Exploring the variability of soil nutrient outflows as influenced by land use and management practices in contrasting agro-ecological environments

Temesgen Mulualem; Enyew Adgo; Derege Tsegaye Meshesha; Atsushi Tsunekawa; Nigussie Haregeweyn; Mitsuru Tsubo; Kindiye Ebabu; Birhanu Kebede; Mulatu Liyew Berihun; Misganaw Walie; Shigdaf Mekuriaw; Tsugiyuki Masunaga

doi:10.1016/j.scitotenv.2021.147450

Exploring the variability of soil nutrient outflows as influenced by land use and management practices in contrasting agro-ecological environments

Sci Total Environ. 2021 Sep 10:786:147450. doi: 10.1016/j.scitotenv.2021.147450. Epub 2021 Apr 30.

Affiliations

¹ College of Agriculture and Environmental Sciences, Bahir Dar University, Bahir Dar, Ethiopia; Amhara Region Bureau of Agriculture, Bahir Dar, Ethiopia. Electronic address: tommm2008@gmail.com.
² College of Agriculture and Environmental Sciences, Bahir Dar University, Bahir Dar, Ethiopia.
³ Arid Land Research Center, Tottori University, 1390 Hamasaka, Tottori 680-0001, Japan.
⁴ International Platform for Dryland Research and Education, Tottori University, 1390 Hamasaka, Tottori 680-0001, Japan.
⁵ College of Agriculture and Environmental Sciences, Bahir Dar University, Bahir Dar, Ethiopia; The United Graduate School of Agricultural Sciences, Tottori University, 4-101 Koyama-Minami, Tottori 680-8553, Japan.
⁶ Faculty of Civil and Water Resources Engineering, Bahir Dar Institute of Technology, Bahir Dar University, Bahir Dar, Ethiopia.
⁷ College of Agriculture and Environmental Sciences, Bahir Dar University, Bahir Dar, Ethiopia; Amhara Region Agricultural Research Institute, Andassa Livestock Research Center, P.O. Box 27, Bahir Dar, Ethiopia.
⁸ Amhara Region Agricultural Research Institute, Andassa Livestock Research Center, P.O. Box 27, Bahir Dar, Ethiopia.
⁹ Faculty of Life and Environmental Science, Shimane University, Shimane, Matsue 690-0823, Japan.

PMID: 33965819
DOI: 10.1016/j.scitotenv.2021.147450

Abstract

Improving our understanding of how different land uses and management practices affect soil nutrient outflows in sub-Saharan Africa could aid in developing sustainable practices. The objective of this study was to analyse the variation in outflows of soil total nitrogen (TN) and available phosphorus (P_av) as influenced by land use types (cropland, grazing land, and bushland) and land management practices (soil bunds for cropland and exclosures for non-croplands) in the three contrasting agro-ecological zones of the Upper Blue Nile basin, Ethiopia. Field data were collected for TN and P_av outflows by water erosion (Eo), leaching (Lo), product harvest (Ho), and gaseous emissions (Go) from 18 runoff plots (30 m × 6 m) for two years (2018-2019). TN and P_av losses significantly varied (p < 0.05, p < 0.01) among agro-ecological zones, land use types, and management practices. Losses of TN ranged from 39.6 to 55.5 kg ha^-1 yr^-1 and those of P_av from 4.1 to 5.9 kg ha^-1 yr^-1, with a total replacement cost of US$26-38 ha^-1 yr^-1. Nutrient losses and cost generally increased from lowland (Dibatie) to midland (Aba Gerima) to highland (Guder), although the highland and midland sites did not differ significantly (p > 0.05) in nutrient losses. Cropland showed significantly higher TN and P_av losses than other land use types, but TN loss did not differ significantly between grazing and bushland. In all land use types at all sites, the magnitude of nutrient losses was Ho >Eo >Lo >Go. In plots with land management practices, TN and P_av losses associated with Eo, Lo, and Go were reduced on average by 44-76%, 9-47%, and 1%-36%, respectively. These practices were most effective to reduce Eo nutrient losses. Further study is required to analyzing the soil nutrient balance and identify priority areas for implementing mitigation measures.

Keywords: Drought prone; Ethiopia; SLM practices; Soil nutrient losses; Upper Blue Nile basin.