Physico-chemical properties and enzyme activities of the arable soils in Lhasa, Tibet, China

An understanding of the physical, chemical, and biological properties of a soil provides a basis for soil use and management. This paper reports the major physico-chemical properties and enzyme activities of the soils of Lhasa's main arable lands and the factors that influence these soil properties. Composite and core samples were taken from the three main arable soil types (alluvial soil, subalpine arable steppe soil, and subalpine arable meadow soil) and were analysed using standard methods. The bulk density and the ventilation porosity ratio of the soils were close to the recommended values for arable lands, and the dominant soil texture was sandy. The soil moisture release rates were arable steppe soil > alluvial soil > arable meadow soil. Soil organic matter content, Cation-Exchange Capacity (CEC), total and available nitrogen content, and catalase activity of the arable meadow soil were higher than those of the alluvial and the arable steppe soils, while soil pH in the arable meadow was lower. Most of the measured properties did not show a significant variance among these three soils. However, the measured indices (apart from the total potassium) indicate that there are notable differences among the three types of soil. The results implied that the utilisation patterns of the arable soil or human activities, such as tillage practices and fertiliser applications, have a substantial effect on the soil properties in this region. Our results suggest that the cultivation practices in the region have apparently positive impact on the soil organic matter, nutrient contents and bulk density probably due to the sound fertiliser management such as the applications of farmyard manure and chemical fertilisers. However, intense cultivation practices lowered the activity of most soil enzymes. The results demonstrate that the choice of soil management strategy had a significant impact on the soil physicochemical and biological properties in the region studied.