Coupling Effects Of Soil Water And Fertilizer On Intercropped Soybean And Spruce In Black Soil Region

In rolling hills with black soil in Northeast China, through pot experiment, effects of different water and fertilizer treatments on growth indices and photosynthetic rate of pure planting and mixed planting soybean and Picea koraiensis and soybean yield were compared and studied by test and analysis of factors, such as plant height, ground diameter, biomass, net photosynthetic rate and transpiration rate of pure planting and mixed planting soybean and Picea koraiensis and yield of soybean, etc.. Influence mechanism of two factors (water and phosphorus) and their coupling effect on soybean yield was discussed, to search for optimum proportion of water and phosphorus with best growth and highest yield of soybean in Black Soil Region, and to provide theoretical basis for reasonable fertilization and management and broadcast of agroforestry. The research result shows:(1) Effect of W and fertilizer coupling was significant on growth factors of pure planting and mixed planting soybean. For pure planting soybean, the main influencing factor in its growth period was W, and the best was under medium W and medium P. For mixed planting soybean, the main influencing factor was P for plant height and ground diameter at flowering and pod formation stage and seed-filling stage, and was W for all the three growth factors at other stages; generally, medium W and high P could meet the demand of soybean for W and nutrient. For pure planting Picea koraiensis, P was the main influencing factor for plant height, while WxP was the main influencing factor for ground diameter and biomass, and low P and W can meet the demand of all the three growth factors. For mixed planting Picea koraiensis, WxP was the main influencing factor for plant height and ground diameter, W was the the main influencing factor for biomass, and only high W and high P can meet its demand. From the above, we can see that the best combination was W2P2 for optimum growth factors of pure planting and mixed planting soybean and Picea koraiensis, that is, water was controlled at 65%-70% of field capacity and P fertilizer level at 1.05g per kg soil.(2) W was the main influencing factor for photosynthetic charateristics of pure planting and mixed planting soybean and Picea koraiensis. During the whole growth period, pure planting soybean had highest net photosynthetic rate at medium W and medium-low P, highest transpiration rate at medium W, and highest WUE at high W and medium-low P. Mixed planting soybean also had highest net photosynthetic rate at medium W and medium-low P during the whole growth period, highest transpiration rate at medium W and medium-low P, and highest WUE at low W and medium-low P. Pure planting Picea koraiensis had highest net photosynthetic rate at medium W and medium-low P, highest transpiration rate at medium-low P, and highest WUE at low W and medium-low P. Mixed planting Picea koraiensis had highest net photosynthetic rate at medium W and medium-high P, highest transpiration rate at high W and medium-high P, and had highest WUE at low W and medium-high P. For pure planting and mixed planting soybean and Picea koraiensis, the best combination was all W2P2 with optimum photosynthetic characteristics, that is, water was controlled at 65%-70% of field capacity and P fertilizer level at 1.05g per kg soil.(3) For pure planting soybean, the main influencing factor of yield and 100-seed weight was W, the main influencing factor of pod number per plant and seed number per plant was P, and yield and yield components were best at medium W and high P. For mixed planting soybean, the main influencing factor of yield, pod number per plant, seed number per plant and 100-seed weight was W, and yield and yield components were best at high W and high P. For pure planting soybean, the best combination was all W2P3 with optimum yield and yield components, that is, water was controlled at 65%-70% of field capacity and P fertilizer level as high level,1.4g per kg soil. For mixed planting soybean, the best combination was all W3P3 with optimum yield and yield components, that is, water was controlled at 80%-85% of field capacity and P fertilizer level as high level,1.4g per kg soil.