College of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China.
College of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China.
Sci Total Environ. 2022 Mar 1;810:152244. doi: 10.1016/j.scitotenv.2021.152244. Epub 2021 Dec 8.
Nitrogen (N) fertilization and plastic film mulching (PFM) are two widely applied management practices for crop production. Both of them impact soil organic matter individually, but their interactive effects as well as the underlying mechanisms are unknown. Soils from a 28-year field experiment with maize monoculture under three levels of N fertilization (0, 135, and 270 kg N ha yr) and with or without PFM were analyzed for soil organic C (SOC) content, total soil nitrogen (N), root biomass, enzyme activities, and SOC mineralization rates. After 28 years, N fertilization increased root biomass and consequently, SOC by 26% (averaged across the two fertilizer application rates) and total soil N by 25%. These increases, however, were only in soil with PFM, as PFM reduced N leaching and loss, as a result of a diurnal internal water cycle under the mulch. The SOC mineralization was slower with N fertilization, regardless of the PFM treatment. This trend was attributed to the 43% decrease of β-glucosidase activity (C cycle enzyme) and 51% drop of leucine aminopeptidase (N cycle) with N fertilization, as a result of a strong decrease in soil pH. In conclusion, root biomass acting as the main source of soil C, resulted in an increase of soil organic matter after 28 year of N fertilization only with PFM.
氮（N）施肥和塑料薄膜覆盖（PFM）是两种广泛应用于作物生产的管理措施。它们各自影响土壤有机质，但它们的交互作用及其潜在机制尚不清楚。本研究分析了 28 年玉米单作条件下，三种施氮水平（0、135 和 270 kg N ha yr）和有无 PFM 两种处理下土壤有机碳（SOC）含量、土壤全氮（N）、根系生物量、酶活性和 SOC 矿化率。28 年后，N 施肥增加了根系生物量，从而使 SOC 增加了 26%（在两种施肥水平的平均值）和总土壤 N 增加了 25%。然而，这些增加仅在有 PFM 的土壤中出现，因为 PFM 减少了 N 的淋溶和损失，这是由于覆盖下的昼夜内部水循环。无论 PFM 处理如何，N 施肥都会导致 SOC 矿化更慢。这种趋势归因于 N 施肥导致土壤 pH 值大幅下降，β-葡萄糖苷酶活性（C 循环酶）下降 43%，亮氨酸氨肽酶（N 循环）下降 51%。总之，根系生物量作为土壤 C 的主要来源，仅在 PFM 下，经过 28 年的 N 施肥后，土壤有机质增加。
