Soils - Part 4: Soil pH Glossary

ammonium nitrate

A dry granular material manufactured by reacting nitric acid with anhydrous ammonia. One-half of the nitrogen in ammonium nitrate is in the nitrate form, and one-half is in the ammonium form.

anhydrous ammonia

A gaseous material that is compressed and stored as a liquid. At 60oF, a gallon of anhydrous ammonia weighs 5.15 pounds. Due to the fact anhydrous ammonia needs to go through the nitrification process, it is more resistant to losses from the soil by leaching or denitrification because it is converted by bacterial action to the nitrate form more slowly than are other nitrogen sources.

aqua ammonia

Anyhdrous ammonia dissolved in water. It is a low pressure solution and contains free ammonia, the amount of which increases as air temperature increases.

buffer pH

A test used to estimate lime requirements in soil, which means the amount of agricultural lime required to neutralize the H+ from the soil exchange sites and in the soil solution.

cation exchange capacity

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.


As a soil separate, clay refers to mineral soil particles which are less than 0.02 millimeters in diameter. As a soil textural class, clay refers to soil material that is 40 percent or more clay, less than 45 percent sand, and less than 40 percent silt.

elemental sulfur

The most concentrated form of sulfur.  Elemental sulfur must be oxidized to the sulfate form before plants can use it.  It must be finely ground to particle sizes of 80-100 mesh to be oxidized and effective during the same growing season.


An organic material in soil which is a product of plant and animal remains that have decomposed and then synthesized into something new.


Elements needed in very small amounts for plant growth.  Micronutrients include zinc, iron, chlorine, copper, manganese, boron and molybdenum.


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.

parent material

Rock or minerals which are weathered to form smaller particles of a soil. Parent material is one of the five factors contributing to formation of a specific soil. In the Great Plains, much parent material is associated with ancient seas or glacier deposits.


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 sample

A collection of individual cores from a known area.

soil test

Chemical analysis of soil samples to assess soil nutrient levels and determine how fertilizer use can be improved.

soil texture

Determined by the proportion of different soil separates--sand, silt and loam--in a soil.


A dry nitrogen material produced by reacting ammonia with carbon dioxide.  Urea contains the highest percentage of nitrogen of the commonly used dry fertilizers and is rapidly replacing ammonium nitrate. When surface applied, urea is the most rapidly volatilized of the dry nitrogen materials.