Effect Of Trichoderma Bio-organic Fertilizer With Reduced Chemical Fertilizer Application On Tomato Growth And On Soil Microbe In A Monocropped System

Modern intensive agriculture depends on a large amount of chemical fertilizer application and continuous monocropping,both of which lead to serious environmental problems and yield losses.Application of some microbial organic fertilizer is becoming a popular strategy for sustainable agriculture due to its combination of functional microbes and organic fertilizer.Though researches on microbial organic fertilizers affecting soil properties and crop growth also gradually increase,there is still a lot of work to be done in this area.The optimal ratio of chemical fertilizers combined with microbial organic fertilizers and the mechanisms emplyed by microbial organic fertilizers have not been fully studied.Moreover,most of the previous reports only paid attention to 1-2 season of short-term fertilizer efficiency.The effect of long-term use of microbial organic fertilizers is worthy to study.In this study,we set up a pot experiment with different rates of chemical fertilizer plus Trichoderma-enriched bio-organic fertilizer to find the optimized ratio of these two fertilizers to obtain a stable tomato yield.Also,in the continuous pot experiment(monocropping system),tomato yield,quality,soil fertility and soil microbial community were investigated.The main results obtained are as follows:1.In order to find the minimal rate of chemical fertilizer application plus bio-organic fertilizer to obtain the equal tomato yield relevent to the full chemical fertilizer regime,a pot experiment with different rates of chemical fertilizer(100%,90%,75%,50%and 0%)plus bio-organic fertilizer was performed.It showed that the use of<50%chemical fertilizer significantly decreased tomato growth,while using 75%or 90%of the chemical fertilizer together with Trichoderma-enriched bio-organic fertilizer obtained the equal tomato yield relevent to the 100%of chemical fertilizer.2.In this work,field trials and continuous pot experiments on tomatoes were conducted using a reduced application of chemical fertilizer(75%of the conventional application)plus organic fertilizer,Trichoderma-enriched bio-organic fertilizer or Trichoderma spore suspension;100%of the conventional chemical fertilizer was used as the control.The results of the pot and field trials indicated that reduced rates of chemical fertilizer coupled with bio-organic fertilizer produced better fruit quality and tomato yields that were equivalent to those obtained using the full rate of chemical fertilizer.The Trichoderma-enriched bio-organic fertilizer treatment resulted in higher total soluble sugar(35-54%)and Vitamin C(2-23%)contents but lower(32-46%)nitrate accumulation compared with the control.By contrast,the 75%chemical fertilizer coupled with the Trichoderma spore suspension or organic fertilizer resulted in yield decreases of 6-38%or 9-35%,respectively,compared with the control.The efficacy of the bio-organic fertilizer for maintaining a stable tomato yield and improving tomato quality may be due to the increased abundance of soil microflora and enhanced soil fertility because these factors were positively and linearly correlated in most of the pairwise correlation analyses.The overall results suggest that the Trichoderma bio-organic fertilizer can be used in combination with the appropriate rates of chemical fertilizers to obtain maximum benefits in terms of yield,quality and fertilizer savings.3.MiSeq sequencing was employed to evaluate the response of local microbial communities to three different fertilization regimes(CF,OF and BF)in the above continuous five-season pot experiment.The CF-treated soil resulted in a bacterial community with the lowest diversity,while the BF-treated soil had the highest diversity level.The OFtreated soil had the lowest diversity in the fungal community,while the CF-and BF-treated soils had higher diversity.Moreover,better plant growth and soil fertility status were obtained in the BF treatment followed by the OF and CF treatments.Compared to the CF and OF regimes,reduced chemical fertilizer plus Trichoderma-enriched organic fertilizer(BF)is the most suitable regime to control microbiome degeneration of monocropped soil and to thus maintain tomato plant growth and health.