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 CN 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.