Recent studies unexpectedly revealed that losses of fall-applied anhydrous ammonia tended to increase with increase in soil pH. The greatest losses occurred on "calcareous soils", which have free carbonates and pH values in the range of7.5 to 8.4. The studies also revealed that the calcareous soils occur in spatial patterns that often are much more complex than indicated on soil survey maps. Studies were initiated during the 2000 growing season to evaluate the possibility that aerial photographs of soybean crops would provide a simple and effective way to map calcareous areas within fields.