Effect of potassium fertilizers doses on the growth, tuber yield, and resistance to weevil infestation of sweet potato on Latosol soil

Major problems in sweet potato (Ipomoea batatas L.) cultivation are low yield and high weevil (Cylas formicarius) infestation. The effect of potassium (K) on growth and yield has been intensively reported. However, there is less information on the correlation between K and the resistance to weevil infestation. The aim of the research was to determine the optimum dose of K fertilizers for maximum tuber yield and minimum weevil infestation Sweet potato var. Ase Kapas was planted with a K dose of 0, 45, 90, 135, and 180 kg K2O ha-1. The experiment was conducted using a randomized block design with 4 replications in January – July 2020 at Latosol soil. The experimental plot was 4m x 2m which was divided into 4 ridges. Stem cuttings were planted on the center of the ridge with a 0.20 m spacing. Variables of growth, tuber yield, and level of weevil infestation were observed at 3 weeks after planting and at harvest. There were significant quadratic responses of yield variables to the K application. It is recommended the use of 125 kg K2O ha-1 can provide the highest tuber yield and a significant reduce of weevil infestation level. At the K dose of 125 kg K2O ha-1 , tuber yield increased by 179 % (357.4 g plant-1, compared to the control of 127.9 g plant-1) and the weevil infested tuber was reduced as much as 61.6 % (from 6.46, at the control dose to 2.37 tuber plant-1).