| Studies in recent years have found that moderate drought stress has compensatory and overcompensatory effects,which will have a positive impact on the growth and development of crops,yield and quality,etc.Phosphorus fertilizer can enhance the adaptability of crops to the drought environment,promote the growth of crop roots,and increase the yield.In order to clarify the mechanism of the synergistic effect of dry early stress and phosphorus application on the compensation effect of soybean,and to provide a theoretical basis for the improvement of the overall drought resistance and water and fertilizer utilization efficiency of soybean,a pot experiment of soybean was conducted in this paper.There were two factors of water control and phosphorus application,and the water control level was set as mild water stress,moderate water stress and severe water stress.Three levels of phosphate fertilizer treatment were set up:low fertilizer（P2O5,9kg/hm2）,medium fertilizer（P2O5,72 kg/hm2）and high fertilizer（P2O5,129.6 kg/hm2）.Each treatment was applied with 165 kg/hm2 urea and 70 kg/hm2 potassium sulfate（K2O:50%）.Meanwhile,adequate water and high phosphorus control treatments were set.The main results obtained are as follows:（1）The rational combination of drought stress and phosphorus application could effectively improve the agronomic characters of soybean plants.Moderate drought stress at seedling stage can inhibit leaf growth,and leaf growth rate after rehydration has a"recoil"effect.Adequate phosphorus supply plays an important role in leaf growth after rehydration,and is the material basis for leaf to maintain a high"recoil"growth.Moderate drought stress and phosphorus application can effectively promote the growth of soybean stem diameter,build a stable plant shape,and inhibit the extravagant growth of plant height.（2）The rational combination of drought stress and phosphorus application could increase the dry weight of leaf and pod skin of soybean plants,promote the growth of root system,increase the dry matter weight,maintain a larger root-shoot ratio,and coordinate the growth of underground and above-ground parts.（3）The water consumption during the whole growth period of soybean was mainly affected by the degree of drought stress in the earlier period,and the water consumption decreased with the increase of drought stress.The rational combination of drought stress and phosphorus application can effectively reduce the evaporation of soybean water,improve the water use efficiency of soybean,and realize the effect of water saving and increasing yield of soybean.（4）The combined effects of drought stress and phosphorus nutrition had significant effects on the compensation effect of soybean yield and its component factors.Phosphorus nutrition could effectively improve the compensation positive effect of soybean seed number per plant,while drought stress could promote the compensation positive effect of soybean pod number per plant and 100 seed weight.Drought stress and phosphorus nutrition affect soybean yield through different ways respectively.When the two synergies,they can increase the pod number per plant,kernel number per plant and100 kernel weight of soybean plants,so as to promote soybean yield increase.（5）Through the regression fitting of the results of water use efficiency and yield,it was concluded that under the experimental conditions,the maximum water use efficiency appeared when the phosphorus application rate was 130 kg/hm2 and the drought stress degree was 44%（that is,when the soil water content was controlled at about 44%of the field holding）.The threshold range of yield overcompensation stress factor was as follows:phosphorus application rate was 60-160 kg/hm2;When the relative water content of soil is 35-50%;In addition,the maximum yield occurred when the phosphorus application rate was 160 kg/hm2 and the soil relative water content was 42%. |
