Nowdays the ANOVA analysis is very easy by some biometric softwares you just have to put exact data there. your analysis will also depand on data or traits you had studied. during my days i studied it by hand calculations that was very tough job.
Anyway if u can send me some detail then i will try to help you although i am plant Breeder not soil scientist.
I was used this system before several years but I am trying to help you. In the SPSS menu - Analyze list select General linear Model then select Multivariate then add your model. Best wishes.