Water–saving irrigation combined with N–loaded clinoptilolite enhances nutrient yield, and water productivity by improving rice root characteristics: A combined PCA–SEM analysis

Nitrogen (N) –loaded clinoptilolite is renowned for its high–water retention and nutrient supplementation properties, which benefit crop growth. However, its combined effects with water–saving irrigation regime on N mineralization, root system characteristics, and nutrient yield, particularly their regulatory pathways, remain underexplored. This two–year split–plot experiment evaluated the impact of two irrigation regimes (I_CF: continuous flooding irrigation; I_AWD: alternate wet–dry irrigation) and two rates of N–loaded clinoptilolite (NZ₀: no N–loaded clinoptilolite; NZ₁₀: 10 t·ha^–1) on root characteristics, mineralized N, nutrient yield, and water productivity. We employed principal component analysis (PCA) and structural equation modeling (SEM) to analyze the interactions among the factors. The I_AWDNZ₁₀ treatment showed the greatest water–saving potential, increasing the irrigated area by 0.29–fold compared to I_CFNZ₀. N–loaded clinoptilolite under I_AWD increased root surface area by 12.6 %, average root diameter by 14.2 %, and root volume by 13.8 %. Additionally, I_AWD increased mineralized N by 22.4 %, while N–loaded clinoptilolite further boosted it by 34.7 %. Root characteristics (r = 0.78) were crucial mediators in the effect of N–loaded clinoptilolite on protein (r = 0.64) and amylose nutritional yield (r = 0.68). Water usage influenced protein (r = -0.93) and amylose nutritional water productivity (r =-0.67) indirectly via chalky rice rate (r =0.90). In summary, integrating N–loaded clinoptilolite with the I_AWD regime not only enhanced rice root characteristics and mineralized N but also led to substantial increases in nutrient yield and water productivity. These findings underscore the potential for N–loaded clinoptilolite to be adopted as a key component in sustainable agricultural practices, offering a pathway to optimize resource use, reduce environmental impact, and improve crop productivity in water–limited regions.