Sweet potato is among the most important tuberous root crops produced in Ethiopia. However, the yield is far below its potential due to poor agronomic management practices among which poor soil fertility and lack of improved varieties are the major one. A field experiment was conducted to evaluate the influences of different rates of phosphorus (P) on belowground yield of sweet potato varieties in Boloso Sore, Southern Ethiopia during the main cropping season (March to June)of 2016. The treatments consisted of three sweet potato sweet potato varieties (Awassa-83, Kulfo and Local) and five levels of P (0, 10, 20, 30 and 40 kgPha-1). The experiment was laid out in randomized complete block design with three replications. The interaction effect of varieties and P rates was significant on tuber yield of sweet potato. Significantly the highest marketable (30.22 t ha-1) and total tuber (33.57 t ha-1) yield were obtained at 30 kg P ha-1 from variety Awassa-83 and lowest marketable yield (6.57 t ha-1) and total tuber yield (8.76 t ha-1) were obtained from Kulfo at 0 kg P ha-1. The highest marginal rate of return (592.53%) was obtained at P rate of 10 kg ha-1 from variety Awassa-83. Thus, Awassa-83 variety at 10 kg P ha-1 could be suggested for the study area and similar agro-ecology.

Keywords: phosphorus, varieties, root yield, root dry weight