Alleviation of subsoil acidity with lime or gypsum increases carbon (C) accumulation in deep layers by stimulating root growth and C and nitrogen (N) inputs at depth. However, the effects of these amendments combined with N fertilization on soil CO₂ emissions remain controversial. We evaluated the effects of superficial lime and gypsum application and N-fertilizer on C and N dynamics and microbial C use efficiency (Mic_CUE) in samples taken from the topsoil (0–10 cm) and subsoil (40–60 cm) of a no-till field experiment carried out in Brazil. We performed a short-term laboratory incubation with ¹⁴C-glucose and ¹⁴C-arginine to assess C and N mineralization dynamics. Liming increased topsoil pH but had no effect on subsoil acidity. A higher content of organic C, total N, and microbial biomass C and N were found in the topsoil. The addition of soil corrective (lime and gypsum) and N fertilizer had no effect on Mic_CUE of added ¹⁴C-glucose. However, the Mic_CUE of ¹⁴C-arginine was affected by the soil layer, and was higher in the subsoil. After the addition of arginine, net NH₄⁺-N production was highest in the topsoil control, while net NO₃⁻-N content was highest with lime + gypsum plus residual N in the same layer. We conclude that while lime and gypsum ameliorate soil acidity, they have minimal effect on C cycling through the microbial biomass, particularly in the subsoil.

用石灰或石膏缓解底土酸度，通过刺激根系生长以及深层的碳和氮 (N) 输入，增加深层碳 (C) 的积累。然而，这些改良剂结合施氮肥对土壤 CO ₂排放的影响仍然存在争议。我们评估了表土（0 – 10 cm）和底土（40 – 60 cm）的样品中表层石灰和石膏施用以及施氮肥对碳和氮动态和微生物碳利用效率（Mic _CUE）的影响。在巴西进行的免耕田间试验。我们用¹⁴ C-葡萄糖和¹⁴用于评估 C 和 N 矿化动态的 C-精氨酸。石灰增加了表土的 pH 值，但对底土的酸度没有影响。在表土中发现了较高的有机碳、总氮和微生物生物量碳和氮含量。添加土壤矫正剂（石灰和石膏）和氮肥对添加¹⁴ C-葡萄糖的Mic _CUE没有影响。然而，麦克风_CUE的¹⁴ C-精氨酸受土壤层，并在底土更高。添加精氨酸后，表土对照中净 NH ₄ ⁺ -N 产量最高，而净 NO ₃ ^--N含量最高的是石灰+石膏+同层残留N。我们得出的结论是，虽然石灰和石膏改善了土壤酸度，但它们对 C 通过微生物生物量循环的影响很小，特别是在底土中。