Regional modelling of rice yields and nitrogen loss in Hubei Province using the WHCNS model

CONTEXT

Excessive nitrogen (N) fertilization has led to serious environmental problems. Exploring the spatial distribution of rice yields and N loss is crucial to determine optimal N fertilizer management. However, previous studies are mostly based on field scale, it's a big challenge to use model approach to explore the spatial distribution and influencing factors of rice yields and N loss due to lack of field management, soil and crop information at regional scale.

OBJECTIVE

This study aims to evaluate the feasibility of the WHCNS (soil Water Heat Carbon Nitrogen Simulator) model in simulating rice yield and N loss at regional scale, explore the spatial distribution of yield and N loss under traditional water and N management, and determine the main factors causing spatial differences in Hubei Province.

METHODS

The WHCNS model was calibrated and validated using data collected on statistical yields and N losses in Hubei Province. Then, the model was used to simulate rice yield and NH₃ volatilization, denitrification, N leaching and runoff for single, early and late season rice at regional scale. The spatial distribution of yield and N loss and their correlation with meteorological factors and soil properties were analyzed.

RESULTS AND CONCLUSIONS

The WHCNS model performed well in simulation of regional rice yield and N loss compared with other models. R² and d of simulated and measured yields, ammonia volatilization and N runoff were > 0.55 and 0.84 respectively. The yield was higher in central Hubei and lower in western and southeastern Hubei, mainly driven by solar radiation and temperature, soil clay content, pH and bulk density. N runoff loss decreased from east to west of Hubei, mainly affected by rainfall and temperature for single and early season rice, and bulk density for late season rice. Higher N leaching and denitrification in northwestern Hubei were related to high nutrient content (soil total N and organic matter) and poor aeration. Higher NH₃ emission was found in eastern Hubei, mainly affected by temperature and precipitation. The average total N loss for single, early and late season rice was 77.2, 65.6, and 81.5 kg N ha⁻¹, respectively, accounting for 33.6 %, 31.5 %, and 40.8 % of the N application rates.

SIGNIFICANCE

The WHCNS model was used to determine the spatial distribution and main factors influencing rice yields and N loss in Hubei Province. These findings provide a scientific basis for optimizing N management to minimize N loss while maintaining yield.