Effects Of Biochar Application Amount And Depth On Soybean Growth And Soil Environmental Effect

The black soil area in Northeast China has fertile soil layers and strong productivity,making it a good soil resource.In recent years,due to over reclamation and natural erosion,soil fertility has been declining,threatening national food security.Due to its ability to promote crop growth and development,increase yield,and improve soil physicochemical properties,biochar can greatly solve the problems of soil degradation and crop growth and development.At present,research shows that the amount and depth of carbon application have an impact on crop growth and soil environmental effects,respectively.However,there is a lack of experiments that simultaneously study the two factors.Therefore,this experiment explores the impact of carbon application and depth on soybean growth and soil environmental effects by studying the two factors.This study used Heinong 56 soybean varieties as the research object and conducted a pot experiment at the Heilongjiang Bayi Agricultural Reclamation University Pot Experiment Field in Daqing City,Heilongjiang Province.The experiment set up 13treatments.The four carbon application rates were 15,30,45,and 60 t/hm~2,and the three carbon application depths were 12,18,and 24 cm,respectively,as well as the control CK.The experimental treatments were T1(12 cm,15 t/hm~2),T2(12 cm,30t/hm~2),T3(12 cm,45 t/hm~2),T4(12 cm,60 t/hm~2),T5(18 cm,15 t/hm~2),T6(18 cm,30t/hm~2),T7(18 cm,45 t/hm~2),T8(18 cm,60 t/hm~2),T9(24 cm,15 t/hm~2)T10(18 cm,30 t/hm~2)T11(18 cm,45 t/hm~2),T12(18 cm,60 t/hm~2),CK(without biochar).Each treatment was fertilized at 12 cm using conventional methods to investigate the effects of biochar application amount and depth on soybean growth and soil environmental effects.The main conclusions of the study are as follows:(1)Yield:When the depth of carbon application is 12 cm and 18 cm,the yield shows a trend of first increasing and then decreasing with the increase of carbon application,both achieving the highest yield at a carbon application rate of 30 t/hm~2;When the depth of carbon application is 24 cm,the yield shows a decreasing trend with the increase of carbon application,and T6 treatment has the highest yield.(2)Plant height:When the amount of carbon application is low,the plant height shows a trend of first increasing and then decreasing with the increase of carbon application depth.When the amount of carbon application is high,the plant height shows a decreasing trend with the increase of carbon application depth.The plant height of the carbon application treatment at each growth stage is greater than that of the control CK.(3)Dry weight:(1)Stem dry weight:The stem dry weight shows a trend of first increasing and then decreasing with the increase of carbon application amount,reaching its maximum value at 45 t/hm~2.The carbon application treatment is greater than the control CK,and shows a decreasing trend with the increase of carbon application depth.(2)Leaf dry weight:The amount of carbon application required for the maximum leaf dry weight shows an increasing trend with the increase of carbon application depth.When the carbon application amount is 15 t/hm~2,the crop leaf dry weight gradually decreases with the increase of carbon application depth;When the carbon application rate is greater than 15 t/hm~2,the dry weight of crop leaves shows an increasing trend with the increase of carbon application depth Pod dry weight:When the depth of carbon application is 12 cm,the pod dry weight shows an increasing trend with the increase of carbon application amount;When the carbon application depth is 18 cm and 24 cm,the dry weight of pods shows a trend of first increasing and then decreasing with the increase of carbon application amount,both reaching their highest values at 30 t/hm~2.(4)Crop nutrients:Total nitrogen shows a trend of first increasing and then decreasing with the growth period,reaching its maximum value during the grain filling period,while total phosphorus and potassium contents gradually decrease.The nutrient content of plants is characterized by total nitrogen>total potassium>total phosphorus.There is a significant difference in total nitrogen with the depth of carbon application between the flowering and pod setting stages and the grain filling stage.During the flowering and pod setting stage,when the carbon application rate is less than 45 t/hm~2,the total nitrogen shows a trend of first decreasing and then increasing with the increase of carbon application depth;When the carbon application rate is higher than 45 t/hm~2,the total nitrogen shows a decreasing trend with the increase of carbon application depth.The highest total potassium content was observed in CK during the mature stage,indicating that biochar inhibits the total potassium content of soybeans during the mature stage.(5)Soil nutrients:The available nitrogen,phosphorus,and potassium in the soil show a trend of first increasing and then decreasing with the growth period.T1treatment achieved the highest value of available nitrogen,and the carbon application treatment was greater than the control CK.When the depth of carbon application is 12cm,the available phosphorus shows an increasing trend with the increase of carbon application amount;When the depth of carbon application is 18 or 24 cm,the available phosphorus shows a trend of first increasing and then decreasing with the increase of carbon application amount.The content of available phosphorus in the carbon application treatment was higher than that in the control CK,and the maximum value was achieved under T11 treatment.The available potassium content in the soil treated with carbon was higher than that of the control CK,with T7 treatment having the highest available potassium content.Harvesting crops can maintain high soil fertility.(6)Soil microorganisms:The number of soil fungi,bacteria,and actinomycetes shows a decreasing trend with the deepening of the soil layer;The number of three types of microorganisms showed a trend of first increasing and then decreasing with the growth period,reaching the highest value during the flowering and podding stages and the bulging stage.The relationship between the number of microorganisms was bacteria>actinomycetes>fungi.(7)Soil moisture content:The amount and depth of carbon application during the seedling and flowering stages have a significant impact on soil moisture content,while other stages have no significant impact on soil moisture content.Based on various treatments,it can be concluded that T6 is the optimal treatment.