Effects of Reducing Nitrogen Fertilizer and Improving Organic Fertilizer on Crop Yield, Soil Quality and Microbial Community in Five Years Wheat-Rice Rotation Field

Excessive application of nitrogen (N) fertilizer usually causes contamination of soil and groundwater. In this study, the rice yield and soil quality were investigated under different content of N fertilizer and amending organic compost (OC) or (and) crop residue (CR) in five-year wheat-rice rotated fields, and the soil microbial communities were inspected by means of Illumina sequencing. The results showed that rice yields were maintained at a high level although the N fertilizer was reduced to 80% of the normal content with amendment of OC and (or) CR. The PH was decreased and available phosphorus increased whenever the N fertilizer was normally applied or decreased when OC and (or) CR was amended, respectively. Available potassium was significantly increased when N fertilizer was reduced but OC and (or) CR was added. The abundance of bacterial and fungal communities was affected by OC or CR. Function prediction indicated that bacteria involved in DNA repair, carbohydrate digestion and absorption, amino acid degradation, caffeine metabolites were affected by OC or CR. Some plant growth promoting microbes (bacterial genus Pantoea, fungal gena Talaromyces and Scolecobasidium) were increased when OC or (and) CR was added. In addition, some nitrification or denitrification related bacteria (Candidatus nitrotoga, Nitrolancea, Noviherbaspirillum, Thioalkalispira) and fermentative metabolite bacteria (Lactobacillus) were increased when N fertilizer was reduced and OC or (and) CR was amended. These microbes may decompose the complex organic matter and improve nutrient transforming cycle to promote plant growth.