Abstract: In order to study the effects of the different ways of adding 4th urease inhibitor (4th UI) into urea on the growth and some quality indexes of Chinese cabbage, parameters such as the fresh weight, plant height, leaf length, leaf width, chlorophyll content, soluble sugar and root activity of Chinese cabbage were studied by outdoor potting method in this paper. The results showed that the yield, quality index and nutrient index of Chinese cabbage could be improved under three different ways and dosage of adding inhibitors into urea. Among them, 1% of the inhibitor concentration in group B combined with urea had the best yield increasing effect, reaching 32.82%. 0.2% of the inhibitor concentration in group C had the best effect, with yield increasing by 80.49%, plant height increasing by 17.34%, total nitrogen content of plants increasing by 61.36%, and total phosphorus content of plants increasing by 78.85%, the root activity of cabbage increasing by 26.61%. In group D, the best effect was 50.01% when 0.2% urease inhibitor was added into urea. In the same method of administration, the urease inhibitors with low and medium concentration had the best effect on increasing yield of crops. Comprehensive consideration, the group C with adding 0.2% inhibitors into urea was the best way. The results can provide a basis for the application of this new type of slow-release urea in agriculture.

Key words: the fourth type urease inhibitor (4th UI), slow release urea, the ways of adding inhibitors, Chinese cabbage, nutrient and quality indexes