Effect of two irrigation rates on nitrate leaching from diverse or standard forages receiving spring deposited urine

ABSTRACTThe effect of two irrigation rates on nitrogen (N) harvested by diverse and standard forages, and the subsequent effect on nitrate (NO3−) leaching losses from spring deposited urine was investigated. An experiment, using lysimeters (500 mm diameter, 700 mm deep), was conducted to measure herbage dry matter yield, herbage N harvested and NO3– leaching loss beneath a ‘standard forage’ and a ‘diverse forage’. Cow urine was applied to the forages at either 500 or 700 kg N ha–1, and following the urine application, irrigation was applied at a rate of 18 mm approximately every 3 days (high) or 9 mm approximately every 3 days (low) from November to April. Compared with low irrigation, NO3– leaching losses were 88–97% lower under high irrigation at a urine application rate of 700 kg N ha–1, and were less than 4 kg N ha–1 from all high irrigation treatments.