Assessment of long-term soil dynamics at manured fields with field measurement and interviews: a case study in the semi-arid Ethiopian Rift Valley

Abstract

ABSTRACTAssessment of long-term (more than 20 years) soil fertility dynamics is rare in Sub-Saharan Africa (SSA). It is because soil quality assessments have been conducted in research stations, which are difficult to continue in the long term mainly due to lack of funds in SSA. Farmers in the semi-arid Ethiopian Rift Valley (NERV) cultivate maize with long-term manure application to the fields (aradas). The history of manure application was carefully ascertained from farmers, and 40 manured aradas for 20 years and more and 40 unmanured fields were selected. Soil chemical properties (SOC, total N, Olsen P, CEC, exchangeable cations, EC, and pH) were analyzed, while on-site NO3-N and soil physical properties (soil compaction, saturated hydraulic conductivity, and water retention capacity) were measured. The manured aradas increased SOC, total N, P, CEC, K, Na, Mg, EC, and NO3-N and lowered Ca and pH. The arada soils lowered soil compaction and bulk density and increased porosity. No consistent changes in hydraulic conductivity and water retention capacity were observed, probably because of plough pans underlying the surface soil layer across NERV. Soil quality assessment to diagnose farmers’ long-term manure application based on field measurement and interviews can be an appropriate approach in SSA.