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.

摘要
甘薯是全球最重要的粮食作物之一。在各类栽培基因型甘薯中，橙黄色果肉品种因可为人体提供充足的维生素A原类胡萝卜素（provitamin A carotenoids）而备受关注。本研究探讨钾肥与磷肥配施对甘薯类胡萝卜素产量的影响。
本研究于巴西马拉尼昂州圣路易斯市开展两组试验，采用随机区组设计，每组试验设置6个施肥处理：分别为0、30、60、90、120、150 kg·ha⁻¹的氧化钾（K₂O）以及0、60、120、180、240、300 kg·ha⁻¹的五氧化二磷（P₂O₅），每组处理设置4次重复。试验选用类胡萝卜素含量较高的‘博雷加德（Beauregard）’品种，两组试验均在定植后123天收获块根。
本试验测定的指标包括：块根鲜重、干重、干物质含量，以及总类胡萝卜素、α-胡萝卜素（α-carotene）、β-胡萝卜素（β-carotene）、13-顺式β-胡萝卜素（13-cis β-carotene）与9-顺式β-胡萝卜素（9-cis β-carotene）的产量与含量。基于各测定性状的平均数据，本研究进行了方差分析与多项式回归分析。
结果显示，钾肥施用量对甘薯块根类胡萝卜素产量具有显著影响，推荐施用量为73~77 kg·ha⁻¹ K₂O，可最大化总类胡萝卜素、β-胡萝卜素与α-胡萝卜素的产量；磷肥仅对总类胡萝卜素产量存在显著影响，推荐施用量为174.09 kg·ha⁻¹ P₂O₅，以最大化该类营养物质的产出。