Try to get clean tissue and don't include root material with the sample. Brown paper bags may contaminate samples with nitrate, sulfate and boron. Don't use plastic bags because samples will spoil. Indicate whether soil sample information is available. After laboratory analysis of the sample, it is necessary to have some guidelines for interpreting the numbers.
Extensive research is required to determine appropriate nutrient levels for a particular crop.
Some research data are available for Montana. In addition, an attempt has been made to compile data from the Northwest states. Some of the guidelines are shown in Table 2 for alfalfa, potatoes and wheat. The CNR is a more realistic concept than assuming that a plant suddenly becomes nutrient deficient at a particular nutrient level. At nutrient levels above the CNR we are reasonably certain that the plant has an adequate supply of the nutrient.