This pint mixture is the composite soil sample. In some cases, the number of subsamples may be limited by time constraints or availability of labor. Keep in mind, however, fewer subsamples result in less accuracy in evaluating the nutrient or mineral status of the soil. Sampling Depth Take the surface sample to tillage depth. Be sure to separate and discard surface litter.
Deep soil sampling greatly improves nitrogen recommendations for irrigated Crops.
Take deep samples to 2 feet, preferably to 4 feet. There is little point in going deeper unless an unusual situation requires special attention. Keep each depth separate. Request a routine test for the surface composite sample and NO 3 -N only for the subsoil samples. When to Sample Sample fields before each cropping season.