Response of nutrient accumulation, remobilization and yield to combined application of nitrogen and potassium in waxy maize

Unbalanced fertilizers supply with highly intensity and excessive nitrogen (N) and less potassium (K), lead to the decrease of soil fertility year by year. Balanced fertilization is one of the most effective measures to reduce fertilizer use while improving maize yield and efficiency. Two N levels (180 and 225 kg N ha−1, abbreviated N12 and N15) and four K treatments (0, 75, 150, and 75+75 kg K2O ha−1, abbreviated K0, K5, K10, and K5+5) were set to study the effects of combined application of N and K on the biomass and nutrient accumulation and remobilization characteristics in waxy maize. The results demonstrated that grain yield increased when higher amounts of K were applied at constant N levels, showing an average increase of 1,254.8 kg ha−1 (2020) and 727.3 kg ha−1 (2021) compared with K0. Under same N and K application, K5+5 increased grain yield by increasing kernel weight. Under K5+5 treatment, the biomass and nutrient accumulation had no significant difference between N12 and N15. Compared with K10, K5+5 not only enhanced the average remobilization amount (RBA) of biomass, but also increased RBA of N, phosphorus (P) and K. In addition, the average remobilization efficiency (RBE) of biomass, N, P and K in K5+5 were increased 3.3, 4.6, 10.6 and 4.2%, respectively. Furthermore, topdressing K improved the apparent contribution to grain (AC) of biomass, N, P and K, which promoted more nutrient to grains, and significantly increased nutrient harvest index. Considering yield and fertilizer use efficiency, we recommend optimized K application (basal and topdressing 75 kg ha−1) and moderately reduced N application (from 225 to 180 kg ha−1) in the production of spring-sown waxy maize in southern China.