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A series of tests were carried out to examine the relative performance of 3 VIS/NIR sensors used to inform nitrogen fertilizer decisions in crop production. Although the sensors are different in terms of their sensing footprint, wavelengths used and indices produced from their data they have a common management purpose. The sensors used were Greenseeker from Trimble, Crop Circle ACS-470 from Holland Scientific and CropSpec from Topcon. The sensors were tested on five commercial farms over two seasons in New Zealand, two in the North Island and 3 in the South Island. A 24m sprayer was set up on both islands which was equipped with 4 Greenseeker sensors, two Crop CircleACS-470s and two CropSpec sensors, all mounted according to manufacturers instructions. Crops were sensed over a number of growth stages, and sample cuts to estimate plant biomass were taken from in-paddock sites where the NDVI values were high, medium and low. Five samples were cut from each site at each sampling event. The crops sensed included winter wheat, winter barley, ryegrass for seed production and maize. The sites covered approximately 280 ha in both seasons.