Irrigated dairy pasture yield and water use efficiency responses to summer applied nitrogen

Abstract

Two experiments determined the potential of N fertiliser to maximise the conversion of summer (October to April) irrigation water to pasture dry matter (DM) in southwest Victoria, Australia. DM consumed increased with increasing N (0 to 100 kg N/ha per grazing, and 50 to 200 kg N/ha every second grazing). Applications of 75 to 100 kg N/ha every grazing, and 150 to 200 kg N/ha every second grazing resulted in the highest water use efficiencies (improvements of 25 to 70% in Year 1, 40 to 63% in Year 2). Applications of 25 kg N/ha every grazing and 50 kg N/ha every second grazing led to the highest N response efficiencies (10 to 19 kg DM/kg N). The increases in DM consumed in response to N fertiliser were similar to responses noted for N applied during autumn, winter and spring in similar environments to the current experiments. Keywords: dry matter, perennial ryegrass, urea, water use efficiency