Improved tomato yield and quality by altering soil physicochemical properties and nitrification processes in the combined use of organic-inorganic fertilizers

Fertilization is an effective measure to improve crop yield and quality. The combined use of cow manures and inorganic fertilizers is a suggested fertilization method to achieve high tomato yield and maintain soil fertility, but its impacts on soil physicochemical properties and microbial nitrification process in tomato rhizosphere are still unclear. In this study, cherry tomato was cultivated with different fertilizers to explore the relationships between rhizosphere soil physicochemical variables, nitrification process and tomato quality. Our work found that the optimal organic-inorganic fertilizer treatment was 25% cow manure and 75% inorganic fertilizer, which significantly increased tomato yield by 245% (2.35 ± 0.22 kg·pot−1), and enhanced vitamin C, lycopene, total soluble solids concentration, total soluble sugar concentration, sugar-acid ratio by 11.6%, 75.2%, 9.2%, 9.4% and 96.7%, respectively. Application of 100% cow manure significantly increased soil pH, nitrogen and carbon from the full fruiting period to the end-fruiting period, but did not achieve good tomato quality and yield. 100% inorganic fertilizer application could increase tomato yield by 72.9% (1.17 ± 0.31 kg·pot−1), but the soil quality was remarkably degraded. Similar evidence was found from soil microbial biomass carbon/nitrogen (MBC/MBN) and enzyme activities. Application of cow manure changed soil ammonia oxidizing bacterial communities, increasing Nitrosovibrio and Nitrosomonas but decreasing Nitrosospira. These results suggested that the combined use of 25% cow manure and 75% inorganic fertilizer was the best condition for tomato production, explained by a balanced soil physicochemical variables and microbial nitrification process. Our findings offered suggestions to reasonably optimize fertilization strategies.