Pasture degradation and restoration by legumes in humid tropical Costa Rica

Abstract

A system-analytical approach was used to quantify effects of degradation of naturalised pastures and to explore options for restoration by sustainable legume-based pastures in beef production systems in the northern Atlantic Zone (AZ) of Costa Rica. As well as field level analyses, the whole northern AZ is considered by taking competition for land among cattle ranching, cropping and forestry into account. Current beef production systems are unsustainable, with soil-nitrogen mining calculated at 50‐65 kg/ha annually. Over time, stocking rate, pasture area, pasture production and economic returns will decrease. Once naturalised pasture production reaches ≈ 5 t dry matter/ha/yr, half of the current pasture area is expected to be abandoned and beef production to drop to 25% of the current level. Replacement of degrading naturalised pastures by sustainable grass-legumes will maintain beef production at some 90% of its current level. Compared with the end-point for the beef cattle sector if current soil-mining practices continue, this replacement results in a gain of some US $7.1 M/yr in economic surplus. The break-even point for individual farmers for replacement of naturalised pastures by grasslegumes depends on the type of production system, soil resources and pasture age. For some farmers, this moment is already here, whereas for others, it is economically attractive to postpone this replacement for a number of years.