| Environmentally friendly and low-cost cultivation substrates are the main measure to solve the problem of soil degradation in facilities and the key to innovation in soilless cultivation technology.In this study,a new soil-less cultivation system with continuous self-renewal of cultivation substrate and in situ crop rotation was constructed by replacing soil with vermicompost and treating cow manure with earthworms in situ,while replacing part of the total carbon in vermicompost and cow manure with biochar,an inert carbon source that can improve the fertilizer and water retention performance of the substrate,improve nutrient status and increase nutrient uptake by crops.The main results were as follows.1.Effect of vermicompost continuous renewal of soilless cultivation system on the physicochemical properties of substrate and growth and development of tomatoThe first crop is planted with vermicompost on the planting monopoly,and the breeding monopoly is spread with cow dung and placed with vermicompost to produce vermicompost in preparation for the second crop to be planted.(1)The pH,EC and organic matter content of the vermicompost substrate showed a continuous increase as the percentage of total carbon in the biochar replacement vermicompost increased.For substrate nutrients,the highest substrate fast-acting phosphorus content was observed when biochar replaced 3%of total carbon in the vermicompost substrate compared to the control CK,with a significant increase of 10.10%(p<0.05);when biochar replaced 5%of total carbon in the vermicompost,the highest substrate total N content,available N content and available K content were observed,with significant increases of 15.96%,92.20%and 85.74%(p<0.05).For substrate enzyme activity,the highest substrate sucrase activity was observed when biochar replaced 3%of total carbon in the vermicompost substrate with a significant increase of 52.09%(p<0.05),and the highest substrate urease activity and alkaline phosphatase activity were observed when biochar replaced 5%of total carbon in the vermicompost with a significant increase of 86.49%and 18.66%(p<0.05)compared to the control CK.(2)In this study,the results of high-throughput sequencing showed that,compared with the control CK,as the proportion of total carbon in the biochar replacement vermicompost increased,the bacterial Shannon index showed an overall trend of first decreasing and then increasing;the bacterial Simpson index showed an overall trend of first increasing and then decreasing,and both indices indicated that the bacterial abundance in the substrate was first decreasing and then increasing,where the biochar replacement proportion was 2%,3%and 5%.The lowest bacterial diversity was observed at 2%,3%and 5%of biochar substitution.For the dominant microbial phylum,the dominant bacterial phylum in the tomato inter-rhizosphere substrate with more than 10%were Actinobacteria,Proteobacteria,Chloroflexi and Firmicutes.Among them,the dominant fungal phyla with more than 10%were Ascomycota,unclassified and Mortierellomycota.(3)Stomatal conductance,transpiration rate,intercellular CO2 concentration,total plant nitrogen content,total plant potassium content in the lower part of the plant,and tomato vitamin C content of the leaves of the plants showed a continuous trend of increase as the percentage of total carbon in biochar substituted vermicompost increased.For plant growth,the highest relative growth rate of tomato stem thickness was observed when biochar replaced 3%of total carbon in vermicompost compared to the control CK,with a significant increase of 95.79%(p<0.05);the highest relative growth rate of plant height and relative growth rate of leaf area were observed when biochar replaced 5%of total carbon in vermicompost,with a significant increase of 38.03%and 15.30%(p<0.05).For plant photosynthesis parameters,the net photosynthetic rate of leaves increased significantly by 13.70%(p＜0.05)when biochar replaced 3%of total carbon in vermicompost compared to the control CK;for tomato quality,when biochar replaced 5%of total carbon in vermicompost compared to the control CK,both soluble solids and soluble sugars content of tomatoes were the highest,significantly increasing by 7.31%and 35.64%(p<0.05).For tomato yield,the highest yield of tomato was achieved when biochar replaced 3%of total carbon in vermicompost with a significant increase of 33.28%(p<0.05)compared to the control with a maximum yield of 9378.39 kg/(667 m2).(4)In this study,IC-MS analysis of tomato fruits showed that when the total carbon ratio of biochar replacing earthworm manure in the continuous replacement earthworm manure cultivation system was 3%and 5%,the main differential metabolites in fruits were L-serine,L-glutamine and L-tryptophan,all of which were involved in the biosynthesis process of aminoyl tRNA.These three amino acids are converted into sugars through glycolysis,gluconeogenesis and the tricarboxylic acid cycle,thus affecting the content of sugars in fruits.According to the comprehensive evaluation of principal components,it was found that when biochar replaced 5%of the total carbon in vermicompost,it had the best effect on the traits of nutrients and enzyme activity of vermicompost substrate,the best quality of tomato fruits and the highest yield,which was the best ratio for this study.2.Effect of vermicompost continuous renewal of soilless cultivation system on the physicochemical properties of substrate and growth and development of melon.After the first crop is harvested,the farming monopoly is switched with the planting monopoly,and the second crop of melons is planted on the vermicompost generated from the original farming monopoly,and the cow manure continues to be spread on the original planting monopoly to make it produce vermicompost in preparation for the next crop to be planted.(1)The pH,EC and organic matter content of the produced vermicompost substrate showed a continuous increase as the percentage of total carbon in cow manure replaced by biochar increased.For substrate nutrients,the highest amount of available phosphorus was produced when biochar replaced 2%of total carbon in cattle manure compared to the control CK’,with a significant increase of 18.00%(p<0.05);when biochar replaced 3%of total carbon in cattle manure,the highest amount of total N,available N and available K were produced in vermicompost,with significant increases of 21.40%,162.1%and 23.48%(p<0.05).For substrate enzyme activities,the highest vermicompost alkaline phosphatase and sucrase activities were generated when biochar replaced 2%of the total carbon in cow manure compared to the control CK’,with significant increases of 36.13%and 33.96%(p<0.05);the highest vermicompost urease activity was generated when biochar replaced 5%of the total carbon in cow manure,with significant increases of 41.35%(p<0.05).(2)The stomatal For plant photosynthetic parameters,the net photosynthetic rate of melon leaves was greatest when 5%of total carbon in cow manure was replaced by biochar,significantly increasing by 59.54%(p<0.05)compared to the control CK’.For melon quality,compared to the control CK’melon soluble solids and soluble sugars content were highest when biochar replaced 2%of total carbon in cow manure,significantly increasing by 24.18%and 23.31%(p<0.05);melon fruit vitamin C,significantly increasing by 58.65%when biochar replaced 3%of total carbon in cow manure(p<0.05);melon yield was highest when biochar replaced 3%of total carbon in cow dung,significantly increasing 62.67%(p＜0.05)with a maximum yield of 4277.35 kg/(667 m2).According to the comprehensive evaluation of principal components,it can be seen that when biochar replaces 3%of the total carbon in cow dung,it has the best effect on the nutrients,enzyme activity and other traits of the generated earthworm dung,the best quality of melon and the highest yield,which is the best ratio for this study.Taken together,the substrates of both models had significant effects on the growth and development of crops and the improvement of quality and yield.The overall effect of replacing part of the total carbon in cow manure with biochar was better than replacing part of the total carbon in vermicompost,providing a theoretical basis for low-cost,high-yield and high-quality soilless cultivation of facility horticulture crops. |
