analysisBy Abdoulie G. Dibba
This Column is meant to monitor and report on issues that are impeding food security in the Gambia as well as the interventions of Government and Non-governmental Organisations.
In today's edition,
we shall bring to the attention of our readers the presentation made by Joko Kutubo E. Sanyang, Agronomist and Principal Research Officer, during the Groundnut Value Chain Analysis with respect to quaility held at Jenoi.
The most important prerequisite for good crop production is the availability of good quality seeds of high yielding varieties, adapted to the growing area, and preferred by the farmers. The quality of seeds alone is known to account for an increase in productivity of at least 10-15%(H.A.Ajiegbe et al).
To achieve this high quality, all the factors in production that will affect viability, and genetic purity should be taken into account.
The production techniques should be mastered and the environmental conditions (soil fertility and climate) known.
The choice of field is an important component of good seed production. Cowpea is less demanding than groundnut and can be grown in soils of diverse types, ranging from predominantly clay to predominantly sand, and from acidic to basic. For both cowpea and groundnut, the best soil is a well-drained, sandy loam to clay loam soil with pH 6 and 7.
To manage disease, insects, and weeds, the history and crop rotation of the field should be known. It is important to select a field that was not planted in the previous year with another variety of cowpea (or groundnut, in the case of groundnut seed production). The field should be isolated from other fields of the same crop by at least 3 m for certified seed production and by 5 m for foundation seeds.
Cowpea and groundnut are both self-pollinated crops and seed production does not differ significantly. Agronomic practices in both crop and seed production are similar to those used for producing food grain. The difference lies in the standard of the output. Good quality seeds should meet the following characteristics:
- Genetic purity and uniformity conform to the standards of the particular cultivar.
- Seeds are disease-free, viable, and free from admixtures of seeds of other crops and weeds, and inert material.
- Seeds are uniform in size, shape, and color.
To be successful, seed producers must understand seed quality, know how it is achieved and maintained, and how they can process the seeds from harvest to their delivery to the farmers.
Characteristics of seed lot quality
Improved seeds have five related components.
Genetic purity: Genetic superiority is inherent in the variety and has an effect on the maturity date, disease and insect resistance, and nutritional quality. Protecting genetic purity depends on accurate record keeping, the use of clean equipment, and good handling.
Crop purity: Crop purity means that crop is free from contaminants, including the seeds of weeds and other crops, and inert material.
Seed health: Seed health refers to the absence of seed-borne diseases existing on or in groundnut or cowpea seeds.
Germination: Germination is the measure of a seed's ability to produce a normal seedling when planted in ideal conditions (with optimal temperature and moisture plus good aeration). The seed germination test is the universal standard measure of seed quality.
Vigor: Seed vigor has an important implication in the emergence rate and the final plant stand. According to their vigor, seeds can withstand stress during germination and early seedling development.
Classes of seeds
Breeder seeds: This is the primary source for the entire system. They are usually produced by crop breeders or at least under their supervision. Breeder seeds are usually produced in a limited quantity at a time (from about 100 kg to 2-3 t/variety). This is to ensure high quality. Breeder seeds should have not less than 100% variety purity
Foundation seeds: These are the seeds produced from the breeder seeds. An enlightened farmer can produce foundation seeds under a contract agreement with a national seed regulation body, such as the National Seed Council (NSC). Other agencies such as research institutions, ADPs, and NGOs can also be commissioned to produce foundation seeds. Foundation seeds should have 99.9% varietal purity and are used for certified seed production.
Certified seeds: Certified seeds are produced from foundation seeds, usually by seed companies and other private seed producers certified by the NSC. Production is guaranteed by inspection and certification by an agency independent of the seed production agencies. Certified seeds are used for grain production.
Seed selection: It is important to use genetically pure seeds of a given variety from a reliable source (registered seeds). Pure seeds should be obtained from the breeder or the research institution responsible for developing the variety, or from registered growers in your area.
Planting equipment should be tuned-up to maximize planting efficiency with uniform plant spacing and planting depth.
Big seeds versus small seeds
In general, many farmers and seed producers think the bigger the seeds, the better the seed quality. Others believe that smaller seeds germinate faster and are therefore better than larger seeds. Although this is true, it does not mean that larger seeds are poor quality but they take more time to hydrate and germinate. Small seed size is usually associated with immaturity. This is not always true, as some larger seed sizes can be immature.
Good quality seeds are essential to grow a strong and healthy crop. Healthy seeds can be bought from trusted sources or farmers can produce their own seeds. In that case, seed selection can be used to improve the quality of seeds.
There are several diseases that are transmitted via the seeds. If seeds from an infested field are used to grow the next crop, these seed-born diseases will immediately cause serious problems. Seed selection should thus start by obtaining seeds from healthy plants.
Small, shriveled and broken seeds contain less nutrition for the developing seedling. By removing these inferior seeds, the farmer is able to grow stronger and healthier seedlings.
Even if seeds are selected carefully, they still may carry diseases. In these cases seed treatment (e.g. hot water treatment or chemical seed treatment) could be used to further improve the quality of the seeds.
While seed selection is mainly aimed at obtaining healthier seeds, it can be used also to maintain and improve the quality of the crop variety. In a crop field, there are always differences between plants. Some plants may have characteristics that are more suitable than those of other plants.
During the growing season, the farmer can try to observe these differences and mark preferred plants with a ribbon or with a stick. During the harvest, the seeds of these plants can be reserved for growing the next crop. In this way, the farmer can slowly improve the quality of his variety.
The selection of these plants may be based on characteristics such as the size of the plant, color or size of fruits, number of grains per ear, etc. But selection can also be done to keep seeds of plants that suffered less attacks by insects or diseases
In this way, the farmer will select at harvest time the best seeds to be kept apart for the next season. Still, just before starting the next season, it is recommended to select once more to remove seeds that are too small, spotted, deformed, discolored, etc. for sowing only the very best seeds should be used.
The production of high quality groundnut and cowpea seeds necessitates a high level of management that covers the period from planting to the delivery of seeds to the growers.
Seed growers should plan all farm operations well in advance to ensure the seed crop has the highest priority. Lastly, agronomic practices (disease management and maturity at harvest) should be applied properly in seed fields.