Agricultural organic amendments may hold the key to conserve soil productivity while alleviate non-point source pollution of intensified hillslope cropping

Synthetic nitrogen (N) fertilizer has substantially increased crop yield and played a crucial role to feed the growing population. However, reactive N can loss via different pathways and induce severe environmental problems such as non-point source pollution and ground water contamination when not properly applied. Considering the economic and ecological importance of the Yangtze River, its protection is now attracting great attentions from not only scientists but also the public. Purple soil concentratedly distributed in the Sichuan Basin and covered the upper reaches of the Yangtze River. Therefore, reducing nitrogen loss from sloping cropland of purple soil via improved fertilization strategies could make an important contribution to mitigate non-point source pollution in the upper Yangtze River.

As a leading scientist, Prof. Bo Zhu from Institute of Mountain Hazards and Environment, Chinese Academy of Sciences has led a team to evaluate how different fertilization strategies especially organic-substitution fertilization may influence nitrogen loss from sloping cropping system of purple soil. The results of this study are expected to establish fertilization regime with minimum nitrogen loss from this ecologically fragile area.

Crop residue and pig manure are common agricultural organic by-products, the organic carbon from these organic amendments may slow down nitrogen release compared with synthetic nitrogen fertilizer thus reducing nitrogen loss through synchronized nutrient release and crop demand. This study clearly indicates that the nitrogen loss of synthetic nitrogen fertilizer can be high and the main loss is through interflow followed by sediment and overflow losses. Using crop residue and pig manure to partly replace (20%–40%) synthetic nitrogen can maintain high crop yield and significantly reduce the N loss from the main pathways by up to 68%. Additionally, the yield-scaled nitrogen loss can also be reduced by synthetic N substitution of crop residue and pig manure. Introducing agricultural by-products to the fertilization regime can achieve the dual-purpose of recycling the wastes while reducing the risks of non-point source pollution of the Yangtze River by minimizing nitrogen losses from sloping cropland.

This study has been published on Frontiers of Agricultural Science and Engineering in 2022, DOI: 10.15302/J-FASE-2022456

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