Effects of applying biogas slurry instead of chemical fertilizer on the growth of melon and soil microorganism

【Objective】 The effects of different biogas slurry application rates instead of chemical fertilizer on plant growth,fruit quality and soil microorganisms were studied to provide scientific theoretical basis for melon production with reducing chemical fertilizers and pesticides.【Method】 In this experiment,chemical fertilizer group(CK)and biogas slurry groups were set up,the CK group was treated with the compound fertilizer of 600 kg/ha,the application amounts of biogas slurry in T1,T2,T3 and T4 groups were 100,140,180 and 220 t/ha respectively,the basal fertilizer and fruit expansion fertilizer in the ratio of 1:1 of each group. The plant height,stem diameter,disease index,chlorophyll content,dry weight of plant organs,fruit quality of melon and the diversity of soil microbial were measured regularly.【Result】 When the amount of base fertilizer was 70 t/ha between 110 t/ha,there was no obvious difference in plant height and stem diameter.The chlorophyll content of T4 group was the highest,the SPAD value was 86.61,and the disease index of T3 and T4 groups was the lowest,which were both 14.06. Except for T1 group,there was no significant difference in dry matter accumulation between biogas slurry groups and CK group(P>0.05),the highest dry material accumulation in T3 group was240.66 g. The T4 group had the highest soluble sugar content and the ratio of sugar and acid,which were 9.71% and 88.27 respectively,and there were significant differences with CK group(P<0.05). The relative abundance of Proteobacteria in the biogas slurry groups were lower than that of CK group,with the increase of biogas slurry dosage,the relative abundance decreased. The relative abundance of Actinobacteria in T3 group was the highest(10.08%)and the Gemmatimonadetes and Firmicutes was the lowest(2.92% and 2.23% respectively). The highest relative abundance of Ascomycota in T3 group was 81.19%,while the Basidiomycota and Mortierellomycota in T3 and T4 groups was lower than that in CK and T1 and T2 groups. Moreover,the Chao1 index and Shannon index of bacteria in T3 group were higher than those in other groups,while the Chao1 index of fungi were lower than those in CK,T1 and T4 groups,and Shannon index was the lowest.【Conclusion】 Biogas slurry can promote plant growth and dry matter accumulation under the condition of 180 t/ha(base fertilizer 90 t/ha,fruit expansion fertilizer 90 t/ha),the fruit quality are improved significantly,the richness and diversity of bacteria are increased and the diversity of fungi is decreased. This method can be promoted in melon plantation.