Soil erosion assessment under different land use types using modified Gerlach trough in North-Western Thailand Highland

Soil erosion is a severe risk on the sloping agricultural land due to improper managements. This study aimed to evaluate and compare the dynamics of soil loss and runoff under different land use types in order to find the best soil erosion control for sustainable land use planning. A field trial was conducted in Bor Krai village, Mea Hong Son Province, North-Western Thai Highlands during 2008-2009. Four land use types were selected for comparative measurement, including i) 4-year -fal-low land (FaL), ii) mixed orchard (MixO), iii) maize (M) and iv) upland rice (UR). Surface runoff (SR) and soil loss (SL) were monitored after each effective rainstorm using modified Gerlach troughs (GT). The GT was made of a bamboo and linked to a 50-litre container by a rubber hose. The size of GTs was 0.5-0.7 m long and 0.1-0.2 m diameter. The GTs were installed perpendicular to the con-tour line at the lower part of each land use. The results showed that, during the 2-yr, monoculture with inappropriate soil water conservation caused the first average highest values of SR and SL (SR=299 m3 ha-1) and (SL=3.4 t ha-1) while FaL yielded the lowest SR (41 m3 ha-1) and SL (0.01 t ha-1) amounts. Moreover, further study is required for long-term prediction to estimate annual soil loss under different land use types.