Variations in the nutritive value of soybean straw and their use with agronomic traits for breeding assays

1 SUMMARY To make full use of soybean [ Glycine max (L.) Merr.] straw (SBS) as roughage, the SBS nutritive values with agronomic traits of 35 varieties were evaluated for breeding. The plant height of all soybeans ranged from 47.2 to 175.5 cm, and grain yield ranged from 2030.6 to 5059.7 kg ha –1 . The contents of crude protein, crude fibre, crude ash, nitrogen-free extract (NFE), neutral detergent fibre (NDF), acid detergent fibre (ADF), and acid detergent lignin (ADL) of SBS were 31.8–63.6 g kg –1 , 447.5–566.9 g kg –1 , 45.7–67.8 g kg –1 , 284.3–427.1 g kg –1 , 722.1–808.5 g kg –1 , 491.2–572.2 g kg –1 , and 128.3–195.8 g kg –1 , respectively. In vitro dry matter digestibility (IVDMD) and relative feed value (RFV) were 31.68–43.86% and 52.14–65.38%, respectively. The straw composition, excluding crude ash, hemicelluloses and cellulose, was significantly different among varieties ( P < 0.05). The plant height and contents of NDF, ADF, and ADL had negative correlations with IVDMD ( P < 0.01), and IVDMD was positively correlated with grain yield, NFE content and RFV ( P < 0.01). Considering the straw quality and grain yield, varieties with short plants and high grain yield should be selected as soybean breeding materials.