Effects Of Reeds Biochar On Rice Growth,Nitrogen And Phosphorus Loss And Soil Physicochemical Properties

In the process of agricultural production,excessive application of chemical fertilizer leads to the loss of soil nitrogen and phosphorus into the water body through the surface or underground leaching,which seriously reduces the utilization rate of chemical fertilizer and causes a series of agricultural non-point source pollution problems such as eutrophication.The application of biochar to control agricultural non-point source pollution has become a research hotspot.As an aquatic plant,reeds have an important impact on the environmental and ecological problems in Dongting Lake.Therefore,this research adopts the Dongting lake rushes straw preparation biochar,choose reddish clayey and granite of quaternary red soil development of hemp sand mud two kinds of typical southern paddy soil,set different dosage of gradient’s brink biochar,conducted in 2020 rice pot experiment,explored the rushes biochar addition amount on paddy soil physical and chemical properties of soil nitrogen and phosphorus loss effects of rice growth,development and nutrient uptake.The main findings are as follows:(1)In the granitic sandy soil paddy soil,application of biochar could significantly reduce ammonia volatilization by 12.7% to 46.8%.Application of biochar could increase the average p H value of soil surface,but the difference was not significant.Application of biochar significantly reduced the concentration of ammonium and nitrate nitrogen in surface water by 3.8% to 65.4% and 17.0% to32.4%,respectively,and reduced the risk of nitrogen loss by runoff.Application of biochar significantly reduced the cumulative leakage of total ammonium nitrogen and nitrate nitrogen by 2.1% to 26.4% and 11.2% to 54.5% and 11.2% to 26.2%,respectively.In the reddish clayey soilpaddy soil,application of reed biochar could increase the p H value of surface water by 0.56 to 1.25 units,and increase the ammonia volatilization degree of soil at the early stage of rice growth.When the biochar supplemental level was 4% or less,the concentrations of total ammonium nitrogen and nitrate nitrogen in the surface water and water leakage of the two kinds of soil were reduced,and the loss of nitrogen was reduced.The addition of biochar at6% or above increased the concentrations of total ammonium nitrogen and nitrate nitrogen in surface water and seepage water of both soils,and increased the risk of nitrogen loss.(2)When the biochar supplemental level was 4% or less,the concentrations of total phosphorus,soluble phosphorus and granular phosphorus in surface water and water leakage of different types of paddy soil were decreased,and the phosphorus loss was reduced.When the biochar supplemental level was 6% or above,the concentrations of total phosphorus and soluble phosphorus in surface water were significantly increased,and the risk of phosphorus loss was increased.(3)Application of biochar from reed grass significantly increased nutrient content in 0 to 40 cm soil layer of granitic sandy soil and paddy soil of reddish clayey soil,and total nitrogen content increased by 6.7% to 29.5% and 14.4% to 130.2%,respectively.The total phosphorus content increased by 2.4% to 41.9% and 1.3% to138.9%,respectively.The available phosphorus content increased by 3.0% to 127.2%and 0 to 40.0%,respectively.The content of available potassium increased by 56.1%to 2650.0% and 237.2% to 6129.0%,respectively.The organic matter content increased by 8.9% to 93.8% and 141.2% to 987.3%,respectively.Application of biochar significantly increased soil p H value of the two paddy soils,and with the increase of biochar application rate,biochar significantly decreased the soil bulk density of 0 to 20 cm root layer of the two paddy soils by 2.6% to 13.1% and 2.7% to16.1%,respectively,and decreased with the increase of biochar application rate.(4)Application of biochar significantly increased rice plant height by 6.5% to15.9% and 3.3% to 20.0%,but decreased SPAD value and tiller number of rice.The total dry matter of shoot of rice was significantly increased by 0.6% to 18.6% and15.6% to 42.4%,respectively,and the actual yield was increased.The addition of 2%and 4% biochar had the best effect on the growth of rice.Significantly increased the accumulation of N,P and K uptake in rice plantsIn conclusion,the addition of 2% to 4% biochar can effectively reduce nitrogen and phosphorus loss in granitic sandy soil and reddish clayey soil,significantly increase soil nutrient content and availability,improve soil structure,promote rice growth and nutrient absorption,and achieve the effect of increasing yield.Therefore,in the actual production process,on the premise of full consideration of fertilizer application and economic costs,the application of biochar between 2% and 4% can produce good environmental and economic benefits.