Dry matter production and chemical composition of tropical forage legumes under different shading levels

ABSTRACT. This study aimed to evaluate the shading influence on production and qualitative traits of four tropical forage legumes (calopo, puero, archer and perennial soybean). Legumes were cultivated under levels of artificial shading (0; 30; 50 and 70%) from January 2006 to June 2007. Dry matter production (DM), crude protein (CP), neutral detergent fiber (NDF), cellulose (CEL), hemicellulose (HEM) and lignin contents were evaluated. In the summer, increases in legumes DM yield were observed when grown under increasing shading levels. Calopo, puero, and archer production showed quadratic effect. Regression analysis derivation for dry matter yield showed levels of maximum values at 35.0; 33.78 and 45.45% in the summer and 34.94; 34.83 and 33.29% in the fall. Significant effect of species for CP, NDF, CEL, HEM and L/S (leaf/stem) ratio and shading level effect for NDF, CEL, HEM and L/S ratio were observed in the summer, however, no interaction was reported. In addition, significant effect of species for CP, NDF, CEL, HEM and L/S ratio was observed in the autumn. Only L/S ratio presented a negative response according to increasing shading levels. The shading promoted an increase in the fiber components and a decrease in the leaf/stem ratio, and the perennial soybean was the most tolerant to the increased shading.

摘要：本研究旨在评估遮阴对四种热带饲用豆科植物（calopo、puero、archer及多年生大豆（perennial soybean））的产量与品质性状的影响。供试豆科植物于2006年1月至2007年6月期间，在0%、30%、50%及70%梯度的人工遮阴条件下种植。本研究测定了干物质产量（dry matter production, DM）、粗蛋白（crude protein, CP）、中性洗涤纤维（neutral detergent fiber, NDF）、纤维素（cellulose, CEL）、半纤维素（hemicellulose, HEM）及木质素含量。夏季时，随遮阴梯度提升，供试豆科植物的干物质产量显著升高；calopo、puero与archer的产量表现出二次效应。对干物质产量的回归分析推导显示，夏季时三者的最大产量对应的遮阴梯度分别为35.0%、33.78%及45.45%，秋季时则分别为34.94%、34.83%及33.29%。夏季观测到品种对CP、NDF、CEL、HEM及叶茎比（leaf/stem ratio, L/S）存在显著影响，同时遮阴梯度对NDF、CEL、HEM及叶茎比存在显著影响，但二者未表现出交互作用。此外，秋季观测到品种对CP、NDF、CEL、HEM及叶茎比存在显著影响。仅叶茎比随遮阴梯度升高呈现负向响应。遮阴处理可提升纤维组分含量并降低叶茎比，其中多年生大豆对遮阴强度升高的耐受性最强。