Carotene Yield in Sweet Potato After Potassium and Phosphorus Fertiliser Application

Abstract

Sweet potato is one of the most important foods in the world. Among the different cultivated genotypes, it is worth highlighting those with orange pulp due to their ability to supply adequate amounts of provitamin A carotenoids to humans. This study evaluates the effect of potassium and phosphorus fertiliser application on carotenoid yield in sweet potatoes. Two experiments were carried out in São Luis City, Maranhão State, Brazil. The experimental design was a randomised block design, with six treatments for each of the studies (0, 30, 60, 90, 120 and 150 kg ha-1 K2O and 0, 60, 120, 180, 240 and 300 kg ha-1 P2O5), with four replicates. Cultivar 'Beauregard' was used, which has high levels of carotenoids. Roots were harvested at 123 days after planting for both experiments. The following variables were evaluated: root fresh and dry weight, dry weight content, in addition to the yield and contents of total carotenoids, α-carotene, β-carotene, 13-cis β-carotene and 9-cis β-carotene. With the average data of the evaluated characteristics, we performed analysis of variance and polynomial regression analysis. Potassium rates influenced carotenoid yield in sweet potato roots, with the rates of 73 to 77 kg ha-1 K2O being recommended to maximise the production of total carotenoids, β-carotene, and α-carotene. Phosphorus, in turn, influenced only total carotenoids, and is recommended at the rate of 174.09 kg ha-1 P2O5 to maximise the production of these nutrients.

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).…”

Chemical quality and bioactive compounds of sweet potatoes under phosphate fertilization

“…The influence of P doses can be explained by the fact that phosphorus is a component of pyrophosphates, which are essential intermediate constituents in the biosynthesis of carotenoids important for the color of fruits, causing an increase in carotenoid content (Li et al, 2022). Nascimento et al (2019) observed that P influenced the content of total carotenoids in the Beauregard sweet potato cultivar, with a recommended P 2 O 5 dose of 174.09 kg ha -1 . Cordeiro et al (2023) mentioned that soils with P concentration < 5.0 mg dm -3 require 68 kg ha -1 of P for maximum production of sweet potato, showing similarity for some variables in the present study, since the P concentrations here were 4.20 and 2.37 mg dm -3 , respectively, for depths of 0-0.20 m and 0.20-0.40 m, that is, P < 5.0 mg dm -3 .…”