Effects of long-term fertilization on soil microbial quantity and community structure in saline-sodic paddy fields
The objective of this study was to elucidate the effects of long-term fertilization measures on soil microbial quantity and community structure in saline-sodic paddy fields.A long-term fertilization experiment was carried out at a study site of the Da'an National Field Observation and Research Station of Agroecosystem.The level of phospholipid fatty acid(PLFA)was measured as an indicator of the effects of different fertilization measures on the soil microbial community.The specific fertilization measures included single application of nitrogen treatment(N),combined application of nitrogen,phosphorus,and potassium fertilizer treatment(NPK),single application of manure treatment(M),combined application of manure and chemical fertilizer treatment(MNPK),and chemical fertilizer with straw returning treatment(RNPK).The results showed that 57 PLFAs were detected in soil under different fertilization treatments;the PLFA contents of M,MNPK,RNPK and NPK treatments increased by 26.47%,29.76%,25.07%,and 13.20%,respectively,compared with the contents under N treatment,and the PLFA contents of M,MNPK and RNPK treatments were significantly higher than those of N treatments(P<0.05).Furthermore,the ratio of fungi to bacteria in the MNPK treatment was highest and the radio in the M treatment was lowest(6.00%lower than the maximum)in the above five treatments,which demonstrates that the combination of organic fertilizer and chemical fertilizer is the optimal treatment in terms of stability of the soil ecosystem in saline-sodic paddy fields.The minimum of Gram-positive bacteria(G+)/Gram-negative bacteria(G-)was found in RNPK treatment,which decreased by 13.71%compared to the maximum ratio,which was obtained in the M treatment.This finding indicated that the combination of straw returning and fertilizer application resulted in less soil nutrient stress and could effectively improve the nutrient status of the soil.The diversity of microbial communities in the N treatment was highest under different fertilization treatments,with index values considerably higher than that under the NPK treatment:Shannon-Wiener index(H)(10.91%higher),Pielou index(J)(12.00%higher),and Simpson index(D)(13.79%higher).Redundancy analysis(RDA)revealed that electrical conductivity(EC),soil organic matter,and soil pH all had significant effects on soil microbial community,explaining 54.8%,39.8%,and 33.1%,respectively.In summary,these measures including combined application of manure and chemical fertilizer,the single application of manure and straw returning with the chemical fertilizer effectively increase soil microbial biomass and optimize microbial community structure,thereby improving the soil ecological environment.
saline-sodic soilriceapplication of organic fertilizersoil microbephospholipid fatty acid(PLFA)straw returning
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