Effect of straw returning on the environment of degenerated soil in centr al Tibet

Effect of different methods of spring barley straw returning in dry se ason on soil environments and relation to soil physico-chemical properties and b iological factor of degenerated soil were studied in wind erosion district of ce ntral Tibet. Preliminary results showed that there was marked effect of higher s tubble and soil covered with straw could protect the soil environment of arable layer, reduce the bulk density, and improve the porosity, water-stable aggregat e , increase organic matter and soil nutrient contents, amount of soil microbes un der the ecological conditions of the central Tibet, and regenerated soil present ed a distinct improvement under the affected of physico-chemical properties and biological factor during the straw returning period. However, the comprehensive effect and soil water content was relative lower under incorporation of straw in dicated that soil moisture was a key factor that impair the effectiveness of str aw returning under the arid region and semiarid region in Tibet. The amount of b acterium account for overwhelming majority of the soil microbes under the differ ent methods of straw returning and it made a greater contribution to soil nutrit ion. In calcareous soil the content of the rapidly available phosphorus had high er level and it increased significantly by the increase of the pH.