Agronomic performance of sweet potato with different potassium fertilization rates

Abstract

Sweet potato is a vegetable with great potential due to its versatility of use, which covers human food, animal feed and biofuels. However, it is still little studied, especially regarding mineral nutrition and potassium. Thus, a study was conducted to evaluate potassium fertilizer doses (0, 30, 60, 90, 120 and 150 kg/ha K 2 O) on mineral nutrition and yield of 'Beauregard' sweet potato in a typic Hapludult soil with low K level (0.3 mmol c /dm 3 ). The experimental design was of randomized blocks with four repetitions. Harvest took place 123 days after seedling transplanting. Foliar K content, shoot, root and total dry matter, root total yield, root commercial yield, K accumulation, K content in the soil and K optimal economic dose were assessed. The highest foliar K content was observed at the dose of 100 kg/ha K 2 O, with K value of 44.6 g/kg on leaf dry matter. In soils with low K availability, the highest yield (38 t/ha) was observed at the dose of 87 kg/ha K 2 O. Maximum commercial yield (24.3 t/ha) was obtained at the dose of 85 kg/ha K 2 O, and K accumulation of 150 kg/ha in the shoot and 57 kg/ha in the root, respectively, were observed (72.5 and 27.5%). Optimal economic production was of 71 kg/ha K 2 O, which corresponds to 83% of the dose that maximized commercial production.

Sweetpotato responses to potassium rate and timing in tropical sandy soils

“…The application of 240 and 183 kg ha −1 K 2 O divided between plantings plus 3 MP also provided yields similar to treatments with three K application times, and the response to K application rates was greater when the K application was split. When K application occurred exclusively at planting, other studies also reported a lower response of sweetpotatoes to K rates in K‐deficient soils (Cecílio Filho et al., 2016; Nascimento et al., 2019). According to Nogueira et al.…”

“…Brazilian guidelines for sweetpotato fertilization in K‐deficient soils recommend K application rates between 90 and 120 kg ha −1 K 2 O (Casali, 1999; Echer et al., 2015; Lorenzi et al., 1997; Silva et al., 2002). However, in Brazilian K‐deficient soils, positive productive responses of sweetpotatoes were observed up to 85 kg ha −1 K 2 O when K fertilizer was applied exclusively at planting (Cecílio Filho et al., 2016; Nascimento et al., 2019), and positive responses were observed up to 174–180 kg ha −1 K 2 O when K was split applied (Brito et al., 2006; Nogueira et al., 1992). However, in the case of K‐deficient soils, our results showed that if K fertilization was split applied three times, the total and marketable sweetpotato root yield increased up to 153 and 179 kg ha −1 K 2 O, respectively, with no further response to higher K application rates.…”

“…greater when the K application was split. When K application occurred exclusively at planting, other studies also reported a lower response of sweetpotatoes to K rates in K-deficient soils (Cecílio Filho et al, 2016;Nascimento et al, 2019). According to Nogueira et al (1992), K splitting in K-deficient soils is more important than other management practices in increasing storage root yield, especially when the K fertilizers were divided three times (planting plus 2 and 4 MP).…”

“…In contrast, our study showed that split K application less frequently produced larger roots (greater weight) when compared to the exclusive application at planting. However, some studies indicate that the use of high rates of saline fertilizers (such as potassium chloride) in planting affects root development (Cecílio Filho et al., 2016).…”

“…K application only during the initial stage of the sweetpotato cycle may be insufficient to sustain high yields in sandy soils with a high potential for K leaching. In addition, an excessive supply of K in sweetpotato planting furrows leads to an increase in soil salinity around the roots (Cecílio Filho et al., 2016), thereby compromising the uptake of water and nutrients from the soil (Marschner, 1995). Therefore, splitting K fertilization would prevent excessive loss of K from tropical sandy soils (Rosolem & Steiner, 2017) and help reduce soil salinity around the root system.…”