Seed Production
Successful models in promoting seed varieties:
Government of Odisha under OMM has shown the way of how agro-biodiversity can be promoted through participation of local communities. Constituted the Working Group on Seeds, Odisha and issued guidelines for standard operating protocols for Alternate seed systems for landraces to mainstream them.
This system need not be a replica of existing institutional framework but it has to be done systematically and scientifically. The discussion started with finger millet and now extended to other crops too-in Kharif 2022, there are 33 crop diversity blocks , 17 multi-location trails, 41 participatory varietal trails and 16 seed production plots are there in different locations of Odisha. There is a small pilot is going on mapping the landraces in 11 Districts and 254 village and understand quality parameters of non-ragi millets, pulses, oil seeds, paddy from farmer’s and scientific community perception. All these will bring them into one umbrella i.e. alternate seed systems for landraces/ traditional varieties. The details are in this report by WASSAN
Seed Conditioning
The process of removing unwanted materials such as trash, weeds, leaves, other crop seeds and insects etc from a seed lot along with overall improvement of seed quality, is known as seed conditioning or seed processing. It is the complete procedure which utilized all the technologies such as drying, threshing, pre-cleaning, cleaning, size grading, treating, quality testing, packaging and labeling in making high quality seed of improved varieties available to the farmers with minimum adulteration. Seed conditioning assure maximum quality seed as if seed is not conditioned and handled properly, all efforts of a plant breeder in varietal development and seed production can be lost.
The ultimate goal of seed conditioning is to obtain the maximum percentage of pure crop seed with maximum germination potential, thereby seed enhancement. Seeds can be separated by mechanical means only if they differ in some physical characteristics such as size (length, width, thickness), shape, weight/density, Surface texture (rough, smooth, pointed) surface color and also affinity for specific liquids and electrical properties etc. that can be detected by a mechanical or electrical process.
Thus, the seed conditioner uses differences in physical characteristics of the seed crop being cleaned and those of seeds of other crops and weeds as well as inert matter. Basic steps involved in seed conditioning/processing are drying (air drying, sun drying and mechanical seed drying), cleaning (pre-cleaning, basic cleaning and fine cleaning or grading), weighing, packaging, storage and labeling.
Seed Conditioning in Millets Sorghum Seed processing is an integral part of Sorghum seed production which follow the steps such as drying, cleaning, grading, treating, and bagging. Optimum moisture should be about 20 per cent at harvest to minimize harvest losses and drying expense (Sumner, 2017). Sorghum stalks contain more moisture and are more likely to be chopped up and carried with seed. Seed properly threshed cleaned to the desired purity on the air screen cleaner. However, the gravity separator is commonly used to remove light materials. The threshed seeds should be physically pure.
The ultimate goal of seed conditioning is to obtain the maximum percentage of pure crop seed with maximum germination potential, thereby seed enhancement. By removing weed seeds, disease and pest infested seed, other crop seed, other cultivar seed, undesirable seed, and damaged seeds.
Drying Sorghum has more trash mixed in the grains than other common crops. Pieces of green stems and foliage often mix in with the grains. This trash is difficult to remove before drying but can cause a fire hazard in dryers and offers resistance to air movement. Trash is usually removed from the grains by sifting through a screen or sieve. The seed fall through while trash remains. By rotary screens, the grain falls through and trash is retained but most rotary drum cleaners are designed to retain the seeds and drop the fines. Seeds contain varying amounts of moisture at harvest, and if they are to be stored for subsequent planting it is essential that their moisture content is reduced to a safe level. Sorghum seeds should be dried to 10-11 per cent moisture content to avoid the multiplication of insect during storage. In sorghum, proper sun drying of ear heads is essential to bring down the seed moisture to desirable level to avoid seed deterioration.
To dry bulk quantities of seeds mechanical seed dryer can be used. Maximum recommended air temperature for seed drying is 40° C, if seed moisture is more than 18 per cent, maximum recommended drying temperature is 32° C and if lower than 18 per cent, 40° C is the temperature for drying. The screen of dryer should not be finer than ¼ inch mesh or air movement may be restricted (Sumner, 2017). Dryers do not force air through grain sorghum as easily as through bold seeded cereals like corn because the smaller grains leave less space for air movement, the moisture content is usually high and the resistance to air flow is extremely high. As a result, grain sorghum dries slowly as compared to bold seed. The recommended air flow rates for drying sorghum are 0.02 m3/s per m3 of sorghum at 14 per cent moisture content to 0.04 m3/s per m3 of sorghum at 20 per cent moisture content (McFarlane et al., 1995). Seed cleaning and upgrading In order to maintain the physical purity to the required standards seed cleaning is the essential step to separate the inert matter, weed seed, other crop/variety seed, disease and pest infested seed and any other undesirable contaminants. Sorghum seed Seeds contain varying amounts of moisture at harvest, and if they are to be stored for subsequent planting it is essential that their moisture content is reduced to a safe level. Sorghum seeds should be dried to 10-11 per cent moisture content to avoid the multiplication of insect during storage. cleaning and upgrading is mainly based on physical differences in seed volume, test weight and density. The sieve aperture sizes of top and bottom screens of air screen cleaner differ with genotypes. Generally the top screen has holes measuring 12/64” or 4.75mm with round holes and the bottom screen at 9/64”or 3.5mm with round holes (Tonapi et al., 2015). The specific gravity separator helps in upgrading the quality of seeds by rejecting the seed that is inferior in specific gravity. Seed treatment and packing Seed treatment refers to the application of fungicides, insecticides, or a combination of both to disinfect the seed from seed borne pathogens and to protect from soil borne organisms. Sorghum seed after seed treatment can be protected from systemic pathogens like loose smut and head smut and non systemic pathogens like Helminthosporium blight, Fusarium and bacterial blights. Seed treatment also provides protection against storage pests (rice weevil) and shoot fly. Processed seed can be packed in cloth bags or poly lined bags at the rate of 3-4kg per bag, sewed with proper label of particular seed class and should be sealed with lead seal. Seed quality control Seed quality in India is legally controlled by the Seed Act, 1966. According to this Act all the seeds of notified varieties/ kinds when sold to farmers must meet the minimum standards of germination and physical purity. The seed should be packed in a suitable container and a label has to be affixed on the container. Information about germination, physical purity, variety, date of test, name of the seed producer has to be given on the label. The germination as given on the label is valid for eight months and after which it has to be revalidated for a subsequent period of four months after retest. Seed certification is the process designed to secure, maintain and make available high quality seed and propagating material of superior crop plant varieties, so grown and distributed as to ensure desirable standards of genetic identity, physical purity and other quality attributes. Certification is performed in five phases.
Verification of land requirements
Verification of seed source
Inspection of the seed crop in the field The specific gravity separator helps in upgrading the quality of seeds by rejecting the seed that is inferior in specific gravity. SEED TIMES January - April 2020 Seed Conditioning 53
Inspection and testing of each lot and seed sample during the processing and bagging
Tagging, labeling and sealing to identify the seed Pearl millet Cleaning Seed is passed through an air screen cleaner to remove inert material. Precautions have to be taken to ensure that machine is cleaned before using, desired screen is selected and samples are taken to assure that seeds are well cleaned. Threshed and cleaned seeds are graded using round perforated metal sieve of 4/64” size OSAW cleaner cum grader (Yadav et al., 2015). De-stoning During this, heavy impurities, such as stones, metallic particles etc. are separated from the seed. Gravity separators are used for grading of seeds to the highest standards of physical purity. Near-size grains are separated according to the differences in their specific weight. It also helps in removing damaged seeds and premature light weight seeds. Chemical Treatment Seed is treated with suitable chemicals to protect it from pests and diseases. Calibration is important for uniform seed coating. Slurry volume and dump speed are calculated for uniform coating. Seed is treated with metalaxyl 35 per cent WS at the rate of 2g a.i./kg seed for controlling downy mildew when the seed is used for planting. Delta-methrine at the rate of 0.04 g/ kg seed is used for controlling stored pests (Yadav et al., 2015). Care should be taken in metalaxyl treatment of seed that is likely to be stored at room temperature for a longer time as metalaxyl treated seed stored at 40°C has been reported to show phytotoxic effects (Thakur et al., 2011). Packing and labeling Care is taken to ensure that each primary seed bag contains the proper quantity of seed, is sealed properly and final seed moisture does not exceed 12 per cent. The samples are again tested for warm germination test and accelerated aging test. Samples are taken during bagging to ensure that the seed meets Seed is treated with suitable chemicals to protect it from pests and diseases. Calibration is important for uniform seed coating. SEED TIMES January - April 2020 Seed Conditioning 54 quality assurance standards. Information on the label should be as per country seed laws. Pearl millet bag size in India is usually of 1.5 kg and 3.0 kg. Label on each bag specifies name of crop and variety, seed class, seed lot number, year and date of production, expiry date of validity, germination percentage and seed purity (Yadav et al., 2012). Storage Storage conditions for nucleus seed include temperature of 4°C and relative humidity of 20 percent as the seed is stored for use in next few seasons. For breeder seed, temperature is 10°C and relative humidity of 20 percent. Foundation and certified seeds are stored at room temperature. For controlling storage insectpests, fumigation is done. The cleaned and graded seeds can be stored up to 12 months with proper pre-storage treatment. Small millets (Finger millet, Foxtail millet, Little millet, Kodo millet, Barnyard Millet and Proso millet) Physiologically mature plants are either harvested intact with ear-heads or ear-heads alone. The ear-heads are dried before threshing and threshed by stone roller or trampling under the feet of bullocks. While in Proso millet ripening is not uniform throughout the panicle as the seeds in the upper portion of the panicle are ripe while the lower seeds are still green. These are harvested and swathing be done until most of the panicle has lost its green color. Seed cleaning Traditionally there are two techniques of cleaningWinnowing: In this process approximately 2 to 3 kg of threshed millet grains are placed on a flat reed or raffia-woven basket and winnowed by up and down strokes so that the grains are thrown up in the air and allowed to fall back onto the basket. During this, the sand and other light contaminants are separated to the front of the basket from where they are thrown off. The process is labourious, and time consuming, and may take up to 1 hour to clean 1 bag of 100 kg. Foundation and certified seeds are stored at room temperature. For controlling storage insectpests, fumigation is done. The cleaned and graded seeds can be stored up to 12 months with proper pre-storage treatment. SEED TIMES January - April 2020 Seed Conditioning 55 Aspiration: In this process the difference in densities between the good millet grains and contaminants is exploited to separate the contaminants from grains. About 10 kg of threshed millet grains are placed in a tin or basket and poured from above the head to fall on to the ground. The separation effect is best obtained when it is slightly windy, so that the wind current blows the light contaminants from the relatively heavy grains (Kajuna, 2001). This method is much faster than the traditional winnowing as four to five bags may be winnowed in one hour. However the method is not effective in separating sand, stone and metal contaminants which are as heavy as the millet grains. Apart from these two techniques screening is done, where a set of sieves is used to separate abnormally small grains/ broken seed pieces or sand particles from the good ones. Drying and Storage The threshed and clean millet grains should be dried under the sun to attain a safe moisture level of 12 per cent. Care should be taken to avoid mechanical injury and contamination to the seeds while drying. Apart from the traditional sun drying, unheated air drying could be employed. This is a simple method to operate, and requires minimum attention to achieve uniform drying (McFarlane et al., 1995). However, unheated air drying is weather dependent, and in case of prolonged wet conditions with high relative humidity, the drying process may take a long time. In such circumstances, one may therefore, have to select the airflow rate very carefully to optimize the drying process. Most millet has excellent storage properties and can be kept for up to 4-5 years in simple storage facilities such as traditional granaries as the seeds are protected from insect attack by the hard hull covering the endosperm (FAO and ICRISAT, 1996). After drying and threshing, millets may be stored as loose grain in bags or in loose containers (Kanuja, 2001). However, the essential pre-requisites for storage of millets are the same as those for other grains. Major challenges in small millet seed processing are: • The grains are very small in size. • Variability in seed due to variable cultivation practices and micro climatic conditions among seed production regions. Care should be taken to avoid mechanical injury and contamination to the seeds while drying. Apart from the traditional sun drying, unheated air drying could be employed. SEED TIMES January - April 2020 Seed Conditioning 56 • The processing machines currently used for small millets processing are improvised form of paddy processing machines. These remove bran containing fibers, minerals and many other nutrients thereby reducing the nutrition of small millets. • These machines as large scale mills are available only in some part of the country so resulted in movement of small millets away from the production areas. • With existing machinery there is lower head rice recovery, it is very difficult to remove extraneous matter and to separate hulled and un-hulled grains. So there is urgent need to develop appropriate dehuller models. • There is little or no local processing infrastructure in the villages which needs to be developed
Seed Production Manual for Cereals and Millets by Centre for Indian Knowledge Systems (CIKS)
A brochure on millet seeds with information on Seed Production Technology, Harvesting & Post-Harvest Management, Processing & Storage, useful for SHGs and CSOs.
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