Kan plianplaeng that-ahan nai din chak kan chai prayot thidin praphet tang tang nai boriwen padip khao Changwat Chiangmai.

The investigation of soil nutrient variation under various land use practices was conducted by collecting soil samples at different sites in Chiangmai from June, 1980 to March, 1981. The sampling sites were as follows: the natural hill evergreen forest at Kog-Ma watershed Doi Pui, which was considered as control, the enrichment planting, forest plantation, shifting cultivation and agriculture at Tung Jaw, were considered as the representative areas of those land use practices. The results indicated that the change of land use practices from the hill evergreen forest to other land use types deteriorated the physical properties of soil. The texture of soil trend to change from sandy clay loam to sandy loam. The bulk density of the top soil, 0-25 and 25-50 cm in depths was increased and soil porosity was decreased especially in the shifting cultivation and agriculture areas, but there was no difference at the depth of 50-75 and 75-100 cm in all types of land use. There was no difference of particle density at each depth in all types of land use. The change of land use practices did not affect the color of soil except for the top soil of forest plantation area which was probably due to fire. The amount of organic matter and sulfur in the soil was decreased in all types of land use except in the agriculture area that the amount of sulfur was increased due to the use of chemical fertilizers. In all types of land use, the organic matter content decreased with increasing soil depth, however, the amount of sulfur increased with increasing soil depth. The pH was slightly increased in all depths and types of land use. It was seen that the changes of the hill evergreen forest to other land use practices would effect the balance of nutrients in the system as well as the amount and rate of nutrient cycling.