Nitrogen Soil Budgets in Contrasting Dairy Grazing Systems of Southern Chile, a Short-Term Study

Abstract

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 (Σ inputs) and all N outputs (Σ 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.

Ammonia and nitrous oxide emissions as affected by nitrification and urease inhibitors

“…as N 2 O precursor (Erisman et al 2007) (Denmead et al 1977) and the small wind tunnels methods (Lockyer 1984) on permanent grasslands in Southern Chile have shown that NH 3 volatilization ranged from 1.4 to 26.7% of the N applied as urea, being the main pathway for N losses on grassland soils (Salazar et al 2012a;Salazar et al 2014), grazing systems (Nuñez et al 2010), and from livestock production systems (Muñoz et al, 2016), probably contributing more to GHG emissions from grassland soils than direct N 2 O emissions. Studies in this area have also shown a low contribution of N losses by nitrate leaching (Salazar et al 2012b) and Vistoso et al 2012;Hube et al 2017).…”