Sequential micro-dose fertilization strategies for rice production: Improved fertilizer use efficiencies and yields on P-deficient lowlands in the tropical highlands

Abstract Localized micro-dose fertilization near the seed or root zone can maximize returns from minimal fertilizer inputs. In transplanted rice production systems, two opportunities exist for implementing localized micro-dose fertilization: Micro-dosing the nursery bed at sowing and dipping seedling roots at transplanting. Previous studies have focused on the individual effects of these management options, whereas none have identified how a combination of these techniques affect rice yields and fertilizer use efficiencies. Herein, we examined the effects of nursery bed micro-dosing combined with dipping seedling roots in an N-enriched solution (N-dipping) and P-enriched slurry (P-dipping) at transplanting. On-farm experiments were conducted at three sites with nutrient-poor soils in the central highlands of Madagascar. The results demonstrated that phosphorus is a key element for localized micro-dose fertilization, while single and sequential N applications could hinder initial growth and grain yields in severely and moderately P-deficient fields. Grain yields were significantly improved by nursery bed N and P micro-dosing (16 %–23 %) and by P-dipping at transplanting (33 %–46 %), except for nursery bed micro-dosing in a relatively high-yielding and less P-deficient site. The effect of these treatments were independent, and thus the yield additively increased by 55 %–67 % in the severely and moderately P-deficient sites. Moreover, the nursery bed micro-dosing and P-dipping additively shortened the number of days to heading by 17–21 days in these sites, which reduced the risk of cold-induced stress at the reproductive stage. We conclude that the combination of N and P nursery bed micro-dosing and P-dipping at transplanting can be recommended for improving yields while reducing the risk of climate-induced stress for lowland rice production under low-input and P-deficient soils.