EXTRACTION PATTERN OF SOIL MOISTURE IN BARE SOIL, TEA PLANTATION AND SOIL COVERED WITH FOREST SPECIES (Alstonia macrophytla wall)

Abstract

The present study conducted at the research farm, Faculty of Agriculture, University ofRuhuna, Mapalana and adjacent site of well established tea plantation from January toJuly 2003, to assess the moisture extraction patterns under tea (Camellia sinensis L.) andforest speices (Alostonia macrophylla wall) compared to bare soil

Diviner 2000 is used to assess the soil moisture in different sites. The experiment wasconducted in two sites, viz well managed tea plantation and an experimental site whereAlstonia macrophylla wall is planted, and bare spots were kept randomly

The soil under tea was loamy sand with bulk density of lBgcm" in surface layers whichincrease with the depth. The soil under forest species was silt loam with a bulk density of1.4gcm-3 in surface layers. Bulk density of bare soil was highly varied with an average of1.49gcm-3. A thick laterite layer was found in 40-5Ocm layer in tea soil and 50-60cmdepth in forest and bare soils. The results revealed that the water holding capacity of teasoil is high by about 16% compared to that of bare soil and water-holding capacity offorest soil is low by 8% compared to bare soil.

According to the moisture extraction pattern of soils, somewhat highest retentioncapacity was in bare land followed by tea soil and then forest soil. The probable reasonfor this may be high evapotranspiration rate from tea plantation and forest species. Themoisture retention of the tea plantation is higher than the forest soil, due to the highevapotranspiration by forest species

The rate of moisture depletion is remarkably high in forest soil with an average of4.8mmlday constituting 60% increment over bare soil evaporation. Soil moisturedepletion rate of the soil under tea is about 4.2mmlday, which is 40% higher comparedthat to the bare soil evaporation. Well-established canopy cover of the tea plantationappeared to be a good barrier to reduce surface evaporation

Parameters like porosity, soil texture, soil temperature, rainfall, wind speed and rootdistribution pattern appeared to have an influence on the soil moisture depletion