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为了在降水不足的旱作农业区,充分接收、贮存大气降水,减少无效蒸发和因径流引起的水、土、肥的流失,笔者设计了作为农田土壤、作物、大气连续系统的调节措施之一,旱农沟种垅覆集水试验;提出了旱作农田沟作地段的水分平衡方程.通过试验说明,该措施使作物沟地的水分收入增加,支出减少,土壤增墒、保墒能力增强.它既有利于抗旱增产,建立稳定的节水型旱作农业,又减少了径流引起的水、土、肥的流失,有明显的经济效益与生态效益. 相似文献
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笔者在从事地质教学和地质录像过程中，于１９８８年在浅水沉积的砂岩底面发现了类似沟模、槽模现象，与国内沉积岩石学教科书引用的国外沟模、槽模实便有两点不同之处：①所见沟模是水流冲刷模而不是工具压刻模；②所见沟模、槽模下伏沉积物质是砂质的而不是泥质的。该现象的发现是对沟模、槽模现象的补充和完善，对探讨沟模槽模、的成因及填补国内沉积岩石学教科书缺少的国内沟模、槽模实例的空白很有意义。 相似文献
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Soil pipe collapses in a loess pasture of Goodwin Creek watershed,Mississippi: role of soil properties and past land use 
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下载免费PDF全文 Little is known about the association of soil pipe collapse features with soil properties or land use history. Three loess covered catchments in northern Mississippi, USA were characterized to investigate these relationships. Soil pipe collapses were characterized for their size, type feature and spatial location along with soil properties across the three catchments. Although mapped as the same soil, one of the catchments did not contain pipe collapse features while the other two had 29.4 and 15.4 pipe collapses per hectare. These loess soils contained fragipan layers that are suspected of perching water, thereby initiating the piping processes. Pipe collapses associated with subsurface flow paths were not always consistent with surface topography. The surface layer tended to be non‐erodible while layers below, even the upper fragipan layers, were susceptible to erosion by pipeflow. Soil properties of the lowest fragipan layer were highly variable but tended to prevent further downward erosion of soil pipes and thus formed a lower boundary for gullies. Middle to lower landscape positions in one of the piped catchments contained anthropic soils that were highly erodible. These anthropic soils were previously gullies that were filled‐in in the 1950s when forested areas, assumed to have been established when land was previously converted from crop to forest land, were converted to pasture. Three decades after this land use change from forest to pasture, pipe collapses became evident. In contrast, the adjacent catchment that does not exhibit pipe collapse features experienced severe sheet and rill erosion prior to the 1930s while in cotton production. The surface horizons above the lower fragipan layer were completely removed during this period, thus the top‐soil layer that tends to form a bridge above soil pipes in the more erodible subsoil layers was removed. This study showed that knowledge of soil characteristics or topography alone do not explain the distribution of soil pipe collapses as past land use can play a definitive role. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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