Interactive Effects of Nitrogen and Potassium on Grain Yield and Quality of Waxy Maize

Reasonable fertilization of nitrogen (N) and potassium (K) had significant effects on maize growth. In this experiment, two N levels (N180 and N225 kg ha^-1) and four K treatments (K0, K75, K150 and K75 + 75 kg ha^-1) were set to study the effects of combined application of N and K on the grain yield and quality of waxy maize. The results showed that grain yield increased with increasing K under the same N level, and top-dressing K further increased the grain yield. K application increased starch content significantly at N180 and decreased significantly at N225, while the protein content increased significantly at the two N levels. The grain starch content with the K75 + 75 treatment increased by 5.8% and 9.0% compared with K150 at the two N levels, and the protein content decreased by 2.9% and 4.7%. Application of K increased the retrogradation enthalpy (ΔH_ret) and retrogradation percentage (%R) at N180. At N225, the ΔH_ret and %R of K75 and K150 decreased, while those of K75 + 75 increased. The ΔH_ret and %R under K75 + 75 at N180 were lower than N225. Under these experiment conditions, 75 kg ha^-1 K₂O at sowing date and top-dressed 75 kg ha^-1 K₂O at jointing stage (V6) under the conditions of appropriate N reduction could not only effectively improve the pasting and thermal properties of waxy maize flour, but also stabilized the grain yield.