Seed Production of Vegetable, Tuber and Spice Crops

Principles and objectives

• The quality of seed is improved during processing in two ways
1. Separation of other tree seeds or inert matter and
2. Upgrading or the elimination of poor quality seeds.
• The ultimate goal of seed processing is to obtain the maximum percentage of pure seed with maximum germination potential.
• The threshed produce is heterogeneous in nature.
  
• Processing brings homogeneity in the produce.
  
• This homogeneity helps in obtaining uniformity in the field.
  
• Processing of seeds is carried out in approved (By Director of Seed Certification) seed processing plants.
• Seed processing is to narrow down the level of heterogeneity of the seed lot by using suitable processing methods.
  
• The heterogeneity occurs in a seed lot due to following reasons:
Causes for heterogeneity

1. Variability in soil for fertility, physical, chemical and biological properties
2. Variability in management practices (irrigation, application of nutrients etc.)
3. Variability in ability of the seedling for utilizing the inputs
4. Variability in pest and disease infestation
5. Position of pod or fruit in a plant or the position of seed in a pod.
• This heterogeneity can be narrowed down in the processing of seeds by eliminating the undersized, shriveled, immature, ill filled seeds using appropriate sieve size.
  
• The germinability and vigour of the seed lot can be upgraded by grading the seeds according to size, specific gravity, length and density of the seeds.
  
• The inherent qualities such as germinability and vigour are exemplified by certain physical characteristics of the seed i.e., large size, a denser seed, optimum length etc., So, if grading is done to obtain a particular range of size, shape, length and density of the seeds, the quality of the lot is upgraded.