groundwater; and (iii) N mass balance components. The two plans for a potato-maize crop sequence were: (1) 'standard' management using N fertilizer input rate and application timing typifying producer practices in North Dakota, USA; and (2) 'conserving' management using lower N fertilizer rates, more frequent and later N applications, and a rye cover crop to scavenge N. The first crop (potato) was planted in 1992 and measurements continued to 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 (alpha=0.05). After two cycles of the potato-maize sequence standard and conserving plans had, 934 and 628 kg N/ha applied as fertilizer; 519 and 478 kg N/ha removed in harvested crops; 244 and 92 kg N/ha lost in soil water effluent; and 14 and7 mg nitrate/litre 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 previous studies. Nitrate concentrations in lysimeter effluent were low considering total N applied during the entire study.