NDVI Crop Health Calculator

Healthy, chlorophyll-rich crop canopy absorbs red light for photosynthesis rather than reflecting it, so a higher Red Reflectance reading signals less healthy or less dense vegetation. Since NDVI is calculated as (NIR minus Red) divided by (NIR plus Red) -- the formula introduced by Rouse et al. in 1974 and still documented today by NASA's Earth Observatory program as the standard vegetation-health index -- a higher red value shrinks the numerator and grows the denominator at once, pulling NDVI down.

NDVI Value is sorted into one of five health bands, each carrying a fixed assumed Yield Impact percentage (0% for Excellent down to -60% for Bare Soil / Severe Stress). That percentage is applied to your Expected Yield to get a per-acre yield loss, which is then multiplied by Crop Price and Affected Area to produce Total Revenue Loss.

The dollar figure scales linearly with Expected Yield, Crop Price, and Affected Area once a stress band with a nonzero yield impact applies, so a higher expected yield does produce a larger loss estimate at the same stress level. Treat it as a rough planning figure, though -- the underlying yield-impact percentages are fixed approximations, not calibrated to your specific crop or field history.

Not necessarily -- NDVI Value moves continuously with both reflectance inputs, but Health Assessment only changes when that NDVI crosses one of the five band boundaries (0.70, 0.50, 0.30, or 0.15). A small reflectance change can shift the NDVI number without moving it across a boundary, leaving the health category and Yield Impact percentage unchanged.