توليد و دوام آنزيم اوره از خاك در شرايط شور

چكيده انگليسي :

The Response of Soil Urease Production and Persistence to Salinity Hamid Reza Khani H khani2007@gmail com Department of Soil Science Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi F Nourbakhsh E mail Farshid@cc iut ac ir Abstract Sustainable agriculture is regarded to human beneficial preservation which has more efficiency in using of resources and balancing with environment Agricultural management systems are sustainable when soil quality is preserved or increased Since the enzymatic assessments are simple and inexpensive they have the potential for soil quality evaluation Changing in surface soil chemical characteristics such as salinity increasing can affect soil microbial activity In this study the effect of soil salinity on production and persistence indices of urease and the nitrogen mineralization immobilization rates were investigated For this purpose sampling was carried out in 0 15 cm depth of Chamasman and Shervedan soil Soil samples were salinized with pure sodium chloride salt to achieve electrical conductivities 13 S1 18 S2 23 S3 and 28 S4 dS m 1 Salinity control soil was also run S0 The soils were incubated for three weeks in proper temperature and humidity for stabilization of microbial activity In order to stimulate the microbial population soils were amended with aqueous solutions containing carbon and nitrogen After the addition of carbon and nitrogen samples were incubated at 25 C and urease activity was measured at 0 1 2 3 4 5 6 7 9 11 13 16 20 30 40 and 50 days of incubation The enzyme production and persistence indices were calculated The results showed that in both soils salinity reduced urease activity Increasing in soil salinity to 18 dS m 1 resulted in decreasing the enzyme production index in Chamasman soil Increased soil salinity from 4 to 28 dS m 1 also cause a decrease in enzyme production index in Shervedan soil Enzyme persistence index in both soil decreased when soil salinity increased The urease persistence index was reached zero in 18 and 28 dS m 1 in Chamasman and Shervedan soils respectively In order to evaluate the salinity effects on nitrogen mineralization immobilization rate soil inorganic nitrogen were measured at sampling time 20 and 70 days after incubation Net nitrogen mineralization immobilization were calculated by subtracting the values of the inorganic nitrogen in sampling time from those of the 20 and 70 days of incubation Results showed that in Chamasman soil increasing the length of incubation from 20 to 70 days caused net N mineralization Salinity effect on nitrogen mineralization immobilization rate was significant in Chamasman soil Net N immobilization was occurred in 4 and 13 dS m 1 while N mineralization was occurred in 18 23 and 28 dS m 1 in Chamasman soil Effect of soil salinity on rate of N mineralization immobilization was not significant in Shervedan soil Net N immobilizing was happen when soil incubated which probably indicate great values of C N ratio It seems that salinity increasing caused significant reduction in microorganisms activity which product urease and that the limited activity of microorganisms reflected in less urease production as well as persistence indices Keywords Urease activity Enzyme production Enzyme persistence Soil salinity mineral nitrogen

خاني، حميدرضا

توليد و دوام آنزيم اوره از خاك در شرايط شور

فعاليت اوره آز , شوري خاك , نيتروژن معدني