Acidulated: Fertiliser manufacturing process where acids are used.
Aeration: Process where air gets into the soil pores.
Aggregate: Cluster of soil particles (sand, silt and clay).
Allophanic soils: Soils containing aluminium and silicon formed from volcanic ash.
Alluvial soils: Soils deposited on land by water.
Ammonium nitrate: Inorganic fertiliser with 33% or rapidly available N.
Ammonium phosphates: Inorganic fertiliser containing N(33%).
Ammonium sulphate: Inorganic fertiliser containing N(21%) and S(24%).
Ammonium nitrogen: Inorganic soluble form of N.
Anion: Ion carrying one or more negative charges.
Anion storage capacity (ASC): Measure of the capacity of soil to store nutrients e.g. P and S: Previously known as phosphate retention capacity.
Ash soils: Yellow-brown loams, brown granular loams and clays, and red brown loams, derived from volcanic eruption.
Available nutrients: Nutrients in soil easily absorbed by plants.
Available water: Proportion water in soil that is easily absorbed by plants.
Available water-holding capacity: Sum of available water capacity of each root-containing layer.
Bare fallowing: Fallow leaving bare soil.
Base saturation: Percentage of cation exchange capacity of a soil saturated with basic cations.
Base cations: Calcium (Ca), magnesium (Mg), sodium (Na) and potassium (K).
Biomass: Living organisms in the soil.
Borax: Trace element fertiliser containing 11% boron.
Border dyking: Levees or borders to control flow of water on to land.
Brassica crops: Cauliflowers, cabbages, turnips and Swedes.
Brown earths: Aerobic soils with brown colour due to iron particles on soil particles.
Buffering capacity: Ability to resist changes in pH; also changes in concentration in nutrient concentration.
Bulk density: The mass of a standard volume of soil.
C:N ratio: Concentration of carbon in organic matter divided by the concentration of nitrogen.
Calcareous: Containing calcium carbonate (limestone).
Calcined magnesite: Inorganic fertiliser containing 50-55% magnesium in rapidly available form.
Calcium sulphate: Gypsum. Inorganic fertiliser containing S(20%) in rapidly available form.
Cation: Ion carrying one or more positive charges.
Cation storage capacity (CSC): Measure of capacity of a soil to store nutrients e.g. Ca, M.G., K and Na. Also called cation exchange capacity.
Chelates: Trace elements combined into organic molecules which makes them readily available to plants.
Clay soils: Soil containing fine mineral particles no bigger than 0.002mm in diameter.
Clod: Large dense lump of soil.
Coarse soil texture: Soil dominated by sand-sized mineral particles.
Cobalt sulphate: Trace element fertiliser containing Co (21%).
Compaction: Soil where heavy machinery of stock have destroyed air-filled pores.
Concretion: Soil particle composed mainly of a single chemical compound e.g. Calcium carbonate or iron oxides.
Copper sulphate: Trace element fertiliser containing Cu(25%).
Cover crop: Crop planted to protect the soil surface or seed planted after it has started to grow e.g. Grass seed in crop of barley.
Crop residue: Unharvested part of a crop (roots and straw).
Crop rotation: Sequence of different crops grown on an area of lad which could include a fallow.
Crumb structure: Small, rounded, porous aggregates in soil.
Denitrification: Reduction of nitrate or nitrate nitrogen to gaseous form.
Development fertiliser: Fertiliser applied to boost the overall fertility of a farm.
Diammonium phosphate: Inorganic fertiliser containing N (18%). P (21%) and K(0), S(2%).
Dolomite: Form of limestone containing calcium or magnesium carbonate. Has 10% Mg in slow release form.
Effective root depth: Depth of soil before root penetration stops.
Elemental Sulphur: Inorganic fertiliser which is 100% S in slow release form.
Equivalent acidity: Weight of pure calcium carbonate (limestone) to neutralise the acidity caused by applying 100kg of fertiliser.
Erosion: Loss of soil by wind, water or ice.
Essential plant nutrients: Chemical elements essential for normal plant growth.
Eutrofication: Enrichment of surface water with plant nutrients causing weed and algal growth, and anaerobic conditions.
Fallow: Period when no crop is grown.
Ferrous sulphate: Trace element fertiliser containing 19% Fe.
Fertiliser: Any organic or mineral material added to soil to supply essential nutrients for plant growth. (Not the legal definition).
Field capacity: Soil water content 2-3 days after a saturated soil has been allowed to drain, and when free drainage has stopped.
Fine texture soils: Soils in which fine particles (clay and silt) predominate.
Fixation: Process that converts plant nutrients from soluble form to less soluble form.
Friable soil: Soil which breaks down with ease to desirable tilth.
Gley soil: Soil developed under poor drainage.
Granular structure: Soil with well-defined crumb structure.
Green manuring: Growing a crop e.g. oats, lupins to plough back into the soil.
Ground water: Zone below soil surface in which water can move freely.
Growing degree days: Number of days when air temperature is above 10ºC.
Gumland soils: Soils containing the resin from kauri trees.
Gypsum: Inorganic fertiliser containing 20% S in rapidly available form. Calcium sulphate.
Heavy metal: Toxic metallic elements e.g. Cadmium, mercury, arsenic, chromium, lead and nickel.
Horizon: Horizontal layers in the soil profile differing in appearance and chemical properties.
Hump and hollow: Reshaped land surface to help drain off surface water.
Humus: Stable form of organic matter in soil containing plant and animal residues decomposed by micro-organisms.
Impeded drainage: Condition where no free movement of water through soil is possible.
Impervious: Resistant to water or plant roots.
Infiltration: Entry of water into the soil surface.
Immobilisation: Reverse of mineralisation.
Inorganic: Mineral substances containing carbon only in the form of carbonates.
Intrazonal soils: Soils influenced when formed by parent material or temporary or permanent saturation.
Ions: Electrically charged particles formed when substances dissolve in water. Anions have negative charge and cations have positive charge.
Iron pan: Narrow layer of soil in which individual particles are cemented together by iron oxides.
Labile nutrients: Plant nutrients in soil that are able to replenish the soil solution rapidly to maintain plant growth.
Land classification: Grouping land into categories based on suitability for purpose.
Leaching: Removal of nutrients from upper soil layers by downward movement of water.
Limestone: Rock made up mainly of calcium carbonate.
Liquid fertilisers: Fertilisers spread in liquid form.
Loam: Soil containing sand, silt and clay-sized particles without any one type dominating.
Macronutrient: Element required in large amounts for plant growth.
Magnesium oxide: See Calcined magnesite.
Magnesium sulphate: Inorganic fertiliser containing 10% Mg in rapidly available form.
Maintenance fertiliser: Fertiliser applied to replace nutrients removed from the soil.
Manganese sulphate: Trace element fertiliser containing 24% Mn.
MAX: Maximum available water-holding capacity of soil root zone.
Melanic soils: Soils with dark surface horizon rich in nutrients such as Ca and Mg.
Micronutrient: Element required in small amounts (ppm) for plant growth.
Mineral nitrogen: Soluble N compounds in nitrate, nitrite or ammonium forms.
Mineral soil: Soil consisting mainly of mineral materials and less than 20% organic matter.
Mineralisation: Process where micro-organisms convert plant nutrients from organic to inorganic form.
Mole drainage: Dragging metal plug (mole) through soil to make drainage tunnels.
Monoammonium phosphate: Inorganic fertiliser containing N(11%). P(21%) and K(0), S(2%).
Mulch: Material applied to soil to prevent water loss by evaporation and suppress weed growth.
Nitrate nitrogen: Inorganic soluble form of N.
Nitrogen assimilation: Incorporation of N into organic materials by living organisms.
Nitrogen cycle: Process of how nitrogen is used in a grazing system incorporating N from the air, the role of N fixing by legumes, and return of dung and urine from the animal.
Nitrogen fixation: Conversion of nitrogen gas in the air by rhizobia bacteria on roots of legumes into forms that can be used by plants.
Nutrient budget: Exercise to balance nutrients applied with nutrients removed from the farm.
Nutrient cycling: Process of nutrients moving from soil to plants and returned again to soil.
Olsen P test: Measure of plant available P.
Organic soil: Soil containing more than 20% organic matter.
Over liming: Applying more lime than needed to achieve optimum pH.
Oxidation pond slurry: Content of farm oxidation pond used as organic fertiliser.
Parent material: Material from which the soil is formed.
Partially acidulated phosphate rock (PAPR): Inorganic fertiliser containing P in both soluble and slow release form. Total P content around 15%.
Peat: Soil formed by accumulation of undecomposed or partially decomposed plant residues.
Permanent wilting point: Water content of soil at which plants wilt and don’t recover.
Permeability: Ease which with water, gases or water can pass through a soil.
pH: Measure of acidity or alkalinity of soil.
Phosphate retention capacity: Soils capacity to absorb phosphate anions.
Plasticity: Ability for soil to stay in shape after being moulding with fingers.
Plough pan: Soil layer with poor permeability formed below depth of regular cultivation.
Poaching: Same as pugging.
Podzols: Strongly leached acid soils with clearly defined bleached horizon.
Porosity: Volume of pores as percentage of volume of soil.
Potassium chloride: Inorganic fertiliser containing 50% potassium in rapidly available form.
Potassium sulphate: Inorganic fertiliser containing 40% K and 17% S in rapidly available form.
Profile: Vertical section through soil exposing different horizons.
Pugging: Destruction of surface structure of wet soils by stock or traffic.
Pumice soils: Soils formed from volcanic pumice.
Quick test K(QTK): Measure of plant available K.
Quick test Mg(QTMG): Measure of plant available Mg.
Raw soils: Very young soils with no distinct profile.
Reaction: Acidity or alkalinity of soil expressed as pH value.
Reactive phosphate rock (RPR): Natural occurring, slow-release P fertiliser containing between 12-15% P. An unacidulated fertiliser.
Recent soils: Weakly weathered soils with little profile but with distinct topsoil.
Rhizobia: Bacteria live in root nodules on legumes that convert atmospheric N into plant available N.
Rhyolite: Derived from rhyolite, a fine-grained igneous rock that occurs in larva flows.
Rill erosion: Erosion forming small gullies or rills on soil surface.
Ripping: Same as subsoiling.
Root nodules: Small growth on roots of legumes containing rhizobia bacteria.
Root zone: Depth to which roots penetrate.
Run-off: Rainfall or irrigation water which flows off soil surface.
Saline soils: Salt-affected soils.
Sand: Mineral soil particles between 0.02 and 2mm in diameter.
Sandy soil: Soil with texture dominated by sand fraction.
Saturate: To fill to capacity e.g. Soil pores with water.
Sedimentary soil: Soil formed by layers of material deposited by wind or water.
Sheet erosion: Small amounts of soil eroded in a uniform manner from soil surface.
Silt: Mineral soil particles between 0.002 and 0.02mm.
Silting: Deposition of water-borne soil particles in a stream or lake or on flooded land.
Sulphur leaching index (SLI): Index of likely loss of sulphate Sulphur from root zone by leaching.
Slow-release fertiliser: Fertilisers that release their nutrients over an extended period.
Sodium molybdate: Trace element fertiliser containing 39% Mb.
Sodium selenate prills: Trace element fertiliser containing 1% Se.
Soil cap: Dense layer on surface of soil.
Soil solution: Water in soil and materials dissolved in it.
Soil structure: Arrangement of primary soil particles (sand, silt, clay) into aggregates.
Soil tests: Chemical estimates of soil‘s ability to supply nutrients available to plants.
Soil water deficit: Difference between actual amount of water in soil and its water holding capacity.
Solubor: Trace element fertiliser containing 20% Bo.
Sorption: Combination of adsorption and absorption where ions are removed from soil solution by reacting with soil particles.
Subsoil: Soil below B horizon, below cultivated layer or below the root zone.
Subsoiling: Breaking the compact subsoil with tines and without inverting it.
Subsurface tillage: Cultivation with blade to cut plant roots to loosen soil without inverting it.
Sulphate of ammonia: See ammonium sulphate.
Sulphate Sulphur: Inorganic soluble form of S.
Sulphur leaching index: Empirical assessment of potential for sulphate Sulphur to be leached from soil.
Superphosphate(Single super): Rapid release inorganic fertiliser containing around 9%P and 12% S. A fully acidulated P fertiliser.
Superphosphate(Triple super): Rapid release inorganic fertiliser containing around 20%P and 2% S. A fully acidulated P fertiliser.
Surface drains: Reshaped land surface to help removal of surface water.
Texture: Relative proportion of solid primary particles (sand, silt and clay) in a soil.
Tile drain: Clay pipes in subsoil to remove surface water.
Tilth: Fine texture of topsoil required before sowing.
Topsoil: Uppermost layer of soil. The cultivated area.
Ultic soils: Strongly weathered soils with accumulation of clay in the subsoil.
Unacidulated: Process in fertiliser manufacture involving acid.
Urea: Inorganic fertiliser with N (46%) in rapidly available form.
Whey: Byproduct from cheese manufacture used as cow feed or fertiliser.
Virgin soil: Uncultivated soil.
Volcanic rock: Rock derived from volcanic activity e.g. Basalt, pumice and rhyolite.
Volumetric water content: Volume of water in soil as percentage of soil volume.
Water stress: Stress in plants caused by inadequate water.
Water table: Level below which a soil is saturated with water.
Weathering: Physical and chemical changes caused by atmospheric forces occurring near the surface.
Wilting point: Same as permanent wilting point.
Wind erosion: Caused by particles blown by wind.
Zinc sulphate: Trace element fertiliser containing 23% Zn.
Zonal soils: Soils in which climate and vegetation are the most important soil-forming factors.
Information source: I.S. Cornforth (1998). Practical soil management. Lincoln University Press. ISBN 0-909049-15-7