soil testing, involves measurements made in the field or laboratory of soil properties that indicate the physical, chemical, and biological condition of the soil (see soil fertility). Soil testing is a necessary adjunct to soil mapping to determine soil ph (see soil acidity, soil alkalinity), the amounts of available vine nutrition, and any adverse conditions such as salinity or too much sodium (see cation exchange), a lack of healthy biological activity (see soil biota), or high populations of pathogenic organisms (see soil preparation). Soil tests can give useful preliminary information as to which macronutrients are needed. When the tests are carried out before planting, the results allow the application of any necessary nutrients such as phosphorus, potassium, calcium, magnesium, and boron under the vines, at depths where they will remain readily, and more or less permanently, available to the roots. However, because the grapevine is a perennial plant, tissue analysis of leaf blades or petioles, rather than soil testing, usually gives a better guide to any ongoing fertilizer requirements.