Nitrate salts may accumulate at the soil surface during dry weather and can give excessively high readings at the surface while the soil as a whole may not be excessively high in salts. Representative soil samples taken as a slice of soil from the surface to six inches give a better picture of the overall salt condition in a soil than a more shallow sample. Where high rates of soluble salts are found in a routine soil test sample for a commercial crop, it is usually advisable to resample the field at a later date or in more detail. Try to obtain representative samples from potentially different areas. If the cause of a high reading on a garden sample can be determined from the method of sampling or fertilizer history, no additional sample may be necessary.
Salts accumulate in the soil when they are added faster than they can be removed.
Only under certain circumstances are excessive salts a problem in areas of high rainfall. The salts that concern us when found at high rates in Arkansas soils are often some of the same ones needed by plants for growth. The problem where it exists is usually only in the amount present. The salts themselves are not toxic in the usual concentrations. The action of the salts is to cause water uptake by the plants to be more difficult as the soils dry out.