Forage mass and stocking rate of elephant grass pastures managed under agroecological and conventional systems

The objective was to evaluate elephant grass (Pennisetum purpureum Schum.) pastures, under the agroecological and conventional systems, as forage mass and stocking rate. In the agroecological system, the elephant grass was established in rows spaced by 3.0 m from each other. During the cool season ryegrass (Lolium multiflorum Lam.) was established between these rows, which allowed the development of spontaneous growth species during the warm season. In the conventional system the elephant grass was established singularly in rows spaced 1.4 m from each other. Organic and chemical fertilizers were applied at 150 kg of N/ha/year with in the pastures under agroecological and conventional systems, respectively. Lactating Holstein cows which received 5.0 kg/day supplementary concentrate feed were used for evaluation. The experimental design was completely randomized, with two treatments (agroecological and conventional systems) two replications (paddocks) and independent evaluations (grazing cycles). The pastures were used during the whole year for the agroecological system and for 195 days in the conventional year. The average values of forage mass were 3.5 and 4.2 t/ha and the stocking rates were 2.08 and 3.23 AU/ha for the respective systems. The results suggest that the use of the elephant grass under the agroecological system allows for best distribution of forage and stocking rate to be more uniform throughout the year than the use of elephant grass in conventional system.

本研究旨在评估农业生态系统（agroecological system）与常规系统（conventional system）下象草（*Pennisetum purpureum* Schum.）牧地的牧草生物量与载畜量。农业生态系统中，象草以3.0米的行距成行种植；凉季期间，在行间播种多花黑麦草（*Lolium multiflorum* Lam.），并预留空间供暖季自然萌发的物种繁衍。常规系统中，象草以1.4米的行距单行单一种植。农业生态系统与常规系统牧地分别以有机肥、化肥为肥源，年施氮量均为150 kg/ha。本试验选用泌乳期荷斯坦奶牛，每日补充精饲料5.0 kg。试验采用完全随机设计，设置2个处理（农业生态系统与常规系统）、2次重复（牧小区），并按放牧周期开展独立评估。农业生态系统牧地全年可利用，常规系统牧地年利用时长为195天。两个系统的平均牧草生物量分别为3.5 t/ha与4.2 t/ha，平均载畜量分别为2.08 动物单位/公顷（Animal Unit, AU）与3.23 AU/ha。研究结果表明，与常规系统相比，农业生态系统种植的象草可实现更均衡的牧草分布，全年载畜量也更为均匀。