Regulating Effects of Fertilizing Models on Root Morphological Restructure and Yield Formation of Soybean in Loess Arid Region of China

In order to explore the relationship between root system construction, biomass distribution and yield formation of dry land soybean through the innovation of soybean fertilization mode in Loess Plateau, so as to realize high-quality, high-yield and high-efficiency cultivation of soybean in Loess Hilly and arid area, we took Fendou 78 as the research object, six treatments arranged as CK(bare land, N-30 kg·ha^-1), N(film mulched, N-30 kg·ha^-1), NPK(film mulched, N-60 kg·ha^-1; P₂O₅-30 kg·ha^-1; K₂O-30 kg·ha^-1), 2 NPK(film mulched, N-90 kg·ha^-1; P₂O₅-45 kg·ha^-1; K₂O-30 kg·ha^-1), NPK-O(film mulched, N-90 kg·ha^-1; P₂O₅-45 kg·ha^-1; K₂O-30 kg·ha^-1; optimized organic soil-2.5 t·ha^-1)and NPK-B(film mulched, N-60 kg·ha^-1; P₂O₅-30 kg·ha^-1; K₂O-30 kg·ha^-1; microbial fertilizer-10 kg·ha^-1), with randomized block design and repeated 3 times. The relationship between soybean root-shoot development and yield formation was analyzed under different fertilizer strategies. The results showed that:（1） Optimized chemical fertilizer strategies improved soybean yield to a significant increase level by 27.4%, but along with the 2.1% yield loss due to chemical fertilizer application amount increase. Inversely, NPK-O and NPK-B significantly promoted the soybean yield by 53.3% and 11.1%.（2） The harvest index（HI） of soybean increased by 7.0%-22.2% and root to shoot rate（RSR） decreased by 3.3%-14.1% under NPK-O and NPK-B, which provided an efficient way for preventing the root superfluous growth, and then motivated the carbohydrate simulating to soybean seeds.（3） Root dry weight was astricted but root length and surface area improved by 17.7%-21.6% and 30.7%-36.7% respectively under NPK-O and NPK-B, compared with that in only chemical NPK application, indicated that root spatial arrangement was optimized, and then stimulated root function and established a foundation for the seeds yield and water use efficiency increase in dryland soybean. Finally, additional organic and microbial fertilizer input improved root water-nutrients uptaking and soil environmental adaptation in soybean, based on the root thinner and longer in the vertial soil layers, all the regulations in root and shoot biomass stimulation were beneficial to soybean yield increase stably, and to a favourable in agricultural ecolotical-economical benefits on the Loess Plateau.