Humic acid urea enhanced productivity and reduced active nitrogen loss in summer maize-winter wheat cropping system: A field lysimeter experiment

Context

Humic acid urea (HAU) has become the leading product of high-efficiency nitrogen (N) fertilizer worldwide. Value-added urea products represented by HAU account for 80 % of the market share of high-efficient urea in China. To our knowledge, precise field monitoring of the agronomy and environmental performance of HAU has not been conducted.

Objective

We aimed to examine the effect of HAU on grain yield, N uptake, NH₃ volatilization, N₂O emission, and NO₃^- leaching and to clarify the differences in productivity levels and N footprints between HAU and common urea (U) applied in field grain production.

Methods

From 2021–2023, a randomized design experiment was conducted during a summer maize-winter wheat rotation system using field lysimeters. Three N treatments, no N (CK), U, and HAU, were administered in the experiment, and each treatment was repeated three times.

Results

Compared with U, HAU increased the grain yield of winter wheat by 5.14–6.24 % and the grain yield of summer maize by 4.48–11.18 %. In the summer maize seasons, the NH₃ volatilization accumulation and N₂O emissions of HAU were significantly reduced (14.92–19.32 % and 21.01–25.16 %, respectively). In the winter wheat seasons, the NH₃ volatilization accumulation and N₂O emission of HAU were significantly reduced (19.44–19.94 % and 17.79 %–26.10 %, respectively). In summer maize, NO₃^- leaching losses occurred in 2021 and 2022 under HAU treatment was 8.40 % and 54.65 % lower, respectively, compared with U. Leaching losses in the 2021–2022 winter wheat season were reduced by 38.31 % under HAU compared with that under U. The N footprint of HAU was significantly reduced in the summer maize and winter wheat seasons by 10.57–20.52 % and 15.11–15.91 % compared with that under U. Furthermore, HAU reduced N loss and improved N use efficiency and soil residue rate in the summer maize-winter wheat rotation system.

Conclusion

HAU application reduced the loss of active N in all three main pathways and increased shoot N uptake and soil N residual, thereby contributing to not only the increase in grain yield but also the mitigation of nitrogen field pollution and the minimization of unnecessary urea waste.

Implications

This lysimeter-based study provides quantification of the evidence supporting HAU as a highly efficient fertilizer, which contributed to increased productivity of the rotation system and enhanced resilience in environmental sustainability.