NITROGEN SOIL BUDGETS IN CONTRASTING DAIRY GRAZING SYSTEMS OF SOUTHERN CHILE, A SHORT-TERM STUDY

In recent years, the intensification of livestock production in Southern Chile has resulted in a high potential for environmental damage through nitrogen (N) losses, creating the need for the evaluation of N flows from these systems. The aim of the research was to determine N budgets and N use efficiency in two grazing systems in Southern Chile. For this, inputs and outputs were measured during one year on two grazing systems (heavy grazing, HG; and light grazing, LG). Also, a control treatment with no grazing (C) was considered. The annual N soil budget was determined by the difference between all N inputs (£ inputs) and all N outputs (X outputs). The results of the experiment indicate that HG treatments received the biggest N input (427, 359 and 288 kg N ha-1 yr-1 for HG, LG and C treatment, respectively), however this treatment also had the biggest N losses (406 kg N ha-1 yr-1), with a nitrogen recovery efficiency from fertilizer of 71%. In addition, herbage dry matter yield (DM) was greater in the HG than in the LG and C treatments (10.4; 8.1 and 7.1 t N ha-1 yr-1, respectively). Also, N concentration in the forage was higher in this treatment (2.9%) than in the LG (2.7%) and C (2.5%) treatments. The results indicate that HG increases N use efficiency in pastures in Southern Chile, increasing the herbage production and quality, but also increasing the potential for N losses to the wider environment. Farmers should consider this when choosing the appropriate grazing system.