The nutritional status of your crop or field can be established by laboratory analysis. Proper sampling is essential for valid results. A sample should be randomly obtained composite that represents the area to be evaluated.
For uniform fields (or for an average of a field), samples should be taken from the entire field. Divide the area into 10 or 40 acre lots (or any appropriate size) based upon the following:
Non-uniform fields should be sampled by taking a composite sample from areas with the same characteristics.