SOIL AND WATER LOSSES IN REFORESTATION INTERCROPPED WITH VETIVERSTRIPS AT THE PING, WANG, YOM AND NAN SUB-RIVER BASINSOF NORTHERN THAILAND

摘要

Determination of soil and water losses in reforestation intercropped with vetiver strips was conducted inrnfour upper watershed research station (WRS) areas which lie in the Ping (Mae Taeng WRS), Wangrn(Wang WRS), Yom (Yom WRS) and Nan (Khun Sa Than WRS) sub-river basins in Northern Thailandrnduring 1994-98. The investigation was carried out on three replications of 4 × 20 m, 4 × 40 m and 4 × 60rnm runoff plots, which were constructed on 20, 30 and 40-percent sloping areas of natural forest, furrow,rnreforestation and reforestation intercropped with strips of vetiver. It was found that, for the 20-percentrnsloping area at the Mae Taeng WRS, the natural forest produced minimum runoff and soil loss withrnvalues of 5.5 mm and 3.429 t/ha/yr. The reforestation intercropped with the grass strip yielded minimumrnwater and sediment loss when compared to the plantation and furrow plots with the values of 8.0, 15.2rnand 12.2 mm and 2.501, 7.325 and 3.962 t/ha/yr, respectively. Similarly, in the Yom watershed, thernreforestation plot intercropped with grass strips generated runoff and soil loss with the values of 54.6,rn57.8 and 51.8 mm and 0.388, 0.553 and 0.442 t/ha/yr, respectively. Likewise, on the other slopes, thernresults showed minimum loss of soil and water in the plots intercropped with grass strips due to therndense grass hedges, which decreased surface flow velocity. However, the natural forest yielded thernminimum runoff and soil loss on average during the study period.