In Ethiopia population is growing in more rate than the agricultural production does. To feed this increasing population the agricultural production should grow accordingly with the same pace or even more. Horticultural crops are the most important crops in the national strategy of food self-reliance and the national income earnings. So to increase the productivity of the farmers, it is crucial to increase the awareness of farmers towards the usage of different improved technologies that increase their production and accelerate food security through proper implementation. Access to new and improved agricultural technologies is highly limited in Guji zone of Oromia most probably due to remoteness from the center and inaccessibility of the area.
Agriculture is the basis of the Ethiopian economy and the main source of livelihood of the population. The potential for developing agricultural production is high but despite this, Ethiopia is currently unable to produce enough food to meet the demands of its ever increasing population. According to the International Food Policy Research Institute, 5-7 million people in Ethiopia are chronically food insecure. The reasons for this are diverse and complex but declining soil fertility and soil degradation is a primary factor.
The originated in the highlands of the Andes in South America, potato was introduced to Ethiopia in 1859. Since its introduction potato remains important garden crop in many parts of Ethiopia and Western Oromia too. However, today potato production is at an increasing step in most highland parts of the country. Potatoes production is possible by rain fed, residual moisture and irrigation systems. Welldistributed rainfall between 600 to 1200mm over a period of three to four months is enough for potato cultivation. The optimum temperature for good potato tuber growth lies between 15-18 oc. sandy loams with slightly acidic soil is ideal for potato production. For production of economic yield potato performs best within the altitude ranges of 1500 to 3000 masl. It is one of the cheapest sources of starchy food and provides a source of low cost energy to human diet. It is also good source of income for many farmers in the country. Potato (Solanum tuberosum L) is an annual, herbaceous, tuber crop of family Solanaceae that contains all the essential food ingredients required for proper health. Potato is the world's leading vegetable crop and is grown in 79% of the world’s countries. It is second to maize in terms of the number of producing countries and fourth after wheat, maize and rice in global tonnage. The average composition of the potato is about 80% water, 2% protein, and 18% starch. As a food, it is one of the cheapest and easily available sources of carbohydrates and proteins and contains appreciable amount of vitamins B and C as well as some minerals.
Both yield and quality of potato are affected by variety, environmental conditions, and cultural practices. Fertilizer application has important effects on the quality and yield of potato. Potato is highly responsive to N fertilization and N is usually the most limiting essential nutrient for potato growth, especially on sandy soils. Nitrogen supply also plays an important role in the balance between vegetative and reproductive growth for potato. Many previous studies have shown that fertilizer N applications can increase dry matter content, protein content of potato tubers, total and/or marketable tuber yield also reported similar effects of N doses on dry matter content and specific gravity of potato.
The potential of horticulture & spice crops is not exploited in this part of the region due to lack of improved varieties, poor management practices, biotic factors (weeds, diseases and insect pests etc.), a biotic factors (frost), high intensity and long duration of rainfall. So far the national and regional research institutions in the country have released many varieties adaptable to a wide range of environments for commercial production. However, these technologies did not reach the smallholder farmers living in inaccessible parts of Oromia such like Guji zone due to lack of testing sites and centers. Therefore, to overcome the above stated problems and to acquaint smallholder farmers with new technologies of widely grown Horticultural and Spice crops production. As mentioned earlier, absence of improved variety and management practices are the main production constraints of the area. Because the area has long rainy season and the fertility status of the soil is scientifically not well known, adjustment of planting dates and fertilizer rates is very crucial. Therefore the objective of this study was to determine the impact of planting date and NP fertilizer rate on Irish potato growth, yield and yield components and to determine an optimal planting date and NP fertilizer rate for Irish potato.
The study was conducted to evaluate four different planting dates and four combined fertilizer rates for potato production in bore area. An experiment was conducted to determine the best combination of planting date (IMD, 7days later, 15 days later and 3 weeks later) and combined application of NP2O5 rate (0, 61.5*69, 82*92, 114*115 kg·ha-1) for Irish potato of Gudene variety produced on a clay loam soil during the year of 2011-2013. The results revealed that the interaction effect between N and FYM fertilizer application rates had highly significant (P<0.05) effect on days to 50% emergency, 50% maturity, plant height, number of tubers per hill, stem number per plant and fresh yield. On the other hand non-significant effect by the planting date and rate of fertilizer on days to flowering and average tuber weight.
In this study, there was a significant difference between date and rate of fertilizer in the phenological, growth and yields and yield components of potato produced. Such difference between date and rate of fertilizer could be attributed to weather difference between the date and rate of fertilizer besides other probable causes. This may be due to the weather difference between the three seasons in terms of rainfall, temperature so and so on. Our recommendation to planting date and rate of fertilizer provide a new opportunity to manipulate planting date and rate of fertilizer to maximize use of appropriate time and nutrient resources. Application of NP2O5 fertilizer rate of (82*92 kg ha-1) has significantly and positively increased the tuber yield of Irish potato at Bore area. The highest economic yield was obtained from the combined application of 82 kg N *92 kg P2O5 ha-1.
Therefore it can be concluded that different planting date and combined application of NP2O5 have remarkable effect on growth and development of Irish potato. Generally, as a conclusive and recommendation, potato growers at Bore and surrounding area need to plant immediately at the start of rain (mid of march) in combination with 82 kg N *92 kg P2O5 ha1, in order to maximize the yield of Irish potato on the study area. Therefore it is recommended that there is a need for verification and demonstration of 82 kg N *92 kg P2O5 ha-1 for potato production in Bore area of Southern Ethiopia.