The Application Of Caragana Compost And Bacillus Subtills In Soils Showing Continuous Cropping Obstacle:Soil Remediation Efficiency And Crop Response

In this study,soil microbiological obstacles to cucumber continuous cropping in Ningxia have become increasingly prominent and the sustainable use of soil has been inhibited.The soil under continuous cropping of cucumber for 10 years was used as the research object,to study the effects of different nitrogen substitution amounts of compost of Caragana korshinskii on soil quality of continuous cropping,according to indicators such as cucumber plant growth,fruit quality,soil and chemical properties,and soil microbial community characteristics,to evaluate the relationship between the indicators and crop productivity,to explore the effect of different nitrogen substitutions of compost of Caragana korshinskii on the biochemical properties of continuous cropping soil,and to clarify the effect of single or dual factor action of Caragana compost and Bacillus subtilis on the continuous cropping of cucumber soil,and screen out the best matching scheme for crop growth,it provides a theoretical basis for the sustainable use of cucumber plants in continuous cropping.The results are as follows:I.The effects of different dosage of Bacillus subtilis on the growth and soil quality of continuous cropping cucumber(1)With the increase of application rate of Bacillus subtilis,transpiration rate,photosynthesis and Vc contents of fruit increased gradually,the contents of nitrate and organic acid decreased,cucumber yield EB(chicken manure + 800 g/667 m2 Bacillus subtilis)increased by 508.24 kg/667 m2 compared with CK(single application of chicken manure).(2)Soil available nutrients,organic matter content and EC value of Bacillus subtilis treatment groups were lower than CK,EB treatment with the largest amount of microorganisms,the score of EB treatment was the highest.(3)In summary,application of 800 g/667 m2 Bacillus subtilis can significantly promote the growth of plant roots,photosynthesis,fruit quality,cucumber yield,soil ecological environment and soil quality were improved effectively.II.The effects of Caragana compost and Bacillus subtilis on the plant growth of continuous cropping cucumber and the soil biochemical properties(1)With the increase of cultivation stubble,the relative growth rate of stem diameter increased first and then decreased,the length of root system and the total surface area showed a decreasing trend,early spring stubble was more favorable to plant root growth,the addition of Bacillus subtilis could promote root growth and increase root biomass,FCB(Caragana compost 50%N replacement + 800 g/667 m2 Bacillus subtilis)had the best effect on promoting root growth after multi-crop cultivation.(2)With the increase of crop rotations,the content of soluble solids in cucumber decreased first and then increased,the nitrate content could be reduced by reducing the amount of N fertilizer applied in the base fertilizer,application of Bacillus subtilis in fruit soluble sugar and Vc contents increased,each crop SCB(Caragana compost 75%N replacement + 800 g/667 m2 Bacillus subtilis)and FCB could increase yield and FCB yield was the best.(3)The activities of catalase and phosphatase in continuous stubble soil decreased first and then increased,urease activity increased first and then decreased.Application of Bacillus subtilis to increase catalase activity,urease activity increased with the decrease of N application rate in Caragana compost,the activities of phosphatase and sucrase in soil treated with FCB were strong,sucrase activity increased by 41.43%over FDB(chicken manure + 800 g/667 m2 Bacillus subtilis),the pH of soil treated with FCB decreased significantly,Bacillus subtilis could effectively regulate soil nutrient content.(4)The total amounts of bacteria in soil cultivated in successive stubble showed a tendency of decreasing first and then increasing,the number of actinomycetes was decreased,the application of Bacillus subtilis significantly reduced the number of fungi,B/F increased,the B/F value of FCB treatment was higher,the application of Bacillus subtilis can alleviate the continuous cropping obstacle of soil microorganism.(5)As a whole,the differences in AWCD values were obvious,application of Caragana compost alone,the utilization of carbohydrates and esters by microorganisms decreased with the decrease of N content,principal component analysis of AWCD value of each carbon source at 96 h,it was found that FD was obviously separated from other treatments,except chicken manure treatment group,The Shannon-Wiener and Shannon evenness index increased after adding Bacillus subtilis,application of Bacillus subtilis significantly increased soil microbial diversity.(6)First stubble,HC(Caragana compost 100%N replacement)comprehensive score was the highest,the higher N content in base fertilizer of Bacillus subtilis treatment group,the higher its comprehensive score,but the second,third,fourth stubbles,the best comprehensive effect of FCB,the scores of HC and FC(Caragana compost 50%N replacement)were lower when applying base fertilizer alone,It is indicated that the excessive and insufficient amounts of N in the base fertilizer are not beneficial to the growth and development of the plant and the improvement of soil quality,the application of Bacillus subtilis can alleviate the adverse effects caused by the continuous cropping.