The end-of-season test for corn stalk nitrate is used to assess the degree of nitrogen (N) sufficiency for corn (Zea mays L.). However, the test gives point estimates of N sufficiency and it is difficult to select sampling areas because of spatial variability within fields in supply of N from the soil, manure, and fertilizer.  Differently, remote sensing of corn canopy can be used to guide corn stalk sampling within fields and focus on the range of variability of interest.  A survey was conducted to evaluate various N management practices in production agriculture by using guided corn stalk nitrate testing on a scale of individual fields, farms, and watersheds.  The survey included more than 500 fields within two watersheds in Iowa during 2004-2006. Some fields received various N treatments (rates, N forms, timing, and manure) in replicated strips. Other fields were fertilized by producers using their normal practices. Sampling areas within fields were selected by using geo-referenced aerial images of corn canopy taken in late August. Three areas were selected within three major soil map units where corn canopy did not show symptoms of N deficiency while the fourth sampling area was targeted specifically where the plants showed N stress. For the fields with replicated N treatments, three samples were collected from each treatment.  A procedure was developed to interpret results of corn stalk evaluations for individual fields by making adjustments for early-season rainfall.  Remote sensing helped detect N stressed areas in more than half of the targeted locations and the stalk nitrate data helped identify less efficient N practices within the watersheds. The survey type approach using the corn stalk nitrate test and remote sensing was found to be useful in evaluating and improving N management practices at various scales.