Saturday, 15 July 2006

Erodibility Status of Soils under Different Landuses in Shiwalik Hills of Himachal Pradesh, India.

J.C. Sharma, Dept of Soil Science & WM, Dr Y. S. Parmar Univ of Horticulture and Forestry, Nauni, Solan (HP), India and Vipin Kumar, Dept of Soil Science & WM, Dr Y. S. Parmar Univ of Horticulture and Forestry, Nauni, Solan (HP), India.

Assessment of soil erodibility associated with different land uses is vital for the management of hill and mountain agro-ecosystems and establishment of sustainable soil and water conservation practices. The objective of this study was to compare the erodibility status of soils under five dominant land uses viz. forest, agriculture, grass lands lands, scrub lands and barren lands in Shiwalik hills of Himachal Pradesh, India. On the basis of reconnaissance survey and area under different landuse classes, stratified random sampling technique was followed for the selection of sampling sites. The sample size (number of sampling sites) varied from 10-30 per cent, depending upon proportion of area under a particular land use. Accordingly, 23 representative sites were exposed upto 0.45 m depth under different land uses. A total of 69 representative soil samples from three depths i.e. 0-0.15, 0.15-0.30, and 0.30-0.45 m were collected for laboratory analysis. Different erodibility indices viz. clay ratio (CR), suspension percentage (SP), silt: clay ratio (SCR), dispersion ratio (DR), erosion ratio (ER), erosion index (EI) etc were computed and compared. Interrelationships between erodibility indices and some soil properties were also established. Considering 15 a threshold value of DR between erodible and non-erodible soils, agriculture, barren and scrub lands were found more vulnerable to sheet erosion than the soils under forest and grass lands. On the basis of DR, these land uses could be arranged in the order of their erodibility status as: agricultural lands > barren lands > scrub lands > forest lands > grass lands. ER and EI gave almost similar results and the soils under scrub and barren lands were found highly erodible and the order for the erodibility status among the land uses was also similar i.e. scrub lands > barren lands > agricultural lands > forest lands > grass lands. ER and EI were found effective indices for assessing the erosional behaviour of soils as both were positively and significantly correlated under all the land uses except grass lands suggesting that these can be used interchangeably. According to the threshold limit of 10 for ER and 2.8 for EI between erodible and non erodible soils, the soils under all the land uses were recorded to be erodible in nature. However, as per DR, slight variation in the order for erodibility behaviour of soils among landuses than as per ER and EI could be due to coarse texture of the soils i.e. silt +clay less than 30 per cent. Hence, DR can not be used as an effective index for assessing the erodibility behaviour of Shiwalik hill soils. The study clearly indicated that land use has significant effect on erosional behaviour of soil. Considering the soil physico-chemical characteristics, land uses, physiography and soil erodibility status, the marginal lands such as barren and scrub lands in Shiwalik hills need special management practices for soil and water conservation to check further degradation. Such lands need to be replaced by more effective soil and water resource conserving systems like agro-forestry, agri-horticulture, silvi-pasture, controlled and rotational grazing and enclosure of degraded sites for natural regeneration. Agricultural lands need to be supplied with sufficient quantity of organic matter to improve soil aggregation, moisture retention and their health.

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