TAILIEUCHUNG - Current Issues of Water Management Part 5

Tham khảo tài liệu 'current issues of water management part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Assessing Environmental and Social Dimensions of Water Issues Through Sustainability Indicators in Arid and Semiarid Zones 69 l. Physical loss of soil m. Hardening of subsurface horizon and n. High temperature on the soil surface. In arid soils dryness and salinity and their interaction under mismanaged irrigation are the main causes of soil degradation. Effluent irrigation results in increased soil sodicity because of the medium-to-high salinity and sodium concentration Balks et al. 1998 . Bare soils exposed to rainfall are subjected to physical and chemical processes that change the hydraulic properties of the soil near the surface Arie and Resnick 1996 . When the soil is dry a hard layer is formed in the soil surface that is often called desert crust commonly enriched with calcite or silica. Desert crust decreases the infiltration rate of soils thereby increasing runoff and soil erosion reducing the availability of water through the root zone and impeding seedling and plant growth Figure . Other kind of crusts are formed in agricultural plots irrigated with saline waters Figure . Understanding the formation and properties of such crusts as well as developing engineering methods to break it are essential to control the runoff-infiltration groundwater recharge ratio and to maintain successful and sustainable agricultural activities. When desert crusts are a result of microbial activity these kinds of crusts could help to protect the soil surface Campbell et al. 2009 . Besides arid soils typically possess within a predominant sandy soil a very low organic matter content with a consequent low fertility. In this sense crop productivity under dryland conditions is largely limited by soil water availability. Soil organic matter SOM contents have been found to be a reliable index of crop productivity in semiarid regions because it positively affects soil water-holding capacity Diaz-Zorita et al. 1999 . b a Fig. 1. Soil salinity symptoms and consequences. A .

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