Reducing nitrogen leaching losses in grazed dairy systems using an Italian ryegrass-plantain-white clover forage mix

Abstract

In grazed agricultural systems, animal urine patches are the major source of nitrogen (N) leaching losses and can cause a decline in water quality. Urine-N rates often exceed plant requirements, and there is a need for mitigation options to reduce the impact of agriculture on the environment. One approach is to use alternative forages to reduce urine-N loading rates, or to increase N uptake. This study used lysimeters to determine the N leaching losses, dry matter yields and N uptake following ruminant urine application to an Italian ryegrass-plantain-white clover forage mix (IRPWC, Lolium multiflorum Lam.-Plantago lanceolata L.-Trifolium repens L.) or perennial ryegrass-white clover (PRWC, Lolium perenne L.-T. repens L.). Three urine treatments were applied: Control (no urine), Urine Actual (urine from cows grazing each of the forages: 508, and 664 kg N/ha, for IRPWC and PRWC, respectively) and Urine 700 (700 kg N/ha). Compared with PRWC (113 kg N/ha), N leaching losses were 88.9% lower from IRPWC-Urine Actual (12.5 kg N/ha) and 45.5% lower from IRPWC-Urine 700 (61.8 kg N/ha). These reductions were attributed partly to the IRPWC having higher cool season activity and ability to take up N during the cool period, and partly to the lower concentration of urine-N, compared with PRWC. IRPWC is a promising alternative forage for future farm systems with the ability to reduce urine-N excretion from grazing animals and cause large reductions in N leaching losses while producing the same herbage dry matter yields as PRWC.