Soil reclamation (both desalinization and desodification) is frequently required in arid and semiarid regions in order to keep the irrigated agriculture sustainable. Intermittent and continuous ponding are the most widely used leaching methods in this aspect. This study examined the efficiency of these two leaching methods in desalinization and desodification of two saline and sodic soils : a gypsyferous sandy loam and a nongypsiferous clay loam. Soil columns (100 and 200 mm high) were leached with irrigation water (EC=1.8 dS/m, SAR = 3.2) under both methods. Effluent from the columns was collected continuously, and its cationic and anionic composition was analyzed. Intermittent ponding was more efficient than continuous ponding in desalinization and desodification of the clay loam. By contrast, in the sandy loam, efficiency was similar under the two leaching methods in desalinization, whereas desodification was more efficient under intermittent ponding. In the clay loam where soil aggregation is higher, unsaturated water flow that occurs in micropores under intermittent ponding resulted in higher leaching efficiency on desalinization compared with continuous ponding under which condition water flow is saturated and much of the water is conducted by the macropores. Conversely in the sandy loam, unsaturated water flow prevails under both intermittent ponding and continuous ponding explains the similar leaching efficiency on desalinization observed under the two leaching methods. Soil desodification was enhanced by intermittent ponding in both soils, because Na replacement is a slow process which is controlled by intra-aggregate diffusion of Na+ and Ca2+ and the rate of gypsum dissolution. In the clay loam, the rate of intra-aggregate diffusion of Na+ and Ca2+ determines the efficiency of desodification, and in the gypsiferous sandy loam, the rate of gypsum dissolution determines the efficiency of desodification.
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