A seed treatment is a treatment of the seed with either chemical agents or biological or by physical methods. Usually done to provide protection to the seed and improve the establishment of healthy crops. Not to be confused with a seed coating. In

agriculture Agriculture encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created ...

and

horticulture Horticulture (from ) is the art and science of growing fruits, vegetables, flowers, trees, shrubs and ornamental plants. Horticulture is commonly associated with the more professional and technical aspects of plant cultivation on a smaller and mo ...

, coating of the seed is the process of applying exogenous materials to the seed. Also referred to as seed dressing. A seed coating is the layer of material added to the seed, which may or may not contain a "protectant" ( biological or chemical pesticide) or biostimulant applied to the seed and possibly some color... By the amount of material added, it can be divided into: * A Film coating, a layer of thin film applied to the seed typically less than 10% of the mass of the original seed. * Encrustment, where the applied material is typically 100%–500% of the original seed mass, but the shape is still discernible. * Pellet, where the applied material is so thick that the seed's original shape is not discernible. Seed coating provides the following functions: * For formulations with pesticides, direct application to seeds can be environmentally more friendly, as the amounts used can be very small. * Color makes treated seed less attractive to birds, and easier to see and clean up in the case of an accidental spillage. * A thick coating can improve handling, by hand or by machine. Thinner coatings may also help with characteristics like flowability. * Thick coatings may accommodate additional features such as fertilizers,

plant hormones Plant hormones (or phytohormones) are signal molecules, produced within plants, that occur in extremely low concentrations. Plant hormones control all aspects of plant growth and development, including embryogenesis, the regulation of Organ (anat ...

, plant-beneficial microbes, and water-retaining polymers. Specialist machinery is required to safely and efficiently apply the chemical to the seed. A cement mixer is enough for non-hazardous coating materials. The term "seed dressing" is also used to refer to the process of removing

chaff Chaff (; ) is dry, scale-like plant material such as the protective seed casings of cereal grains, the scale-like parts of flowers, or finely chopped straw. Chaff cannot be digested by humans, but it may be fed to livestock, ploughed into soil ...

, weed seeds and straw from a seed stock.

History

The earliest seed dressings were of organo-mercurials used to control pests such as oat smut and bunt of wheat. These were available from the 1930s but were ineffective on ''

Pythium ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but '' Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are fre ...

'' and ''

Fusarium ''Fusarium'' (; ) is a large genus of filamentous fungi, part of a group often referred to as hyphomycetes, widely distributed in soil and associated with plants. Most species are harmless saprobes, and are relatively abundant members of the s ...

'' species which are pathogens of many crops including cotton, maize and soya.

Thiram Thiram is the simplest thiuram disulfide and the oxidized dimer of dimethyldithiocarbamate. It is used as a fungicide, ectoparasiticide to prevent fungal diseases in seed and crops and similarly as an animal repellent to protect fruit trees and ...

was therefore developed as a seed treatment in the 1940s to extend the spectrum of diseases that could be controlled. In 1949 ICI commercialised a seed treatment with

trade name A trade name, trading name, or business name is a pseudonym used by companies that do not operate under their registered company name. The term for this type of alternative name is fictitious business name. Registering the fictitious name with ...

Mergamma A, containing 1% mercury and 20%

lindane Lindane, also known as ''gamma''-hexachlorocyclohexane (γ-HCH), gammaxene, Gammallin and benzene hexachloride (BHC), is an organochlorine chemical and an isomer of hexachlorocyclohexane that has been used both as an agricultural insecticide an ...

, an early example of a product designed to protect the seed from both fungal and insect attack.

Biocide

One seed pesticide,

imidacloprid Imidacloprid is a systemic insecticide belonging to a class of chemicals called the neonicotinoids which act on the central nervous system of insects. The chemical works by interfering with the transmission of stimuli in the insect nervous system. ...

, from the

neonicotinoid Neonicotinoids (sometimes shortened to neonics ) are a class of neuro-active insecticides chemically similar to nicotine, developed by scientists at Royal Dutch Shell, Shell and Bayer in the 1980s. Neonicotinoids are among the widest-used insecti ...

family of

insecticides Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, in ...

, is controversial and was banned in France for use on maize, due to that government's belief that the chemical was implicated in recent dramatic drops in bee counts, and possibly in

Colony Collapse Disorder Colony collapse disorder (CCD) is an abnormal phenomenon that occurs when the majority of worker bees in a honey bee bee colony, colony disappear, leaving behind a queen bee, queen, plenty of food, and a few nurse bees to care for the remaining ...

. Dust from treated seed is known to have caused at least some health and safety problems particularly from crops such as maize drilled during the main honey flows. Improvements to pneumatic drills to reduce dust release, and improvements to seed treatment compounds to prevent the compound breaking up into dust (dust-off) have been introduced in Europe led by Germany and the

Netherlands , Terminology of the Low Countries, informally Holland, is a country in Northwestern Europe, with Caribbean Netherlands, overseas territories in the Caribbean. It is the largest of the four constituent countries of the Kingdom of the Nether ...

from 2009 to 2012. Information on seed treatments including the information above can be seen on the registration authority databases. In order to qualify for the

United States Department of Agriculture The United States Department of Agriculture (USDA) is an executive department of the United States federal government that aims to meet the needs of commercial farming and livestock food production, promotes agricultural trade and producti ...

Organic certification Organic certification is a certification process for producers of organic food and other organic agricultural products.Labelling, article 30 o''Regulation (EU) 2018/848 of the European Parliament and of the Council of 30 May 2018 on organic pr ...

, farmers must seek out organic seed. If they cannot find organic seed, they are allowed to use conventional, untreated seed. Seed treated with pesticide however, is never allowed.Electronic Code of Federal Regulations

Water-retainer

Water-absorbing polymers may be added around seeds to help with absorbing water dry conditions, or to delay the germination until drought has passed. It has seen some use in the industry.

Fertilizer

Seed coating may contain a dose of fertilizer, typically of plant micronutrients, but also occasionally containing slow-release macronutrients.

Inoculum

A sufficiently-thick seed coating can allow for seeds to be distributed pre-inoculated with symbiotic microbes such as

rhizobia Rhizobia are diazotrophic bacteria that fix nitrogen after becoming established inside the root nodules of legumes (Fabaceae). To express genes for nitrogen fixation, rhizobia require a plant host; they cannot independently fix nitrogen. I ...

for legumes. The formulation of the coating slurry plays a huge role in maintaining the viability of these microbes. The state-of-the-art academic formulation (as of 2019) is able to maintain microbial populations for 9 months, quite a bit behind the viability of the seeds themselves. Despite these drawbacks, inocula have been used in commercially coated seeds, with much obscurity as to whether and how they maintain viability.

References