Effect of soil conservation system as hillside ditch with mixed cropping among banana and arabica sp. upon hydologic behavior at Ban Sado Phong watershed
1995
Somchai Inthasothi | Sompong Limsakul | Chukit Aemsaard | Pinit Hutawathana | Churai Thongmark (Land Development Department, Bangkok (Thailand))
Study the effect of conservation practices in agricultural land use on upland watershed was conducted during the year 1987-1993 at Amphoe Kao-Ko, Phetcharboon province. The area has elevation ranging between 600-700 m of mean sea level.Soil properties was in group soil no. 29 and 62. Three mini watersheds were selected for different conservation practices which are buffer strip, contouring and hillside ditch. The results were concluded that annual streamflow and subsurface flow were correlated with annual rainfall and rainfall distribution. The efficiency of these three systems of soil conservation practices are not significant in controlling soil erosion which not only the magnitude of soil loss are under the tolerable limit but also the streamflow quantity are equal in all water sheds. The intensive exploitation of agricultural land has caused decline not only annual streamflow but also subsurface flow. The rate of subsurface flow has 53 percent of total flow in the fifth year. But contouring conservation system can improve subsurface flow to more than 90 percent of total flow because of higher infiltration rate. Its amount has however declined after construction of contouring in 2.2 percent per year, and has become to 82 percent of total flow in 5 years. It was also found that soil erosion was increased with time after constructing contour which caused the rate of about 4 times of begining year in 5 years. The changes of land use from field crop to coffee orchards under soil conservation system as hillside ditch caused higher annual streamflow and decrease subsurface flow. The single conservation method without soil improvement program not being effectively conserved soil fertility.
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