Improving the nitrogen cycling in livestock systems through silvopastoral systems

Abstract

Conventional livestock are monoculture systems where the major species are native grasses or African grasses, with biomass production being limited by seasonality of rainfall and low soil fertility. In animal production systems, the pasture degradation is associated with the nitrogen (N) cycle. Therefore, if farmer applied no subsequent fertilizer, milk production or live weight gains have been gradually reduced. As animals slowly gain weight, they produce more methane (CH4) and nitrous oxide (N2O). This has led to the search for strategies to help minimize the impacts of livestock, and the excessive application of fertilizers, on the environment and natural resources. One strategy with promising results that has been developed in Latin America is the conversion of traditional livestock systems to silvopastoral systems (SPS), which include the establishment of shrub legumes at high densities and forage grasses aimed at increasing livestock profitability. With the association of legumes and forage grasses, forage quality can increase, more than 100%, compared to monoculture-based pastures and, consequently, production costs related to the purchase of imported cereal grains and nitrogen fertilizers are reduced. On the other hand, changes in climate and graz-ing pressure to increase stocking rate have resulted in extensive degradation of existing vulnerable pastures, which favour poorly palatable, perennial species affecting directly livestock production and enhancing greenhouse gas (GHG) emissions and the loss of soil carbon and nitrogen stock severely affecting soil fertility. The importance of the association of species of legumes with grasses and Leucaena (Leucaena leucocephala L., (Lam.) de Wit) is an environmentally friendly proposal of positive interactions to improve soil fertility and animal productivity. Overall, improving forage quality and N efficiency of dietary nutrients is an effective way of decreasing GHG. Silvopastoral systems (SPS) are used successfully in many regions around the world, and there is considerable evidence that SPS can increase production efficiency, increase carbon sequestration and improve N cycling on land used for livestock production.