Limited effect of organic matter on soil available water capacity
Limited effect of organic matter on soil available water capacity
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DOI：
10.1111/ejss.12475
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发表时间：
2018-01-01
影响因子：
4.2
通讯作者：
McBratney, A. B.
中科院分区：
文献类型：
--
作者：
Minasny, B.;McBratney, A. B.
土壤持水能力是陆地生物圈水分和能量平衡的重要组成部分。它控制着蒸发蒸腾速率，是作物生产的关键。提高土壤有机质含量可以提高土壤有效水容量，这一观点已被广泛接受。然而，随着有机质的增加，植物可利用的水量的增加仍然是不确定的，可能被高估。为了澄清这个问题，我们对60项已发表的研究进行了荟萃分析，并分析了大型数据库（全球超过50，000个测量值），以寻求有机碳（OC）与饱和含水量，田间持水量，萎蔫点和可用水容量之间的关系。我们发现，土壤中有机碳的增加对土壤含水量的影响很小。土壤有机质（或10 g C kg（-1）土壤矿物）质量增加1%，饱和含水量、田间持水量、萎蔫点和有效水容量平均分别增加2.95、1.61、0.17和1.16 mm H2O/100 mm土（-1）。在桑迪土壤中增加较大，其次是壤土，粘土中最小。总的来说，可用水容量的增加非常小; 75%的研究报告的值在0.7和2 mm 100 mm（-1）之间，增加10 g C kg（-1）土壤。与采用保护性农业系统后报告的碳固存年速率相比，对土壤有效水的影响可以忽略不计。因此，固碳以增加水储存的论点是值得怀疑的。相反，全球变暖可能导致土壤碳的损失，但对土壤水储存的影响及其对水文循环的影响可能比以前想象的要小。
Soil water-holding capacity is an important component of the water and energy balances of the terrestrial biosphere. It controls the rate of evapotranspiration, and is a key to crop production. It is widely accepted that the available water capacity in soil can be improved by increasing organic matter content. However, the increase in amount of water that is available to plants with an increase in organic matter is still uncertain and may be overestimated. To clarify this issue, we carried out a meta-analysis from 60 published studies and analysed large databases (more than 50 000 measurements globally) to seek relations between organic carbon (OC) and water content at saturation, field capacity, wilting point and available water capacity. We show that the increase in organic carbon in soil has a small effect on soil water content. A 1% mass increase in soil OC (or 10 g C kg(-1) soil mineral), on average, increases water content at saturation, field capacity, wilting point and available water capacity by: 2.95, 1.61, 0.17 and 1.16 mm H2O 100 mm soil(-1), respectively. The increase is larger in sandy soils, followed by loams and is least in clays. Overall the increase in available water capacity is very small; 75% of the studies reported had values between 0.7 and 2 mm 100 mm(-1) with an increase of 10 g C kg(-1) soil. Compared with reported annual rates of carbon sequestration after the adoption of conservation agricultural systems, the effect on soil available water is negligible. Thus, arguments for sequestering carbon to increase water storage are questionable. Conversely, global warming may cause losses in soil carbon, but the effects on soil water storage and its consequent impact on hydrological cycling might be less than thought previously.