A new long-term field study demonstrates that combining organic manure with synthetic fertilizer can enhance soil quality, maintain high crop yields, and dramatically reduce harmful nitrous oxide emissions—one of the most potent greenhouse gases contributing to climate change.
Researchers at Hainan University, the Chinese Academy of Sciences, and their partners have revealed how different soil management strategies impact the soil microbiome and the ecological processes that control the nitrogen cycle. Their findings show that when manure is integrated with synthetic nitrogen fertilizer, both soil organic carbon and total nitrogen are significantly increased. This synergy leads to better soil fertility and improved crop performance without the environmental burden commonly associated with traditional fertilizers.
The experiment, conducted in the North China Plain, compared four fertilizer treatments: no fertilizer, conventional synthetic fertilization, an optimal synthetic fertilizer rate, and a balanced combination of manure and synthetic fertilizer. Plots treated with the manure-plus-synthetic blend registered the highest soil quality scores and maintained yields comparable to those managed with high synthetic input alone.
Crucially, the integrated manure approach produced much lower nitrous oxide emissions than conventional synthetic fertilization. Nitrous oxide, also known as N2O, is roughly 300 times more potent than carbon dioxide as a greenhouse gas. The key to this reduction lies in the soil microbes responsible for nitrogen cycling. Manure-amended plots had a much larger population of microbes carrying the nosZ gene, which enables the final step of denitrification—the conversion of N2O to benign nitrogen gas.
By using advanced molecular approaches, such as high-throughput gene sequencing and new ecological modeling, the researchers traced how fertilizer strategies select for different groups of nitrogen-cycling microbes. Conventional fertilization was shown to favor microbes that produce more N2O, whereas integrated manure management stimulates those that can break N2O down.
The study also highlights the roles of both deterministic and random (stochastic) forces in shaping microbial communities under various fertilizer treatments. Notably, key microbes for nitrification and denitrification are largely steered by environmental selection, which means that fertilizer choices can predictably drive soil microbiome function toward either higher or lower emissions.
The authors point out that their results offer a practical roadmap for sustainable agriculture: farmers can maintain, or even increase, yields while helping to meet climate targets by fine-tuning fertilizer applications. The team believes that such ecological engineering of soil microbiomes may be the next frontier for reducing greenhouse gases from agriculture.
Future research should investigate how these findings apply to different agroecosystems and explore the economic and logistical factors needed for wide-scale adoption of integrated manure management.
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Journal Reference: Wang Z, Li Y, Liu X, Ju X. 2025. Integrated manure application enhances soil quality and reduces nitrous oxide emissions by deterministically shaping N cycling guilds. Nitrogen Cycling 1: e007 https://www.maxapress.com/article/doi/10.48130/nc-0025-0007
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