Optimizing nitrogen management diminished reactive nitrogen loss and acquired optimal net ecosystem economic benefit in a wheat-maize rotation system

Excessive nitrogen (N) application results in substantial losses, as N fertilizers are wasted along with the loss of reactive N (Nr), thereby posing substantial threats to both human and ecosystem health. Nitrification inhibitors (NI) and urease inhibitors (UI) have the potential to reduce Nr loss as well as improve grain yields. However, comprehensive benefit assessments of these inhibitors from an environmental and economic perspective, including insights into the mechanisms of N fertilizer reduction, are lacking. Conducting a two-year study of a wheat-maize rotation system, urea (Ur), NI, UI, and joint inhibitors (UI + NI, UN) was established at three N rates (N1: suboptimal rate, N2: recommended rate, and N-3: farmers' rate), including a N fertilizer-lacking site (N0) as a control. N fertilizer increment stimulated foreground Nr loss, and increased field Nr loss through NH3 volatilization, N2O emissions, and NO3- leaching. There was seasonal variation in the Nr loss pathway between the maize and wheat seasons, and NO3- leaching only occurred during the maize season. Compared with farmers' N practice (N3Ur), N reduction and inhibitor application decreased field Nr losses by 10.9-85.2%. The efficiency of inhibitors also varied seasonally, and UI exhibited higher efficiency in the wheat season while UN in the maize season. N reduction and inhibitor application decreased the NDC by 18.4-83.1%, where N1UN and N1UI exhibited higher efficiency. Compared with N3Ur, N1Ur had a risk of yield reduction (7.6-13.9%), with N1UN and N1UI exhibiting no significant difference. The use of suitable inhibitors effectively compensated for the increase in NDC and reduction in yield under the N1 rate. Moreover, N1UN obtained the highest net economic benefits (NEB) in the maize season while N1UI in the wheat season. The combination of N1UN for maize season and N1UI for wheat season as optimizing N management, which improved the NEB by 24.7% on average compared with the farmers' N practice in the wheat-maize rotation. This optimizing N management for minimal environmental damage and maximum economic benefits could be conducive for sustainable, intensive wheat maize cropping systems in the North China Plain.

Automated summary

Excessive nitrogen application leads to significant losses and poses threats to both human and ecosystem health. Nitrification inhibitors and urease inhibitors have the potential to reduce nitrogen loss and improve grain yields. This study conducted a two-year experiment and found that using inhibitors significantly reduced nitrogen loss and increased grain yields. The efficiency of inhibitors varied seasonally and depending on the fertilizer rate. Proper use of inhibitors can compensate for yield reduction and nitrogen loss while maximizing economic benefits.