Agriculture is the fundamental driver for Ethiopia’s economy and long-term food security as it offers about 80-85% of employment, more than 61% of the total export and 38.5% of gross domestic product of the country (Degaga and Angasu, 2017). Ethiopia has diverse agro-ecology that permits different agricultural systems and production of different crops. The existence of this diverse agro-ecology together with diverse farming systems,  socio-economic,   cultures  and  climate  zones provided Ethiopia with various biological wealth of plants, animals, and microbial species, especially crop diversity (Atnaf et al., 2015).

Cereals are the most important food crop which provides daily food calories to people. Hence, cereal production and marketing are the means of livelihood strategy for millions of smallholder households in Ethiopia (Taffesse et al., 2012). Teff, wheat, maize, sorghum and barley are the major cereals that occupy almost three-quarters of the total area cultivated (Taffesse et al., 2012), and households spend an average of 40% of their total food budget on cereals (GAIN, 2014). Cereals are the major food crops for ensuring food security in Ethiopia as they constitute the major component of staple diet for majority of the population and contribute approximately 70% of the average Ethiopian calorie intake (Solomon, 2011). The 2004/2005 National Survey of Consumption Expenditure indicated that maize accounted for 16.7% of the national calorie intake followed by sorghum (14.1%) and wheat (12.6%) in descending order (Berhane et al., 2011).

In Ethiopia, wheat grain is used in the preparation of different traditional as well as modern processed food products such as injera and other industrial processed products like pasta and macaroni (Nigussie et al., 2015). Wheat is one of the most important food grain crop; people use the grain for food utilization in different forms like bread, porridge, soup and roasted grain (“Kolo”), enjira,dabokolo, nifro, tella, arki. In addition, farmers use wheat grain for marketing (selling purpose) to generate income and cover other required costs. Its straw is also important for animals feed, thatching house roof and bedding. Wheat with low yield leads to wheat varieties with low yield, moisture stress, and wheat rust disease (Arega and Setu, 2014).

Barley (Hordeum vulgare L.) is an important crop in Ethiopian cereal production and in food security (Berhanu et al., 2005).  Food barley is principally cultivated in the highland areas of Ethiopia where the highest consumption is in the form of various traditional foods and local beverages from different barley types (Zemede, 2000). Teff (Eragrostis tef (Zucc.) Trotter) is a small-grained cereal that has been grown as food crop in East Africa for thousands of years (D’Andrea, 2008). It is a staple food for the majority of the population in Ethiopia and Eritrea. Teff is adapted to a large variety of environmental conditions and widely grown from sea level up to 2800 m above sea level (a.s.l.) under various rainfall, temperature, and soil conditions (Seyfu, 1997). The average teff grain yield of 1228 kg/ha (Anonymous, 2010) is low compared to other cereals, which is attributed to nutrient limitations, drought and water logging (Tulema et al., 2005).

Farmers using improved cultivars and management practices, however, can obtain yields up till 2500 kg/ha (Tefera and Belay, 2006), while the yield potential under optimal management and when lodging is prevented, is as high as 4500 kg/ha (Teklu and Tefera, 2005). Finger millet (Eleusine coracana (L.) Gaertn) subspecies coracana belongs to the family Poeceae (Hilu et al., 1976). The archaeological findings of finger millet from Ethiopia date to about the third millennium BC (Hilu et al., 1979). The crop is mainly grown in the northern, north western and western parts of the country, especially during the main rainy season.

The national annual production area of finger millet in 2016/2017 cropping season is estimated at around 456,171 hectares, with a total production of 10.3 million quintals (CSA, 2017). In Ethiopia, the grain is used for making native bread, injera, porridge, cake, soup, traditional breakfast called “Chachabsa” malt, local beer, and distilled spirit (Areki) alone or in mixture with teff, maize and barley (Adugna et al., 2011; Wedajo, 2015). Its productivity is very low mainly due to shortage of improved varieties (Birhanu, 2015), weeds, insect (termite), diseases (blast), rat damage, shortage of rainfall worm attacks improper application of inputs (fertilizers and seed) and traditional management practices (Tefera and Adane, 2013). Ethiopia is the primary center of origin and center of diversity for sorghum. In lowland areas of Ethiopia, where moisture is the limiting factor, sorghum is one of the most important cereal crops planted as food insurance, especially in the lowlands of eastern Ethiopia and in the north and north-eastern parts of the country where the climate is characterized by unpredictable drought and erratic rainfall (Degu et al., 2009).

Maize is one of the most important cereals broadly adapted worldwide (Christian et al., 2012). In Ethiopia, it is grown in the lowlands, the mid-altitudes and the highland regions. It is an important field crop in terms of area coverage, production and utilization for food and feed purposes. However, maize varieties mostly grown in the highlands at an altitude ranging from 1,700 to 2,400 m.a.s.l of Ethiopia are local cultivars with poor agronomic practices (Beyene et al., 2005). In Ethiopia, its total annual production and productivity exceeds all other cereals (23.24% of 13.7 Million tons), and second after tef (Eragrostis tef) in area coverage (16.12% of the 8.7 000 000 ha); maize is one of the most important crops grown in Ethiopia (Wende et al., 2007).Rice is currently considered as a strategic food security crop in Ethiopia (Teshome and Dawit, 2011). Relatively, it has higher productivity as compared to other main staple crops. It can be used in a range of traditional food recipes. It provides by-products such as straws and husks that are fed to livestock and/or used as an alternate source of fuel (Dawit, 2015). Oat (Avena sativa) is widely utilized in the highland farming system of Ethiopia. One of the bottlenecks of livestock production in Ethiopia is feed shortage. Integration of food and forage crops is a useful practice in area where both crop and livestock farming are simultaneously practiced (Leulseged et al. 1986). Ethiopia is endowed with diverse agro-ecologies suitable for cereal production. Cereals crop productions in Ethiopia were under rain fed production system.  However, the success of this production system relies more on climate condition. The facts about land use at the national level have potentially imposed limits on the areas sown as a major source of increase in production. This causes inverse relationship between area and production because expansion area which is unsuitable for agriculture. Therefore, this study is initiated to analyze trends of; cereal crop production area and productivity in Ethiopia.

Data of meher season for cereal crops productivity (qt/ha) and area of production (ha) in Ethiopia for the period 2007-2018 were collected from Central Statistical Agency (CSA). Trend test was carried out using the non-parametric Mann-Kendall’s trend test which is less sensitive to outliers and test for a trend in a time series without specifying whether the trend is linear or non-linear (Partal and Kahya, 2006; Yenigun et al., 2008; Hadgu et al.,2013). The Mann-Kendall’s test statistic is given as:

Where S is the Mann-Kendal’s test statistics; x_i and x_j are the sequential data values of the time series in the years i and j (j > i) and N is the length of the time series. A positive S value indicates an increasing trend and a negative value indicates a decreasing trend in the data series. The sign function is given as,

The variance of S, for the situation where there may be ties (that is, equal values) in the x values:

Where, m is the number of tied groups in the data set and t_i is the number of data points in the i^th tied group. For n larger than 10, Z_MK approximates the standard normal distribution (Partal and Kahya, 2006; Yenigun et al., 2008) and computed as follows,

The presence of significant trend is evaluated using the Z_MK value. In a two-sided test for trend, the null hypothesis Ho should be accepted if Z _MK < Z_1-a/2 at a given level of significance. Z_1-α/2 is the critical value of Z_MK from the standard normal table.

Sen’s slope value in Tables 1 to 4 indicated that the country level area of cereal crops production for most of the cereal crops showed significant (P < 0.05) increasing trend by different factors (63718.13, 27651.44,37924.15, 10262.44, 3091.988) ha/year for teff, wheat, maize, finger millet and rice respectively for 2007-2018 production year. But only sorghum production area indicated non-significant (P = 0.108) increasing trend. Oats and barley production area have indicated decreasing trend. Oats production area indicated significant (P = 0.047) decreasing trend by factor of -816.39 ha/year. In contrary, barley indicated non-significant (P = 0.127) by the factor of -7505.08 ha/year.

Sen’s slope value in Table 4 indicated that the country level of all cereal crops production in Ethiopia showed significant (P < 0.0001) increasing trend by different factor from 2004- 2018 production period, except rice productivity that indicated non-significant (P = 0.15) decreasing trend. Productivity of barley significantly increased despite non- significant decreasing production area. Similarly productivity of oat’s significantly increased despite significant decreasing production area; while the productivity of the rest crops (teff, wheat, maize, finger millet and rice) increased significantly with significant increasing trends of production area. However, differently from the others, productivity of sorghum significantly increased despite non-significantly increasing area of sorghum production. In general, the analyses of this study have indicated increasing trends of production area for most the cereal crops in Ethiopia. In agreement with this result, MEDaC (1999) indicated that in Ethiopia, changes in areas sown constitute the major sources of production increase. This can be attributed to the domination ofsmall-scale farmers, characterized by low input and low output rain-fed mixed farming with traditional technologies. Small-scale farmers constitute over 95% of total area sown and over 90% of agricultural output (MEDaC, 1999). Despite the long history of agricultural research in Ethiopia, farmers in the country have benefited little from modern agricultural technologies. Currently, improved seed is used on only 2% of the country's cultivated area (Wolday, 2001). Cereal production is predominantly rain-fed and that fluctuations in  rainfall   from   the  long-term  average  are  increasing (Webb et al., 1992). Modern inputs are unlikely to dominate the effect of weather on cereal production. According to Jaeger (1991), cereals are the most susceptible crop to moisture stress, and for most countries, variations in average yields of cereals result primarily from variations in weather. Moreover, the increase in the area cultivated is made possible by the expansion of cultivation to areas that were previously designated as permanent pasture or forests, or land previously categorized as unsuitable for farming. Forests covered 40% of the land area at the turn of the century, but less than 4% today (Alemu, 2002) (Figures 1 to 8).

Sen’s slope analysis indicated that the country level area of cereal crops production for most of the cereal crops showed significant (P < 0.05) increasing trend by different factors (63718.13, 27651.44,37924.15, 10262.44,  3091.988) ha/year for teff, wheat, maize, finger millet and rice respectively for 2007 - 2018 production year. But, only sorghum production area indicated non-significant (P = 0.108) increasing trend. Oats and barley production area have indicated decreasing trend. Oats production area indicated significant (P = 0.047) decreasing trend by factor of -816.39 ha/year. But, barley was non-significant (P = 0.127) by the factor of -7505.08 ha/year.

The result of this study indicated country level of all cereal crops productivity in Ethiopia showed significant (P < 0.0001) increasing trend by different factor  from  2007- 2018 production years, except rice productivity which indicated non-significant (P = 0.15) decreasing trend. Productivity of barley significantly increased despite non- significant decreasing production area. Similarly, productivity of oat’s significantly increased despite significant decreasing production area; while the productivity of the rest crops (teff, wheat, maize, finger millet and rice) increased significantly with significant increasing trends of production area. However, differently from the others, productivity of sorghum significantly increased despite non-significantly increasing area of sorghum production.

In general, the analysis of this study has indicated increasing trends of production area for most cereal crops in Ethiopia except barley and oats which showed decreasing trend. Moreover, productivity of all cereal crops showed significant increasing trend except rice which showed non-significant decreasing trend in Ethiopia for 2007-2018 production year.

The authors have not declared any conflict of interests.