Long-term Fertilization On Soil Microbial Production Of Methane And Ammonia Oxidation

Soil microorganisms are sensitive indicators of the climate and soil conditions, and the change of soil quality may have a significant impact on soil microorganisms. Routine applications of inorganic fertilizer and manure are an essential component of soil management in arable crop production systems. These amendments are used primarily to increase nutrient availability to plants, but they can also affect soil microorganisms. Red soils cover about1.13million km2or11.8%of the country’s land surface, and support22.5%of the nation’s population. Red soils are heavily weathering and leaching soils, and are characterized by low pH and deficiencies in available nutrients, which is very likely to affect crop production. Therefore, it is instructive to study the long-term effects of inorganic fertilizers and manure on the microorganisms, which affect the soil carbon and nitrogen cycle in red soil, for rational fertilization, agricultural production and environmental protection.Phospholipid fatty acid analysis (PLFA) was conducted to investigate the long-term effects of different fertilizer and groundwater level management on microbial diversity of a paddy soil derived from Hunan province. These fertilization treatments were:High groundwater-level with chemical fertilizer (HCF), Low groundwater-level with chemical fertilizer (LCF), High groundwater-level with normal amount of organic manure (HNOM), Low groundwater-level with normal amount of organic manure (LNOM), High groundwater-level with high amount of organic manure (HHOM), Low groundwater-level with high amount of organic manure (LHOM). In the present study, we identified44PLFAs in soil with the different fertilization and groundwater level managements. Among them, there are32bacteria PLFAs,3fungal PLFAs and3actinomycetic PLFAs. The result of one-way ANOVA (analysis of variance) showed that there was no significant difference in the concentrations of soil total PLFAs between the six different treatments (p>0.05). The concentrations of soil bacteria PLFAs and Gram-negative bacteria PLFAs were the highest in LHOM treatment while the lowest in the HNOM treatment. The concentrations of fungal PLFAs and actinomycetic PLFAs didn’t show significant differences among the different fertilization and groundwater level managements. Besides, the ratio of anaerobe to aerobe showed differences among the different fertilization and groundwater level managements, the ratio was higher in the treatments applying organic manure than in the treatments applying chemical fertilizer, and was significantly different between the LCF and LHOM treatment(p<0.05). Two-way ANOVA analysis showed that groundwater level significantly affect the types of PLFAs and the concentrations of total PLFAs and bacterial PLFAs, at the same time, the concentrations of fungal PLFAs were significantly influenced by fertilization x groundwater level interactions(p<0.05).In the meantime, a laboratory incubation experiment was carried out to investigate CH4emission from paddy soils of different fertilization and groundwater level managements. The influence of nitrate addition on CH4emission was investigated as well. The molecular biological techniques, including qPCR and DGGE, were used to investigate the effect of different fertilization, groundwater level and nitrate addition on methanogenic archaeal communities. We observed the highest production rate of CH4in HHOM treatment and the lowest rate in HCF treatment and LCF treatment(p<0.05). Production rate of CH4were significantly higher in high amount organic manure treatments(HHOM and LHOM) than in chemical fertilizer treatments(p<0.05). The abundance of methanogenic archaeal16S rRNA gene in HNOM treatment was different from the other5treatments(p<0.05), and there was no significant distinctions among the treatments. Two-way ANOVA analysis showed soil CH4production rate was significantly influenced by different fertilizantion managements (p<0.05); groundwater level managements didn’t have a remarkable impact on the CH4production rate(p>0.05), but it significantly changed the aboundance and composition of methanogenic archaeal community(p<0.05). Besides, the CH4production rates in all treatments decreased after nitrate addition, and were significantly decreased in the LNOM, LHOM and HHOM treatments with nitrate addition. The abundance of methanogenic archaeal16S rRNA gene also significantly decreased after the addition of nitrate.Long-term effects of mineral fertilizer and organic manure on the abundance, composition, and activity of ammonia-oxidizing bacteria (AOB) and archaea (AOA) are poorly understood, particularly in acidic red soils. Abundance and composition of AOB and AOA in these upland red soils from Jiangxi province were evaluated using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) after long-term (24-year) fertilization. These fertilization treatments were:the control (CK, without fertilization), fertilizer N (N), fertilizer NPK (NPK), organic manure (OM), and organic manure plus fertilizer NPK (OM+NPK). The abundance of bacterial and archaeal amoA gene significantly increased after long-term treatments with organic manure, with or without NPK. fertilizer. The shift in DGGE patterns of AOA was more significant than that of AOB. The Shannon and richness indices of AOA were the highest after organic manure applications, higher after mineral fertilizer applications, and least in the control. Only richness index of AOB was significantly higher in OM treatment than the control. Then, the DGGE bands of AOA were excised for sequencing. Phylogenetic analyses showed that most of AOA sequences from different fertilization treatments were affiliated with group1.1b thaumarchaea and only one with the group1.1a-associated thaumarchaea.