Evaluating the Growth and Yield Response of Sweet Potato [Ipomoea batatas (L.) Lam] to Combined Application of Nitrogen and Farmyard Manure Fertilizer

Abstract

Sweet potato is the most common and valuable food security crop grown for its edible tubers in Ethiopia as well as in many other countries. Even thought the crop is the most important among the other root and tuber crop, the yield obtained from per hectare is lower due to inappropriate and poor application of fertilizer.Sweet potato requires adequate fertilizer to form good-sized tubers. Therefore, a field experiment was conducted to determine the response of sweet potato to the combined application of nitrogen fertilizer and farmyard manure in the study area. The experiment included three levels of farmyard manure (0, 5, and 10 t ha^-1) and four levels of nitrogen fertilizer (0, 40, 70, and 100 kg N ha^-1). The factorial combination of the treatments was laid out in a randomized complete block design with three replications. Different growth and yield parameters were collected,and analysis of variance was undertaken using SAS (version 9.3). Treatment means were separated using the least significant difference at 5% level of probability. The results showed that the interaction effect between nitrogen fertilizer and farmyard manure significantly (P <0.05) affected yield and yield components of sweet potato. The highest vine length (160.23 cm), shoot fresh weight (1009.6 g hill^-1), shoot dry weight (141.35 g hill^-1), days of bud sprouting (13.27), days of physiological maturity (147.8), number of branches per plant (7.30), harvest index (0.36%) tuber diameter (22.5 cm), total tuber yield (22.45 t/ha), marketable tuber yield (21.85 t/ha), and unmarketable tuber yield (3.25 t/ha) were recorded in plots that received 10 t ha^-1 farmyard manure and 100 kg/ha nitrogen fertilizer. The findings showed that the application of inorganic nitrogen fertilizer along with farmyard manure might improve the growth, production, and yield components of sweet potato. However, as the experiment was conducted for only one season at one location, it needs to be undertaken at different locations and times to reach a conclusive result.