Land application of farmyard manure (FYM) is a widespread agronomic practice used to enhance soil fertility, but its long-term effects on soil microbial carbon (C) and nitrogen (N) cycling have not been investigated in detail. Topsoils (0–23 cm) and subsoils (23–38 cm) were collected from a field trial on a sandy-textured soil where FYM had been applied at high (50–25 t ha⁻¹ yr⁻¹, 28 yr) and low rates (10 t ha⁻¹ yr⁻¹, 16 yr), and compared to soil treated only with synthetic NPK fertilisers. The turnover rate of key components of soil organic matter (SOM; proteins, peptides, amino acids, cellulose, and glucose) were evaluated by ¹⁴C labelling and measuring cellobiohydrolase, β-glucosidase, β-1,4-N-acetylglucosaminidase, L-leucine aminopeptidase, protease, and deaminase activities, whereas gross NH₄⁺ and NO₃⁻ production and consumption were determined by ¹⁵N-isotope pool dilution. Microbial communities were determined using phospholipid fatty acid (PLFA) profiling. Our results indicate that long-term FYM addition significantly enhanced the accumulation of soil C and N, soil organic N (SON) turnover, exoenzyme activity, and gross NO₃⁻ production and assimilation. Rates of protein, peptide, and amino acid processing rate were 169–248, 87–147, and 85–305 mg N kg_DWsoil⁻¹ d⁻¹, respectively, gross NH₄⁺ and NO₃⁻ production and consumption were 1.8–5.8 mg N kg_DWsoil⁻¹ d⁻¹, and the highest rates were shown under the high FYM treatment in topsoil and subsoil. The half-life of cellulose and glucose decomposition under the high FYM treatment were 16.4% and 31.0% lower than them in the synthetic NPK fertiliser treatment, respectively, indicating higher rates of C cycling under high manure application as also evidenced by the higher rate of CO₂ production. This was ascribed to an increase in microbial biomass rather than a change in microbial community structure. Based on the high pool sizes and high turnover rate, this suggests that peptides may represent one of the dominant forms of N taken up by soil microorganisms. We conclude that long-term FYM application builds SOM reserves and induces faster rates of nutrient cycling by boosting microbial biomass rather than by changing its community composition.

农田施肥（FYM）在土地上的应用是提高土壤肥力的广泛农艺方法，但尚未对其土壤微生物碳（C）和氮（N）循环的长期影响进行详细研究。表土（0-23厘米）和底土（23-38厘米）从其中FYM已在高（50-25吨公顷施加在沙质感土壤田间试验收集^-1年^-1，28岁）和低率（10吨公顷^-1年^-1，16岁），并与只用合成NPK肥料处理的土壤。土壤有机质关键组分（SOM；蛋白质，肽，氨基酸，纤维素和葡萄糖）的周转率通过¹⁴Ç标记和测量纤维二糖水解，β葡糖苷酶，β-1,4-N-乙酰氨基葡，L-亮氨酸氨肽酶，蛋白酶，和脱氨酶的活动，而毛NH ₄ ⁺和NO ₃ ^-的生产和消费通过确定¹⁵的N-同位素池稀释。使用磷脂脂肪酸（PLFA）分析确定微生物群落。我们的研究结果表明，长期FYM此外显著增强土壤C和N，土壤有机N（SON）的营业额，胞外酶的活性，和总NO的积累₃ ^-生产和同化。蛋白质，肽和氨基酸的处理速率分别为169–248、87–147和85–305 mg N kg _DWsoil ^-1 d ^-1分别毛NH ₄ ⁺和NO ₃ ^-的生产和消费是1.8-5.8毫克N-公斤_DWsoil ^-1 d ^-1，最高率表土和底土高FYM治疗下所示进行。高FYM处理下纤维素和葡萄糖分解的半衰期分别比合成NPK肥料处理下的半衰期低16.4％和31.0％，这表明高肥料施用下碳循环的速率更高，这也证明了较高的施用率。一氧化碳₂生产。这归因于微生物生物量的增加而不是微生物群落结构的改变。基于高池大小和高周转率，这表明肽可能代表了土壤微生物吸收氮的主要形式之一。我们得出结论，长期FYM应用通过增加微生物生物量而不是通过改变其群落组成来建立SOM储备并诱导更快的养分循环速率。