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

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. [ABSTRACT FROM AUTHOR]