Compatibility, persistence and productivity of grass-legume mixtures for sustainable animal production in the Atlantic Zone of Costa Rica

The main objective of this study was to identify compatible and persistent grass-legume mixtures of high feeding value for forage improvement in the Atlantic Zone of Costa Rica. The study was conducted between September 1989 and October 1992 at LA)s Diamantes research station, Guápiles, Costa Rica. The treatments consisted of a factorial of three legumes (Centrosema macrocarpum(Cm) CIAT 5713, Stylosanthes guianensis (Sg) CIAT 184 and Arachis pintoi (Ap) CIAT 17434), two grasses (Brachiaria brizantha (Bb) CIAT 6780 and Brachiaria humidicola (Bh) CIAT 6339) and two stocking rates (1.75 (LSR) and 3.00 (HSR) AU/ha). Measurements were made on dry matter yields and botanical composition, legume persistence, nutritive value, liveweight gain (LWG) and soil fertility, carbon storage and soil compaction.

Dry matter yields were high in all mixtures in particular at the LSR and with Bb. Cm and Sg failed to persist during the 2.5 years of grazing while Ap was persistent, especially at the HSR. Ap proved to be too aggressive for Bh. Ap was more or less stable with Bb and it performed better at the HSR. Bh mixtures were invaded with unpalatable weeds while those of Bb were practically weed free.

Nutritive value of the mixtures was adequate for high beef production. LWG on Bb + Ap at the HSR was 937 kg/ha/year which was six times that reported for native pastures in the region and 459 kg higher than that of the monoculture of Bb.

Soil organic matter and total organic carbon were similar to those measured under primary forest and there was no evidence of high degree of soil compaction. From the results it is concluded that Ap was the most persistent legume studied and the mixture of Bb + Ap at the HSR was the most suitable combination for forage improvement in this region.