Evaluation of forage quality in various soybean varieties and high-yield cultivation techniques

The rising demand for animal protein has intensified forage shortages and restricted pasture availability, underscoring the critical need for effective dual-purpose animal feeds. This study aims to evaluate the potential of vegetative soybeans as animal feed by assessing their nutritional value and productivity. Specifically, it explores the feasibility of using late-maturing soybean varieties, adapted to low latitudes, as forage in high-latitude regions and examines the impact of different planting dates on their growth and effectiveness during limited growing seasons. To achieve these objectives, a series of field and controlled experiments were conducted. The first experiment assessed 418 mid-maturing soybean varieties from the Huang-Huai-Hai Basin in China for their nutritional value as forage during 2020 and 2021. The second experiment tested late-maturing and photoperiod-sensitive soybean varieties, including "ZGDD" and the methionine-enhanced material "Ox-CGS," under tropical conditions with extended daylight. The third experiment evaluated forage soybeans sown on June 19th, July 14th, and August 8th, 2022, to determine their yield and protein content. Results showed that the first experiment yielded an average protein content of 24.7 %, ether extract content of 1.9 %, neutral detergent fiber content of 41.9 %, and acid detergent fiber content of 27.3 %, with a relative feeding value of 153, surpassing local standards for high-quality leguminous forage. The second experiment demonstrated that extended daylight increased crude protein yield by 3.7 times compared to Chinese soybean seed yields, and "Ox-CGS" showed a 24.2 % increase in methionine content. The third experiment revealed that forage soybeans achieved a crude protein yield of 0.95 t/ha within 60 days, exceeding the 2022 average of 0.68 t/ha for seed soybeans in China. The findings indicate that photoperiod-sensitive soybeans can be effectively used as forage over extended periods, utilizing artificial lighting or cultivation in higher latitudes, and that short growth cycles enhance crude protein accumulation. This research highlights the potential of soybeans to alleviate forage shortages, improve land use efficiency, and contribute to food security and agricultural development, especially on marginal lands and in regions with limited growing seasons.