Forage mass and nutritional value of elephant grass intercropped with forage legumes1

ABSTRACT Forage-legume systems are a sustainable and competitive alternative for improving pasture yield and quality because of the symbiotic nitrogen fixation capacity and high nutritional value of legumes. This study aimed to evaluate the forage mass, nutritional value, and nutrient export rate in three forage systems (FS): FS1, with elephant grass (Pennisetum purpureum) (EG), annual ryegrass (Lolium multiflorum) (AR), and spontaneous growth species (SGS); FS2, with EG + AR + SGS + arrowleaf clover (Trifolum vesiculosum); and FS3, with EG + AR + SGS + forage peanut (Arachis pintoi ). The experiment was arranged in a completely randomized design, with three replicates, and repeated measures over time. Results of pre-grazing forage mass were 3.5, 3.8, and 3.9 t/ha, and crude protein export were 1.4, 2.1, and 2.3 t/ha, for the treatments FS1, FS2 and FS3, respectively. Highest crude protein, in situ dry matter digestibility and total digestible nutrients, and lowest neutral detergent fiber were found in the intercropping system with forage peanut, especially in winter. Nutritional values were also better in legume-systems than the non-legume system.摘要 饲草-豆科种植体系凭借豆科作物的共生固氮能力（symbiotic nitrogen fixation）与较高营养价值，成为提升牧场牧草产量与品质的可持续且兼具竞争力的替代方案。本研究旨在评估三种饲草种植体系（forage systems, FS）的饲草生物量（forage mass）、营养价值（nutritional value）及养分输出率（nutrient export rate），具体体系如下：FS1由象草（elephant grass, *Pennisetum purpureum*, EG）、多花黑麦草（annual ryegrass, *Lolium multiflorum*, AR）与自然生长物种（spontaneous growth species, SGS）构成；FS2为象草+多花黑麦草+自然生长物种+箭叶三叶草（arrowleaf clover, *Trifolium vesiculosum*）；FS3为象草+多花黑麦草+自然生长物种+饲用花生（forage peanut, *Arachis pintoi*）。本实验采用完全随机设计（completely randomized design），设置3次重复，并开展重复时间序列测量。针对FS1、FS2、FS3三个处理，放牧前饲草生物量分别为3.5、3.8与3.9 t/ha，粗蛋白（crude protein）输出量分别为1.4、2.1与2.3 t/ha。其中，搭载饲用花生的间作体系粗蛋白含量、原位干物质消化率（in situ dry matter digestibility）与总可消化养分（total digestible nutrients）均为最高，中性洗涤纤维（neutral detergent fiber）含量最低，该优势在冬季尤为显著。此外，豆科参与的种植体系其营养价值亦优于非豆科种植体系。