What is the optimal statistical method for the analysis and presentation of the results of 28 treatments of NPK combinations and characterized by 15 parameters?
The answer depend on what is your treatments?if it consist of 3*3*3 plus control treatment in controlled environmental conditions you can use CRD treatments and analyzed the results using SAS or SPSS and compare means by LSD or Duncan, s multiple range test .
RBD factorial method or if doses/levels or other combinations exist then split plot design will be the best as it will also give interaction effect.You can use any softwate like SAS,SPSS or MSTAC.