Organic fertilizer replacing 20% of chemical nitrogen improves yield and soil quality while reducing N2O emissions in waxy maize

Abstract

Background and aims

Waxy maize is highly preferred by consumers due to its high nutritional value. However, farmers' long-term intensive cultivation, driven by the sole pursuit of high yield, has led to a decline in soil quality and an increase in environmental costs. Optimal combined application of organic and inorganic fertilizers (CAOIF) has been demonstrated to improve soil fertility and crop yield. However, it remains to be further studied whether this model can enhance soil quality and reduce N₂O emissions while maintaining crop yield. This study aimed to explore the responses of N₂O emissions, soil quality and yield in a maize field to the replacement of different proportions of equivalent N in chemical fertilizer (CF) with organic fertilizer (OF). It also analyzed the relationships between soil properties and N₂O emissions, soil quality, and yield.

Methods

This experiment used a completely randomized block design with five treatments of OF replacing different ratios of CF, including 0% (NPK), 10% (OF1), 20% (OF2), 30% (OF3), and 40% (OF4).

Results

Soil N₂O emissions and N₂O warming potential (GWP) decreased as proportion of OF substitution increased. Compared with the NPK treatment, N₂O emissions in the OF2, OF3 and OF4 treatments decreased by 7.9%, 13.6% and 17.1%, respectively. This reduction was primarily attributed to the biological fixation of inorganic nitrogen by OF in place of CF. Furthermore, compared with the NPK treatment, the OF1, OF2, OF3 and OF4 treatments significantly improved soil properties (SOM, TP, BD, C: N, MBC and MBN), and increased soil quality index (SQI) by 12.3%, 30.0%, 19.7% and 16.2%, respectively. The yield of fresh ears (EY) and fresh grains (GY) of waxy maize treated with OF2 increased by 6.1% and 6.7%, respectively, compared to the NPK treatment. The structural equation model (SEM) showed that soil quality had a significant positive effect on crop yield.

Conclusion

Replacing 40% of CF with OF achieved the greatest reduction in N₂O emissions. However, its yield and soil quality were significantly lower than when 20% of CF is replaced by OF. Therefore, using OF to replace 20% of CF is recommended as a nitrogen management strategy for waxy maize production, as it improves soil fertility, increases yield, and reduces N₂O emissions. This study is helpful to guide the scientific application of CAOIF in agricultural production, and provide valuable insights for reducing fertilization and increasing yield of crops while promoting the development of environment-friendly agriculture.