Effect Of Biochar And Nitrogen Coupling On The Growth And Nitrogen Uptake And Utilization For Tomato Based On ¹⁵N Tracing

With the increasing tension of water and soil resources,the adoption of efficient water-saving irrigation techniques,optimized nitrogen management and green soil improvement measures are effective means for sustainable agricultural development.Alternate partial root-zone irrigation is a new water-saving irrigation technology that can effectively improve crop water use efficiency.Biochar is a soil amendment that can promote nutrient uptake.The application of nitrogen fertilizer can effectively increase crop yield,but unreasonable nitrogen management can cause serious pollution problems.Based on this,this study was conducted to investigate the effects of carbon and nitrogen coupling on tomato growth indicators,nitrogen uptake and distribution utilization,yield,water use efficiency,quality and soil environment in the alternate partial root-zone irrigation conditions using ¹⁵N tracer technology.The main conclusions were as follows:（1）Under alternate partial root-zone irrigation,both biochar additi on and increased nitrogen application were effective means to promote tomato growth,with the maximum plant height and stem thickness obtained in the B2N3 treatment.The accumulation of dry matter mass of tomatoes was most favorable when biochar was added at 2%（6 t/ha）and nitrogen was applied at 300 kg/hm ².（2）Under alternate partial root-zone irrigation,the total N content,fertilizer contribution and ¹⁵N uptake of tomato organs at different fertility stages were mostly concentrated in leaves and fruits,and a small portion was present in roots and stalks.The addition of biochar and increased N application were beneficial to improve 15N uptake and total N content of all tomato organs;the addition of biochar reduced fertilizer contribution and ¹⁵N fertilizer loss,but significantly increased soil N uptake,¹⁵N recovery and ¹⁵N utilization in tomato,with the best enhancement effect at 2%biochar addition.In the spring and autumn trials,the ¹⁵N recovery and ¹⁵N utilization rates of B2N2 treatment were both maximum at 75.53%,72.66%and 31.84%,30.88%,respectively.（3）Different charcoal and nitrogen coupling patterns had greater effects on tomato yield.Tomato yield was positively correlated with biochar addition and tended to increase and then decrease with increasing N application,reaching a maximum at300 kg/hm².B2N2 treatment obtained maximum yield in both seasons of the experiment and differed significantly（P<0.05）from the treatment without biochar addition（B0）.The trend of water use efficienc y of tomato was consistent with the yield,and the water use efficiency of B2N2 treatment was more than 13%higher than that of the treatment without biochar addition（B0）.（4）Appropriate charcoal-nitrogen coupling pattern could improve tomato quality.B2N2 treatment obtained the highest vitamin C,soluble sugar,soluble protein and sugar-acid ratio,and the difference was significant for the treatment without biochar addition（B0）.The evaluation of the overall benefits of tomatoes by the TOPSIS method based on the combined assignment method showed that the B2N2 treatment was the best biochar and nitrogen coupling mode under the conditions of this experiment.（5）Under alternate partial root-zone irrigation,different charcoal and nitrogen treatments had a greater effect on the soil environment in the root zone of tomato.The organic matter content,organic carbon content and total nitrogen content in the root zone gradually increased with the addition of biochar,with the maximum value reached at 2%of biochar and 450 kg/hm² of nitrogen application.Soil p H was proportional to the amount of biochar added and gradually decreased with the increase of nitrogen application.Soil organic matter content,organic carbon content and total nitrogen content in the root zone of tomato showed a trend of maturity stage>flowering and fruiting stage>seedling period at each fertility stage.