Department of Crop Sciences - Research Articles

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    Impacts of calcium cyanamide application as a nitrogen source on growth, yield, quality, and storage durability of short-day onion.
    (American Society for Horticultural Science, 2024-05-30) Simelane, Mzwakhile Petros Zakhe; Soundy, Puffy; Maboko, Martin Makgose
    Rapid leaching of soluble nitrogen (N) sources in soil poses a significant challenge in agricultural practices. Therefore, gaining a comprehensive understanding of crop responses to slow-release N application rates has become crucial to contributing valuable insights to optimize N management strategies in agriculture. A field study was conducted to investigate the influence of preplant calcium cyanamide fertilizer on the growth, yield, quality, and shelf life of short-day onion. Six levels of calcium cyanamide (CaCN2, 19.8% N), 0, 90, 120, 200, 400, and 600 kgha21 CaCN2, which are equivalent to 0, 17.82, 23.76, 39.6, 79.2, and 118.8 kgha21 N, respectively, replicated four times were broadcasted and incorporated into the top 5 to 10 cm of soil. Using 400 kgha21 of CaCN2 yielded noteworthy improvements in various parameters of onion growth, such as plant height, leaf count, bulb weight per plant, bulb diameter, bulb length, and overall plant weight, as indicated by the study results. The application of different levels of CaCN2 as an N source exerted a significant influence on these growth factors. Moreover, the study revealed a direct correlation between CaCN2 application levels and the storage life of onions. Specifically, the findings demonstrated that the application of 400 kgha21 CaCN2 resulted in enhanced yield and overall onion plant growth. However, the application of 600 kgha21 CaCN2 increased the incidences of bulb weight loss, rots, and sprouting during the 8-week storage period at room temperature. These findings provide valuable insights for onion investors and farmers in the region and offer practical recommendations for optimizing fertilizer use and storage practices to improve onion production and minimize postharvest losses.
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    Cooking African pumpkin leaves (Momordica balsamina L.) by stir-frying improved bioactivity and bioaccessibility of metabolites—metabolomic and chemometric approaches.
    (MDPI, 2021-11-22) Mashiane, Petunia; Manhivi, Vimbainashe E.; Shoko, Tinotenda; Slabbert, Retha M.; Sultanbawa, Yasmina; Sivakumar, Dharini
    The leaves of African pumpkins (Momordica balsamina L.) are a commonly consumed traditional vegetable. They are a good source of polyphenolic antioxidants and carotenoids, which are, however, affected by cooking or digestion. We investigated the effect of household cooking methods (stir-frying or boiling) on the changes in bioactive metabolites, antioxidant capacity, release and accessibility of -carotene and also inhibition of inhibitory activity against -amylase and glucosidase enzymes during in vitro digestion of African pumpkin leaves compared to the raw leaves. Compared to boiled or raw leaves, stir-frying improved the availability of bioactive metabolites at the gastrointestinal phase. Quercetin 3- galactoside and rhamnetin 3-O-glucoside (marker compounds) discriminated the stir-fried leaves from raw leaves and boiled leaves after digestion. Stir-frying improved the release and accessibility of -carotene and enhanced the antioxidant activities compared to boiling. Dialysable fractions of stir-fried leaves exhibited the greatest inhibitory activity against - amylase and -glucosidase enzymes compared to the raw and boiled leaves, as well as acarbose. Stirfrying, therefore, is recommended for use in household cooking to benefit consumers by increasing the intake of phenolics and -carotene.
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    Co-Ingestion of Natal plums (Carissa macrocarpa) and marula nuts (Sclerocarya birrea) in a snack bar and its effect on phenolic compounds and bioactivities.
    (MDPI, 2022-01-04) Manhivi, Vimbainashe E.; Slabbert, Retha M.; Sivakumar, Dharini
    This study investigated the effect of co-ingesting Natal plums (Carissa macrocarpa) and Marula nuts (Sclerocarya birrea) on the bio accessibility and uptake of anthocyanins, antioxidant capacity, and the ability to inhibit -glucosidase. A Natal plum–Marula nut bar was made by mixing the raw nuts and the fruit pulp in a ratio 1:1 (v/v). The cyanidin-3-O-sambubioside (Cy-3-Sa) andcyanidin-3-O-glucoside content (Cy-3-G) were quantified using the ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF-MS). Inclusion of Natal plum in the Marula nut bar increased the Cy-3-Sa, Cy-3-G content, antioxidants capacity and -glucosidase inhibition compared to ingesting Marula nut separately at the internal phase. Adding Natal plum to the Marula nut bar increased bio accessibility of Cy-3-Sa, Cy-3-G, quercetin, coumaric acid, syringic acid and ferulic acid to 80.2% and 71.9%, 98.7%, 95.2%, 51.9% and 89.3%, respectively, compared to ingesting the Natal plum fruit or nut separately.