Determining the Agronomic Potential of Avocado-seed Biochar in Comparison to Other Locally Available Biochar in Ethiopia

The primary objective of this study was to compare the physicochemical characteristics of six biochar types made from four feedstock and two pyrolysis temperatures (450 and 550°C), based on selected parameters relevant to reclaiming degraded agricultural soil. Biochar is a promising option for improving soil fertility and agricultural productivity. Biochar from avocado seed (municipal waste) had better quality in terms of biochar production, and key agronomic parameters. The potential of biochar for specific purpose depends on its physicaland chemical characteristics. Avocado seed is widely available as a leftover after the fleshy part is used for food and as a byproduct of avocado-oil producing agro-industries in Ethiopia. Its potential as a biochar for agronomic purpose has not been studied. This study was conducted in Sidama National Regional State,located at 275 km South of Addis Ababa, the Ethiopian capital. It was identified that on a mass-base, the produced biochar yields were in a range of 29.68 to 47.45%, higher for ASB pyrolyzed at 450°C. The scanned images of the biochar types showed a remarkable surface morphology for bamboo biochar (BB) and ASB. The bulk density of the biochars were in the range of 0.21 to 0.49 g/mL. The highest volatile matter and ash content was measured for BB-450°C, fixed carbon for BB-550°C. The mean pH values were in the range of 9.1 to 11.3. The ASB-450 and 550°C exhibited higher nutrient content. The highest cation exchange capacity (CEC) was recorded for ASB-450°C; organic carbon (OC) for corncob biochar(CCB) followed by ASB-450 and 550°C. The calcium carbonate (CaCO3) content of ASB-550°C was the second-highest value next to coffee husk biochar (CHB). In this study, ASB and BB were found to have important qualities for improving degraded agricultural soils in terms of soil acidity, nutrient content and soil fertility. Therefore, ASB-450°C and BB-450°C can be suggested to be promising candidates for reclaiming acid-soils and for improving nutrient-depleted infertile soils into agriculturally productive soils. The application of avocado seed biochar to a soil is an alternative strategy that improves soil physicochemical properties and the soil functioning as a component of the ecosystem as well as the whole environment on a sustainable basis.