Manure Phosphorus and Surface Water Protection I: Basic Concepts of Soil and Water P Glossary


The process by which P is taken from the soil solution of soil atmosphere and retained on soil particle surfaces by chemical and physical binding.

bio-available P

This water P fraction, also refer to algal-available P, is a combination of dissolved P plus the estimated portion of P to be released from sediment P within a short time, e.g. 45 hours, after the particles enter surface water.


A soil inorganic separate of less than 2 micrometers (< 0.002 mm.). This is smallest of the mineral soil separates.

cover crops

Any crop grown to provide soil cover and prevent soil erosion by wind or water.

dissolved P

This water P fraction, a near equivalent with dissolved reactive P, is readily available to aquatic plants and animals.


The excessive growth of aquatic plants and algae caused by the addition of nutrients and sediments to water.


Oxygen deficiency in bodies of water created by pollution from nutrients and sediments.

labile P

This soil P fraction is typically accounts for less than 1% to less than 5% of the P in soils, and is less tightly bond than stable P. Some labile P, as well as solution P, is measured with agronomic soil tests.

most limiting nutrient

Justus von Liebig formulated the law of the minimum: plant growth is limited by the most deficient nutrient, even if the other elements are abundant.

non-labile P

A slowly available form of phosphorus.


The downward movement of water through the soil, made possible by pore space in the soil.


An enzyme produced by some algae species under conditions of low P availability.  Phosphatase converts organic P to inorganic P, which the algae can, in turn, use for growth.


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.


The portion of precipitation or irrigation on an area that does not infiltrate but, instead, is discharged from the area. That which is lost without entering the soil is called "surface runoff."

sediment P

This water P fraction, also referred to as particulate P, often is the greatest fraction in water bodies. It consists of organic and inorganic sediments. Its not available to most aquatic plants and animals, but phosphatase producing algae can cause organic sediment P to become available.


Occurs when eroded soil deposits and/or settles out in water.


A soil inorganic separate in the range of 2 to 50 micrometers (or 0.002 to 0.05 mm.). Silt is smaller than sand but larger than clay.

solution P

This soil P fraction is typically accounts for less than 1% of the P in soils and is readily available to plants.


This soil P fraction is also called non-labile P. It accounts for most of the P in soils, typically more than 95% of the total, and includes tightly bond P in secondary and primary minerals and in organic forms.

water infiltration

Water movement in the soil.  Pore space in soil is the conduit that allows water to infiltrate and percolate (downward movement of water through the soil).