Manure Applications Combined With Chemical Fertilizer Improves Soil Functionality, Microbial Biomass and Rice Production in a Paddy Field

Synthetic fertilizer with organic fertilizer (OF) is an approach for the improvement of soil health and quality without compromising crop yield. Therefore, a two-year field experiment was conducted to explore optimal chemical fertilizer (CF) management strategies in the context of OF, such as cattle manure (CM) and poultry manure (PM) fertilization to Ultisol soil to improve soil microbial biomass production, enzyme activities and nutrient contents, as well as grain yield of rice. A total of six treatments in the following combinations were used: i.e., T1— CF0; T2—100% CF; T3—60% CM + 40% CF; T4—30% CM + 70%CF; T5—60% PM + 40% CF, and T6—30% PM + 70% CF. Results showed that the combined fertilization significantly increased soil enzymatic activities such as soil invertase, acid phosphatase, urease, catalase, ꞵ-glucosidase, and cellulase as compared to sole CF application. Similarly, the integrated manure and inorganic fertilizers led to significant increases in soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), soil pH, soil organic carbon (SOC), total nitrogen (TN), available nitrogen (AN), available phosphorous (AP) and grain yield of rice. Average increases in soil MBC, MBN, SOC AN, and AP in the 0–20 cm soil depth were 62.2%, 54.5%, 29.2%, 17.4%, and 19.8%, respectively, across the years in treatment T3 compared with T2. Interestingly, the linear regression analysis displayed that soil enzymatic activities were highly positively correlated with MBC and MBN. Furthermore, the PCA exhibited that the improved soil enzyme activities and microbial biomass production played a key role in the higher grain yield of rice. Overall, the results of this study demonstrate that the combined use of CF and OF in paddy soil could be beneficial for the farmers in southern China by improving soil functionality and yield of rice on a sustainable basis.