Potassium rate and source effects on potato yield, quality, and disease interaction

Abstract

Field experiments were conducted over eleven site-years where five K rates (0, 93, 187, 280, and 373 kg K ha−1) as KC1 or K2SO4 were band-applied at planting to potato (Solanum tuberosum L. ). Significant yield increases up to 332 kg K ha−1 were observed in five of eleven site-years when soil test K ranged from 75 to 110 mg kg1. The increase in tuber yield was associated with an increase of tuber size (170 to 370 g) and above in the US#1A category. Lack of yield response at the other site-years may be due to the high soil test K (125 to 180 mg kg−1). Statistically significant differences in total tuber yield were not evident between the two sources of K fertilizer studied; however, there was a tendency for a significant rate x source interaction (p > 0.15) in five site-years where K2SO4 increased tuber yield more than KC1 at rates up to 280 kg K ha−1. Above this rate, tuber yield decreased for K2SO4 but remained stable for KC1. Based on the tuber yield data and initial soil test K from the controls of each site-year, data from this study suggest that 104 mg K kg−1 is a critical pre-plant soil test level.