Abstract: Automated fertigation systems and methods determine crop N status from a vegetation index calculated from acquired image data of indicator blocks having at least two plots, one with a reduced N application rate (canary) and one with an increased N application rate (reference) versus a bulk area N application rate. In a preferred method, sub-regions are defined in a field being managed. In each sub-region, N (nitrogen) is applied to create adjacent canary and reference plots, wherein a canary plot is given less than a designated N amount and a reference plot. The sub-regions are subsequently imaged. A fertigation decision is made for each sub-region based upon automatic analysis of the vegetation indices of the canary and reference plots in each sub-region.