Glossary

Here are some definitions of terms and acronyms that you will encounter during the upcoming weeks.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A

Acidification

• Soil acidification is a process where the soil pH decreases over time (becomes acidic). This process is accelerated by agricultural production and can affect both the surface soil and subsoil.

Adenosine triphosphate (ATP)

• The source of energy for use and storage at the cellular level. Animals store the energy obtained from the breakdown of food as ATP. Likewise, plants capture and store the energy they derive from light during photosynthesis in ATP molecules.

Autotroph

• An organism that is able to form nutritional organic substances from simple inorganic substances such as carbon dioxide.

Archaea

• Single-celled organisms.

Avermectins

• A series of drugs and pesticides used to treat parasitic worms and insect pests.

B

Basidiomycetes

• A fungus whose spores develop in basidia. They include the majority of familiar mushrooms and toadstools.

Biosynthesis

• Production of a chemical compound by a living organism.

C

Carbon sequestration

• The process of capturing and storing atmospheric carbon dioxide. Carbon dioxide (CO₂) is naturally captured from the atmosphere through biological, chemical, and physical processes. These changes can be accelerated through changes in land use and agricultural practices.

Cation exchange capacity

• The measure of how many cations can be retained on soil particle surfaces.

Chelate

• An agent that creates multiple bonds with a metal ion, such as zinc or iron. It may also bond with minerals such as nitrogen, potassium, or phosphorous, all of which are important elements for a plant’s health.

Compaction

• Soil compaction occurs when soil particles are pressed together, reducing pore space between them. Heavily compacted soils contain few large pores, less total pore volume and, consequently, a greater density. Compacted soil has a reduced rate of both water infiltration and drainage.

C3, C4 and CAM plants

• C3, C4 and CAM are the three different processes that plants use to fix carbon during the process of photosynthesis. Fixing carbon is the way plants remove the carbon from atmospheric carbon dioxide and turn it into organic molecules like carbohydrates.

CAM plants

• Plants that use CAM photosynthesis gather sunlight during the day and fix carbon dioxide molecules at night.

C3 plants

-Plants in which the initial product of the assimilation of carbon dioxide through photosynthesis is 3-phosphoglycerate, which contains 3 carbon atoms.

C4 plants

• C4 photosynthesis makes an intermediate four-carbon compound that splits into a three-carbon compound for the Calvin cycle.

D

Deciduous trees

• Trees that shed their broad, flat leaves at the end of the growing season. It contrasts with most trees that are evergreen which typically retain needle foliage throughout seasons.

Delimbing

• The process of removing branches from a standing or fallen tree trunk.

Denitrification

• The conversion of soil nitrate to the nitrogen gases N2O and N2 by a diverse array of bacteria that use nitrate in the absence of oxygen.

Desalination

• The removal of salts and minerals from a target substance, such as soil or water.

Downy mildew

• A widespread, serious disease of grapevines. Initial leaf symptoms are light green to yellow spots, called “oil spots” because they appear greasy. Under humid conditions, white, downy spore masses can be seen on the lower leaf surface. These spores are wind dispersed.

E

Evapotranspiration

• The loss of water from the soil both by evaporation and by transpiration from the plants.

F

Feedlot

• A feedlot or feed yard is a type of animal feeding operation which is used in intensive animal farming, notably beef cattle, but also swine, horses, sheep, turkeys, chickens or ducks, prior to slaughter.

Flower primordia

• The formation of little buds at the end of stems from which a flower can develop.

Fulvic and humic acids

• Humic acid and fulvic acid represent up to 80% of dissolved organics of natural waters. Humic substances are weak acidic electrolytes with carboxylic- and phenolic-OH groups with a molecular weight between 500 (fulvic) and 100,000 (humic).

G

Granulometry

• The measurement of the size distribution in a collection of mineral grains.

H

Haber-Bosch process

• An industrial process for producing ammonia from nitrogen and hydrogen by combining them under high pressure in the presence of an iron catalyst, was developed by the German physical chemist Fritz Haber. He received the Nobel Prize for Chemistry in 1918 for this method, which made the manufacture of ammonia economically feasible. The method was translated into a large-scale process by Carl Bosch.

Heterotroph

• A heterotroph is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter.

Humification

• A process of formation of humic substances (organic matter that has reached maturity) decomposed from plant remains.

Humus

• A dark-brown or black organic substance made up of decayed plant or animal matter.

I

Intercropping

• The practice of growing two or more crops in proximity. The most common goal of intercropping is to produce a greater yield on a given piece of land by making use of resources that would otherwise not be utilised by a single crop.

L

Leaching

• The loss of soluble substances and colloids from the top layer of soil by percolating precipitation. The materials lost are carried downward (eluviated) and are generally redeposited (illuviated) in a lower layer. This transport results in a porous and open top layer and a dense, compact lower layer.

Lignin

• A class of complex organic polymers that form key structural materials in the support tissues of most plants.

Liver fluke cycle

• A type of parasite. After being ingested by the grazing host, the immature fluke migrate to the liver, which they then tunnel through to the bile duct, causing damage to the cells of the liver and blood vessels. Depending on the number of fluke in the liver, the effects can range from death to loss of productivity as the liver is not processing all the food for the animal’s needs.

M

Microbial assimilation

• The process of absorption of minerals, and other chemicals as part of the nutrition of an organism. It is an important process in global carbon cycling.

Mineralisation

• The process by which chemicals present in organic matter are decomposed or oxidised into easily available forms to plants.

Monoculture

• The cultivation of a single crop in a given area.

Mycorrhizal associations

• A symbiotic association between a fungus and a plant. Fungus colonise the host plant’s root tissues. The association is sometimes mutually beneficial or can be a parasitic association with the host plant.

N

Nematodes

• A type of roundworm which helps distribute bacteria and fungi through soil and along roots by carrying live and dormant microbes on their surfaces and in their digestive systems. Some nematode species are responsible for plant diseases, but the majority of the nematode community play a beneficial role in soil.

Nitrification

• The biological oxidation of ammonia (NH4) to nitrite (NO2) followed by the oxidation of the nitrite to nitrate (NO3) occurring through separate organisms] or direct ammonia oxidation to nitrate in bacteria. The transformation of ammonia to nitrite is usually the rate-limiting step of nitrification. Nitrification is an essential step in the nitrogen cycle in soil. Nitrification is an aerobic process performed by small groups of autotrophic bacteria and archaea.

O

Osmosis

• The process in plants by which a liquid moves gradually from one part of the plant to another through a membrane (cell covering).

P

Pastoralism

• A form of animal husbandry where livestock are released onto large vegetated pasture lands for grazing, historically by nomadic people who moved around with their herds. The animal species involved include cattle, camels, goats, yaks, llamas, reindeer, horses and sheep.

Percolation

• The process by which water moves downward through the soil under gravitational forces.

Phenols

• A family of organic compounds characterised by a hydroxyl (―OH) group attached to a carbon atom. Phenols are similar to alcohols but form stronger hydrogen bonds. Thus, they are more soluble in water than alcohols and have higher boiling points. They occur either as colourless liquids or white solids at room temperature and may be highly toxic and caustic.

Plough

-A large farming tool with blades that digs the soil in fields so that seeds can be planted.

Phytoplasma

• A group of bacteria that are related to mycoplasmas, cause plant diseases by infecting phloem tissue and are transmitted especially by homopteran insect vectors. For almost half a century, plant pathologists thought phytoplasmas were viruses. To this day, the inability to grow these bacteria outside plants or insects has hindered efforts to get a handle on their biology and genomes.

Porosity

• Gaps between soil aggregates that can be filled with water or air.

Pyrolysis

-Decomposition brought about by high temperatures.

R

Rainfed crops

• Crops that rely on natural rainfall rather than irrigation.

Rhizosphere

• The area around a plant root that is inhabited by a unique population of microorganisms.

S

Sowing

• Plant (seed) by scattering it on or in the earth.

V

Volatilisation

• The loss of N through the conversion of ammonium to ammonia gas, which is released to the atmosphere.