The aim of this study was to disclosed the activity of extracellular enzyme (amidase) in vertical and horizontal developing directions of rhizosphere (0-5 and 5-10) cm . The plots experiment was performed in Agriculture college / Al-Qadissiyah University for the spring season 2013 ,the sandy loam soil was used and cultivate Tomato (Lycopersicon Esculentum mill) and Bean (Phaseolus Vulgaris L.) plants under salinity levels (without salinity , 6 , 8 and 10) dS.m-1 and compost levels (0,10 and 20)T.h-1 , and their interactions completely randomized design (CRD) was used with six replicates, and the means of treatments were compared by L.S.D test 5% level .
The results were summarized as :
1- The enzyme activity were increased with increasing of the adding compost level 20Ton.h-1 and its interactions with salinity levels .
2- The enzymes activity were varied in rhizosphere development directions and the plants were differed in the site of highest activity , the enzyme activity in horizontal rhizosphere development direction was higher than the vertical direction .
3- The enzyme activity in tomato rhizosphere was higher than bean rhizosphere in all rhizosphere vertical and horizontal directions .
4- The high inhibitor percent of enzyme activity was at the level of 10 dS.m-1 salinity and the lowest was at the 6 dS.m-1. The inhibition percent were increased in vertical direction of rhizosphere developing (5-10)cm in tomato plant. The adding compost levels were varied by increasing or decreasing of enzyme activity according to rhizosphere development and it sites . .