Effects of Rape Straw Returning Method and Reduction of Potassium Fertilizer on Potassium Use Efficiency of Tobacco in Tobacco-rape Rotation

  Objective  Effects of straw returning on potentiality of potassium (K) fertilizer reduction and K use efficiency of tobacco were studied under a tobacco-rape rotation. The results would provide theoretical basis and technology reference for straw unitization and reduction of K fertilizer in this rotation.

  Method  A located field experiment was carried out under a tobacco-rape rotation. K326 tobacco variety and rape straw were used as experimental materials. Eight different treatments of straw direct returning (S) and decomposed straw returning (DS) were designed: (1) NP; (2) NPK(CK); (3) NP + 85%K + S; (4) NP + 70%K + S; (5) NP + 55%K + S; (6) NP + 85%K + DS; (7) NP + 70%K + DS; (8) NP + 55%K + DS. Yield, output value, K absorption, K use efficiency of tobacco and K balance in soil were studied.

  Result  The results showed that output value of tobacco with the treatment of decomposed straw returning + reduction 30% K fertilizer(NP + 70%K + DS) was the highest in all treatments. Output value of tobacco with the treatment was 78662 yuan hm⁻² in 2018 and 81071 yuan hm⁻² in 2019. Potassium absorptions of tobacco in treatments with decomposed straw returning were higher than these with straw direct returning. Potassium absorptions of tobacco with NP + 70%K + S treatment was the highest in all treatments. Potassium use efficiency of tobacco with the treatment of continuous straw returning was improved. Potassium use efficiency of tobacco with the treatment of decomposed straw returning was higher than that with the treatment of straw direct returning. Surplus K in soil with treatments of reduction 15%-30% K fertilizer were more than that with CK. Surplus K in soil with the treatment of reduction 15% K fertilizer was the highest in all treatments.

  Conclusion  The results showed that 30% K fertilizer can be reduced with tobacco season under tobacco-rape rotation with the decomposed straw returning or straw direct returning pattern. Yield, output value, K use efficiency of tobacco with decomposed straw returning were better than those with straw direct returning.