Soil Physicochemical Properties under Selected Avocado Cultivars in Ethiopian Smallholder Agroforestry

This study investigated the impact of three avocado cultivars on selected soil physicochemical properties in Central Ethiopia, to enhance the knowledge on the influence of avocado cultivars on soil physicochemical properties, and assist smallholders in cultivar selection in agroforestry. Trees planted in farmers´ fields 8 years earlier were revisited. Soil samples were collected from 0–20 cm and 20–40 cm depth at three radial distances from trees (1 m and 2 m from tree trunk, and at 5 m from the canopy edge as a control). Soil texture, bulk density, moisture content, pH, electrical conductivity, soil organic carbon, total nitrogen and available phosphorus were determined. Soil moisture content and electrical conductivity were overall higher and bulk density was lower (p < 0.05) under the canopies of the avocado trees than in the control and soil organic carbon, total nitrogen and available phosphorus tended to increase in spite of nutrient inputs to the control whilst the trees were unfertilized. Differences between the studied cultivars were small, but Hass tended to have the largest impact on soil nutrient levels, whilst Ettinger and Nabal tended to have a somewhat larger effect on the soil organic carbon concentration. Integrating these avocado cultivars on farms can improve soil fertility in the study area. However, for optimal agricultural soil health and sustainable avocado production, cultivar and site-specific soil management practices must be applied.