The resources of desertified soil and the effect of biological soil building measures in Hexi Corridor

In the region of Hexi Corridor,gray desert soil,gray brown desert soil and brown desert soil are extensively distributed.Their geographic distribution,soil forming conditions,physico-chemical properties and main subgroups were discussed.And the effect of cultivation of alfalfa(Medicago sativa)on soil building of the gray brown desert soil was also studied.The results show that on this desertified soil three years of cultivation turned out 55.2 t·hm^-2 of fresh grass,equal to 24.8 t·hm^-2 of hay,while it increased natural moisture content in 0～20 cm soil layer by 90.65 g· kg^-1,water-stable granular structure(>0.25 mm)by 17.23%,and total porosity by 7.93%,but decreased bulk density by 0.21g·cm^-3,soil pH from 8.45 to 8.20 and total salt by 4.63 g·kg^-1 forming a desalinization rate of 70.36% as compared to that in CK.At the same time,soil organic matter,readily available N,readily available P and readily available K all increased too.