Effects of Planting Density and Cutting Time on Hay Yield and Nutritional Value of Forage Soybean HN389

Forage soybean is an important source of high protein forage. Variety screening and breeding not only can solve the adjustment of agricultural planting structure, but also can provide a large amount of high-protein forage material, and effectively solve the problem of a serious shortage of high-protein forage in herbivorous animal husbandry in China. In this study, the feeding-type soybean strain HN389 was selected as experimental material, with three planting densities of 270000, 405000 and 540000 plants · hm-2 and three cutting periods of the initial pod stage (R1), the initial grain stage (R2) and the early mature stage (R3) were set to determine the yield and feeding quality, in order to obtain the best planting density and harvest time of the variety. The results showed that in forage soybean strain HN389 at the R1 and R2 stages, plant height increased with increasing planting densities, while fresh and dry weight per plant decreased with increasing planting densities, and there was no significant difference at the R3 stage. The yield of hay at the R1, R2 and R3 stages increased firstly and then decreased with the increase of planting densities, and the yield per hectare was R3>R2>R1. The order of contents of crude protein (CP), neutral detergent fibers (NDF) and acid detergent fiber (ADF) in feeding quality of HN389 were R2>R1>R3, and ether extract (EE) content order was R3>R1>R2, and there was no significant difference among different groups. Two principal components were extracted from five forage indexes including CP, NDF, ADF, EE and fresh grass yield by principal component analysis. The cumulative contribution rate of principal components 1 and 2 was 90.053％, and their characteristic values were 3.617 and 0.885, respectively. After a comprehensive evaluation, harvested at the R3 stage and the density was 405000 plants · hm-2, HN389 had the highest comprehensive score of 0.344, yield of 38035.53 kg · hm-2, CP, NDF, ADF and EE contents of 17.61％, 17.61％, 21.54％ and 3.81％, respectively.