Abstract
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.
Highlights
Sweet potato (Ipomoea batatas L.) is a vegetable that is among the most important foods worldwide, especially in developing countries, where it can provide food security to the population
Considering the affirmation of Silva et al (2011), who state that it is important to know the effect of K and P fertiliser application on carotenoid behaviour and based on the hypothesis that potassium and phosphorus fertiliser application affects carotenoid contents in sweet potato roots, this study evaluated the effect of potassium and phosphorus fertiliser application on carotenoid yield in sweet potatoes
B) Root dry weight: two roots from the useful area were weighed, cut into small pieces, placed in paper bags and put to dry in an oven with forced air circulation at 65 °C until constant weight. They were again weighed and the values converted to kg m-2. c) Root dry mass content was calculated by dividing root dry weight by root fresh weight. d d) Carotenoid content: after determining root dry weight, a portion was used to quantify the levels of total carotenoids, α-carotene, β-carotene, 13 -cis β-carotene and 9-cis β-carotene
Summary
Sweet potato (Ipomoea batatas L.) is a vegetable that is among the most important foods worldwide, especially in developing countries, where it can provide food security to the population This vegetable has a great phenotypic diversity derived from its genetic constitution, since it is a hexaploid species. Isomers in the cis form appear in much lower concentrations (KOBORI et al, 2010) Among these carotenoids, β-carotene stands out, because it has a provitamin A potential higher than others have (COSTA; ORTEGA-FLORES; PENTEADO, 2001). Phosphorus, in turn, is active in respiration, photosynthesis (BAILEY et al, 2009) and nucleotide formation (DNA and RNA) When one of these elements is not present in satisfactory conditions for the plant, its deficiency generates anomalies due to changes in metabolism (SOUZA; CHAVES, 2016). Considering the affirmation of Silva et al (2011), who state that it is important to know the effect of K and P fertiliser application on carotenoid behaviour and based on the hypothesis that potassium and phosphorus fertiliser application affects carotenoid contents in sweet potato roots, this study evaluated the effect of potassium and phosphorus fertiliser application on carotenoid yield in sweet potatoes
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