Impact of Land Use on Soil Nutrient at Doi Pui and Tung Jaw, Chiangmai

Abstract

The change of land use practices from the hill evergreen forest to other land use types deteriorated the physical properties of soil. The bulk density of the top soil, 0 - 50 cm in depths was increased and soil porosity was decreased especially in the shifting cultivation and agroculture areas, but there was no difference at the depth of 50 - 100 cm in all types of land use. The amount of organic matter and sulfer in the soil was decreased in all types of land use except in the agroculture 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, but in the contrary, the amount of sulfur increased with increasing soil depth. The pH was slightly increased in all depths and types of land use. The amount of phosphorus, potassium and magnesium was increased and mostly accumulated at the top soil and decreased with increasing soil depth. However, the amount of phosphorus was increased in agroculture and forest plantation areas and decreased in areas of shifting cultivation and enrichment planting. The potassium and magnesium content were highest in forest plantation areas and lowest in the hill evergreen forest, while the amount of calcium was highest in agroculture area and lowest in the hill evergreen forest. All of the phenomena mentioned above may be due to the influence of fire and chemical treatments. It was revealed that the change of the hill evergreen forest to other land use practices would impact the balance of nutrients in the system as well as the amount and rate of nutrient cycling. Most of the nutrients were moved and accumulated in the soil instead of storing in the form of plant biomass, Therefore, if the land were not properly used, the nutrients could be easily leached and lost from the system.