Multi-year vertical and life cycle impacts of C-N management on soil moisture regimes

Understanding the long-term impact of C-N management practices on soil moisture content (SMC) is crucial for sustainable agriculture, particularly in mitigating seasonal droughts and storm rainfall constraints. A multi-year (2014–2018) field experiment was conducted, with high-frequency measurements and consideration of a full life cycle, as well as multiple vertical layers (0–100 cm, with intervals of 20 cm). Treatments were arranged in a split plot design with nitrogen (N) fertilizer input (N80% and N60%) as the whole-plot factor, and Carbon (C) treatments (Corg=organic fertilizer, Cstraw=straw mulching and full returning, Cinteg= Corg + Cstraw) were considered as the split-plot factor. The results demonstrated the Cinteg treatment resulted in the highest increase in the five-year averaged SMC (approximately 6.60% greater than Corg), followed by the Cstraw treatment. Additionally, the N60% treatment resulted in significantly higher SMC compared to the N80% treatment, with a range of 1.71–4.12% increase across the life cycle. Furthermore, the research revealed that the average SMC increased the most during the jointing-heading period and the least during the heading-maturity period across all treatments. The vertical results indicated a higher efficiency in water retention within the shallow layers (0–20 cm, 20–40 cm) compared to the deeper layers (80–100 cm) for all treatments. The study recommends adopting integrated C-N management practices, considering life cycle periods and vertical layers, to optimize soil moisture content. It offers valuable insights for optimizing soil moisture management strategies, alleviating seasonal droughts, enhancing water-use efficiency, and fostering sustainable agricultural practices.