Pasture degradation and restoration by legumes in humid tropical Costa Rica

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 norther n AZ is considered by taking competition for land among cattle ranching, cr opping and forestry into account. Current beef production systems are unsus tainable, with soil-nitrogen mining calculated at 50-65 kg/ha annually. Ove r time, stocking rate, pasture area, pasture production and economic return s will decrease. Once naturalised pasture production reaches approximate to 5 t dry matter/ha/yr, half of the current pasture area is expected to be a bandoned and beef production to drop to 25% of the current level. Replaceme nt of degrading naturalised pastures by sustainable grass-legumes will main tain beef production at some 90% of its current level. Compared with the en d-point for the beef cattle sector if current soil-mining practices continu e, this replacement results in a gain of some US $7.1 M/yr in economic surp lus. The break-even point for individual farmers for replacement of natural ised pastures by grass-legumes depends on the type of production system, so il resources and pasture age. For some farmers, this moment is already here , whereas for others, it is economically attractive to postpone this replac ement for a number of years.