SUMMARYPlectranthus edulis (syn. Coleus edulis) is a tuber-bearing labiate species cultivated in parts of southern Ethiopia. To learn about traditional cultural practices and their rationale, a survey was conducted among farmers from Chencha and Wolaita experienced in growing this crop. A pre-tested questionnaire was used to interview 48 family heads categorized into three wealth groups per site. Information was checked through group discussions and field observations. In Wolaita, poorer farmers cropped a larger portion of their land to P. edulis than richer farmers. Land was usually prepared for planting between January and April. In Wolaita, the crop was mostly grown in a furrow. In Chencha growing in patches and on flat land also occurred. Farmers mostly used a digging hoe for land preparation. Tuber pieces were planted about 5 cm deep. According to farmers, using tuber pieces resulted in more stems, more progeny tubers and higher yields than using whole tubers. Tubers were broken into pieces 0-1 day before planting. Tuber pieces were planted with sprouts or after desprouting. Crops were usually fertilized with manure, but in Wolaita sometimes also with compost. Applying fertilizer was thought to give more and bigger tubers. Earthing up took place 1-3 times (usually twice), to increase yield. Tipping was also done 1-3 times (usually once), to increase the number of stems. Based on the survey, an overview of the practices and their rationale is compiled for use in further research into this orphan crop.
SUMMARYPlectranthus edulis (Vatke) Agnew is one of the tuber crops of the genus Plectranthus that is widely cultivated in Africa and Asia. P. edulis produces below-ground tubers on stolons originating from the stems, comparable to the potato (Solanum tuberosum L.). Farmers apply several laborious cultural practices to enhance shoot growth and yield, among which shoot tipping is very common. Tipping (pinching) is the removal of the shoot apex with one or two pairs of leaves from the main stems and branches. The rationale of this practice, especially when repeated more than once during one cropping season, is not fully understood. One similar experiment with two cultivars was carried out at two locations (Awassa and Wondogenet) in Ethiopia to assess and analyse the effects of shoot tipping and its frequency on crop development and tuber production. Tipping treatments included zero tipping, tipping once, tipping twice and tipping thrice, with the first tipping taking place 68 days after planting (DAP), a stage at which most of the stems reached a height of about 0·15 m, and the remainder following at intervals of 44-46 days. Tipping stimulated stem branching; it significantly increased the number of primary, secondary and tertiary stems in both experiments. Soil cover increased with an increase in the frequency of the tipping in Awassa, because of the tipping effects on the different canopy development variables. Tipping also enhanced the soil cover in Wondogenet, but the crop did not gain any extra benefit from a third tipping. Tipping enhanced early stolon formation, but did not consistently affect the number of stolons per hole later in the growing season. The number of tubers increased with an increase in the frequency of tipping in both cultivars in Wondogenet and in one cultivar in Awassa. Tuber dry matter yield increased with an increase in the frequency of tipping at both sites. Fresh tuber yield in the final harvest at 208 DAP was c. 1·9 kg/m 2 . Tipping on average increased fresh tuber yield by 17% in Wondogenet, whereas the difference was not detectable in Awassa. Because senescence was delayed slightly by tipping, yield effects of tipping might be larger when harvesting later. In general, there was a positive effect of tipping on canopy development and tuber yield.
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