Impact on the Fates of Fertilizer Nitrogen under Different Soil Managements on Black Soil Farmland.

Abstract: The utilization efficiency of fertilizer N decreased during the grain production in the black soil region of northeast China. A ten-year experiment with different soil management patterns in a crop rotation was conducted to evaluate the soil capacity of keeping and supplying N using 15N isotope technique. The results showed that no significant difference of soil N removal was found among the three management patterns for wheat cropping. The residual rate of fertilizer was 12.8% in pattern ¢ñ(chemical fertilizer application), with 2.4 and 4.7 percentage higher in pattern ¢ò (chemical fertilizer together with organic manure) and pattern ¢ó (the sweet clover to feed ox and the cow dung returned to the field) for wheat cropping, and the loss rates of fertilizer N in the three patterns were 57.9%, 49.5% and 42.1%, respectively. Under the pattern¢ñ for corn cropping, no significant difference of the soil N removal between patterns ¢òand ¢ó was probably due to the equal effect of higher level chemical fertilizer plus organic fertilizer in pattern ¢ò and lower level of chemical fertilizer plus sweet clover in pattern ¢ó. The loss rates were 54.2%, 46.6% and 39.9% for the three patterns, respectively. Soybean tested to fertilize soil needed relatively less chemical fertilizer N due to symbiotic fixation. However, the utilization efficiency of chemical N was significantly different with 26.9%, 39.6% and 31.3% for the three patterns. Under pattern¢ñ, the utilization efficiency of chemical fertilizer N of wheat, corn and soybean were 29.9%, 32.0% and 26.9%, respectively, while the utilization efficiency was 35.2%, 37.2% and 31.3% under Pattern ¢ò, as well as 40.4%, 42.0% and 39.6% under Pattern ¢ó, respectively. Keywords: Black soil, utilization efficiency of fertilizer nitrogen, soil managements