The highland agriculture of nothen Thailand is in full transition. As the land pressure is rapidly increasing, farmers and forced to reduct the fallow area. (Semi) permanent landuse, combined with the traditional siash and burn techniqus, results in a producitivity decline. Depletion of nutrients, erosion and increased weed pressure and the main causes. Five long term experimental field, where different alternative systems are tested, were studied on their effect on soil quality. Continued traditional monocropping cleanrly results in a yield decline and soil deterioration. Benched terraces can greatly reduce erosion, but not the fertility decline. Vegetative conservation measures, combined with cereal-legume crop rotation, seems to result in an appropriate soil environment and sustainable yields. Two different types of buffer strips and used: strips with grasses and strips with nitrogen fixing trees. Both systems can be suitable,depending on the physical and socioeconomic conditions.