Evaluation of the effects of plastic mulching and nitrapyrin on nitrous oxide emissions and economic parameters in an arid agricultural field

Plastic film has been widely applied to address water shortages by reducing soil evaporation in arid and semi-arid regions, but it simultaneously affects soil nitrous oxide (N2O) emissions. Moreover, after the application of plastic film, the ability of nitrification inhibitor to reduce N2O emissions remains unclear. In this study, the chamber method was used to measure N2O emissions and a modified diffusion equilibrium sampler was used to obtain N2O concentrations in an oasis cotton field. Non-mulched and mulched treatments were used to investigate the influence of plastic mulching on soil N2O dynamics, and mulched plus nitrapyrin treatment was used to evaluate the ability of nitrapyrin to reduce N2O emissions under plastic mulching. Moreover, we also estimated the net economic return and cost related to an eventual environmental taxation on N2O emission of these practices. In all treatments, the ridge soil was the origin of most N2O (82–87%) emissions, which remained at low levels during the non-fertigation period (ranging from 0.4–17.1 g N ha−1 day−1) and sharply increased after the split application of urea; emissions during the fertigation periods accounted for 57–85% of the total N2O emissions in all treatments. Compared with the non-mulched treatment, the use of plastic film is a “win-win” strategy for both agricultural income (net economic returns increased by $436–522 ha−1 year−1) and N2O mitigation (emissions reduced by 19–28%), even without incentives. Although the addition of nitrapyrin to the urea reduced the cumulative N2O emissions by 23–39% under plastic mulching, and therefore reduced the costs related to an eventual environmental taxation on N2O emission by approximately $2 ha−1 year−1, this benefit could not compensate for the additional cost of inputting nitrapyrin ($24 ha−1 year−1) because this technique did not have a significant effect on cotton yields. Therefore, the use of nitrapyrin is probably a “lose-win” strategy for farmers and N2O mitigation and not suitable for reducing N2O emissions in oasis cotton fields.