Agriculture plays an important role in Ethiopia’s political, economic, and social development. It forms one of the largest components of the Ethiopian economy, contributing over 35% of the Country’s gross domestic product (GDP), 66% of employment and over 76% of total export earnings (NBE Annual Report 2017–2018). Crop production makes up 72% of the total agricultural GDP, whereas livestock accounts for 20% and other areas contribute 8.6%. Cereals (such as wheat, maize, tef, sorghum, and millet), comprise the biggest share of crop production as principal staples. In the 2019/20 season alone 33.52 million tons of grains were produced by smallholder farmers in Ethiopia and 1.16 mil ton in East Wollega Zone (CSA, 2019/20). In addition, vegetables, fruits, root crops, pulses, oilseeds, and spices are grown widely. With a total area of about 113 million hectares (ha) and about 36 million ha of arable land, the country has tremendous potential for agricultural development. However, only about 12.86 million ha of land, just over 35 per cent of the total arable area is currently being cultivated (CSA, 2019/20).
The average productions of cereals, pulses and oil crops are 2.83, 1.92 and 1.03 tons per hectare, respectively (CSA, 2019/20). Over the past decade, cereal production has more than doubled and increased by 6.21% over the last season because of horizontal expansion, increased yields and improved soil management (CSA, 2019/20). There is consistent upward trajectory for key staple crops over the last year (2018/19), resulting a national average productivity increment of 5.68% for maize, 5.33% for tef, 7.3% for wheat, and 14.87% for barley (CSA, 2019/20). Nevertheless, food security remains a critical issue for many households, and for the country as a whole. For example, 5.6 million people in Ethiopia in 2017 were categorized under crisis requiring severe humanitarian assistance (WFP, 2017).
One of the main constraints for food insecurity is low level of agricultural production and productivity, which in turn affected by low soil fertility and soil degradation. The main cause of soil fertility degradation in Ethiopia is human activity through cultivating sloppy areas without soil conservation methods and poor soil cover (Kassaye Gurebiyaw and Abay Gelanew, 2019). Soil degradation in the Eastern African highlands is mainly due to soil erosion, gully formation, soil fertility loss, which results in reductions in crop yield (Meseret, 2016). Among others, nutrient deficiencies, sub-optimum management, and availability of limited information on soil nutrient contents are factors constraining yields (Hengl et al., 2017). Crop response to application of fertilizers is mainly governed by the characteristics and topographic sequence of landscapes (Amede et al., 2020b), whereby crop response to inputs is significantly higher in valley bottoms and flatlands compared to hill slopes and degraded uplands (Amede et al., 2020b; Getnet et al., 2020). Therefore, in order to achieve optimum agronomic efficiency of inputs, fertility status of the soils need to be known.
Soil fertility assessment indicates the plant nutrient status which is useful for decision making on fertilizer advisory services including fertilization and liming. Despite the application of high rates of fertilizers, marginal soils produce low yields compared to moderately fertile soils (Vanlauwe et al., 2015; Agegnehu and Amede, 2017). Soil chemical, physical and biological properties can vary extensively within fields. Therefore, characterizing and mapping the fertility status of agricultural fields by district level is important for decision making on sources and rates of fertilizers and soil amendment materials.
Jimma Arjo is one of the rural districts of Ethiopia that inherited the physical and economic situations prevailing in the country due to declining soil fertility and increasing soil acidity. Some farmlands were abandoned due to soil degradation and acidity (Mulata, 2009). It is located in high rainfall receiving area where there were leaching of nutrients and topsoil removal which caused nutrient loss and aggravate soil acidity. Most areas of the district were covered with Nitisol (MoA, 2005). This soil has good workability, good internal drainage and fair water holding capacity; these are complemented by chemical fertility properties, and being susceptible for soil acidity problem. Therefore, assessing and maintaining the chemical fertility of the soils of the district is very important to obtain optimum and sustainable crop production. The objectives of this research were to understand farming practices of smallholder farmers, assess and map the acidity status of the soil, identify and recommend the right sources and rates of agricultural lime for acidic soils reclamation of the soils in the Jimma Arjo district.