State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, PR China; University of Chinese Academy of Sciences, Beijing 100081, PR China,; Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, As N-1432, Norway.
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, PR China; University of Chinese Academy of Sciences, Beijing 100081, PR China.
Sci Total Environ. 2022 Jun 25;827:154338. doi: 10.1016/j.scitotenv.2022.154338. Epub 2022 Mar 4.
Soil acidification along with base cations loss degrades soil quality and is a major environmental problem, especially in agroecosystems with extensive nitrogen (N) fertilization. So far, the rates of proton (H) production and real soil acidification (loss of base cations) remain unclear in subtropical agricultural watersheds. To assess the current status and future risk of soil acidification in subtropical red soil region of China, a two-year monitoring was conducted in a typical agricultural watershed with upland, paddy fields, and orchards where high N fertilizers are applied (320 kg N ha yr). H production, neutralization and base cations losses were quantified based on the inputs (rainwater, inflow of water, and fertilizer) and outputs (outflow of water, groundwater drainage, and plant uptake) of major elements (K, Ca, Na, Mg, Al, NH, NO, SO, Cl, and H). The result showed that total H production in the watershed was 5152 mol ha yr. N transformation was the most important H source (68%), followed by excess plant uptake of cations (25%) and H deposition (7%). Base cations exchange and weathering of minerals (3842 mol ha yr) dominated H neutralization, followed by SO adsorption (1081 mol ha yr), while H and Al leaching amounted to 431 mol ha yr, only. These results state clearly that despite significant soil acidification, the acidification of surface waters is minor, implying that soils have buffered substantially the net H addition. As a result of soil buffering, there was abundant loss of base cations, whose rate is significantly higher than the previously reported weathering rate of minerals in red soils (3842 vs 230-1080 mol ha yr). This suggests that the pool of exchangeable base cations is being depleted in the watershed, increasing the vulnerability of the watershed, and posing a serious threat to future recovery of soils from acidification.
土壤酸化伴随着基础阳离子的流失会降低土壤质量，是一个主要的环境问题，特别是在广泛施氮肥的农业生态系统中。到目前为止，亚热带农业流域的质子（H）产生速率和实际土壤酸化（基础阳离子损失）仍不清楚。为了评估中国亚热带红壤地区的土壤酸化现状和未来风险，在一个典型的农业流域进行了为期两年的监测，该流域有旱地、水田和果园，施用了大量氮肥（320kg Nha yr）。根据主要元素（K、Ca、Na、Mg、Al、NH、NO、SO、Cl 和 H）的输入（雨水、水流入和肥料）和输出（水流出、地下水排水和植物吸收），量化了 H 的产生、中和和基础阳离子的损失。结果表明，流域内总 H 产生量为 5152mol ha yr。氮转化是最重要的 H 源（68%），其次是阳离子的过量植物吸收（25%）和 H 沉积（7%）。基础阳离子交换和矿物风化（3842mol ha yr）主导 H 中和，其次是 SO 吸附（1081mol ha yr），而 H 和 Al 的淋溶量仅为 431mol ha yr。这些结果清楚地表明，尽管土壤酸化显著，但地表水的酸化程度较小，这意味着土壤已大量缓冲净 H 增加。由于土壤缓冲作用，基础阳离子大量流失，流失率明显高于以前报道的红土矿物风化率（3842 比 230-1080mol ha yr）。这表明流域内可交换基础阳离子的储备正在减少，增加了流域的脆弱性，并对未来土壤从酸化中恢复构成严重威胁。
