Managing Soil To Keep It Productive
Module 2

Lesson 2 - Glossary
Acknowledgement: Taken from "Living on the Land 2001"

Acidic Soil: Soils with a pH less than 7.

Alkaline Soil: Soils with a pH greater than 7.

Capability Class(es): A classification system developed by the U.S. Department of Agriculture to show the potential or suitability of a soil for growing crops.

Chemical Fertilizer: Fertilizer manufactured from non-living materials, such as rock phosphate.

Clay: A flat or plate shaped mineral or soil grain, less than 0.002 mm across. Clay is also the name of a specific soil texture that contains 40 percent or more particles of clay size.

Compaction: Elimination of pore space in soil and destruction of soil structure, resulting in reduced soil volume and increased soil density. Compacted soils have poor tilth and limited production capabilities.

Compost: Organic material, rich in humus, formed by decomposed plant material and other organic material. Compost is used as a soil amendment or improver and as a mulch.

Cover Crop: A crop planted to protect the soil by reducing or stopping erosion.

Droughty Soil: A soil that is unable to store enough water to meet plant requirements. Sandy and gravelly soils are droughty because they have low water-holding capacities.

EC, Electrical Conductivity: A measurement of the readiness or ease with which a soil transmits electricity. This number directly correlates to salinity or salt concentration, since salts ions conduct electricity.

ESP, Exchangeable Sodium Percentage: The percentage of available absorption sites on soil particles filled with sodium.

Fertilizer: Any of a large number of natural and synthetic materials spread on or worked into the soil to increase its fertility.

Fertilizer Grade: The guaranteed analysis of the contents of a fertilizer bag, generally given as a string of three or four numbers. By convention, the first three numbers represent the percentage of nitrogen, phosphorous and potassium in the fertilizer; if there is a fourth number, it indicates the percentage of sulfur.

Green Manure Crop: A crop that is grown then plowed under to help put organic material into the soil and keep nutrients from leaching away.

Horizon: A layer of soil that is roughly parallel to the earth’s surface and has distinct characteristics formed by the soil formation process.

Humus: A product of microbial decomposition of plant and animal residues that resists further decomposition and accumulates in the soil as organic matter. Humus has a dark color and darkens the A horizon in soils layers.

Infiltration: The rate at which water enters the soil. Infiltration depends on the texture, structure and layering of the surface horizon.

Loam: A specific class of soil texture that contains a balanced mixture of sand, silt and clay. Clay must not exceed 27 percent. Loams have enough sand to feel some grit and enough

clay to give the soil some body, but the properties and behavior of the soil is dominated neither by sand nor clay.

Macronutrients: The essential nutrients needed by plants in large quantities; generally they include hydrogen, oxygen, carbon, nitrogen, phosphorous, potassium, calcium, magnesium, and sulfur.

Microorganisms / Microbes: Tiny, microscopic living organisms, including bacteria, fungi, algae, protozoa, and viruses. Microbes live in the soil and decompose dead plant and animal residues, converting them into humus. Some microbes help make soil nutrients more available for plant use.

Micronutrients: The essential nutrients needed by plants in small quantities; generally they include iron, manganese, zinc, boron, molybdenum, nickel, copper, cobalt and chlorine.

Nutrients: Substances required by plants for growth; see macronutrients and micronutrients.

Organic Fertilizer: Fertilizer made from materials derived from living things, such as manure, bone meal, and blood meal.

Organic Matter: The sum of all plant and animal material, living or dead, that is mixed into the soil. Living microorganisms are part of soil organic matter, and so is the humus they produce. Living and dead plant roots are also part of the soil organic matter. Organic matter promotes good soil structure, reduces compaction, improves rates of movement of air and water through the soil, increases the water storage capability for plant use and provides nitrogen and other elements needed by plants.

Parent Material: The original geologic material from which the horizons of soil are formed. This can be bedrock, sediments, windblown material or volcanic ash.

pH: A number on a scale from 1 to 14 that indicates the relative degree of acidity or alkalinity of the soil. A pH of 7 indicates a neutral soil, one that is neither acid nor alkaline. Smaller numbers indicate acidic soil; higher numbers indicate alkaline soils.

Pores or Pore Spaces: Spaces between the mineral grains of a soil. The size, shape and arrangement of soil pores determines the rates of water and air movement into and through the soil. They also control the amount of available water that a soil can store for plant use.

Porosity: The total amount of pore space in a soil. Porous soils have plenty of pore space; compact, dense soils have low total porosity.

Restrictive Features: A general term for a host of soil features that restrict or limit the use of that soil for a specific purpose. Restrictive features tend to assist users in identifying soil features important for use and management.

Sand: A specific grain size in the soil. Sand grains range in size from 0.05 mm to 2.0 mm in diameter. Sand grains are big enough to see with the naked eye and they feel gritty. Sand is also the name a specific soil texture that has 90 percent or more sand and almost no clay.

Silt: A specific grain size in the soil. Silt grains range in size from 0.002 mm to 0.5 mm in diameter. The grains of silt are too small to see with the naked eye and they feel smooth, like flour, cornstarch or talcum powder.

Soil Aggregation: Formation of soil structure when soil particles loosely or tightly stick together into peds. Organic matter (humus) and soil clays are important agents of soil aggregation.

Soil Ped: A single unit of soil structure. Ped shapes include granular, platy, blocky and prismatic. Ped sizes can range from 1mm granules to 10 cm prisms.

Soil Structure: The arrangement of individual grains of sand, silt and clay into larger units, called peds or aggregates. Plant roots, humus and clay minerals all help to hold the grains together. Soil structure is characterized by the type, or shape, of the peds and their degree of development.

Soil Texture: The amounts of sand, silt and clay that make up a soil sample. Names are given to specific combinations of sand, silt and clay to form textural classes, such as loam, silty loam, sandy loam, etc.

Soluble Salts: A measure of inorganic chemicals that are more soluble than Gypsum, such as sodium, calcium, magnesium, chloride, sulfate and bicarbonate.

Suitability Ratings: Values given to identify the degree to which a soil is favorable to a given use; they are generally given in the terms "good," "fair," or "poor."

Tilth: The physical condition of the surface soil. Good tilth requires plenty of organic material, good soil structure, and good porosity for air and water movement into and through the soil. Soils in good tilth are easy to work, easy for plant seedlings to emerge from and easy for plant roots to grow in.

Topography: The physical features, relief and contour of the land.

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