Effects of chemical fertilizer reduction combined with biochars-based fertilizers on yield and quality of flue-cured tobacco and soil enzyme activity

【Objective】To study the effects of different ratios of chemical fertilizer and biochars-based fertilizers on the yield and quality of flue-cured tobacco and soil enzyme activity,in order to clarify the optimal reduced application amount of chemical fertilizer and the application amount of biochars-based fertilizers,and provide some theoretical basis and technical support for the popularization and application of reduced application of chemical fertilizer and biochars-based fertilizers.【Method】Tobacco variety K326 was taken as the test material,four treatments of chemical fertilizer and biochars-based fertilizers were set upcontrol(CK) :100% chemical fertilizer;T1:80% chemical fertilizer+20% biochars-based fertilizers;T2:60% chemical fertilizer+40% biochars-based fertilizers;T3:40% chemical fertilizer+60% biochars-based fertilizers. The agronomic traits and SPAD value of flue-cured tobacco under different treatments were measured at 30,60 and 90 d after transplanting. After curing,the appearance quality and economic properties of flue-cured tobacco in each treatment were investigated,the main chemical components and their coordination were determined and analyzed,and the rhizosphere soil was collected to determine the soil enzyme activity.【Result】Compared with the CK,the treatment of biochars-based fertilizers had less effect on the growth of flue-cured tobacco in the early growth stage,but its promoting effect was gradually highlighted in the middle and late growth stage. Except the number of effective leaves,the agronomic traits of T1 treatment were the best as a whole,and the number of effective leaves was the most in T3 treatment,which was 10.20% higher than CK at 90 d after transplanting. With the increase of biochars-based fertilizers ratio,SPAD value,appearance quality,economic traits and chemical components increased first and then decreased,and T2 treatment was the best(SPAD value was 4.04% higher than CK,the total score of appearance quality was 2.65% higher than CK,the yield,average price,output value and the proportion of medium and top grade tobacco were 1.82%,5.50%,7.43% and 0.88% higher than CK respectively,and the total score of chemical components of flue-cured tobacco was 9.45% higher than CK),T3 treatment was not conducive to the formation of yield and quality of flue-cured tobacco;the activities of soil urease and catalase were the highest in T3(0.612 mg/g) and CK(7.384 mL/g) treatment,and the activities of sucrase and acid phosphatase were the highest in T2 treatment,7.01% and 5.34% higher than CK treatment,respectively.【Conclusion】The reduction of chemical fertilizer combined with biochars-based fertilizer can significantly promote the growth of flue-cured tobacco in the middle and late growth stages,and has a significant effect on soil improvement.Among them,the treatment effect of 60% chemical fertilizer+40% biochars-based fertilizer is the best,while the excessive amount of biochars-based fertilizer has the risk of inhibiting the growth of flue-cured tobacco and reducing soil quality.