Seed multiplication of improved open-pollinated varieties
Practical Action
Planted first
(a) By time
(b) by space
Planted 30 days
or more later
Maize field (OPV)
Commercial
crop
Isolation by time and space of an OPV maize seed field
Bush fallow/other crops
Adapted from" Strategies for Strengthening and Scaling Up
Community-Based Seed Production (CIMMYT), 2006.
Isolation by time requires a planting interval (difference in sowing time) of 4 to 6 weeks to ensure
that there is no pollen contamination of seed plots by other maize fields. The number of days to
tasseling and silking of the seed field and neighbouring fields helps to determine the proper time
isolation. If farmers cannot isolate by time or distance, they may harvest from the middle of their
fields to minimise contamination, and the field should be at least about one hectare.
Field Management for Seed Multiplication of Open Pollinated Varieties (OPVs)
Planting
• Grow seed of chosen variety alone (sole crop) to allow proper management
Plant clean, viable seed
• Get support from extension staff, trained farmers or crop guidelines so as to:
• Plant using the correct spacing
Use the correct seed fertiliser rates
• Plant in rows for easy weed control and removal of off type plants
Learn of the appropriate planting periods (use of seasonal calendar).
Weeding (why we should weed)
• Weeds reduce yield
• Weeds reduce crop quality
• Weed within four weeks after planting
Inspect for pests and diseases
• Thereafter, weeding depends on weed growth
Weeding can be done mechanically using hoes, cultivators hand picking or chemically using
herbicides.
Rouging
• Is the removal of off type plants
• Off types are plants that do not resemble the variety grown
Rouging is meant to have pure seed
• Remove plant tha look different from the variety, e.g. plant height, leaf shape, leaf colour,
flower colour
• Rouge at least three times.
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