An attempt was made to establish a relationship between the reduction of urease activity and 

 other measured properties in a brackish marsh during long-term drying (Table 4). Variation in the 

 urease activity data (r^=0.74) was best accounted for by the following multiple regression equation: 



Urease Activity (UA) = 29.64 - 4.598 pH - 0.041 EC + 0.008 MC - 0.002 Na [1] 



It is noteworthy that soil pH, EC, and Na had significant effects on the level of urease activity. It 

 is likely that high salinity can partially or totally block the mechanism of urea hydrolysis because 

 of increased energy expenditures required for the hydrolysis of urea at increasing ionic strength in 

 the soils (Tanji 1969; Ponnamperuma 1972; DeLaune et al. 1976). Soil EC and soil pH were also 

 significantly affected by soil and soil-related factors. Regression equations developed to explain 

 variation in EC and pH were: 



EC = 6.234 - 0.016 MC + 0.008 Mg [2] 



r 2 = 0.96 



pH = 6.451 - 0.016 EC + 0.001 MC + 0.003 Na - 0.069 Mn - 0.0001 S 



- 0.039 Fe + 0.003 Mg [3] 



r 2 = 0.89 



Table 4. Numerical coefficients (b-values) of soil and soil-related 

 properties in equations and significance of these coefficients. 



Significant at p = 0.05 ** Significant at p = 0.01 



92 



