Dry matter accumulation and crude protein concentration in <i>Brachiaria</i> spp. cultivars in the humid tropics of Ecuador

Climatic conditions throughout the year and age of plants affect both yield and quality of forage grasses. In this research, we evaluated the effects of age of regrowth and seasonal conditions on dry matter accumulation and crude protein concentration in 5 cultivars of Brachiaria spp.: Señal, Xaraés, Marandú, Piatá and Mulato II, harvested at 2, 4, 6, 8 and 10 weeks after a uniformity cut, during the rainy and dry seasons. The variables were: total dry matter (TDM), leaf dry matter (LDM) and stem dry matter (SDM) yields, leaf area index (LAI), specific leaf area (SLA) and crude protein (CP) concentration. For TDM yield, in the rainy season there was no significant difference (P>0.05) among cultivars, with mean DM yield over 10 weeks of 6.34 t/ha; however, during the dry season Xaraés presented a higher (P<0.05) yield over 10 weeks than other cultivars (5.09 vs. 3.14‒3.89 t/ha).

Overall, mean DM yield in the dry season was only 62% of that in the wet season. In both periods, Señal tended to have the highest SDM yields, while Xaraés had the greatest (P<0.01) LDM yields in the dry season. Mulato II tended to have the highest CP concentrations throughout, especially in the dry season. This study was conducted in plots with plants only 12 weeks old at commencement. However, it indicated that all cultivars performed well and larger-scale studies of longer duration are warranted to test these cultivars under grazing, especially Mulato II, which showed both high dry matter yield and retention of high protein concentration throughout the study.