Effects Of Biochar On Rice Growth And WUE Under Different Water And Fertilizer Conditions

Shortage of water resources and serious pollution of water bodies have posed new challenges to the mode of agricultural irrigation in China.On the one hand,rice,as the main grain crop in China,accounts for 70%of the total water used for agriculture.The irrigation mode of rice is mainly irrigated irrigation,with serious waste and the utilization rate of irrigation water is only about 40%,far less than 80%of developed countries.On the other hand,excessive use of chemical fertilizers,especially nitrogen fertilizers,has caused a series of problems such as non-point source pollution and so on.In the drought field tests of wheat,corn,soybean and tomato,the relevant scholars found that the application of biological carbon to soil could effectively improve the soil properties and increase the crop yield.In paddy rice production,the soil environment of paddy field with saturated unsaturated circulation alternated with irrigation is quite different from that of upland soil.In this paper,the effects of biochar on soil physical and chemical properties,rice growth and water productivity（WUE）under different water and fertilizer conditions were studied.The effects of biological charcoal on soil bulk density,saturated water content,field water holding capacity and soil moisture characteristics were studied through laboratory experiments.The performance and effects of biological charcoal on different irrigation,fertilization and cultivation methods were studied in two year field experiments,and the effect of biological carbon on soil water in paddy soil was verified.The effects of fertilizer conservation on the parameters of rice growth and the effect on rice yield were studied,and the effects of water and fertilizer management and cultivation methods and their interaction effects on rice production,soil nitrogen leaching,water and nitrogen resources consumption and utilization ratio were analyzed.The main conclusions are as follows:1.biochar can effectively reduce soil bulk density,and soil bulk density has a linear negative correlation with the amount of carbon application.The greater the amount of carbon application,the smaller the soil bulk density.Therefore,the addition of biological carbon in the soil consisting of solid and liquid gas can reduce the soil roughness and increase the permeability of the soil,which is beneficial to the seed germination and the growth of the root system.2.the soil saturated water content and the field water holding capacity increased after the application of biological carbon,and the saturated water content and the field water holding capacity of the soil increased with two changes with the amount of carbon applied.It can be seen that the application of biological carbon can increase the soil saturated water content and field water holding capacity.With the increase of the amount of biological carbon,the soil saturated water content and the growth rate of field water holding capacity gradually decrease,and finally stop the growth.Using the van Genuchten-Mualem model,the soil moisture characteristic curve can be fitted well.The water content of each soil water characteristic curve decreased rapidly from 0 to 500cm suction,and then remained stable until the same.Under the same suction,the soil moisture content increased with the increase of carbon and soil ratio.The saturated water content and the residual water content also increased with the increase of carbon application,indicating that the application of biological carbon to improve the water holding capacity of soil.3.biochar can reduce the leaching loss of nitrogen by three reasons.（1）the porous structure of biological carbon itself,its huge specific surface area enhanced its adsorption capacity to ions,making the soil NH₄⁺,NO₃^-plasma adsorption capacity enhanced.（2）its porous structure reduces soil bulk density,increases soil permeability,inhibits anaerobic microbial growth,and reduces soil denitrification.So that nitrogen will not be released in the form of ammonia,and further reduce the leaching loss of nitrogen fertilizer.（3）increased soil carbon and nitrogen ratio,thereby promoting microbial immobilization of nitrogen and increasing nitrogen fixation.4.biological carbon can increase the number of tillers in rice,reduce the number of invalid tillers,increase the effective tillering rate of rice,increase the height of rice plant and increase the growth parameters of the leaf area index LAI,and so on.5.in this study,direct seeding treatment increased the tiller number and plant height later than the transplanting treatment,and the growth process was about 12D later than the transplanting treatment.The addition of biochar to a certain extent makes up for the shortage of direct seeding.The addition of biochar can also reduce crop water consumption and increase water productivity.And as the amount of biochar increased,the productivity of water also increased.