人口的增长和畜禽产品需求的增加导致大量粪肥产生，这些粪肥可用于维持土壤的可持续发展和作物的生产力。但是，过量粪肥施用如何影响作物产量、氮循环过程及其介导微生物尚不清楚。本研究探析和不施肥以及常规施用粪肥（9 Mg ha^-1 yr^-1）相比，20年过量粪肥施用（18 和 27 Mg ha^-1 yr^-1）对夏季和冬季酸性红壤花生产量、土壤养分含量、氮循环过程和氮循环功能微生物丰度的影响。研究发现，长期过量粪肥施用，尤其是高量粪肥（27 Mg ha^-1 yr^-1），显著提高土壤养分含量、氮循环功能基因丰度、硝化和反硝化潜势，但对花生产量和生物量的提升相对较弱。与施用粪肥相比，季节变化对氮循环功能基因丰度的影响大大减弱。随机森林模型分析表明，速效磷（AP）含量是影响氮循环功能基因丰度最关键的环境因子，并与所有氮循环微生物功能基因丰度呈正相关。综上，我们的研究结果清晰地表明，过量粪肥施用会增加土壤氮循环功能基因丰度和氮损失潜力，但却没有显著提高作物产量。该结果对酸性红壤农田管理和农业可持续发展具有重要意义。

Population growth and growing demand for livestock products produce large amounts of manure, which can be harnessed to maintain soil sustainability and crop productivity. However, the impacts of excessive manure application on crop yields, nitrogen (N)-cycling processes and microorganisms remain unknown. Here, we explored the effects of 20-year of excessive rates (18 and 27 Mg ha^–1 yr^–1) of pig manure application on peanut crop yields, soil nutrient contents, N-cycling processes and the abundance of N-cycling microorganisms in an acidic Ultisol in summer and winter, compared with none and a regular rate (9 Mg ha^–1 yr^–1) of pig manure application. Long-term excessive pig manure application, especially at the high-rate, significantly increased soil nutrient contents, the abundance of N-cycling functional genes, potential nitrification and denitrification activity, while it had a weaker effect on peanut yield and plant biomass. Compared with manure application, seasonality had a much weaker effect on N-cycling gene abundance. Random forest analysis showed that available phosphorus (AP) content was the primary predictor for N-cycling gene abundance, with significant and positive associations with all tested N-cycling genes. Our study clearly illustrated that excessive manure application would increase N-cycling gene abundance and potential N loss with relatively weak promotion of crop yields, providing significant implications for sustainable agriculture in the acidic Ultisols.