Effects of Bio and Water-Soluble Fertilizers on Sweet Potato Yield, Quality and Soil Properties in a Continuous Cropping System Under Plastic Film-Mulched Drip-Fertigated Field Conditions

To verify an effective scheme for alleviating obstacles during continuous cropping, the effects of biofertilizer (BF) and water-soluble (WS) fertilizer applications on yield, quality, and soil properties were evaluated during the 2018-2019 growth seasons in fields continuously planted with sweet potato over five years. The following five treatments were designed under plastic film-mulched drip-fertigated conditions: no fertilizer application, basic application of WS fertilizer, basic application of BF and WS fertilizer, split application of WS fertilizer, and combined basic application of BF and split application of WS fertilizer. In comparison with the control, fertilizer application treatments exhibited significant positive effects on increasing soil activities and nutrients, especially in the second year. Compared with a single application, split fertigation with WS fertilizer significantly increased the activities of soil dehydrogenase (DHA), alkaline phosphatase (ALP), and soil organic matter (SOM) in the second year. In both years, split fertigation exhibited positive effects on increasing dry matter (DM) accumulation in tuberous roots and significantly increased the productive efficiency in nitrogen (N), phosphorus (P), and potassium (K) fertilizers and improved root yield. In comparison with the no BF application, the BF application for two consecutive years significantly increased the activities of soil sucrase, DHA, ALP, soil available P, and SOM. BF also significantly increased root yield, carotenoid content in tuberous roots and K utilization efficiency. Overall, the combination of BF and split fertigation for two consecutive years was most conducive to the activation of soil nutrients, maintenance of soil fertility, and improvement in yield and quality, which could effectively relieve problems associated with the consecutive monoculture of sweet potato