Effects Of Green Manure Rape Combined With Biochar On Soil Properties And Crop Growth In New Greenhouse

The soil fertility of the new greenhouse is not compatible with the requirements of high yield and efficiency of the greenhouse.It is increasingly important to improve the soil capacity of new greenhouses.In view of the problem that the current fertilization measures in the newly-built greenhouse do not have enough in-depth and systematic research on various indicators of soil fertility,this paper takes rice husk biochar and overturned rape as the test materials,designs 4 rape overturning levels and 2 biochar application levels,and deeply studies the soil physical and chemical properties and plant growth,yield and nutrient absorption under the combined fertilization measures,with a view to obtaining the best combination of rape overturning amount and the application of biochar,Thus,the soil fertility quality of the newly-built greenhouse will be continuously and steadily improved,and the sustainable development of facility agriculture will be promoted.The results are as follows:（1）The biochar application had a significant effect on the growth of rape,and the T4 and T6 treatments with suitable planting densities and biochar application were the most advantageous.In terms of dry matter quality and nutrient absorption,biochar application can significantly promote the dry matter quality and nutrient absorption of rape.The total dry matter quality is 2152.02～3474.37 kg·hm^-2,the nitrogen absorption is 73.06～166.93 kg·hm^-2,and the phosphorus absorption is 7.86～17.34 kg·hm^-2.T4 treatment has the best effect,followed by T6 treatment,while the potassium absorption is the largest in T8 treatment.（2）The combination of rape overturning and biochar application significantly improved soil fertility.In terms of soil physical properties,the F6 treatment combined with rape returning and biochar application had the best effect in reducing soil bulk density,which decreased by 26.58%compared to before overturning.The field water holding capacity and aggregate structure of soil under F6 treatment increased by 43.69%and 64.58%,respectively,compared with those before overturning,which could significantly improve the formation of soil aggregates and better improve the soil structure;In terms of soil chemistry properties,F6treatment had the largest increase in soil Total organic carbon,light group organic carbon,humic acid,DOC,total nitrogen,recombinant total nitrogen,total phosphorus,available phosphorus,available phosphorus source,slow available phosphorus source,available potassium and CEC,which were 85.60%,86.98%,177.27%,65.09%,24.59%,19.81%,24.85%,56.37%,709.74%,156.46%,57.84%and 9.56%higher than basic soil,respectively.The maximum increase in soil recombined organic carbon and slow-release potassium was observed in the F4 treatment,with increases of 19.40%and 50.78%compared to the base soil,respectively.The maximum increase in soil light group total nitrogen was observed in the F5treatment,with a significant increase of 86.96%compared to the base soil.The soil p H decreased most significantly in the F7 treatment,with a decrease of 2.86%compared to the base soil.The maximum increase in soil fulvic acid and potential phosphorus sources was observed in the F8 treatment,with a significant increase of 86.49%and 13.62%compared to the base soil,respectively;In terms of soil biology properties,soil urease activity,alkaline phosphatase activity and microbial biomass carbon and nitrogen in F6 treatment increased by26.16%,99.26%,170.73%and 266.99%respectively from the base.（3）The combination of rape overturning and biochar application had a significant promoting effect on the growth of sweet and glutinous corn.In terms of growth,the plant height,stem diameter,leaf area,leaf number,leaf color and net photosynthetic rate of sweet waxy corn were the most obvious in F6 treatment at the early and middle stages of growth;In terms of total dry matter mass,yield and its constituent factors,the total dry matter mass of each treatment was 5733.67～18899.94 kg·hm^-2,the number of grains per ear was525.40～611.70,the 1000-grain weight was 135.27～243.25 g,and the yield was1799.00～4919.33 kg·hm^-2,all of which were the largest in F6 treatment.Compared with CK treatment,each index was 127.79%,6.36%,76.17% and 129.44%higher respectively;In terms of nutrient absorption,the absorption of nitrogen,phosphorus and potassium in F6treatment was the highest,which was 82.61%,19.78%and 190.77%higher than that in CK treatment;In terms of correlation between crop yield,total dry matter quality,nutrient absorption and soil C,N,P,K and other indicators,the highest correlation is found with soil urease activity,DOC,organic matter,light organic carbon,available phosphorus,and available potassium.The above results showed that the growth and dry matter quality of rape were better when 1%biochar was applied and the planting density was 0.90-1.35 million plants·hm^-2.The treatment of 1%biochar application and 22500 kg·hm^-2 returning（F6）had the best effect on soil fertility,the most significant effect on the dry matter quality,yield and nutrient absorption of subsequent crops,followed by F4 treatment.Under the combined fertilization of green manure and biochar in the new greenhouse,soil urease activity,DOC,organic matter,light group organic carbon,available phosphorus and available potassium have the greatest correlation with the improvement of soil fertility,which can be used as important indicators for the evaluation of soil fertility in the future.