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Rebahlotse Mapula Moloto Lesiba Harry Moremi Puffy Soundy 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2018,68(7):575-584
Deficiencies of vitamin A, iodine, iron and zinc (Zn) in humans are caused partly by the consumption of food that has insufficient quantities of these. Their deficiency has a negative impact on the health, wellbeing, social and economic status of human beings. A national survey conducted in 2012 identified deficiencies of vitamin A, Fe, and Zn among other nutrients in South Africans and regarded the deficiencies of vitamin A and Fe as a moderate but not Zn. This review discusses causes of Zn prevalence in low-income South Africans and that it is largely caused by the low content of Zn in their diets. Initiatives to reduce Zn deficiency include fortification of wheat products and maize meal which has failed to address it successfully. Weaknesses of fortification include high cost of fortified food products to low-income populations, poor regulation in ensuring compliance in fortification, non-fortification of sorghum meal, and leaching of fortified nutrients during processing. This review suggests Zn-biofortification of locally-preferred common bean cultivars as an alternative strategy to compliment fortification. The review also discusses advantages of adopting biofortified Nutritional Andean common beans. Furthermore, the review suggests initiatives including evaluation of the common bean genotypes’ adaptation to different agro-ecologies. 相似文献
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Effective irrigation management in arid and semi-arid regions, like South Africa, could increase crop yield and thereby improve productivity of scarce fresh water resources. Experiments were conducted at the Hatfield Experimental Farm of the University of Pretoria, South Africa, from 2004 to 2006, to investigate the effect of soil water depletion regimes on rose-scented geranium (Pelargonium capitatum × P. radens cv. Rose) essential oil yield, essential oil composition and water-use efficiency in an open field and a rain shelter. Four maximum allowable soil water depletion levels (MAD), 20, 40, 60 and 80% of the plant available soil water (ASW) in the top 0.8 m root zone, were applied as treatments. Plant roots extracted most soil water from the top 0.4 m soil layer. Increasing the soil water depletion level to 60% and higher resulted in a significant reduction in herbage mass and essential oil yield. Water stress apparently increased the essential oil concentration (percentage oil on fresh herbage mass basis), but its contribution to total essential oil yield (kg/ha oil) was limited. Irrigation treatments did not affect essential oil composition. An increase in maximum allowable depletion level generally resulted in a decrease in leaf area and an increase in leaf to stem fresh mass ratio. Up to 28% of irrigation water could be saved by increasing maximum allowable depletion level of ASW from 20 to 40%, without a significant reduction in essential oil yield. 相似文献
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A field study was conducted to evaluate the nitrogen status and yield of spinach grown in soils amended with prunings of Leucaena leucocephala, (applied at a rate of 3, 5, 7 or 11 t ha?1). A ‘no fertilizer’ 0 nitrogen (N) and 150 kg N ha?1 (recommended) were the control treatments. SPAD readings were recorded for the top six leaves. Nitrogen sufficiency indices were used to indicate the N status of plants. Application of L. leucocephala prunings increased spinach yields (8.98–13.86 t DM ha?1) relative to the 0N treatment (1.35 t DM ha?1) and yields increased with increasing rate of pruning application. SPAD readings showed a linear increase with the increase in applied prunings. There was preferential distribution of N to upper leaves. The relationship between shoot N concentration and SPAD readings was linear and strongest for the top three leaves (r2 = 0.84–0.92). The results indicate the potential of chlorophyll meter readings in assessing N status of leafy vegetables grown on soils amended with different levels of legume tree prunings. 相似文献
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Utilization of nitrogen(N) element is a common practice used to reach profitable yields in horticultural crops and N supply can be used as a tool to manipulate the enhancement of phytochemicals and minerals in vegetable crops to address consumeroriented quality production. Hence the study was aimed to investigate the effect of N application on leaf morphology, ascorbic acid content, phenolic acids, flavonoids, mineral content, and nitrate residues in three lettuce varieties(two green leafy lettuce, Multigreen 1 and Multigreen 3; one red leafy lettuce, Multired 4) grown in a closed hydroponic system(gravel-film) at harvest. Nitrogen was applied as ammonium nitrate(NH_4 NO_3) at six different concentrations of 0, 60, 90, 120, 150 and 180 mg L~(–1). The results obtained during 2015 and 2016 seasons were similar and demonstrated variety dependent responses with respect to different N application rates. Multigreen 3 was more sensitive to N supply and showed higher amount of nitrate residue at harvest. Variety Multired 4 was less sensitive to N supply followed by Multigreen 1. Although N supply at 120 mg L~(–1) improved the yield and the number of leaves in Multigreen 3, overall 90 mg L~(–1) can be recommended for these lettuce varieties to improve the yield and the accumulation of ascorbic acid content, phenolic acids mainly caffeic, caftaric acids, quercetin(the important flavonoid in lettuce), and Fe and Mn contents. Furthermore, the concentration of 90 mg L~(–1) improved the antioxidant property(FRAP and ABTS~+) and reduced the nitrate accumulation, ensuring safe food for consumers. 相似文献
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Madonna N. Mashabela Martin Maboko Puffy Soundy 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2019,69(6):503-510
Application of nitrogen (N) is a common practice used to achieve profitable yields in horticultural crops and N application can be used as a tool to manipulate the enhancement of phytochemicals in vegetable crops to address consumer-oriented quality production. Our previous findings recommended 90?kg?ha?1 for certain types of cauliflower varieties without compromising yields. Thus, this study was aimed to investigate the effect of N application on glucosinolates and phenolic acids, at harvest, in varieties ‘Largardo’, ‘Eskimo’ and ‘CF-744’ grown in the field. N was applied as ammonium nitrate (NH4NO3) at concentrations from 0, 60, 90, 120, 150 to 180?kg?ha?1. Variety ‘CF-744’ was more sensitive to N supply and at 180?kg?ha?1 N it showed the highest accumulation of glucosinolates (sinigrin, glucoiberin, progoitrin, 4-methoxyglucobrassicin) at harvest. However, 90?kg?ha?1 N supply demonstrated the highest accumulation of majority of the glucosinolates in varieties ‘Largardo’ and ‘Eskimo’. Different varieties responded differently to N supply and glucosinolate levels in cauliflowers. Also, different varieties responded differently to N supply and antioxidant property. In all three varieties, the N supply at 120?kg?ha?1 showed the highest accumulation of protocatechoic acid, 4-hydroxy benzoic acid, ρ-coumaric acid and caffeic acid. 相似文献
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Limited information is available on the influence of preharvest N application rates on postharvest quality of different lettuce genotypes. Two green leafy lettuce(Multigreen 1 and Multigreen 3) and red leafy lettuce(Multired 4) were grown in gravel film technique and fertigated with five different N application rates: 60, 90, 120, 150 and 180 mg L~(–1). The 120 mg L~(–1) N application is commercially recommended for lettuce. After harvest, lettuce samples were packed in a bioriented poly propylene packaging(5% O_2 and 5% CO_2) and held at 5°C and 85% RH for 3, 6, 9 and 12 days. The genotypes, preharvest N application rates and storage time affected the leaf colour coordinates, phenolic acids(dicaffeoyltataric acid, caffeoyl tartaric acid, 3-caffeoylquinic acid and 3,4-dihydroxycinnamic acid) and browning enzyme activities(phenylalanine ammonia-lyase(PAL), polyphenol oxidase(PPO) and peroxidase(POD)). Lower rates of N application at preharvest stage showed higher weight loss with the storage time increasing in Multigreen 3. In Multigreen 1, colour coordinate b* value decreased remarkably with N application rates from 60 to 120 mg L~(–1) due to the onset of browning during storage. While in Multigreen 3 and N application higher than 60 mg L~(–1) influenced the decrease in b* value. Browning occurred due to the increased activity of PAL enzyme and the availability of the substrates caftaric, chlorogenic, caffeic acids, PPO activity and production of browning pigments due to the activity of POD. Higher, N application rates(120 mg L~(–1)) influenced the browning mechanism and showed brownish red leaves in Multired 4 during storage. Higher ascorbic acid concentration played a role in reducing the onset of browning in the fresh cuts leaves of Mulitired 4 and Multigreen 3 fertilized with lower preharvest lower N application rates(120 mg L~(–1)). Preharvest N application at 90 mg L~(–1) retained the colour, ascorbic acid content and the phenolic acid components and extended the shelf life of Multired 4 lettuce up to 6 days. 相似文献
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Madonna N. Mashabela Martin M. Maboko Puffy Soundy 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2018,68(6):541-545
The influence of five nitrogen (N) application rates (60, 90, 120, 150 and 180?kg?N/ha) were evaluated using limestone ammonium nitrate on the curd fresh and dry mass, size, chromaticity coordinates, L*, a*, b* and ascorbic acid content in cauliflower varieties (Largardo, Eskimo and CF-744) during the 2015 and 2016 seasons. Commercial standard 120?kg?N/ha was included as a control. Variety ‘Largardo’ showed weak response to N application rates and can be regarded as the least sensitive variety for lower N use. Curd fresh and dry mass and size were not affected at lower N application rates of 60 and 90?kg/ha in ‘Largardo’ compared to the other two varieties. However, L*, b* colour value and ascorbic acid content was higher at lower N application rates <90?kg?N/ha in all three varieties. With increasing N application rates, curd became darker and less intense in yellow colour. Increasing rates of N application clearly posed a negative effect on ascorbic acid content. Therefore, ‘Largardo’ can be recommended as a suitable variety that produces higher yield and ascorbic acid content at 60 or 90?kg?N/ha, with the application rates lower than the commercially recommended rate (120?kg?N/ha). 相似文献
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Lucia L.M. Ntsoane Puffy Soundy John Jifon 《The Journal of Horticultural Science and Biotechnology》2016,91(5):520-528
This study illustrates the effects of light quality as influenced by photo-selective shade nets (red, yellow, and pearl with 40% shade) and the widely used commercial black net (25% shade) on overall retail quality and phytochemical contents of three lettuce (Lactuca sativa L.) varieties (two green varieties, Ashbrook and Aquarell, and a red variety, Exbury) at after postharvest storage. Variety-specific responses were observed with respect to different coloured shade nets with regards to the accumulation of β-carotene, ascorbic acid, flavonoids (kaempferol, isorhamnetin, quercetin, myricetin, anthocyanin), and antioxidant activity at harvest. Growing var. Ashbrook under the pearl net improved the ascorbic acid and myricetin contents after postharvest storage. Var. Exbury (red) produced under the black net showed higher retention of ascorbic acid, and anthocyanin contents after postharvest storage. Also pearl net production improved the β-carotene content after postharvest storage in var. Aquarell. All lettuce types produced under the pearl nets showed less weight loss, and overall acceptance after postharvest storage. Spectral quality under the shade nets enabled us to improve the phytochemical content and antioxidant properties in light-sensitive varieties Ashbrook Aquarell and Exbury, during winter season. 相似文献
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The objective of this study was to determine the effect of nitrogen fertilization rate on growth and quality of leafy lettuce grown during the winter season in non-circulating hydroponic system. Plants were subjected to seven nitrogen (N) concentrations, i.e. 0, 30, 60, 90, 120, 150 and 180 mg L?1 N using ammonium nitrate. Nitrogen treatments did not have a significant effect on leaf fresh and dry mass, root fresh and dry mass, number leaves and leaf area. Leaf ascorbic acid and total phenolic content, and antioxidant capacity peaked at 100 and 120 mg L?1 N, whereas leaf chlorophyll concentration linearly increased with increasing N application. The results indicate that a solution N concentration of 100 and 120 mg L?1 may be sufficient to improve growth, yield and quality parameters of leafy lettuce grown in non-circulating hydroponic system. 相似文献
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