Soils - Part 9: Fundamentals of Soil Testing Glossary


in the context of soil testing -- A means of establishing a relationship between a given soil test value and the yield response from adding a nutrient to soil as fertilizer.

cation exchange capacity

(CEC) - The ability of a soil to hold certain elements which have a positive charge; mainly a function of clay content and organic matter. Some plant nutrients, such as potassium and caldium are cations, so a soil with higher CEC will generally be more fertile because of its greater ability to hold these nutrients.  Measured in milliequivalents/100 grams.


In the context of soil tests -- The relationship between the amount of nutrient extracted from soil by a laboratory test and nutrient uptake by plants in the greenhouse or field and/or crop yield.

critical point

The point at which soil test values delineate responsive soils (those where fertilizer additions increase yields) and nonresponsive soils.


Element needed in large amounts for plant development; found naturally and in applied fertilizers.

organic matter

Material that contains carbon and is found in the soil. Most soil organic matter comes from previously living organisms.  Temperature and moisture are the two main factors affecting its development.


The measurement of an aqueous solution’s acidity and alkalinity; measured on a scale of 1 to 14. Pure water has a pH of 7.0 and is neutral. Different crops grow best at different pH levels; pH influences herbicide activity and nutrient uptake.


A key element in the complex nucleic acid structure of plants which regulates protein synthesis; important in cell division and development of new tissues.  Next to nitrogen, the most limiting nutrient in Nebraska crop production; naturally found in sufficient amounts in many Nebraska soils.


An essential plant nutrient needed in large amounts.  Postassium is vital to plant nutrient absorption, respiration, transpiration and enzyme activity. The major portion of potassium is contained in minerals such as feldspar and mica, and clays such as montmorillonite, vermiculite and illite.

soil sampling

A collection of individual cores from a known area.