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Open Agriculture. 2017; 2: 155-159 length was significantly affected by nutrient solutions. Nutrient solution C resulted the maximum root length (300.8 cm), while nutrient solution A produced minimum root length (135.5 cm). Plant height was not significantly affected by nutrient solutions. Small size tubers (<8 g) were not significantly affected by either tuber number or weight. Medium (8-12 g) and large size tubers (>12 g) were significantly affected by nutrient solutions both in number and weight. The maximum tuber numbers was obtained from treatment B. Therefore, the experiment indicated that treatment B represents the optimum nutrient concentration rate to use in an aeroponics minituber production system under Holetta conditions.

Quality seed is one of the major bottlenecks hampering the production and productivity of potato not only in Ethiopia but also in Sub-Saharan Africa. Since the 1970’s, the Ethiopian Institute of Agricultural Research has generated a number of improved potato production technologies such as improved varieties with accompanying agronomic practices, crop protection measures, postharvest handling techniques and utilization options. The developed technologies were promoted from 2013-2015 via technology promotion and popularization to the Wolmera, Adea-Bera and Ejere districts with the objective of creating awareness and up scaling of improved potato production and utilization technologies. The Potato Improvement Research Program and the Research and Extension Division of Holetta Research Center in collaboration with extension staff of the Ministry of Agriculture (MoA) undertake this activity. The farmers were selected and organized in Farmer Field Schools and all stakeholders were engaged before distributing potato seeds and planting on selected farmers’ fields for demonstrating of potato production technologies. A total of 899 farmers and 40 agricultural experts were trained and 27.7, 9 and 5.5 tons of quality seeds of Gudanie, Jalenie and Belete potato varieties, respectively, were delivered as a revolving seed with their recommended agronomic packages; this amount of seed covered 21.1 ha. A total of 16 farmer groups from Wolmera, 7 from Adea-Berga, and 11 from Ejere participated. They produced over 434 tons of relatively clean seed and constructed 8 diffused light stores. In addition to the demonstration of improved potato varieties, information dissemination was also an important component of the program to raise awareness for a large numbers of potato growers through farmers’ field days, pamphlets, and mass media. Each year about three field days were organized and more than 1500 pamphlets were distributed to farmers invited from neighboring districts and ‘Kebeles’ to enhance speed. Through this intervention farmers are now harvesting a yield of about 26-34 t/ha up from 8t/ha when they were using inferior quality potato seed; this has made the farmers in the intervention area more food secure especially during the usually food scarce months of August to October when cereal crops are generally yet to mature. The farmers are also getting additional income from the sale of excess potato and are able to better meet other necessary costs like school fees, for their children.

On-site assessment and detection of plant diseases is a prerequisite to inspect the health status of seed potatoes and to make cost-effective disease management decisions. The present study was conducted in 60 major seed potato producing cooperatives of Ethiopia to assess the extent of potato bacterial wilt disease and to generate information on current status of R. solanacearum. The field assessment and inspection survey was conducted during 2015/16 for 3 seasons in 140 potato fields covering 123.30 hectares of seed potato. Symptomatic plants were confirmed for R. solanacearum by Agri Strip kit, potassium hydroxide (KOH) test and vascular flow (VF) techniques. The results of the study indicated that out of 140 seed potato fields assessed, 26 (equivalent to 18.57%) or some 33.3% of seed cooperatives were infested by bacterial wilt. The highest disease incidence (82.5%) was recorded in Jeldu district followed by Wonchi district (60%) where most of seed potato is being distributed to the country. Based on the results of three disease confirmation tools (Agri Strip, KOH and VF) implemented, 34.75 (28.18%) hectares of the fields showed positive results. Disease prevalence ranged from 0 to 100%. In some districts like Cheha, Doyo-gena and Shashamane, the disease prevalence was 100%, whereas 50% disease prevalence was recorded in Arsi-Negelle and Kofole districts. This study describes the current infestation level of bacterial wilt in major seed producing cooperatives of Ethiopia and potato production is highly threatened by Ralstonia solanacearum in most of the areas addressed by this survey.

to potato production for reasonable yield at sites similar to experimental locations. It can be concluded that, interaction of nitrogen and potassium rates significantly affected plant height and marketable tuber numbers.Keywords: Potassium, Nitrogen, Potato, marketable and unmarketable yield IntroductionPotato (Solanum tuberosum L.) is very important for food and income generation as it produces a high yield per unit land and time. About 70% of cultivated agricultural land of Ethiopia is suitable for potato production (Yilma 1991). The annual potato production in Ethiopia was 1.62 million ton from an area coverage of 0.18 million hectares (CSA 2014). The national average yield is 9 tons/ha (CSA 2014) which is very low compared to the world mean of 16.4 tons/ha (Husna and Eliakira 2014). One of the contributing factors was poor use of optimum plant nutrition. This way of application can lead to excessiveness or shortage. When excessive nitrogen is applied, crop yield is reduced; cost of production increased and the environment is polluted, especially soil and ground water is acidified (Honisch et al. 2002). Cultivation with low or no fertilizer usage (Gezu 2015) is common practice in Ethiopian farmers. Lower levels of fertilizer use and/or inappropriate type of fertilizers application is one of the productivity problems in Ethiopia (Chillot and Hassan 2010). It was mentioned that there was soil nutrient depletion due to human interventions (Chillot and Hassan 2010) which can significantly influence food security in Ethiopia (MOARD 2101). Inappropriate soil fertility management is a cause of food shortage and malnutrition of tremendous numbers of people which also have associated health impact (Gete et al. 2010). Furthermore, information about potassium fertilizer and its levels on potato product is also scarce in Ethiopia. Even though the crop requirement of potassium Abstract: To determine the required levels of nitrogen and potassium, an experiment was conducted at Holetta Agricultural Research Center and Jeldu sub Center from 2014-2015 using three factors (Jalenie, Gudenie and Belete potato varies; 87, 110, 133kg/ha nitrogen rates and 0, 34.5, 69, 103.5kg/ha potassium in the form of K 2 O levels) and as a completely randomized block design arrangement with three replications. In each location every year the 36 treatments (4 potassium oxide levels x 3 nitrogen levels x 3 varieties) were assigned in random combinations to 36 plots of one block in a random case which was replicated in to two additional blocks of different randomizations in order to make total of three replications/blocks. Data were analyzed by SAS software Version 9.2. Potassium rates significantly affected the total yield and marketable yield as compared to the control treatment. Application of potassium at 103.5 kg/ha produced significantly a higher marketable yield than all rates. As compared to Jeldu, the Holetta location produced the maximum highly significant yield and yield component. Interaction of potassium and nitrogen fertilizers aff...