Abstract
Field experiment was conducted during the 2019 irrigation season to evaluate the growth and tuber yield responses of potato varieties in the highlands of Ethiopia. The treatments consisted of four potato varieties (Belete, Shonkolla, Gudanie and Local) and three seed tuber sizes (small (31.5 ± 2.5 g), medium (57 ± 2.5 g) and large (77.5 ± 2.5 g). The experiment was laid out in factorial arrangement using randomized complete block design with three replications in factorial arrangement. The results showed that, variety and seed tuber size in their main effects significantly influenced almost all the tested parameters of potato. Tuber size and variety also interact to influence days to 90% maturity, plant height, large-sized tuber yield, marketable and total tuber yields. Large-sized seed tubers of Belete and Gudanie varieties recorded the highest marketable tuber yields of 39.13 t ha(-1) and 38.63 t ha(-1), respectively while the lowest (12.12 t h(-1)) was recorded from local variety planted using small-sized seed tubers. Large-sized seed tubers of Gudanie variety gave the highest net benefit (131,376.50 ETB ha(-1)) with unacceptable marginal rate of return (<100%) while Belete variety with small-sized seed tubers recorded the highest marginal rate of return (1657.14%) with relatively lower net benefit. Optimizing the seed tuber size is therefore necessary to increase productivity and profitability of potato production. In this regard, Gudanie variety combined with medium-sized seed tuber recorded relatively higher net benefit (123,410.80 ETB ha(-1)) with acceptable marginal rate of return (100.9%). Accordingly, production of Gudanie variety using medium-sized seed tubers (57 ± 2.5 g) could be recommended for the economical production of potato and improvement of the income and food security of the smallholder farmers in the study area and areas with similar agro-ecologies.