Transient salinity and subsoil constraints to dryland farming in Australian sodic soils: an overview
Transient salinity and subsoil constraints to dryland farming in Australian sodic soils: an overview
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DOI：
10.1071/ea01111
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发表时间：
2002-01-01
影响因子：
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通讯作者：
Rengasamy, P
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文献类型：
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作者：
Rengasamy, P
澳大利亚2000万公顷的种植土壤中有60%以上是苏打土壤，这些土壤上的耕作主要是在旱地条件下进行的。在澳大利亚，超过80%的苏打土壤具有高碱度和碱性pH(>；8.5)的致密粘性底土。由于盐度、碱度、碱度、营养缺乏和硼、碳酸盐和铝酸盐的毒性等底土限制，苏打土壤中谷物的实际产量往往不到气候预期潜在产量的一半。苏打底土的有机质和生物活性也很低。苏打底土水分传输性能差，干旱地区降雨量少，夏季植被蒸腾和高蒸发导致根层盐分积累。这种不受地下水影响的瞬时盐分在澳大利亚的许多苏打土壤景观中都很普遍，那里的地下水位很深。“旱地盐碱化”目前在公众辩论和政府政策中受到广泛关注，但只关注浅层地下水位引起的盐碱化。虽然16%的旱地种植面积可能会受到地下水引起的盐分的影响，但67%的面积有可能出现与地下水和其他底土限制无关的暂时性盐分，每年给澳大利亚农业经济造成的损失约为1.3亿澳元。针对不同类型的旱地盐分采取不同的策略，对于旱地耕作的可持续管理和生产力的提高至关重要。本文讨论了苏打底土的限制条件，旱地地区不同类型的盐分，与苏打底土管理有关的问题，以及解决这些问题所需的未来优先事项。它还强调，旱地农业土壤根区的瞬时盐分是一个重要的问题，可能会比地下水位引起的渗漏盐分更严重。
More than 60% of the 20 million ha of cropping soils in Australia are sodic and farming practices on these soils are mainly performed under dryland conditions. More than 80% of sodic soils in Australia have dense clay subsoils with high sodicity and alkaline pH (>8.5). The actual yield of grains in sodic soils is often less than half of the potential yield expected on the basis of climate, because of subsoil limitations such as salinity, sodicity, alkalinity, nutrient deficiencies and toxicities due to boron, carbonate and aluminate. Sodic subsoils also have very low organic matter and biological activity.Poor water transmission properties of sodic subsoils, low rainfall in dryland areas, transpiration by vegetation and high evaporation during summer have caused accumulation of salts in the root zone layers. This transient salinity, not influenced by groundwater, is extensive in many sodic soil landscapes in Australia where the watertable is deep. 'Dryland salinity' is currently given wide attention in the public debate and in government policies, but only focusing on salinity induced by shallow watertables. While 16% of the dryland cropping area is likely to be affected by watertable-induced salinity, 67% of the area has a potential for transient salinity not associated with groundwater and other subsoil constraints and costing the Australian farming economy in the vicinity of A$1330 million per year. A different strategy for different types of dryland salinity is essential for the sustainable management and improved productivity of dryland farming.This paper discusses the sodic subsoil constraints, different types of salinity in the dryland regions, the issues related to the management of sodic subsoils and the future priorities needed in addressing these problems. It also emphasises that transient salinity in the root zone of dryland agricultural soils is an important issue with potential for worse problems than watertable-induced seepage salinity.