Author(s): K. MUKHOPADHAY, A. HALDER, P, K. TARAFDAR AND K. DAS

Abstract: Efficient use of water resources for optimization of crop productivity and proper land and water management both under irrigated and rainfed farming requires a thorough understanding of the pertinent hydrological properties which includes soil water retention characteristics, available water capacity as well as plant available water capacity (PAWC) of the soils. The moisture retention characteristics of soils which provide information on the ability of soils for storing water and its subsequent availability to the crops as well as moisture releasing behaviour were studied for nine mapped soil units under varying physiographic positions in Mamring micro watershed of Darjeeling Himalayas in West Bengal Variation in water retention characteristics was attributed to textural variations and it had been found that moisture retentivity at 33 kPa and 1500 kPa tension was significantly and positively correlated with clay, silt plus clay and organic carbon, whereas, negative correlation was observed with sand content, porosity and bulk density. The moisture release behaviour of the soils under different range of suctions did not varied widely due to differences in physiographic positions. Plant available water capacity for these soils were also studied and it had been found that the value of PAWC was highest for the soils under hill top ridge and summit (10-15% slope) and lowest in lower side slopes having 25-33% slope. Again variation in PAWC was also observed with land use systems and it followed the trend of forest > vegetable > cereals > fallow land uses.

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