Effects Of Biochar And Regulated Deficit Irrigation On Growth Physiology And Yield Of Soybean

With the steady rise of soybean production in China,the planting of soybeans had also shifted from a single yield increase goal to multiple goals of water saving,high yield and quality.Regulated deficit irrigation was a type of irrigation technology that implements a certain degree of water stress during the crop growth period to reduce vegetative growth and promote nutrient migration and distribution to reproductive organs and achieve water conservation purposes.Although regulated deficit irrigation could improve the water use efficiency of soybean,But the great extent and long duration of deficits would significantly reduce crop yield and quality.Therefore,it was of great significance to introduce water-saving materials into regulated deficit irrigation to alleviate the adverse effects of deficit on soybean yield and to achieve the goal of water-saving,high-yield and high-quality.This study selected biochar as a water-saving material.According to its characteristics of water and fertilizer retention to realize stable yield and yield increase.To study the effects of soybean growth characteristics,physiological characteristics,dry matter accumulation,root characteristics,quality,yield and water use efficiency under regulated deficit irrigation and biochar passed two-year-pot test.Determined the extent of regulated deficit irrigation and the optimal amount of biochar based on the regulated deficit irrigation model.Provide theoretical basis for achieving the goal of water saving and high yield of soybean.It was concluded that:(1)Adding 6t/hm2 of biochar under full irrigation and mild regulated deficit irrigation promoted soybean plant height and leaf area index,there was no significant difference between the two treatments.The increase of biochar under the severe deficit adjustment treatment is smaller than the treatment without adding biochar,and it is greatly different from the normal level.(2)Regulated deficit irrigation significantly inhibited dry matter accumulation in aboveground soybeans,it compared to full irrigation,the reduction is 9.6%-27.54%,mild regulated deficit irrigation did not inhibit dry matter accumulation in soybean roots;the dry matter accumulation of above-ground soybeans and roots increased with the increase of the amount of biochar added under the regulated deficit irrigation.Soybean yield is mainly affected by root volume and root length from the perspective of root morphology.Adding biochar can increase soybean root length under regulated deficit irrigation,but the effect is not significant on root volume.(3)Regulated deficit irrigation significantly reduced soybean SPAD(SPAD was a measure of the relative content of chlorophyll in plants)during flowering stage,regulated deficit irrigation had a certain compensation effect on soybean SPAD value during the pod-setting stage,There was no significant difference between mild regulated deficit irrigation and full irrigation treatment.Biochar could increase soybean SPAD value under the same regulated deficit irrigation,compared with the treatment without adding biochar,the average increase was 5.04%-6.86%.(4)After regulated deficit irrigation,the net photosynthetic rate of soybean showed a decreasing trend,with an average reduction of 23.97%-38.4%,the net photosynthetic rate of soybean began to recover on the 20 th day after flowering stage,The degree of recovery is shown as mild deficit adjustment is greater than severe deficit adjustment;The addition of biochar did not reduce the stomatal conductance of soybean leaves due to water deficit under mildly regulated deficit irrigation,Simultaneous transpiration rate and net photosynthetic rate were not significantly different compeard with full irrigation;With the increase of stomatal conductance,the increase rate of transpiration rate is smaller than the increase rate of net photosynthetic rate under the condition of regulated deficit,and finally the water use efficiency of leaves is improved,the water use efficiency of leaves under regulated deficit treatment and full irrigation treatment increased by an average of 12.62%-64.89%.(5)The effect of biochar was not obvious on soybean quality,Severe regulated deficit irrigation would significantly increase soybean fat content and protein content,compared with full irrigated and mild regulated deficit irrigation,protein and fat content increased by 0.89%-2.4%,1.08%-4.85%,respectively.W3B1 had the best overall quality through queue scoring.(6)The application of biochar increased average yield by 5.03%-28.42.This effect was more pronounced in mild regulated deficit irrigation and full irrigation.The treatments with the highest test yield in two years were the W1B1 and W2B1 treatments,of which the W2B1 treatment had the lowest water consumption and saved 10.37%.Based on the fuzzy optimization model,W2B1 was selected as the optimal treatment by selecting multiple targets for soybean yield,quality,and water use efficiency.To sum up,the application of mildly regulated deficit irrigation(55%-60%?f)and 6t/hm2 of biochar for soybeans can achieve higher yield and quality and WUE under the condition of ensuring normal growth physiological characteristics,it was the best combination of water saving,high yield and high quality.