2.8 statistical analysis
A completely randomized design was used
Data were analyzed using the General linear model (GLM) option of the ANOVA solfware of SAS 9.2 program (SAS Institute,Cary,North Carolina,USA).the application of the least significant ranges among different treatment means was done according to Duncan (1955).Treatment effects were considered significant at p_< 0.05. The statistical model used was as follow: