Title: The effects of applying a combination of bio-slurry and inorganic fertilizers on teff yield and soil properties in the highlands of northern Ethiopia

An investigation on the effects of bio-slurry on teff production and soil properties in combination with inorganic N and P fertilizers was carried out at Mekelle University main campus in Tigray region, northern Ethiopia during the 2020 crop season. The experiment was a randomized complete block design with treatments comprising two levels of inorganic N (23, 46 kg N/ha), two levels of inorganic P (23, 46 kg P/ha) and two levels of slurry (9, 12 tons/ha) including control with no fertilizers and the two levels of bio-slurry alone, set to a total of 11 treatment combinations with three replications. The soil at the study area was a degraded Cambisol and the site had been fallowed for long period of time. Various plant and soil parameters were measured during the experiment and post harvesting, and the treatment effects statistically evaluated. The fertilizer treatments significantly influenced the above-ground biomass growth, straw, and grain yield, and affected soil bulk density, soil moisture content and available phosphorus. However, soil electrical conductivity, soil organic carbon, total nitrogen, cation exchange capacity, exchangeable bases, and soil pH did not show significant variation with treatments. In general, teff biomass, straw and grain yield and number of tillers rose as the combined fertilizer dose increased. A significant difference of between 9 and 12 tons/ha of applied bio-slurry was found only where the highest levels of inorganic nitrogen and phosphorus fertilizer were used. Soil bulk density was reduced while soil moisture content increased due to bio-slurry application. Treatments either with the highest level of inorganic phosphorus or bio-slurry, or both combined applications, significantly increased available phosphorus, compared to other treatments. In general, application of combined bio-slurry with inorganic fertilizers shows promise in increasing yield of teff and an improvement of soil characteristics of degraded soils.