Effects of soil and water conservation practices on soil physicochemical properties in Gumara watershed, Upper Blue Nile Basin, Ethiopia

Abstract

Background: Soil erosion is among the foremost causes of declining soil resources in Ethiopia, which in turn affect agricultural productivity. To limit this problem, for the last two decades in Gumara watershed, soil and water conservation measures have been practiced through free labor community mass-mobilization. However, their effect on soil fertility has not been evaluated. This study investigated the impact of implemented soil and water conservation measures on fertility improvement in the Gumara watershed. Both composite and core soil samples were taken from upstream, midstream, and downstream adjacent conserved and non-conserved cultivated and grazing plots. Selected soil fertility indicators were analyzed using standard laboratory procedures. Results: Soil and water conservation practices have resulted in a statistically significantly higher mean values of total nitrogen, exchangeable Na+ and Mg2+ at p < 0.01, and of soil organic carbon and organic matter at p < 0.05 in the watershed. The clay content, soil reaction, cation exchange capacity, and exchangeable K+ showed non-significant, but higher mean values in conserved plots. Furthermore, the effects of conservation practices on soil properties were found more effective in cultivated land uses as compared to that of grazing land uses. This is because conservation treatments had significant effects on organic carbon, total nitrogen, exchangeable Na+ and Mg2+ in cultivated land uses but only on exchangeable Na+ in grazing land uses. The interaction effect of treatments and land uses did not reach a statistically significant result for any of the soil properties considered in this study. Conclusion: Conservation measures have important implications for improving soil fertility in the Gumara watershed. Therefore, proper guidance and follow-up, use of agro-forestry and grass strips, and maintenance are required for the watershed’s sustainability and good soil conditions.