Effect And Mechanism Of Biochar On Improving Water And Fertilizer Utilization Of Greenhouse Tomato

Unreasonable water and fertilizer application patterns will cause serious waste of water and fertilizer resources and environmental pollution,and will also cause soil fertility to decline,thereby affecting crop growth and yield.As a kind of soil amendment,biochar can promote the conversion of soil effective nutrients,improve crop growth and yield.Tomato is one of the widely cultivated vegetables because of its rich nutrition and delicious taste.However,the effect of biochar on water and fertilizer use efficiency of tomato and its mechanism are not clear.In this study,greenhouse tomato experiment and pot tomato experiment were used to investigate the effects of different biochar additions on soil properties,tomato growth,physiological status,yield and quality,revealing the internal mechanism of different biochar addition on improving water and fertilizer efficiency of tomato.The main conclusions are as follows.(1)Biochar promoted the formation of soil water stable macroaggregates,increased the root soil water content,available nitrogen and available potassium content,and improved the water and fertilizer conservation capacity of soil.Biochar significantly increases the number of soil water-stable aggregates and improves the water holding capacity of the soil.When the addition amount of biochar is greater than 10t/ha,the soil mechanically stable microaggregates are easy to aggregate to form mechanically stable macroaggregates,which significantly promotes the formation of soil water-stable coarse aggregates;Biochar has little effect on the formation of soil water-stable small aggregates and microaggregates;When the addition amount of biochar is 30,50or 70 t/ha,it is most conducive to the stability of soil aggregates.The soil moisture content increases first and then decreases with the increase of biochar addition.When the biochar addition is 50 t/ha,the soil moisture content is the largest.Biochar has a great influence on the pH value of the 15d loess soil.When the amount of biochar added was 30-90 t/ha,the pH value of the louvre increased by 2.30%to 9.55%compared with the control treatment.With the extension of time,the effect of biochar on the pH value of the louvre gradually became smaller.Compared with the control treatment,the pH value of the biochar treatment of sandy loam soil was significantly increased by 22.84%.Biochar significantly affected soil available potassium content,which increased with the increase of biochar dosage;Biochar significantly affects the soil available potassium content,significantly increases the NO₃^-and NH₄⁺content in the 0?60cm soil layer of the root zone,reduces the NO₃^-and NH₄⁺content of 70?100cm soil layer;Biochar enhanced the water and fertilizer conservation capacity of shallow soil,reduced the risk of soil nutrient leaching loss,and improved the nitrogen use efficiency.(2)Biochar significantly increased soil enzyme activity,changed soil microbial community composition,increased soil microbial biomass carbon and nitrogen content,and promoted soil nutrient transformationBiochar significantly increased the activities of urease,catalase,alkaline phosphatase and sucrase,and increased the number of bacteria,fungi,actinomycetes and nitrifying bacteria in the soil,all of which increased first and then decreased with the increase of biochar.The effect of biochar on soil enzyme activity of Tomato in spring and summer was greater than that in autumn and winter,and the soil enzyme activity was the highest when biochar dosage was 30 or 50 t/ha.The effect of biochar on soil microbial quantity of Tomato in spring and summer was greater than that in autumn and winter,and the effect of harvest time was the most significant.When the biochar dosage was 30 or 50 t/ha,the number of soil bacteria,fungi,actinomycetes and nitrifying bacteria was the largest,while the number of denitrifying bacteria was the smallest.When biochar addition was more than 10 t/ha,the contents of soil microbial biomass carbon(MBC)and soil microbial biomass nitrogen(MBN)were significantly increased,and the ratio of MBC/N was significantly decreased.(3)Biochar significantly improved the photosynthetic characteristics of tomato leaves,increased the pH of tomato xylem,did not affect the physiological signal transduction of tomato,and increased the dry matter accumulation of tomatoBiochar significantly improved the photosynthetic characteristics of tomato leaves at different growth stages.In general,when the biochar dosage was 30 t/ha,chlorophyll a,chlorophyll b,total chlorophyll and carotenoids reached the maximum,and increased by18.81%,24.67%,18.38%and 18.83%respectively compared with the control;Biochar significantly increased the photosynthetic gas exchange parameters of tomato leaves,which first increased and then decreased with the increase of biochar content.When the biochar content was 50 t/ha,the photosynthetic gas exchange capacity of tomato leaves was the strongest,with an average increase of 13.66%?39.43%compared with the control.Biochar increased soil pH value,which led to the increase of pH value of tomato xylem juice,but it did not promote abscisic acid(ABA)signal conduction from xylem to leaves.Therefore,during deficit irrigation,it did not inhibit the photosynthetic gas exchange of tomato leaves due to inducing stomatal closure,and thus did not affect the photosynthetic characteristics of tomato.(4)Biochar significantly promoted tomato plant growth,improved tomato quality,increased tomato yield and water and fertilizer use efficiencyBiochar increases the growth rate of tomato.Plant height,stem thickness,root system and dry matter all increase first and then decrease with the increase of the amount of biochar.When the amount of biochar was 50 t/ha,the plant height,stem thickness,root length and root surface area are the largest,which increased by 7.33%?73.20%respectively compared with the control;when the amount of biochar was 30 t/ha,the root diameter and root volume are the largest,which is 47.37%and 57.99%higher than the control respectively.Biochar can reduce the organic acid content of tomatoes and increase the soluble sugar,sugar-to-acid ratio,lycopene and vitamin C(VC).When the biochar amount was 50 t/ha,the soluble sugar and VC content reached the maximum,which increased by 16.78%and28.78%respectively compared with the control;when the biochar amount was 30 t/ha,the tomato sugar-to-acid ratio and lycopene reached the maximum,which increased by 16.78%and 28.78%respectively compared with the control.Biochar significantly increased tomato production,improved tomato water use efficiency(WUE)and nitrogen fertilizer partial productivity(PFP),and all three of them increased first and then decreased as the amount of biochar increased.When biochar was 50t/ha,tomato yield,WUE and PFP increased by 43.46%,45.33%and 43.46%respectively,and total nitrogen,phosphorus and potassium content increased by 68.8%,71.12%and56.26%respectively.Biochar can improve the water and fertilizer supply capacity of soil to crops,especially the effective water and fertilizer that can be absorbed and utilized by crop roots.The goal of reducing crop irrigation quota and fertilization quota can be achieved by adding biochar.(5)The effect of adding biochar in soil was analyzed comprehensively,and the appropriate amount of biochar was put forwardBiochar can improve soil physical and chemical properties,soil microbial activity and soil structure,increase soil water and nutrient supply capacity to crops,and promote soil nutrient transformation;At the same time,biochar can increase the water consumption and improve the water status(leaf water potential and root hydraulic conductivity),improve the photosynthetic gas exchange capacity of tomato leaves,promote the absorption,utilization and transportation of soil nutrients,increase the accumulation of dry matter,and improve the yield and water and nitrogen use efficiency of tomato.A multi-dimensional nonlinear regression model was established.On the basis of comprehensive consideration of tomato high-quality and high-yield,high economic efficiency,water and fertilizer utilization resource utilization and environmental protection,the suitable addition amount of biochar is 30 t/ha and the combined application rate of nitrogen fertilizer is 210 kg/ha.