N-loaded clinoptilolite under water-saving irrigation mitigates ammonia volatilization while increasing grain yield and water-nitrogen use efficiency

Minimizing ammonia volatilization (AV) in paddy fields can not only reduce nitrogen (N) loss but also prevent environmental pollution. While clinoptilolite has been shown to effectively decrease AV, it is important to note that natural clinoptilolite contains non-desorption active sites that can hinder soil N effectiveness, ultimately leading to decreased N utilization. Therefore, we proposed modifying clinoptilolite with a weakly acidic NH4Cl solution (N-loaded clinoptilolite, NZ) to replenish exogenous N while continuously reducing AV. A lysimeter experiment was conducted under two irrigation regimes (I-CF: continuous flooding irrigation; I-AWD: alternate wet-dry irrigation) to examine the effect of N-loaded clinoptilolite on soil N, water-N use, AV loss and grain yield over two rice-growing seasons in Northeast China. The results show that AWD significantly reduced AV during the basal fertilization period and the first top-dressing period in 2020 and 2021. Compared with the control (without N-loaded clinoptilolite), N-loaded clinoptilolite at 10 t.ha(-1) (NZ(10)) significantly reduced the total AV by 29% and 33% in the two years, respectively, with the most significant reduction impact (30% and 36%) occurring in the first top-dressing period. NZ(10) coupled with AWD regime reduced AV more significantly and compared with conventional management (I(CF)NZ(0)), I(AWD)NZ(10) decreased the total amount of AV by 36% and 42% in two years, respectively. N-loaded clinoptilolite also increased the soil NH4+-N and NO3--N content during the tillering and grain-filling stages of rice, which in turn increased the rate of maximum N accumulation, shortened the duration, promoted N accumulation and translocation in rice plants, and finally reduced AV. Additionally, when compared to the control, the utilization of NZ(10) under the AWD irrigation regime resulted in an average 29% reduction in irrigation water usage and a yield increase of 5% over two years. Thus, IAWDNZ(101) was not only highly productive and water-efficient but also significantly reduced AV, making it an environmentally friendly and effective management model for on-farm practices.