Abstract: By means of 15 N experiments,the fate of nitrogenous fertilizer of maize and soybean and wheat in the farmland was studied. The results showed that in the black soil farmland of Songnen Plain,wheat's N fertilizer use efficiency was 33%-40% with average of 37%,the soil residual 12%-16% with average of 14% and the gaseous loss 47%-50%, with average of 48.6%. Maize's N fertilizer use efficiency,the soil residual and gaseous loss was 37%,14% and 49% respectively. Sweet clover's N fertilizer use efficiency,soil residual and gaseous loss was 9%,30% and about 60% respectively. And soybean's N fertilizer use efficiency was 33%-40% with average of 37%,the soil residual 25%-50% with average of 31% and the gaseous loss 15%-35% with average of 27%.

Key words: eddy covariance, snow  evaporation, latent heat, diurnal variation, meteorological factor.