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[Dynamics of urease activity in a long-term fertilized black soil and its affecting factors].

The effect of long-term fertilization on the urease activity in a typical black soil in Northeastern China was examined in this paper. The soil has been fertilized since 1980, and the dynamics of its urease activity was monitored during crop growth season. The results showed that a significant difference in soil urease activity was found at each growth stage between soils treated by different fertilizations. In farmyard manure treated soil, the urease activity was > 160 mg.kg-1.h-1 and with a low seasonal fluctuations. The soil urease activity had a significant positive correlation with soil biological, physical and chemical properties, and the N, P and K contents in plants (P < 0.01), and with soil moisture content and grain crude protein (P < 0.05).