Soil testing traditionally requires mass spectrometry. ChromaSoil bypasses the laboratory entirely on a strip of paper. The internal chemistry uses a VCl₃-Griess reagent reduction to isolate nitrate and a modified Berthelot reaction to target ammonium. A barium chloride scavenging layer eliminates phosphorus interference. A citrate buffer controls pH across different soil matrices. The user photographs the resulting colorimetric reaction with a smartphone. The application normalizes for ambient light and calculates exact parts-per-million concentrations. The chemistry is stable and specific. Each unit costs pennies to manufacture.