Saddie poinl and optimum leveis ai nutrienls in fertulizerials

Abstract

When the response surlace has a saddle point instead ot a point ol maxinlurn, it is of great irnportance, from the practical viewpoin, to obtain alternalivo solutions for me oplimum leveis, i.e,, me
combination ol doeis that gives me maximum yield. Three altemative solutions were studied by simulation: the point of absolute maximuni (frontier point ot maximum) in me experimental region, me experimental point of maximum, and me saddle point. Except the saddie point, the solutions presented good properties as lhe
substitutes ol lhe optimum leveIs. Sy using the criterion ol frequenco ofmaxima, a comparison was also nade among nine treataient designs with three factors and 3, 5, 7 and 9 leveis. The bestlreatnent design was me 33 lactorial with equafly spaced leveis