Effects of chemical fertilizer reduction combined with bio-organic fertilizer application on growth physiology and nutrient absorption of Chinese cabbage in open fields on plateau in summer

Objective This study aims to investigate the effects of chemical fertilizer reduction and application of bio-organic fertilizer on the growth and physiology of Chinese cabbage and nutrient absorption through field experiments. Method The cabbage variety "Wangchun" was used as the test material,and a total of seven fertilization treatments were set up,namely,no fertilization(CK₁),100% conventional fertilization(CK₂),balanced fertilization with chemical fertilizers(T₁),chemical fertilizers with a 30% reduction + 6 000 kg/hm² bio-organic fertilizers(T₂),chemical fertilizers with a 30% reduction + 9 000 kg/hm² bio-organic fertilizer(T₃),40% chemical fertilizer reduction + 6 000 kg/hm² bio-organic fertilizer(T₄),40% chemical fertilizer reduction + 9 000 kg/hm² bio-organic fertilizer(T₅). Result Compared with CK₂,cabbage plant length,root thickness and root length in T₃ treatment increased by 11.17%,13.31% and 18.20% respectively,the content of chlorophyll a,chlorophyll b,carotenoids in the aboveground rosette leaves increased by 39.02%,34.09% and 35%,and the dry matter accumulation of cabbage rosette leaves,leaf bulb and root system increased by 9.71% 19.24%,14.16%,respectively.The treatment also effectively increased the distribution rate of nutrients in the leaf ball.Chemical fertilizer reduction with the application of bio-organic fertilizer increased nitrogen fertilizer utilization by 14.35%-24.17%,phosphorus fertilizer utilization by 7.61%-10.40%,agronomical utilization and bioproductivity increased significantly.The combination effectively reduced the soil nutrient dependence rate.As for the nutrient absorption of cabbage,the reduction of chemical fertilizer by 30% was better than the reduction of chemical fertilizer by 40%,and the dosing of 9 000 kg/hm² bio-organic fertilizer was better than the dosing of 6 000 kg/hm² bio-organic fertilizer.The 30 indicators were analyzed by principal component analysis,and the comprehensive evaluation of T3 treatment had the highest score and the best treatment effect. Conclusion Comprehensive analysis shows that reducing chemical fertilizer by 30% + 9 000 kg/hm² bio-organic fertilizer can promote the growth of Chinese cabbage,increase the chlorophyll content,increase the accumulation of dry matter,facilitate the absorption of nutrients,improve fertilizer utilization,reduced the amount of chemical fertilizer application.This study can provide theoretical basis and technical support for chemical fertilizer reduction in open-field Chinese cabbage production on the plateau in summer.