The best way to grow orange-fleshed sweet potatoes

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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.

Farmers interested in planting material for Orange Fleshed Sweet Potato call 0736 231 949. Farmers from Western region of Kenya can also visit KALRO-Kakamega.

 >>Tell us how useful this information is to your farming enterprise. Share your experience by email to admin@theorganicfarmer.org,  leave a comment below this article or SMS to 0715 916 136.

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