Micro-nano bubbles irrigation improves rice yield under nitrogen deficiency by regulating soil microbial community

Abstract

Nano-bubble water irrigation can increase soil oxygen content, alter soil chemical and microbial properties, and enhance crop yields. However, there is limited research about the impacts of nitrogen fertilizer reduction coupling with different micro-nano bubbles (MNBs) irrigation frequency. In this study, a two-year field experiment with three MNBs irrigation frequencies (2, 4 and 8 times/d) and two nitrogen fertilizer amounts (100 % and 70 % fertilization) was conducted in Shanghai, China. The results indicated that 1) MNBs irrigation increased rice yield by an average of 8.6 % over the two years. 2) Continuous medium and high frequency MNBs irrigation increased the soil organic matter and nitrogen contents. MNBs could effectively reduce the risk of nitrate nitrogen leaching by the inhibition to the conversion of ammonium nitrogen to nitrate nitrogen and compensate for the N deficit of 70 % fertilization treatments, enhancing their soil nutrient retention capacity. 3) The bacterial and fungal community structure were both affected by the frequency and amount of fertilization. Generally, MNBs irrigation reduced bacterial and fungal diversity, and changed microbial co-occurrence patterns, leading to a new stable microbial community. MNBs enhanced soil organic decomposition, nitrogen fixation, phosphorus cycling through the alteration of bacterial and fungal community. The responds of bacteria to MNBs were strong in a short period of time, but didn’t expand to the 20–40 cm soil. The responds of fungi were tardy but significantly affected by continuous MNBs irrigation. Overall, medium MNBs irrigation frequency coupling with 70 % fertilization had the best effect on rice production systems.