The tests may be done in spring or fall. However, the possibility of overwinter loss of residual nitrate makes estimation of carryover more difficult than for phosphorous and potassium. The amount of residual nitrogen in the soil at the end of the growing season must be considered, as well as factors affecting overwinter loss. The crop received moderate to high amounts of nitrogen as fertilizer or as legume or manure nitrogen credits. Yields were below expected levels.
Soils are silt loam or heavier-textured.
Overwinter precipitation amounts are normal or below normal. Sample in the spring. Soil samples should be collected in the spring after the frost has left your fields and before preplant applications of nitrogen fertilizer. Each sample should be placed in a clean container marked for the appropriate depth. Thoroughly mix the soil from each depth and collect a 1-cup subsample.