The effect of nitrogen fertilizer on soil enzymatic activity and rhizosphere microorganisms of Yumai 49 -198 root system was studied in this paper

The results indicated that the activity of the soil protease and urease of Yumai 49-198 increased with the growth period then descending

Protease activity reached its peak period up to jointing stage

Urease activity reached its peak period up to seedling establishment. The activity of the soil protease increased with nitrogen fertilize treatment and reached its peak on N2 level treatment. Urease activity increased with nitrogen fertilizer treatment and reached its peak on N4 treatment. Rhizosphere microorganisms increased with the growth period then descending and reached the peak up to flowering period. The results also showed that the population quantity of rhizosphere microorganisms increased with different nitrogen treatment then descending. On N3 level treatment

the quantity of rhizosphere microorganisms attained the highest value. The difference between treatments is significant.