Optimizing calcium hydroxide addition during wheat straw ammoniation enhances straw decomposition and nitrogen release, improving summer maize yield

Abstract

Context and objective In winter wheat–summer maize rotations, wheat straw decomposition overlaps with early maize growth, and slow decomposition may reduce the benefits of straw incorporation and constrain yield formation. Ammoniation improves straw decomposability, but quantitative field evidence for selecting an appropriate Ca(OH) 2 addition rate is limited. We quantified how Ca(OH) 2 addition during ammoniation affected straw decomposition, summer maize growth, and yield formation, and identified a suitable rate. Methods A two-year field experiment was conducted on the Guanzhong Plain, China. Wheat straw was ammoniated with equal urea inputs and Ca(OH) 2 additions of 0%, 1%, 3%, 5%, 7%, and 9% of straw dry matter before incorporation. Straw decomposition and nitrogen (N) release, soil NO 3 - –N concentration, summer maize growth dynamics, grain yield, and yield components were measured. Results and conclusions Responses generally increased and then declined with increasing Ca(OH) 2 addition rate, with the 3% treatment producing the strongest responses in both years. The 3% Ca(OH) 2 treatment enhanced straw decomposition and increased total growing-season straw N release by 48.2–68.3% relative to the control. At the six-leaf (V6) and tasseling (VT) stages, soil NO 3 - –N concentrations in the 0–20 and 20–40 cm layers were 11.8–37.1% higher than in the control. Compared with the control, the 3% treatment advanced the onset of rapid aboveground biomass accumulation, increased maximum aboveground biomass, and enhanced cumulative light interception by 11.6–14.9%. Grain yield under this treatment reached 9613 and 12,989 kg ha −1 in 2023 and 2024, respectively, representing increases of 17.0% and 20.8% over the control. Under the conditions of this study, Ca(OH) 2 addition at 3% of straw dry matter was the most effective treatment for ammoniated wheat straw incorporation. Significance These findings provide quantitative field evidence for optimizing Ca(OH) 2 addition during wheat straw ammoniation and improving the agronomic effectiveness of straw incorporation in intensive winter wheat–summer maize rotation systems.