Effects of Land Use and Fertilization on Physical Properties of Black Soil

A long-term field experiment,designed to have 4 treatments,i. e.( 1) organic manure only( OM);( 2)chemical fertilizer and straw incorporation( NPKS);( 3) chemical fertilizer only; and( 4) no fertilizer,was carried out at the Hailun Agricultural Ecology Station of Chinese Academy of Sciences,to explore soil water regulating capacity of black soil in Northeast China and its affecting factors,responses of soil moisture to rainfall and vegetational cover,and effects of the four treatments on physical properties and soil water dynamics in the plough layer of the black soil. In the experiment,a neutron probe was used. Results show that compared to fallow land,farmland increased in bulk density by 7. 47%,but decreased in soil total porosity,saturated water content and water holding capacity by 2. 59,6. 04 and 1. 09 percentage points,respectively. Fertilization,especially application of OM and NPKS,improved soil physical properties. Bare land was the worst in soil physical properties. As vegetation consumes much water,farmland and fallow land was significantly lower than bare land in annual mean water content. The treatment of application of chemical fertilizer and straw incorporation significantly lowered annual mean water content. Variation coefficients of soil water content in all the treatments showed a similar trend,i. e. decreasing first and then increasing with soil depth within the 0- 70 cm soil layer. As a result of water consumption by vegetation,soil water content changed more sharply in the fallow land and farmland than in the bare land and incorporation of crop straw exaggerated the change. Dynamic variation of soil water storage was significantly related with precipitation,and land use pattern and fertilization management were the two factors affecting soil water storage in the surface soil layer the most,but with increasing soil depth,the effects of the treatments decreased significantly.