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首页> 外文期刊>Geoderma: An International Journal of Soil Science >DYNAMICS OF SOIL AND VEGETATION DURING CROP AND FALLOW PERIOD IN SLASH-AND-BURN FIELDS OF NORTHERN LAOS
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DYNAMICS OF SOIL AND VEGETATION DURING CROP AND FALLOW PERIOD IN SLASH-AND-BURN FIELDS OF NORTHERN LAOS

机译：老挝北部坡耕地耕作与休耕期间土壤和植被的动态

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Slash-and-burn rice production systems in northern Laos are undergoing dramatic changes. Increased population pressure and regulations limiting access to land have resulted in shorter fallow periods. Limited information is available on nutrient dynamics in slash-and-burn systems of Southeast Asia in general and particularly on effects of reduced fallow length. Crop and fallow effects on soil parameters and fallow vegetation were quantified in slash-and-burn fields in Luang Prabang, northern Laos from 1991 to 1994. Over the cropping season from May to October declines of 8, 7, and 3% organic C and 33, 40, and 53% extractable P, were observed for the depth intervals of 0-3, 3-10 and 10-25 cm; respectively. Over the same period extractable K declined by 34% in the 0-3 cm interval and increased by 15 and 17% in the 3-10 and 10-25 cm intervals. The declining trend continued over the 3 year crop-fallow cycle with losses (depth 0-100 cm) of 29 +/- 7.6 t organic C ha(-1), 2.0 +/- 1.1 t total N ha(-1), and 0.7 +/- 0.8 t extractable K ha(-1). At the end of the fallow period the above ground biomass contained 100 kg N ha(-1), 5 kg P ha(-1), and 140 kg K ha(-1). The fallow vegetation was dominated by Chromolaena odorata with a gradual succession towards tree and bamboo species. The nutrients in the above ground fallow vegetation represent only a small fraction of the N and C lost due to mineralization and leaching. With the present no-till system, mineralization losses are far more serious than losses due to soil erosion. Short fallows will result in a fast decline and low equilibrium of soil organic C levels, reducing the potential for rice yields and limiting farmers choice for other land use options which may become available with better market access.
机译：老挝北部的纵火烧稻生产系统正在发生巨大变化。人口压力的增加和限制土地使用的法规导致休耕期缩短。总体而言，关于东南亚刀耕火种中养分动态的信息有限，尤其是关于休耕期减少的影响方面。 1991年至1994年，在老挝北部的琅勃拉邦砍伐和燃烧的田野中，作物和休耕对土壤参数和休耕植被的影响得以量化。5月至10月的种植季节，有机碳和有机碳的下降分别为8、7和3％。在0-3、3-10和10-25 cm的深度间隔内观察到33％，40％和53％的可提取P。分别。在同一时期，可提取的钾在0-3 cm的间隔中下降了34％，在3-10 cm和10-25 cm的间隔中增长了15％和17％。在3年的农作物休耕周期中，下降趋势持续，损失（深度0-100 cm）为29 +/- 7.6 t有机C ha（-1），总N ha（-1）为2.0 +/- 1.1 t，和0.7 +/- 0.8吨可提取的K ha（-1）。在休耕期结束时，地上生物量包含100 kg N ha（-1），5 kg P ha（-1）和140 kg K ha（-1）。休耕地的植被主要由香椿（Chromolaena odorata）主导，并逐渐向树木和竹种过渡。地上闲置植被中的养分仅占因矿化和淋溶损失的氮和碳的一小部分。在目前的免耕系统下，矿化损失远比土壤侵蚀造成的损失严重得多。短暂的休耕将导致土壤有机碳水平的快速下降和较低的平衡，从而降低稻米单产的潜力，并限制农民选择其他土地使用方式，而这些选择可能会有更好的市场准入条件。

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