Using slow-release fertilizers ensures the maintenance of litchi (Litchi chinensis Sonn.) production by enhancing soil nutrient supply and optimizing microbial communities

Abstract

High temperatures and rainy climate conditions result in a very low nutrient utilization rate during crop cultivation in tropical regions. To determine whether slow-release fertilizers could have a positive impact on the yield and quality of litchi, and the soil ecology of orchards while reducing chemical fertilizer application, a field plot experiment with two fertilizer types (chemical fertilizers and lignin-based slow-release fertilizers) combined with a 0 %, 15 % and 30 % reduction of fertilizer application rates was set up from 2018 to 2019. Subsequently, a demonstration trial with an optimum dose of slow-release fertilizers with chemical fertilizers was carried out from 2019 to 2020 in acidic soils. The results demonstrated that all treatments could maintain the yield of litchi between 11,825–13,056 kg/hm2 in 2018–2019. Furthermore, compared to conventional chemical fertilizer treatment, the treatment of lignin-based slow-release fertilizer application with a 15 % fertilizer reduction significantly reduced the concentration of alkaline nitrogen by 19.9 % and available phosphorus by 22.0 % at the 20–40 cm soil layer during the maturity period of litchi growth. The result of the demonstration trial in 2019–2020 further confirmed that a slow-release fertilizer, along with a 25 % reduction in fertilizer application, could maintain high levels of soil alkaline nitrogen and available potassium at the 0–20 cm soil layer without affecting soil bulk density, total soil porosity, and soil aeration. Moreover, the treatment of lignin-based slow-release fertilizer application with a 15 % fertilizer reduction significantly increased the relative abundance of Proteobacteria (1.21 times) and decreased the abundance of Firmicutes (0.81 times) compared to conventional fertilization treatment at the 0–20 cm soil layer. In contrast, it decreased the relative abundance of Firmicutes (0.67 times) and Proteobacteria (0.37 times) at the 20–40 cm soil layer. Meanwhile, the fertilizer application only affected the soil fungi richness but did not increase their diversity. Applying slow-release fertilizers can realize the goal of reducing chemical fertilizers and ensuring excellent litchi production in tropical acidic soils.