Abstract: The objective of the experiment is to ascertain the effects of different mulching materials on the distribution and physiological activity of apple roots as well as the soil physicochemical pro-perties in the rain-fed Longdong arid areas. With fourteen years old apple trees as test material, the different classes of roots were collected by using soil profile method and stratified sampling in soil profile to investigate the spatial distribution, root biomass, root length and surface area. The activity of root and antioxidant enzymes and some antioxidant indexes were measured. Soil bulk density and soil porosity in different soil layers were determined. The results indicated that ground covering treatment increased the soil moisture, porosity and organic matter content, and the amplification were 2.7%-11.6%, 3.2%-27.7%, 5.1%-36.0%, respectively compared with the control. The soil bulk density was reduced by 88.7%-96.4%. The roots of CK distributed mainly in soil layer of 0-60 cm in depth, 30-120 cm away from the trunk. However, with straw and plastic mulching the roots distributed mainly in the layer of 0-100 cm in depth, 0-150 cm and 0-60 cm away from the trunk, respectively, mostly concentrated in the 20-40 cm layer close to the ground. Plastic mul-ching made a narrower horizontal root distribution than CK and the total fine root amount was 96.4% of that of CK, and that in 0-60 cm layer accounted for 51.6% of the total fine root amount. More-over, the mulching resulted in a higher activity of root and antioxidant enzymes in 0-80 cm layer. The root activity with straw mulching was 111.3%-136.7% as much as the control. For sake of the efficacy on improving root distribution and physiological activity, the straw mulching was suggested as a better way for soil management in apple orchard in dry area of eastern Gansu.

Key words: mulching, soil physicochemical property, fine root, root activity, root distribution