“…The Brazilian guidelines recommend only 120 kg ha −1 K 2 O for K‐deficient soils; for soils with medium or high exchangeable K concentrations, the suggested rates are 90 and 60 kg ha −1 K 2 O, respectively (Casali, 1999; Echer et al., 2015; Lorenzi et al., 1997). Under low or medium soil K availability, K fertilization increases sweetpotato root yield (Brito et al., 2006; Gao et al., 2021; George et al., 2002; Nogueira et al., 1992, Wang et al., 2020), but a negative response to K fertilization can occur in soils with high exchangeable K concentrations. However, some studies on sweetpotato yield in tropical sandy soils have shown a positive response to K fertilization, even in soils with medium to high exchangeable K concentrations (Corrêa et al., 2018; Echer et al., 2009a; Foloni et al., 2013).…”