N leached under autumn urine plus the 200N fertiliser rate is plant root proliferation in response to the split fertiliser applications prior to urine application. Before the autumn urine application, the lysimeters had received 2 split applications of fertiliser, and prior to this, the lysimeter collection site had not received fertiliser for over a year. When plant roots encounter a zone of nutrients, they tend to proliferate within it by deploying primary and secondary lateral roots, and expand their capacity for nutrient uptake It is thought that these root system responses, also often termed “morphological plasticity”, are a natural coping mechanism for plants to overcome the heterogeneous supply of nutrients in the soil and effectively compete underground for nutrients It is possible that root proliferation occurred following the initial fertiliser applications, creating a higher capacity for the pasture to take up N upon urine application, compared to the treatments that received no fertiliser. In the case of the higher (400N) fertiliser rate, although root proliferation and additional plant uptake likely occurred, the additional fertiliser N supply added to the urine-N input possibly exceeded plant requirements that much more, generating the highest losses.