Abstract
Detailed study on soil fertility assessment based on the understanding of the soil system are not available for the most part of Ethiopia. With the cognizance of this fact, the present study was conducted to assess the soil fertility status and to prepare the fertility map of Argo-Gedilala Sub watershed in Dugda District, Central Rift Valley of Ethiopia. Eighteen composite soil samples (0-20cm depth) were taken for fertility assessment of the soil from the land mapping units of the subwatershed and mapping the status of selected soil fertility parameters was done using ordinary kriging technique in ArcGIS 10 software. The bulk density is at an acceptable range 1.3 to 1.4 g cm-3 for mineral agricultural soils. The soil organic matter contents of LUs (04, 05 and 06) 680.47 ha (64.77%) in the study area can be categorized in the range of low soil organic matter content and LUs (01, 02 and 03) 369.31 ha (35.23%) can be categorized in the medium range at the sub-watershed. The average percent total N content of the LUs (02, 04, and 05) 567.7ha (54.05%) were found to be low; LUs (01, 03 and 06) 482.61ha 45.95%) were found to be moderate. The mean available P of soils of LUs (04and05) 443.17 ha (42.19%) was categorized as very low range and LUs (01, 02, 03 and 06) 607.15 ha (57.82%) classified as low range. Exchangeable Ca2+, LUs (01, 02, 03, 05 and 06) 824.88 ha (78.55%) were very high while LU04 which covered an area of 225.44 ha (21.46%) were rated as high. The soils of the study area had low organic matter, available P and total nitrogen content, which can be seen as production constraints of all cultivated lands. To overcome the identified limitations, increasing the organic matter levels through continuous application of manure and/or compost should be integrated with chemical fertilizers. Key words: Fertility status, land-mapping units, ordinary kriging.
Highlights
In Ethiopia, Low agricultural productivity and related shortage of additional cultivable lands are problems to most Sub-Saharan African (SSA) countries (Bationo et al., 2006; AGRA, 2007; Sommer et al, 2013)
The highest bulk density for LU05 could be due to lower soil organic matter content and higher degree of soil compaction due to intensive cultivation since this land units (LUs) has been cultivated for a long period of time
The average percent total N content of the soils in the study area ranged from 0.11% (LU04) to 0.14% (LU01)
Summary
In Ethiopia, Low agricultural productivity and related shortage of additional cultivable lands are problems to most Sub-Saharan African (SSA) countries (Bationo et al., 2006; AGRA, 2007; Sommer et al, 2013). From the many reasons suggested for the current low agricultural production in SSA, are majorly induced by land. Agriculture is the mainstay of the country’s economic activity and its contribution to the national economy is significant. It accounts for about 43% of the growth domestic product (GDP), 90% of exports, and 80% of total employment (CSA, 2013). Increasing pressure due to increased in human population has degraded vital natural resources in the country and became a serious threat to sustainable agriculture (Gete and Hurni, 2001)
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