| The development of high-quality forage resources is one of the ways to develop animal husbandry and adjust the structure of agricultural industry in the Loess Plateau.Soybean（Glycine max（L.）Merrill）is a high-protein legume crop and therefore,in order to explore its feeding potential and enrich the annual legume forage resources in the Loess Plateau.This study introduced some soybeans varieties from the south China to the Longdong Loess Plateau of north China.,.The two year field work was conducted in 2018 and 2019.Thirty-three late-maturing soybean varieties native to southeast,south and southwest China were sown under spring and summer conditions.The agronomic traits such as days from emergence to the beginning of bloom（DTB）,dry matter yield（DM）,dry matter accumulation rate（DMAR）,growing degree-days（GDD）of the different soybean varieties were determined,nutritional quality indicators such as crude protein（CP）,neutral detergent fiber（NDF）,acid detergent fiber（ADF）,crude fat（CF）,ash and relative feeding value（RFV）of the whole plant were analyzed.Furthermore,the principal component analysis（PCA）based on technique for order of preference by similarity to ideal solution（TOPSIS）method with an entropy weight coefficient（EW）was used to comprehensively evaluate the feed traits,so as to judge the feeding potential of the soybean varieties.Main results obtained are as follows:（1）All introduced soybean varieties showed delayed flowering date under spring and summer sown conditions in both 2018 and 2019.DTB under spring sown was79-140 d,and DTB under summer sown was 54-89 d.The flowering date of some varieties in the study area was delayed by more than 40 days compared to when planted in their native environment.The flowering date of Guixia 1 was delayed up to86 d under the spring sown conditions in 2019.In addition,the days of delayed flowering in varieties native to South China were longer than those native to Southeast and southwest China.（2）Throughout the two years of study,the DM of soybean varieties sown in the spring period was significantly higher than summer sown.In 2018,varieties sown in the Spring period had the highest DM and the fastest DMAR.The DM of Guixia 1from South China is the highest,reaching up to 16.31 t·hm-2.Under the spring sown,the varieties with DM greater than 10 t·hm-2 were Guixia 7 and Huaxia 3.Under the summer sown,the varieties with DM greater than 10 t·hm-2 were Lanxidou,Xiaonongqiuyan,Nannong 99-10,Guixia 7,Huaxia 3,Qingpi,Tiegan.Whether in spring or summer sown,Guixia 7 and Huaxia 3 always have better production advantage.（3）On nutritional quality,there were interannual differences in all the quality indicators evaluated on the soybean varieties.The variation of CP among the varieties ranges between 14.25-19.18%in 2018 and 15.26-20.49%in 2019.RFV is highest under the summer sown conditions in 2019（149.2-267.02）.The RFV of Zhexian 85,Nannong 99-6,Guixia 7,Huaxia 3 and Zigondon varieties are always above 100.（4）The result from the PCA-based TOPSIS with EW revealed that under the spring sown conditions,the soybean varieties with comprehensive yield and quality scores above average were Guixia 7,Guixia 6 and Zigondon.While under the summer-sown condition,the soybean varieties with comprehensive yield and quality scores above average were Guixia 7 and Huaxia 3.Therefore,Guixia 7 from South China showed both yield and quality advantages under both spring and summer sown conditions.This study verified the idea of introducing soybeans varieties to higher latitudes areas as forage,by capitalizing using on the sensitivity of soybean to light and temperature.Therefore,based on the two years experiments on 33 southern soybean varieties under spring and summer sown,Guixia 7 variety has the best forage yield and forage quality,and could be studied further as candidate materials for breeding high-quality forage soybean special varieties. |
