Martin Makgose Maboko

Effect of pruning on yield and quality of hydroponically grown cherry tomato (Lycopersicon esculentum)

Abstract The commercial importance of cherry tomatoes is continuously increasing in the South African retail market, with fruit size playing an important role. The effect of pruning on yield and quality of two cherry tomato cultivars (Naomi and Josefina) with an indeterminate growth habit were investigated in an open bag hydroponic system at ARC-VOPI (25° 59’S ; 28° 35’E) Pretoria. The plants were subjected to three pruning treatments (one, two and three stems) in a complete randomized block design with three replications. Fruit were harvested at the full ripe stage and the fruit number, size and mass, marketable yield and total yield, as well as the total soluble solids (oBrix), were determined for all treatments. An increase in fruit size was evident in plants pruned to a single stem compared to plants pruned to two or three stems in both cultivars. The yield of plants increased with an increase in the number of stems. Cultivar Josefina had a significantly higher marketable yield compared to cultivar Naomi. Regardless of cultivar, pruning to two or three stems was effective in increasing yield and reducing fruit size to a size which is currently more acceptable to the market.

Comparative performance of tomato cultivars cultivated in two hydroponic production systems

Cultivar selection for different hydroponic production systems is an important management decision, potentially impacting the tomato grower’s profitability. Knowledge on the performance of tomato cultivars, in specific hydroponic systems (open-bag and closed system) under South African conditions, is still very limited. The performance of four cultivars was evaluated in an open and a closed hydroponic (gravel-film technique) system. The commonly grown cultivars evaluated in each of the two hydroponic systems were ‘FA593’, ‘Malory’, ‘Miramar’ and ‘FiveOFive’. For each experiment a randomized complete block design was used with four replicates. Total, marketable and unmarketable yields, as well as internal fruit quality characteristics (total soluble solids (°Brix) and pH) were determined. Although no significant differences in total yield could be established - neither in the open nor in the closed hydroponic system - differences in marketable yield were observed. ‘Miramar’ and ‘Five-OFive’ produced the highest marketable yield in the closed system; the high unmarketable yield of ‘FA593’ and ‘Malory’ in the closed hydroponic system could be attributed to the high number of cracked fruit due to their inherent larger fruit size. There were no significant differences in °Brix between cultivars in the closed system. Cultivar ‘FiveOFive’, ‘FA593’ and ‘Miramar’ produced higher marketable yields than cultivar ‘Malory’ when grown in the open-bag system. ‘Malory’ and ‘FA593’ produced the highest number of fruit exhibiting fruit cracking in the open bag system. In the open system, only cultivar ‘Malory’ had a higher °Brix than ‘Miramar’ and ‘FiveOFive’. The most promising cultivars for local hydroponic tomato production, with regard to yield and quality, were identified as ‘Miramar’ and ‘FiveOFive’, with ‘FA593’ performing equally in the open system only. Further studies need to be undertaken on economical comparison of the two production systems.

Effect of plant spacing on growth and yield of lettuce (Lactuca sativa L.) in a soilless production system.

Abstract Lettuce production in re-circulating hydroponic systems is done on a limited scale in South Africa with conflicting information on the recommended spacing for optimal yield and quality in such systems. The development and yield of four lettuce (Lactuca sativa L.) cultivars ‘NIZ 44–675’, ‘Nou-gatine’, ‘Tango’ and ‘Natividad’ at five different inter- and intra-row spacings namely: 10x20 (50 plants m-2), 10x25 (40 plants m-2), 15×20 (30 plants m-2), 20×20 (25 plants m-2) and 20x25 (20 plants m-2) cm were evaluated during May/June 2008. The experimental layout was a randomized complete block design and each treatment combination was replicated three times. There was a significant interaction between spacing and cultivar regarding leaf fresh and dry mass while all cultivars reacted similarly to different spacings on other yield parameters. Plant population significantly affected plant height, fresh and dry leaf mass, leaf area and leaf number m-2, with significantly higher values of all variables at the closest spacing (50 plants m-2). The results indicate that an increase in plant population results in a significant increase in yield and yield components of leafy lettuce, with all cultivars producing the highest yield at a spacing of 50 plants m- 2 during winter production. Cultivar differences observed showed that ‘NIZ 44–675’ and ‘Tango’ performed better than ‘Nougatine’ and ‘Natividad’, mostly due to higher leaf area, fresh mass, plant height and leaf number.

Arbuscular mycorrhiza has limited effects on yield and quality of tomatoes grown under soilless cultivation

Abstract A study was conducted investigating the possible utilization of mycorrhiza to enhance yield and quality of tomatoes grown in a soilless culture system using sawdust or coir as growing media. The experiment was carried out in temperature-controlled and non-temperature-controlled (NTC) tunnels. Fertigation was applied at three levels (100%, 75%, and 50%) of the recommended nutrient concentration. Mycoroot™, containing four arbuscular mycorrhizal species (Glomus etunicatum, Paraglomus occultum, Glomus clarum, and Glomus mosseae), was applied at seeding, as well as transplanting. Growing tomatoes under reduced nutrient supply reduced the total soluble solids in the juice of the fruits, but improved total and marketable yield, as well as the number of marketable fruits. This effect was more substantial in the temperature-controlled tunnel than in the NTC tunnel. Fruit firmness and leaf chlorophyll concentrations were significantly higher in plants grown in the temperature-controlled tunnel. Growing tomatoes in sawdust improved the leaf Mn and Ca concentration over that of tomato plants grown in coir. Mycorrhiza colonization did not have a beneficial effect on tomato yield and quality. Further studies, including different media, nutrient composition, and concentration need to be carried out to investigate the possible effect of AMF failing to improve yield, despite AMF root colonization, and to reveal the cause of the poor beneficial effect of AMF on tomato plants grown under soilless culture.

Effect of plant population, stem and flower pruning on hydroponically grown sweet pepper in a shadenet structure

A study was conducted in 2009/2010 and 2010/2011 to investigate the effect of plant population, flower and stem pruning of hydroponically grown peppers in a 40% (black and white) shadenet structure at the ARC-Roodeplaat VOPI. The research was done in an open bag hydroponic system with sawdust as growing medium. Pepper plants were subjected to three plant populations (2, 2.5 and 3 plant/m 2 ), three stem pruning treatments (2, 3 and 4 stems) and three flower pruning treatments (removal of first two or first four flowers or zero flower removal). Experimental layout was a randomized block design with two replicates. Sweet pepper fruits were harvested at a mature green stage. Data was collected on ten plants determining fruit number, fruit mass, unmarketable yield, marketable yield and total yield for all treatments. Stem pruning to four stems without removing any flowers at a plant population of 3 plants/m 2 resulted in the highest yield and quality. Pruning the first two or four fruits seemed to have no significant influence on yield. Results showed that sweet pepper yield and quality can be effectively manipulated by plant population and stem pruning, while flower pruning had insignificant (p<0.05) effect.

High-plant density planting of basil (Ocimum basilicum) during summer/fall growth season improves yield in a closed hydroponic system

The objective of this study was to determine the combined effect of plant densities and leaf harvesting method on yield of hydroponically grown basil. The experiment was carried out during the spring/summer (September–December 2012) and during summer/fall (January–April 2013) seasons. Basil plantlets were transplanted 30 days after seeding, utilising a gravel-film technique hydroponic system under a 40% black-and-white shadenet structure. Plants were subjected to five plant densities, i.e. 10, 16, 20, 25 and 40 plants/m2, with two harvesting methods, i.e. tipping and cutting. Experimental layout was a randomised complete block design with four replicates. During the spring/summer season, the results showed no significant differences in plant growth and total yield per unit area at plant densities of 20, 25 or 40 plants/m2. Results during the summer/fall season showed the highest leaf fresh mass, leaf area and total plant fresh mass at the highest plant density of 40 plants/m2. Harvesting method did not have a significant effect on yield or on the total fresh and dry mass of basil. Results demonstrate that a plant density of 40 plants/m2 can improve growth and yield of basil significantly during the summer/fall season. However, during the spring/summer season, a plant density of 20 and 25 plants/m2 will be more cost effective with no significant effect on yield. Plant density recommendations are, therefore, 40 plants/m2 during the summer/fall season and 20 or 25 plants/m2 during spring/summer season.

High-density planting of tomato cultivar's with early decapitation of growing point increased yield in a closed hydroponic system

Decapitation of tomato growing points results in a shortened growth season with no new flower trusses initiated thereafter. Since less flower trusses could lead to reduced yield, this study was conducted to investigate whether increased plant density could contribute to increase yield per unit area. The response of nine tomato cultivars with early decapitation of growing points at different plant densities (10, 16, 20 and 25 plants/m2) was investigated in a closed hydroponic system under a 40% white shadenet structure. The growing points of all plants were removed between the second and third inflorescence, with two leaves remaining above the second inflorescence. Fruit physiological disorders, number of fruits, as well as total and marketable yield were recorded. Cultivar ‘Miramar’, gave the highest marketable and total yield, followed by cultivars ‘Rodade’ and ‘Alfar’. Cultivars ‘Alexis’, ‘Star9006’ and ‘Zeal’ produced highest average fruit mass compared to other cultivars. There was no significant interaction effect between cultivars and plant densities on tomato yield. Fruit cracking was significantly higher for ‘Linares’ and ‘Star9006’, while raincheck was higher for cultivars ‘Alexis’ and ‘FA593’. ‘Rodade’ showed high incidence of zippering. Plant densities of 20 or 25 plants/m2 produced significantly higher marketable and total yield, while plant densities of 10 or 16 plants/m2 resulted in higher average fruit mass and highest incidence of fruit cracking. Nutrient uptake, as revealed in the mineral content of fruit, was not affected by plant density. Cultivar ‘Rodade’, an open-pollinated determinate cultivar, especially shows potential to compete with more expensive hybrid cultivars in such a production system in terms of yield. Results demonstrate that high-density planting of tomato with decapitated growing points increased yield per unit area in a closed hydroponic system.

Yield and nutritional quality of different short-day onion cultivars as affected by nitrogen application

Onion is one of the most important vegetable crops in the world, cultivated and consumed for its flavour-enhancing and medicinal properties; hence, comprehensive understanding of crop responses to N application is of immense importance. To determine the effects of different nitrogen (N) levels on yield, quality and mineral content of onion, four short-day onion cultivars (‘Mata Hari’ [red onion], ‘Mikado’ [brown onion], ‘Cristalina’ [white onion] and ‘Star 5516’ [brown onion]) were subjected to six different N levels (0, 30, 60, 90, 120 and 180 kg ha−1). Application of 180 kg N ha−1 significantly increased total yield (46.51 t ha−1), whereas no N application resulted in poor yield (15.35 t ha−1). ‘Star 5516’ produced the highest marketable and total yield compared with the other cultivars, and ‘Mata Hari’ had the lowest marketable yield, possibly due to higher bolting percentage. An increase in N application resulted in an elevation of N, magnesium, manganese, zinc and sulphur concentrations in bulbs. Bulbs of the red onion cultivar had higher N, phosphorus, calcium, sodium, iron, zinc and sulphur levels than those of the other cultivars, with a significantly higher percentage total soluble solids and sulphur concentration than the white and brown onion cultivars. The results of this study show that increasing N fertilisation up to 180 kg N ha−1 increases the concentration of certain minerals in bulbs, as well as marketable yield, with ‘Star 5516’ yielding highest and ‘Mata Hari’ showing the best quality.

Development, Yield, and Antioxidant Content in Red Cabbage As Affected by Plant Density and Nitrogen Rate

ABSTRACT Red Cabbages (Brassica spp.) are becoming popular as intact or fresh-cut products for consumers. Head size and yield are important quality parameters for marketing. These factors are influenced by N application and plant density, which can affect anthocyanin content, which is responsible for the red color and ascorbic acid content. The study was undertaken to determine the influence of nitrogen application rate and plant density on yield, head size, anthocyanin and ascorbic acid contents, and antioxidant activity in Red Cabbage (B. oleracea L. var. capitata f. rubra DC.), cv. Red Jewel. Cabbage plants were fertilized with 40, 80, 120, 160, or 200 kg∙ha−1 N using NH4NO3 at plant densities of 100,000, 125,000, or 166,700 plants∙ha−1, achieved by plant spacings of 20 × 25, 20 × 20, or 20 × 15 cm, respectively. Rates of N and plant density did not affect head size or yield. Anthocyanin and ascorbic acid content and antioxidant activity were higher at 80 kg∙ha−1 N and at 125,000 plants∙ha−1, which can be used without negatively affecting cabbage head size and yield.

Response of field-grown indeterminate tomato to plant density and stem pruning on yield

ABSTRACT Plant density and stem pruning are factors affecting production of field-grown indeterminate tomato (Solanum lycopersicum L.). Plants were established at plant densities of 16,000, 20,000, or 30,000 plants ha−1 and pruning treatments were no stem pruning (0S), prune side shoots below the first flower truss (1F), or prune plants to 1 stem (1S) or 2 stems (2S). Increased plant density resulted in fewer fruit, marketable yield, and total yield per plant. Plant density did not affect marketable and total yield per hectare. Plants subjected to no pruning, or pruning of side shoots below the first flower truss, had the highest marketable yield per plant and per hectare. The lowest plant density, and no pruning, tended toward increased total yield per hectare. A plant density of 16,000 plants ha−1, without stem pruning, is recommended based on cost saving of hybrid seed, due to use of fewer plants, and labor for pruning.