M.A. IBRAHIM¹ and L. 't MANNETJE²

¹Centro Agronómico Tropical de Investigación y Enseñanza (CATIE), Turrialba, Costa Rica
²Agricultural University, Department of Agronomy, Wageningen, The Netherlands

Abstract

Dry matter (DM) yields and botanical composition of mixtures of Centrosema macrocarpum, Stylosanthes guianensis and Arachis pintoi with Brachiaria humidicola and B. brizantha were measured over 2.5 years of rotational grazing at 1.75 (LSR) and 3.0 (HSR) AU/ha in the humid Atlantic Zone of Costa Rica.
The legumes C. macrocarpum and S. guianensis virtually disappeared from the mixtures before the end of the experiment, whereas A. pintoi persisted well, especially at the high stocking rate in association with B. humidicola.
Mean monthly DM yields of mixtures exceeded 4 t/ha, but yields decreased significantly during the months of lower rainfall. At the low stocking rate, B. brizantha yielded more than 5 t/ha. A. pintoi formed a stable mixture with B. brizantha. The percentage of A. pintoi was higher with B. humidicola and this grass was practically eliminated in the mixture and replaced by weeds.
At the end of the experiment, A. pintoi represented 26% of total DM with B. brizantha at the high stocking rate. N yields of mixtures of A. pintoi were higher than those of stylo and centro. It was concluded that A. pintoi is the most grazing-tolerant legume of those tested for the humid tropics.