Abstract: Arginine ammonification rate is an indicator of the activity of soil microbial biomass. It is interfered by soil moisture, the quantity of arginine addition and incubation time. The results showed that a large amount of ammonium was released from the soil added with arginine. The arginine ammonification rate kept unchange for 6 hours. Soil moisture greatly affected arginine ammonification rate. Arginine ammonification rate increased with the increase of soil moisture up to 200% WHC. Only a small amount of NH₄-N was oxided to NO₃-N at high soil moisture. The arginine remained in soil extract interfered with ammonium determination. Therefore, a low amount of arginine and long time incubation were necessary when the arginine ammonification method was used for estimating soil microbial biomass.

Key words: cucumber, NaCl stress, brassinolide, photosynthesis, antioxidant system.