Pseudomonas fluorescens affects nutrient dynamics in plant-soil system for melon production

The excessive use of agrochemicals to increase yield and fruit quality can result in soil, freshwater, and groundwater contamination. Designing and using new products based on microorganisms, such as rhizosphere bacteria, could reduce intensive agrochemical application and subsequent potential contamination. Therefore, the effect of a biocontroller (Pseudomonas fluorescens) on the nutrient balance and yield quality of melon (Cucumis melo L.) was evaluated under field conditions. Control and treatment plots without and with a biocontroller applied with an irrigation system were assayed. Soils were monitored by physicochemical and biochemical analysis and plants by nutrient and yield quality analysis during crop development. Pseudomonas fluorescens application significantly promoted salt solubility (416 and 1128 mu S cm(-1)), available Cu concentration (3.8 and 4.3 mg kg(-1)), P availability (104 and 123 mg kg(-1)), and microbial C biomass (56 and 93 mg C kg(-1)) for control and treatment plots, respectively. In addition, biocontroller application did not significantly increase soil total N and exchangeable Na, Mg, and K concentrations. Pseudomonas fluorescens also promoted Mn, N, Zn, and P absorption, which causes competition among nutrients, limiting Cu, Na, Ca, and K absorption by melon plants. The beta-glucosidase activity was also responsible for releasing Fe, Zn, Cu, Mn, P, and N in the soil. Finally, P. fluorescens application increased fruit size and weight (3.0 to 3.8 and 3.3 to 4.3 kg for control and biocontroller treatments, respectively); therefore, biofertilization with this bacterium is a sustainable alternative to increase yield and fruit quality without increasing the use of chemical fertilizers and pesticides.