Effects of alfalfa with different growth years on soil fertility in saline-alkali land

By determining and analyzing water soluble salt,organic matter,pH value,total N,hydrolytic N,total P,available P,total K and available K of each soil layer in alfalfa fields with different growth years, the effect of alfalfa with different growth years on the interannual variability and vertical distribution of soil fertility in saline-alkali land in western Songnen plain. The results showed that growing alfalfa could decrease soil pH value and water soluble salt content effectively. The contents of total N, hydrolytic N, total P and available K of each soil layer in alfalfa field had all declined in the seeding year. The contents of organic matter,total P, total N and hydrolytic N were all increased in alfalfa field sown for more than 2 years. The contents of available P in the CK and each alfalfa field tend to decrease progressively with soil layer’s decline, and the content of available K was highest in the surface layer.