Study On Soil Improvement Of Continuous Cropping Of Cucumber In Greenhouse With Biochar

As a soil modifier,biochar can improve continuous cropping soil.However,at present,a large number of studies only discuss the effects of single application of biochar on continuous cropping soil properties and crop growth and development.There are few reports on the combined application of biochar and its sustained effect on continuous cropping soil.In this thesis,the soil of cucumber continuous cropping for 15 years was taken as the research object,winter and spring stubble experiment set up five treatments: CK(blank control),B(biochar),F(organic fertilizer),BF(biochar+organic fertilizer)and BT(biochar+Trichoderma),to study the effects of biochar combined with organic fertilizer and Trichoderma on soil improvement of cucumber continuous cropping in greenhouse.In the experiment of autumn and winter stubble,no biological carbon,organic fertilizer and Trichoderma were added on the base of stubble,there were five treatments: CK(blank control),BN(biochar was added in the first crop and no other fertilizer was added in the second crop),FF organic fertilizer was added in the first and second biochar),BFF(Biochar and organic fertilizer were added in the first crop and organic fertilizer in the second crop)and BTFT(Biochar and Trichoderma were added in the first and organic fertilizer and Biochar in the second)were set up to explore the sustainable effect of biochar on continuous cropping soil improvement.The results show that:(1)In the first crop(winter and spring)experiment,in the middle of cucumber growth and development,all treatments reduced the height of cucumber plants.Treatments B and BT significantly increased the stem thickness,and treatment BF significantly reduced the stem thickness;The chlorophyll content of B,F,BF,and BT were all higher than that of CK.Treatment B and BF were significantly higher than the control,which increased by 21.63% and 18.51% compared with CK.In the seedling-pulling period of cucumber,the plant height and internode number of each treatment were higher than CK,and BF treatment was significantly higher than CK,which increased by 12.27% and 6.69% respectively.Compared with CK,the soluble solids content of BF and BT fruits increased significantly by 8.33% and 7.78%respectively.The weight of BT single fruit,early yield of plot and total yield of plot were all higher than CK.(2)Soil EC value,available phosphorus and available potassium content were significantly increased,and cation exchange capacity was decreased by treatment BF.After BT treatment,soil organic matter content and cation exchange capacity were increased,soil PH value,total nitrogen and alkali-hydrolyzable nitrogen content were significantly increased,and soil EC value was significantly decreased.The activities of urease,sucrase and catalase in soil were improved by all the treatments,urease and sucrase activities were significantly increased by treatment BF,while catalase activities and neutral phosphatase activities were significantly increased by treatment BT.Compared with single application or combined application of organic fertilizer,the application of Trichoderma combined with charcoal has better effects on increasing yield,soil enzyme activity and improving soil physical and chemical properties.(3)The results of the second crop(Autumn and winter)experiment showed that the stem diameter and soluble solids content of cucumber plants were increased by all the treatments.The yield of the plot was reduced,and the BFF reached a significant level.Soil pH,except BN,other treatments reached a significant level were increased,and soil EC value was significantly reduced by all the treatments.Organic matter content was increased by BTFT treatment,and total nitrogen content was decreased by all the treatments the,among which BN reached a significant level.Available potassium content was significantly reduced by all the treatments,and alkali-hydrolyzable nitrogen content was significantly reduced by BTFT treatment.Soil water content was reduced by all the treatments,and BN reached a significant level.(4)In the second crop,the bacterial species in the soil were basically the same,but there were some differences in the relative abundance of species at different classification levels.The relative abundance of Acidobacteriota and Gemmatimonadota were increased,but the relative abundance of Firmicutes and Bacteroidota were decreased by all the treatments.Adding organic fertilizer and Trichoderma was more effective on improving the richness and diversity of bacteria.There is little similarity between Trichoderma and CK bacterial community,which changes the bacterial community structure.Compared with single application,biochar had better effects in promoting crop growth,improving soil physical and chemical properties,increasing soil enzyme activity,and increasing bacterial abundance and diversity,the effect of biochar combined with Trichoderma was the most outstanding,which had a persistent effect on soil improvement of continuous cropping.