Study On Typical Organic Waste Compost Products As Substrates And Inhibitory Effect On Soil-borne Bacterial Disease

With the accelerated process of urbanization and agricultural intensification, the disposal of organic solid waste such as rural and urban waste, sewage sludge, livestock waste and rural straw has become an increasingly serious problem, and composting is one of the most potential methods to solve this problem. However, because OSW (organic solid waste) are numerous in varieties, different composting products are significantly different from each other in physical, chemical and biological properties. Attention has been attached to the fertility of composting products as organic fertilizer, while little study has been carried out on their characteristics and other functions. This paper takes the typical pig manure, sewage sludge and herb residue compositing products as research objects, focusing on their application potential in substrate utilization and soil-borne bacterial disease controlling. The main results are shown as follows:(1) Firstly, study on the composting process of typical organic waste (take pig manure compost as an example). The C/N ratio was respectively adjusted to25with sawdust, herb residue, mushroom residue or ricechaff and the moisture content was adjusted to65%. After49-day composting fermentation, the four treatments were mature, but different conditioners had obviously different effects on the composting process and the characteristics of composting products. In the composting process, the sawdust treatment warmed the quickest and the high temperature kept for the longest time; on the contrast, the high temperature maintains the shortest with the ricechaff treatment. The total contents of N, P2O5and K2O are above4.0%. Among the four treatments, the herb residue treatment was the highest, next came the mushroom residue and ricechaff treatment, and the sawdust treatment was the lowest. For nitrogenconservation and contents of N, P and K, herb residue was the best conditioner; for improve TK, ricechaff performed best. Due to different wastes have different properties, they fit different conditioners. We have studied the conditioners for sewage sludge and herb residue, finding that for each organic waste, when the original C/N ratio and moisture content of the compositing materials is respectively adjusted to25-30and60-65%, the composting process proceeds the fastest, which coincides with the reported appropriate C/N ratio and moisture content.(2) In order to study the feasibility of substituting peat with three typical composts, the physical and chemical characteristics of these three substitutes were analyzed. The results showed that the herb residue compost (HSC) and sewage sludge compost (SMC) treatments were similar to peat, while pig manure compost (PMC) treatment was largely different from peat. The nutrient content, pH value and EC value of PMC treatment was all significantly higher than that of the peat, its cation exchange capacity was significantly lower than that of the peat, and its pH value, EC value, Cu and Zn contents exceeded the ideal range. Principal component analysis showed that different compost substrates showed differences in physical and chemical properties and the substrates formed by different alternative proportion of the same compost were similar. Three composts pot tests were carried out with cucumber, tomato, bermudagrass and impatiens. The results showed that the plant grew better with HSC when the substitution ratio was50%,75%and100%. And for SMC,50%of substitution ratio could promote the growth, while for PMC,50%of substitution ratio was worse than the peat. From cost accounting, the prices of HRC, SMC and PMC are respective37%,31%and43%of peat. Therefore, HRC and SMC part or all of the alternatives substituting peat for seedling substrate is technically and economically feasible.(3) Treating tomato bacterial wilt as research object, biological control experiments were conducted on three typical composts. The results exhibited that HSC and SMC could effectively control tomato bacterial wilt, but SMC was inferior to HSC, and PMC had little effect. The effect was the best when the mixture proportion of peat and HSC was4:1. However, different ratio of the same compost showed no significant inhibitory effect on tomato bacterial wilt. Comparing with the controls, adding HRC, SMC or PMC could improve the enzyme activity, microbial biomass C and microbial quantity of the mixed substrates and change the physical and chemical properties of substrates. Correlation analysis displayed that tomato bacterial wilt disease index was highly negative correlated with the number of microorganisms (especially actinomycetes and bacteria), pH value and fluorescein diacetate hydrolysis activity, suggesting that tomato bacterial wilt could be effectively inhibited by increasing the pH value, fluorescein diacetate hydrolysis activity and number of microorganisms (especially the number of actinomycetes and bacteria) in the substrate.(4) Culture plate antibacterial test further suggested that HRC and SMC and their extracts had stronger inhibitory effects on P. solanacearum than PMC extract and its extract, which was directly related with the microorganism in compost. Hence, we tried to screen out efficient antagonistic strains from the three composts, five from HRC, five from SMC, and two from PMC. From the pot experiments and culture plate antibacterial tests, HRC had the best inhibitory effect on tomato bacterial wilt, followed by SMC, PMC is the worst. The reasons were that the addition of HRC and SMC created disadvantaged ecological conditions for P. solanacearum; HRC and SMC could increase the enzyme activity, microorganism quantity and number of antagonistic strains. These findings indicated that efficient antagonistic strains chose from the compost provide new approach for the development of functional microbial agents.