Đề tài: Nghiên cứu ứng dụng kết hợp các đồng vị Be-7 và Cs-137 để đánh giá hiệu quả chống xói mòn của các băng cỏ Vetiver
 đối với vùng đất dốc trồng cà phê ở Tây Nguyên

Chủ nhiệm: ThS. Phan Sơn Hải

The combined use of 137Cs and 7Be for assessment of medium- and short-term soil erosion rates for sloping lands with and without soil conservation technologies in the Central Highlands of Vietnam has been carried out. Studies were performed at five 128 m2 runoff plots and two 0.5 ha coffee plots with the slope gradient of about 25%. Experiments carried out at runoff plots showed that: (i) In the case of low erosion rates (less than 30 t ha-1 y-1), soil erosion rates estimated by 7Be technique using the Profile-Distribution Model were consistent with net soil erosion rates obtained by runoff plots when particle size correction factor P is taken into account; (ii) In the case of high erosion rates (greater than 30 t ha-1 y-1), the conversion model overestimated soil erosion rates when P was not allowed for, and underestimated erosion rate when P factor was taken into account.

Studies carried out at two 0.5 ha coffee plots showed that: (i) For the plot without soil conservation, soil erosion occurred for all sampling points with medium-term erosion rates ranging between 1.2 t ha-1 y-1 and 35 t ha-1 y-1 (the average erosion rate was 22.7 ± 1.2 t ha-1 y-1). The short term soil erosion rate estimated by 7Be technique was 32.7 ± 6.1 t ha-1 y-1 for this plot; (ii) For the plot with the last seven year presence of Vetiver strips, about 93% of the area suffered from medium term erosion with erosion rates varying from 3 t ha-1 y-1 to 33 t ha-1 y-1 (the mean is 22,2 t ha-1 y-1), and medium term deposition occurred for only 7% of the area with the deposition rates ranging between 1,3 and 1.4 t ha-1 y-1, resulting in the net erosion rate of 20.4 ± 0.6 t ha-1 y-1. The short term soil erosion rate at this plot estimated by 7Be technique was 2.3 t ha-1 y-1. By using Vetiver strips as a soil conservation technology, soil erosion was almost controlled and the net erosion rate was reduced from 32.7 t ha-1 y-1 to 2.3 t ha-1 y-1.