The
potential for production of orange-fleshed sweet potatoes in Kenya
stands at 4.8 tonnes per acre. However, farmers get only 1.12 per acre.
Though many causes are to blame for low productivity, unavailability of
quality planting material is the most important.
To
reap the benefits associated with orange-fleshed sweet potatoes,
production of clean quality planting material is important. A lot of
vines need to be used per unit of land in production of orange-fleshed
sweet potatoes. You require about 15 bags of cuttings to plant 1 acre of land.
Kenya
Agricultural and Livestock Research Organisation or KALRO [formerly
KARI] uses a three-tier system of orange-fleshed sweet potato seed
production system; the primary, secondary and tertiary seed production
levels. Primary seed multiplication site is located on-station where
closer management of the seed is done. Material from the primary seed
multiplication site is used to establish secondary seed multiplication
sites managed by Non-Governmental Organizations, Community Based
Organizations and Ministry of Agriculture staff. Usually, a selected
place such as Agricultural Training Centres are used as secondary
multiplication sites. Material from secondary multiplication sites are
used to setup tertiary seed multiplication sites. These are the
commercial seed multiplication sites managed by individual farmers with
assistance from extension staff. When you engage in orange-fleshed sweet
potato seed multiplication, you are operating at a higher production
level.
Steps in sweet potato seed multiplication
Sweet
potato vines, or seed, or cuttings, or slips can be multiplied using
conventional (results in a conversion ratio of 1:10, meaning 1 vine
gives 10 other vines] or rapid multiplication techniques (this results
in a conversion ratio of 1:80, meaning 1 vine gives 80 other vines). The
production principles are the same. However, in the rapid
multiplication procedure, more vines are realized within a shorter
period of time.
Site selection: Select
a site close to a water source. Avoid land, which was previously under
sweet potato. Distance between the site and the nearest old sweet potato
field should be at least 100m. Fence off the site if damage by animals
is anticipated.
Land preparation: Plough
land and harrow to a fine tilth and remove all trash. In the
conventional seed multiplication procedure, leave the plot flat. In
rapid multiplication procedure, raise beds of about 1.5m width and a
length based on amount of multiplication material and land available.
The area between adjacent beds should be 50cm wide. Use the soil between
adjacent beds to raise the beds.
The
height of beds should be 10-30cm depending on the soil. In sandy soils,
it is recommended to plough in manure at a rate of one wheelbarrow load
per square metre of bed space or apply farmyard manure at the rate of
2.5kg per square metre before planting.
Preparation of vine cuttings: Select
vines from a secondary multiplication site. They should be from plants
that are healthy and about 2 to 3 months old. Cut up vines into pieces
of two or three nodes. A leaf should be kept on each cutting and the tip
maintained on each vine.
Planting: If
the soils are dry, water the ground first. In the conventional seed
multiplication procedure, the vines are inserted at an angle in the soil
at a spacing of 50cm between rows and 30cm from plant to plant cutting.
In the rapid multiplication method, the vines are planted on the raised
beds. The spacing between rows is 10-20cm and from one cutting to the
next within the row is 10cm. The vines should be inserted at an angle
too. In both methods, leave one node with the leaf outside the soil.
Field management: Ensure
moist soil conditions are maintained at all times (but avoid
waterlogging) by irrigation if it is not raining. Ensure weed free
conditions in the first 4-5 weeks by manually removing the weeds.
Diseased or infected plants must be removed and burnt away from the
field.
Harvesting of vines: This
should be done after 2 to 3 months from the planting day. Cut the main
stem pieces (25cm long) 5cm above the soil level. Two to three sets of
cuttings can be harvested from rationed fields. Each harvest should be
followed by an extra application of Farm Yard Manure (FYM).
Vine storage: Planting
of sweet potato vines should be done preferably soon after cutting. If
not, the vines should be tied in bundles with their bases covered with a
wet cloth and kept in a cool area under a shade. Vines can get spoilt
if kept for more than two weeks
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