agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to ...

and

horticulture Horticulture is the branch of agriculture that deals with the art, science, technology, and business of plant cultivation. It includes the cultivation of fruits, vegetables, nuts, seeds, herbs, sprouts, mushrooms, algae, flowers, seaweeds and no ...

, a seed treatment is any additional material added to the seed. By the amount of material added, it can be divided into: * A seed dressing, typically containing a "protectant" (

pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampri ...

) applied to the seed and possibly some color. * A seed coating, a layer of thin film applied to the seed typically less than 10% of the mass of the original seed. * Seed encrusting, where the applied material is typically 100%–500% of the original seed mass, but the shape is still discernible. * Seed pelleting, where the applied material is so thick that the seed's original shape is not discernible. Seed treatment 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-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 the dry, scaly protective casing of the seeds of cereal grains or similar fine, dry, scaly plant material (such as scaly parts of flowers or finely chopped straw). Chaff is indigestible by humans, but livestock can eat it. In agri ...

, 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 frequen ...

'' 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 soil mi ...

'' 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 o ...

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 a "fictitious" business name. Registering the fictitious name w ...

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 and ...

, 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 Shell and Bayer in the 1980s. The neonicotinoid family includes acetamiprid, clothianidin, din ...

family of

insecticides Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to b ...

, 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 colony disappear, leaving behind a queen, plenty of food, and a few nurse bees to care for the remaining immature bees. While s ...

. 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 ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...

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 the United States federal executive departments, federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, ...

Organic certification, 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. In gene ...

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