School of Engineering and the Environment, Kingston University London, United Kingdom; Department of Soil, Water and Environment, University of Dhaka, Dhaka, Bangladesh.
School of Engineering and the Environment, Kingston University London, United Kingdom.
J Environ Manage. 2022 Mar 1;305:114427. doi: 10.1016/j.jenvman.2021.114427. Epub 2022 Jan 6.
Soil organic carbon (SOC) is a key soil quality indicator, as it is a source and storage of plant nutrients and plays a vital role in soil fertility and productivity maintenance. Intensification of agriculture is known to cause SOC decline; however, much of the evidence stems from field-scale experimental trials. The primary aim of this study is to investigate how more than 20 years of agricultural land use intensification in Bangladesh has influenced SOC levels at landscape levels. This was achieved by revisiting in 2012 four sub-sites from the Brahmaputra and Ganges alluviums which were previously sampled (1989-92) by the Soil Resource Development Institute and collecting 190 new samples. These were located at different elevations and subjected to differing amounts of inundation. The SOC was determined using the same method, potassium dichromate wet oxidation, used in the 1989-92 campaign. A comparison of the SOC in the 2012 samples with their historic levels (1989-92) revealed that overall SOC declined significantly across both alluviums as well at their four sub-sites. Further analysis, however, showed that SOC has declined more at higher sites. The higher sites are inundated to a limited level, which makes them suitable for growing multiple crops. Among the land types considered here, the low land sites (because of their topographical position) remain inundated for a greater part of the year, allowing a maximum of only one crop of submerged rice. As a result of reduced biomass decomposition due to anaerobic conditions when inundated, and lower land use/cropping intensity, SOC accretion has occurred in the lower land sites. The SOC levels in South Asian countries are inherently low and agricultural land use intensification fuelled by growing food production demand is causing further SOC loss, which has the potential to jeopardise food security and increase the environmental impact of agriculture.
土壤有机碳（SOC）是土壤质量的一个关键指标，因为它是植物养分的来源和储存库，对土壤肥力和生产力的维持起着至关重要的作用。众所周知，农业集约化会导致 SOC 下降；然而，大多数证据都来自田间试验。本研究的主要目的是调查孟加拉国 20 多年的农业土地集约化利用如何在景观尺度上影响 SOC 水平。这是通过在 2012 年重新访问先前由土壤资源开发研究所采样的（1989-92 年）布拉马普特拉河和恒河冲积扇的四个子地点并收集 190 个新样本来实现的。这些样本位于不同的海拔高度，受到不同程度的淹没。SOC 是使用与 1989-92 年运动相同的方法（重铬酸钾湿氧化法）确定的。将 2012 年样本中的 SOC 与它们的历史水平（1989-92 年）进行比较，结果表明，两个冲积扇及其四个子地点的 SOC 总体上都显著下降。然而，进一步的分析表明，SOC 在较高的地点下降得更多。较高的地点受到有限的淹没，这使得它们适合种植多种作物。在所考虑的土地类型中，低地站点（由于其地形位置）在一年中的大部分时间仍被淹没，只能种植最多一茬水下水稻。由于淹没时的厌氧条件导致生物量分解减少，以及低地利用/种植强度较低，低地站点的 SOC 积累发生了。南亚国家的 SOC 水平本来就很低，而由于粮食生产需求不断增长而推动的农业土地集约化利用正在导致 SOC 进一步流失，这有可能危及粮食安全并增加农业的环境影响。
