Effects of vermicompost and soil proportion on the microbial property of substrate and the growth and quality of leek

Objectives Vermicompost is a homogenous particle produced by earthworms digesting organic wastes, which has been proved to enhance soil fertility, improve soil structure and promote crop growth. In this paper, the effects of different ratios of vermicompost to soil on the microbial properties of substrate and the growth and quality of leek were preliminarily studied, in order to provide reference for the widely use of vermicompost in high quality vegetable production.

Methods A pot experiment was conducted inside the greenhouse of China Agricultural University from April to June in 2015. The substrate were prepared by mixing 4 mass percentages of vermicompost and soil in pot: 0/100% (CK), 20%/80% (T1), 60%/40% (T2) and 100%/0 (T3). After harvest, the biomass of leek, total soluble protein, total soluble sugar and chlorophyll contents were measured. The NPK contents and the microbial composition of substrate were analyzed.

Results 1) Vermicompost addition significantly increase the total N, readily available K and organic matter in the substrate, and the better the higher proportion of vermicompost in the substrate; 2) Compared with no vermicompost addition CK, the new root ratio of leek was 5.75%, 6.39% and 22.23% higher in T1, T2 and T3 treatments. The contents of total soluble protein of leek were significantly increased by 1.84−5.97 times and the total soluble sugar contents increased by 1.49−1.60 times (P < 0.05); 3) The microbial diversity index of substrate was significantly increased by the addition of vermicompost. The bacterial fragments of 116, 118, 130, 226, 297 were significantly increased (P < 0.05) and the fungal fragments of 71, 91, 153 and 351 decreased (P < 0.05).

Conclusions Vermicompost could improve microbial community structure, improve the bacterial and fungal diversity, increase nutrient availability of the based substrate, and promote the growth and improve the quality of leek. The vermicompost can be directly used as substrate and shows the best result. Considering the profit and cost, adding proportion of 20% will make good enough substrate for high quality vegetable production.