NTech Industries' GreenSeeker® RT200 was first installed on commercial wheat and corn fertilizer applicators in 2004 for nitrogen variable rate application. In the summer of 2005 the first installations were made for variable rate application of defoliant and cotton vigor mapping. Plans are to use the systems for variable rate application of plant growth regulator in 2006. The GreenSeeker® RT200 uses self illuminated sensors mounted to the spray applicator boom to determine the cotton crop status/vigor/biomass in real time, and make on-the-go rate changes. The sensors use LED lights to emit Red and Near Infrared light onto the crop canopy, and measure the reflectance. The GreenSeeker® sensors essentially have the same crop condition measurement capabilities as high resolution aerial imagery, but because they have their own light source, the GreenSeeker® sensors work day or night, in any weather condition. This allows the grower to be in control of their own destiny without needing to schedule aerial or satellite imaging, or worry about weather delays and atmospheric conditions not allowing image acquisition. The GreenSeeker® data is not impacted by row direction, haze or sun angle.