ABSTRACT
Profitability of different rates of nitrogen (N), phosphorus (P) and five potato varieties (Bellete, Gudene, Jalene, Marachere and local check) was investigated in southern Ethiopia to find out rates of the nutrients and varieties that would give acceptable returns and likely to be adopted by smallholder farmers in the locality. Factorial combination of N (0, 55.5 and 111 kg/ha) and P (0, 19.5 and 39 kg/ha) were applied to the main plots while the five varieties were to the sub plots of split-plot design and replicated three times. Both factors had significant effect on tuber yield, but there were no significant interaction effect. Significant treatments of this experiment were, therefore, subjected to economic analysis using partial budget procedure. Economic analysis showed that 0:19.5, 55.5:19.5 and 55.5:39 kg NP/ha and varieties Bellete, Jalene and Marachere were economically superior and stable even within a price variability range of 20% in the locality. In conclusion, application of NP nutrients with the rate of 0:19.5, 55.5:19.5 or 55.5:39 kg/ha for the varieties Bellete, Jalene and Marachere were identified profitable treatments for lucrative production of potato in the study area.
Key words: Dominance analysis, economic analysis, partial budget, smallholder farmers, tuber yield.
Human population of Ethiopia increased from 76.2 million in 2004-06 to 99.0 million in 2014-16, which is an addition of about 22.8 million (29.9% increment) during the last ten years. However, prevalence of food inadequacy was 55.4% in 2004-06 and 41.3% in 2014-16 showing a decrease of only 14.1% within the ten years of time (FAO, 2016). This implies that Ethiopia’s agricultural sector should also provide sufficient amount of food for the rapidly growing population. The need to raise productivity of smallholder farmers is, therefore, important to minimize the problem. The paradox increase of human population also puts high pressure on the static land and other limited resources. This is further aggravated by the impacts of climate change which occurs due to the misuse of manmade and natural resources. For instance, the unusually created drought in Ethiopia after fifty years has exposed more than 10 million citizens to a severe hunger (WFP, 2016). Such problems can be reduced by growing robust crops adaptable to a wide range of agro-ecology (Kyamanywa et al., 2011).
Potato (Solanum tuberosum L.), a food security crop (Kyamanywa et al., 2011), is one of the best choice crops to attempt such problems in Ethiopia in general and in the study area in particular. It produced for home consumption and sale by smallholder farmers in Wolaita zone, southern Ethiopia. Obviously potato has already considered as specialty crop in Ethiopia due to its role in improving food security of the nations. However, its low productivity in the areas is attributed to the present practices of its production without appropriate nutrient management practices (Zelalem et al., 2009) and lack of high yielding varietal options (Mitiku et al., 2015).
Nitrogen and phosphorus are among the essential macro-nutrients identified as the most yield-limiting factors in crop production. Nitrogen is required for good vegetative and reproductive development (Brady and Weil, 2000). It is a component of protein and nucleic acids and when it is inadequate, growth is reduced (Adediran and Banjoko, 1995). It forms part of many important compounds like chlorophyll and enzymes responsible for many physiological processes in the plant. Nitrogen serves as an intermediary in the utilization of P, K and other elements in plants (Brady and Weil, 2000). Phosphorus also has many vital functions in photosynthesis, utilization of both sugar and starches and in energy transfer processes. Therefore, young plants absorb P very rapidly, to provide rapid and extensive growth of roots (Asumadu et al., 2012).
Due to poor cultural practices mainly poor nutrient management practices and lack of high yielding varieties, productivity of potato is still limited to be 11.5 tonnes per hectare (t/ha) (CSA, 2015) in Ethiopia; which is very much less than its yield potential (100 t/ha) (Grewal et al., 1992). Although blanket recommendations of fertilizers that assume homogeneity of farming conditions have partly contributed to the low diffusion of fertilizer technologies within Ethiopia’s smallholder farmers, the need for careful targeting and area specific fertilizer recommendation is crucial. A blanket recommendation of about 111 kg N and 39 kg P per hectare was being advocated by the development agents (DAs) to farmers. Smallholder farmers lacked the financial expense required to apply the recommendation due to their limited resource base, which pointed to the need for a lower rate of fertilizer in line with their low economic status.
Thus, awareness of the need to identify lower fertilizer rates for low smallholder farmers and the importance of raising potato productivity as specialty crop in the country in general and in Wolaita zone in particular is important for the ultimate goal of food security program in the zone where population per unit area is higher. This study was, therefore, designed to test a range of possible alternatives with the objective of selecting economically appropriate rates of NP kg/ha and profitable potato varieties in the study area.
Description of the study area
Two year (2014 and 2015) field experiments were conducted at the research site of School of Agriculture, Wolaita Sodo University. It is located at 6° 49’N, 37° 45’E and an altitude of 1886 m above sea level. The soils are well drained sandy loam with low organic carbon. Monthly air temperature, rainfall, relative humidity and bright sunshine hour ranged from 15 to 28°C, 311 to 790 mm, 62 to 75% and 133 to 247 h, respectively, for 2014 cropping year. During 2015, the ranges were 15 to 30°C, 131 to 641 mm, 46 to 47% and 98 to 248 h, in that order (NMA, 2015). The soil was low in organic carbon (1.5 and 0.54%), total nitrogen (0.15 and 0.06%) and available phosphorus (7.8 and 8.10 ppm) with acidic pH (5.3 and 5.44) in 2014 and 2015, respectively.
Treatments and experimental design
The field experiment was laid in split-plot design with three replications. Factorial combinations of 3 levels of each N (0, 55.5 and 111 kg N/ha) and P (0, 19.5 and 39 kg P/ha) were assigned to main-plots and 5 varieties (Bellete, Gudene, Jalene, Marachere and local check) to the sub-plots. Urea and triple super phosphate were used as nutrient sources of N and P, respectively. The size of each sub-plot was kept 4.5 m x 3.6 m (16.2 m2), consisting of six rows and each row consists of 12 plants. Sub-plots within the main-plots were arranged continuously without paths, but the end rows were used as boarder. One meter and 1.5 m paths were maintained between consecutive main-plots and between replications, respectively. Planting was done keeping row-to-row and plant-to-plant distances of 30 cm and 75 cm, respectively.
Cultural practices
Weeding, hoeing, and earthing up were adopted uniformly for all treatments as recommended by EARO (2004). Ridomil (MZ 63.5% WP) was applied at a rate of 2 kg/ha as soon as the first symptom of Phytophthora infestans was observed on the foliage parts. The vines were removed two weeks before harvesting for proper skin hardening and wound healing. Then, the tubers were harvested after 15 days of vine removal.
Statistical analysis
The data collected on yield parameter was subjected to statistical analysis and Duncan Multiple Range test was used at 0.05 p-values to compare treatment means (Gomez and Gomez, 1984) by employing the SAS computer program, version 9.2 (SAS, 2002). Homogeneity of the variances was tested using F-test (Gomez and Gomez, 1984) and it has shown that the variances of the two cropping years were homogenous. Therefore, combined analysis of the two-year data was carried out.
Economic analysis
The pooled experimental data were compared and analyzed for yield, input and output costs. Economic analysis was done using the existing market prices for inputs (NP fertilizers and seed tubers) at planting time while for the output (marketable yield) at the time the crop was harvested. All costs and benefits were calculated on hectare basis in Ethiopia currency (Eth Birr/ha). Where, 20.5 Eth Birr was equivalent to 1US$. The tools used for economic analysis to assess the total costs and net benefits associated with the treatments were the partial budget analysis, dominance analysis, marginal analysis and sensitivity analysis (CIMMYT, 1988).
Partial budget analysis: This is used to evaluate the differences in costs and benefits among different rates of NP fertilization as well as among varieties. Its components are: (1) Average marketable tuber yield (kg/ha), which was the mean marketable tuber yield of the treatments. (2) Adjusted yield (kg/ha), in which the yield of all treatments were adjusted downward by 10% to minimize plot management effect by the research or to reflect the actual farm level performance. (3) Gross field benefit (GFB) which was the product of field price and the adjusted marketable tuber yield for each treatment:
Total variable costs (TCV) (Eth Birr/ha): Is the sum of field cost of fertilizer and the cost of fertilizer applications. (5) Net benefits (NB) (Eth Birr/ha) which was the difference between the GFB and TCV for each treatment:
Dominance analysis: Is the procedure used to select potentially profitable treatments from the range that was tested. The selected and discarded treatments using this technique are referred to as undominated and dominated treatments, respectively. The undominated treatments were ranked from the lowest to the highest cost treatment (CIMMYT, 1988).
Marginal rate of return (%): For each pair of ranked treatments, a per cent marginal rate of return (MRR) was calculated:
The MRR% between any pair of undominated treatments denotes the return per unit of investment in rates of NP fertilization and variety expressed as a percentage.
Sensitivity analysis: Before recommendation, it is better to test each treatment for its stability despite price changes. Sensitivity analysis, redoing a marginal analysis with alternative prices, is therefore the best way to test a recommendation for its ability to withstand price changes (CIMMYT, 1988).
Statistical analysis of yield data showed that the main effects of rates of NP nutrients and variety significantly (P < 0.01) influenced marketable yield (t/ha) (Table 1). Significant interaction effect between the main effects was not observed on the marketable tuber yield. From the tested and undominated nutrient treatments, the net profit per hectare was highest (Eth Birr=105,864.73) in treatment 55.5:39 kg NP/ha followed by (Eth Birr=95967.99) in treatment 55.5:19.5 kg NP/ha and (Eth Birr=85826.55) in treatment 0:19.5 kg NP/ha and it was lowest (Eth Birr=51,781.68) in the control, 0:0 kg NP/ha. While from the undominated treatments of variety, the maximum (Eth Birr=97,444.80) net profit per hectare was
obtained from Bellete followed by Jalene (Eth Birr=75,761.88) and Marachere (Eth Birr=70,326.36) and comparatively, the least (Eth Birr=52,591.80) was obtained from the local variety. Thus, the per cent increase in net profit was highest (104.44%) in treatment 55.5:39 kg NP/ha over the control. It was followed by 55.5:19.5 kg NP/ha (85.33%) and 0:19.5 kg NP/ha (65.75%) treatments. Economic output is the ultimate target of any farm business and, thus, rates of NP nutrients confirmed to have significant effect on the output. Accordingly, an additional investment of 4,609.55 Eth Birr/ha towards cost of NP nutrients in case of 55.5:39 kg NP/ha treatment offered 54,083.05 Eth Birr extra money over control. In case of 55.5:19.5 kg NP/ha and 0:19.5 kg NP/ha treatments, an additional investment of 3,269.97 and 1,559.49 Eth Birr/ha gave an extra money of 44,186.31 and 34,044.87 Eth Birr, respectively, over control. Similarly, an additional investment of 14,400.00 Eth Birr/ha towards cost of tuber seeds in case of variety Bellete gave extra money of 44,853.00 Eth Birr over the local check. In case of Jalene and Marachere, an additional investment of 12,000.00 and 10,800.00 Eth Birr/ha for tuber seeds gave extra money of 23,170.08 and 17,734.56 Eth Birr, respectively, over the local variety (Table 4).
In agreement with the present study, while the inorganic fertilizer component gave a higher net benefit, lower net benefit was identical with no fertilizer components (Makinde et al., 2007; Yusuf et al., 2015). Similarly, the existence of a significant difference among potato varieties tested in their performances of tuber production potential and their economic profitability could be due to the fact that differences exists among varieties in their adaptability to the specific environment and nutrient use efficiency (Haile, 2009). Crop varieties vary in their physiology, morphology and growth habit and so do in their response to fertilizer application. Thus, species or cultivars having high growth rate respond to fertilizer application more favorably than those with low growth rate (Mengel, 1983).
Since the statistical results of the yield data have indicated a significant effect within the treatments, economic analysis is thus appropriate on the results of rates of NP fertilizers and variety treatments using the partial budget technique (CIMMYT, 1988). Consequently, the result of the partial budget analysis and the economic data used in the development of the partial budget is given in Table 2. While the resulting dominance analysis selected 0:19.5, 55.5:19.5 and 55.5:39 kg NP per hectare for the fertilizer treatments and Bellete, Jalene and Marachere for the variety treatments as the undominated treatments (Table 4).
For both treatments (rates of NP nutrients and variety), the calculations of marginal rate of return (MRR %) between 0:0 and 0:19.5, between 0:19.5 and 55.5:19.5 and between 55.5:19.5 and 55.5:39 treatments were 2183.07%; 592.90%; and 738.79%, respectively (Figure 1). Similarly, the MRR between local check and Marachere, between Marachere and Jalene, and between Jalene and Bellete were 1477.88, 452.96 and 903.46%, respectively (Figure 2).
The calculations of marginal rate of return realized that the MRR% between the selected nutrient treatments (0:0 and 0:19.5, 0:19.5 and 55.5:19.5 and 55.5:19.5 and 55.5:39) were above the minimum acceptable MRR (100%); that is, 2183.07, 592.90 and 738.79%, respectively (Figure 1).
Similarly, all MRRs between the selected variety treatments (local check and Marachere, Marachere and Jalene, and Jalene and Bellete) were greater than 100% (1477.88, 452.96 and 903.46%, respectively). Therefore, from the range of nutrient treatments tested against the check (0:0 NP kg/ha), 0:19.5, 55.5:19.5 and 55.5:39 NP kg/ha gave an economic yield response and also sustain acceptable returns when applied to the improved potato varieties Bellete, Jalene and Marachere (Figure 2).
Sensitivity analysis
The field prices of N and P nutrients were increased from 23.76 and 60.97 Eth Birr/kg to 26.14 and 67.07 Eth Birr/kg, respectively, by 10%. Similarly the field prices of the seed tubers of varieties local, Marachere, Jalene and Bellete increased from 4.00, 4.50, 5.00 and 6.00 Eth Birr/kg to the field prices of 4.80, 5.40, 6.00 and 7.20 Eth Birr/kg, in that order, by 20% and the new prices were used to make the partial budget (Table 3).
The calculations of marginal rate of return realized that the MRR% between the selected nutrient treatments (0:0 and 0:19.5,0: 19.5 and 55.5: 19.5 and 55. 5:19.5 and 55.5:39) were above the minimum acceptable MRR (100%); that is, 2183.07, 592.90 and 738.79%, respectively (Figure 1). Similarly, all MRRs between the selected variety treatments (local check and Marachere,
Marachere and Jalene, and Jalene and Bellete) were greater than 100% (1477.88, 452.96 and 903.46%, respectively). Therefore, from the range of nutrient treatments tested against the check (0:0 kg NP ha-1), 0:19.5, 55.5:19.5 and 55.5:39 NP kg/ha gave an economic yield response and also sustain acceptable returns when applied to the improved potato varieties Bellete, Jalene and Marachere (Figure 2).
The input and output prices used in the economic analysis were those existing during the period of the experiment. Market prices are always changing and as such a recalculation of the partial budget using a set of likely future prices, that is, sensitivity analysis, is necessary to identify treatments which are likely to remain stable and sustain acceptable returns for farmers in spite of price changes. Accordingly, an assumption of price change of the nutrients (N and P) and the potato tubers is from our own experiences and represents a price fluctuation (increment) of 10 and 20% for the fertilizers and the tubers, respectively.
These price changes are currently realistic under the retailer and even union market conditions in Ethiopia. Some of the reasons for projection of the prices were absence of enough irrigation schemes to grow and access potato tubers all the times, semi perish-ability of the crop and lack of appropriate storage facilities are amongst. Deterioration of business environment in the country can also be the main reason for the price fluctuation of the nutrient treatments. Similar reasons were reported by many researchers previously (Shiluli et al., 2004; Odendo et al., 2006; Edward, 2015; Ayele et al., 2016).
From the range of rates of NP nutrient treatments tested, (19.5 kg P), (55.5 kg N and 19.5 kg P) and (55.5 kg N and 39 kg P) gave an economic yield response and also sustain acceptable returns even under a projected future market conditions. Whereas variety treatments such as Bellete, Jalene and Marachere gave an economically feasible yield returns sustainably under increased market prices. Thus, farmers could thus choose any of the three rates of NP nutrients to apply on either of the selected varieties Bellete, Jalene or Marachere, alternatively, depending on their income on the tentative basis. The results of this research can be used to make tentative recommendations, which can be rechecked through multi-location testing over a wider area. Furthermore, as it is difficult to individual farmer, bureaus of agriculture should regularly done soil analysis to monitor critical levels of soil nutrients which have the opportunity to reduce fertilizer costs significantly, maintain a profitable business, and keep the environment healthy and productive sustainably.
The authors have not declared any conflict of interests.
REFERENCES
|
Adediran J, Banjoko V (1995). Response of maize to nitrogen, phosphorus, and potassium fertilizers in the savanna zones of Nigeria. Commun. Soil Sci. Plant Anal. 26:593-606.
Crossref
|
|
|
|
Asumadu H, Adu-Dapaah H, Obosu-Ekyern S (2012). Response of maize to organic foliar fertilizer and its economic implications to farmers in Ghana. Int. J. Agric. Res. 7:439-448.
Crossref
|
|
|
|
Ayele GK, Gessess AA, Addisie MB, Tilahun SA, Tebebu TY, Tenessa DB, Langendoen EJ, Nicholson CF, Steenhuis TS (2016). Biophysical and economic assessment of a community-based rehabilitated gully in the Ethiopian highlands. Land Degradation Dev. 27:270-280.
Crossref
|
|
|
|
Brady NC, Weil RR (2000). Elements of the Nature and Properties of Soils. Prentice-Hall Upper Saddle River, NJ, USA.
|
|
|
|
CIMMYT (International Maize and Wheat Improvement Center) (1988). From Agronomic Data to Farmer Recommendations: An Economics Training Manual. Completely revised edition. Mexico, D.F., 84 p.
|
|
|
|
CSA (Central Statistical Agency) (2015). The Federal Democratic Republic of Ethiopia Central Statistical Agency. Agricultural Sample Survey, 2015/2016 (September – December, 2015), Volume IV, Report on Land Utilization (Private Peasant Holdings, Meher Season). Statistical Bulletin 584. Addis Ababa, Ethiopia.
|
|
|
|
EARO (Ethiopian Agricultural Research Organization) (2004). Directory of Released Crop Varieties and their Recommended Cultural Practices: A Guide. Ethiopian Agricultural Research Organization, Addis Ababa, Ethiopia.
|
|
|
|
Edward T (2015). Economic Evaluation of Soybean Genotypes under Soil Fertility Variability on Northern and Eastern Uganda. An MSc Thesis Presented to Makerere University. Makerere, Uganda, 111p.
|
|
|
|
FAO (Food and Agriculture Organization of the United Nations) (2016). Food Security Indicators - Statistics. Rome, Italy.
View
|
|
|
|
Gomez KA, Gomez AA (1984). Statistical Procedures for Agricultural Research. John Wiley and Sons. New York, USA.
|
|
|
|
Grewal JS, Sharma RC, Saini SS (1992). Agritechniques for Intensive Potato Cultivation in India. Publications and Information Division, Indian Council of Agricultural Research, Krishi Anusandhan Bhauan, New Delhi, 126 p.
|
|
|
|
Haile W (2009). On farm verification of potassium fertilizer effect on the yield of Irish potato grown on acidic soils of Hagere-Selam, southern Ethiopia. Ethiopian J. Nat. Resour. 11:207-221.
|
|
|
|
Kyamanywa S, Kashaija I, Getu E, Amata R, Senkesha N, Kullaya A (2011). Enhancing Food Security through Improved Seed Systems of Appropriate Varieties of Cassava, Potato and Sweet Potato Resilient to Climate Change in Eastern Africa. International Livestock Research Institute (ILRI), Nairobi, 30 p.
|
|
|
|
Makinde E, Saka J, Makinde J (2007). Economic evaluation of soil fertility management options on cassava-based cropping systems in the rain forest ecological zone of south western Nigeria. Afr. J. Agric. Res. 2:7-13.
|
|
|
|
Mengel K (1983). Responses of various crop species and cultivars to fertilizer application. In: Saric MR, Loughman BC (Eds.) Genetic Aspects of Plant Nutrition. Springer, Netherlands, pp. 295-309.
Crossref
|
|
|
|
Mitiku M, Shiferaw W, Tadesse A (2015). Adaptability study of improved Irish Potato (Solanum tuberosum L.) varieties at South Ari Woreda, Ethiopia. Am. Sci. Res. J. Eng. Technol. Sci. 7:26-30.
Crossref
|
|
|
|
NMA (National Meteorological Agency) (2015). National Meteorological Agency, Hawassa Branch. Hawassa, Ethiopia.
|
|
|
|
Odendo M, Ojiem J, Bationo A, Mudeheri M (2006). On-farm evaluation and scaling-up of soil fertility management technologies in western Kenya. Nutr. Cycling Agroecosyst. 76:369-381.
Crossref
|
|
|
|
SAS (Statistical Analysis System) Institute (2002). SAS Version 9.1 © 2002-2003. SAS Institute, Inc., Cary, North Carolina, USA.
|
|
|
|
Shiluli M, Macharia C, Kamau A (2004). Economic analysis of maize yield response to nitrogen and phosphorus in the sub-humid zones of Western Kenya. Afr. Crop Sci. J. 11:181-187.
Crossref
|
|
|
|
WFP (World Foo Program), 2016.
View
|
|
|
|
Yusuf O, Williams N, Abubakar UZ (2015). Measurement of technical efficiency and its determinants in Sampea-11 variety of cowpea production in Niger State, Nigeria. Int. Res. J. Agric. Sci. Soil Sci. 5:112-119.
|
|
|
|
Zelalem A, Tekalign T, Nigussie D (2009). Response of potato (Solanum tuberosum L.) to different rates of nitrogen and phosphorus fertilization on vertisols at Debre Berhan, in the central highlands of Ethiopia. Afr. J. Plant Sci. 3:16-24.
|
