VERTICAL DISTRIBUTION OF MAJOR NUTRIENT ELEMENTS IN TYPICAL BLACK SOIL SECTIONS IN HAILUN, HEILONGJIANG PROVINCE: Before and After Reclamation

The study on the characteristics of major nutrient elements in typical black soil areas before and after reclamation is important for sustainable utilization of black soil resources and protection of the breadbasket in Northeast China. Four sections are laid out in the typical black soil areas where land use has not changed for the past 40 years in Helen area, eastern Songnen Plain, to make a comparative study on the main index elements for soil fertility (organic matter, total nitrogen, total phosphorus, C:N and pH value) in the sections before and after reclamation. The results indicate that the contents of organic matter, total nitrogen and total phosphorus show a change trend of rapid decrease through slow decrease to basically stable with soil depth. Although reclamation has changed the content of nutrient elements in soil, it does not change the content variation rule with soil depth. Reclamation affects the pH value of black topsoil to a certain extent, which led to slow acidification of cultivated land. The research results will expectedly provide scientific basis for sustainable utilization, protection and restoration of black soil resources.