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Pretoria, South Africa

Maboko M.M.,Ornamental Plant Institute | Du Plooy C.P.,Ornamental Plant Institute
Acta Horticulturae | Year: 2012

In spite of the high nutritional value and popularity of amaranth in South Africa, lack of information on the production of amaranth in soilless conditions is a major concern for hydroponic farmers. A study was thus conducted in a shade-net structure in order to evaluate the effect of plant densities and harvesting methods on amaranth when grown in a closed hydroponic system (gravel-film-hydroponic system). Plants were subjected to three plant densities, i.e., 10, 16 and 25 plants/m2, with two harvesting methods, i.e., tipping and cutting. Tipping was done by plucking off the growing point of the shoots, while cutting was done by first cutting the plants at a height of 15 cm, with sequential cutting of 5 cm above the previous cutting. Experimental layout was a randomized complete block design with three replicates. Plants harvested by cutting at a plant population of either 16 or 25 plants/m2, produced significantly higher leaf area, fresh and dry mass, compared to the other treatments. Plants harvested by cutting, had a reduced number of inflorescences, and the yield increased by 37%, compared to the standard method of tipping. Therefore, plant population of either 16 or 25 plants/m2, harvested by cutting, increased production of amaranth, as a result of a reduced number of inflorescences and increased leaf area.

Du Plooy C.P.,Ornamental Plant Institute | Maboko M.M.,Ornamental Plant Institute | Van Den Heever E.,Ornamental Plant Institute | Chiloane S.,Ornamental Plant Institute
Acta Horticulturae | Year: 2012

The Agricultural Research Council, Vegetable and Ornamental Plant Institute (ARC-VOPI), developed an integrated programme to assist hydroponic vegetable farmers in South Africa. The Gauteng Department of Agriculture and Rural Development (GDARD) provides basic infrastructure to resource poor farmers, while ARC-VOPI is responsible for applied research and information dissemination. The research programme is designed to develop new methodology aimed at optimization of cultivation practices. Information dissemination efforts include tailor made training courses to improve the skills of hydroponic vegetable growers. ARC-VOPI utilizes two hydroponic systems, i.e., gravel-flow technique (GFT - closed system) and an open-bag system (OBS) for research and technology development. The research programme focuses on plant manipulation, including plant spacing, fruit and stem pruning, fertigation, cultivar evaluation and comparative performance of vegetables in different production systems. Recent research results in GFT revealed that optimization of plant density and harvest methodology resulted in more than double the yield of leafy vegetables with an additional advantage of a shorter growth season and improved quality. A nutrient solution (EC) concentration of 2 dS/m resulted in optimal yield and quality of leafy lettuce during four different growing seasons. Tomatoes produced in a GFT under a shade net structure and in a temperature-controlled tunnel (OBS) out yielded four other systems utilised in local hydroponic production of tomatoes. Shade net structures increased the incidence of early blight and fruit cracking, while production in a non-temperature-controlled tunnel resulted in a high incidence of fruit cracking. Spacing and stem pruning of tomatoes and sweet peppers in OBS resulted in increased yield and quality. The training facilities at ARC-VOPI are utilized for research, as well as training of resource poor farmers and community members who are trapped in a food security crisis. The beneficiaries are selected by GDARD, the main funder of the project, while ARC-VOPI provides training to empower the trainees to become financially independent.

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