Commercial Vegetables

 

Contact: Silence Chiloane, +27 (0)12 808 8374

The research programme focuses on hydroponic production systems, organic production systems and water use efficiency of commercial vegetables. The vegetable crops for hydroponic production systems include tomatoes, cucumbers and peppers (open bag system) with a variety of leafy vegetables included for the recirculating (closed) system. The organic production systems focus on the effect of organic soil amendments on the characteristics of the soil and the crops included are tomatoes, cabbage, green beans and sweet potatoes. Selecting the best sweet potato cultivars and varieties under drought stress is of great importance. This increases the need to undertake experiments that will identify the best performing cultivars during water deficit conditions. Using various techniques in identifying various mechanisms that the plant uses to tolerate drought can be helpful to address the optimum conditions in which the sweet potato plant can still grow optimally at a certain stress condition.

• Hydroponic vegetable production

• Sweet potato nurseries for multiplication and distribution of cuttings

Research Team

Production Systems

• Organic Production Systems

Organic agriculture is a rapidly expanding sector of agricultural production in many developed countries in the world. The demand for year-round organically-produced foods makes it difficult for any country to source organic food entirely within its own borders. Therefore, farmers in developing countries are looking at the organic sector as a niche market for exports. There is also an economic incentive to engage with organic production, since organic products typically conduct high premium over the same products produced on non-organic farms. Therefore, market returns from organic agriculture could potentially contribute to household food security of emerging farmers by increasing family incomes. In South Africa, there is a small but very active group of organic farmers, some of which are exporting their products to the EU and some are selling locally, certified with Afrisco. Organic growing is a sustainable way of producing healthy, nutritious food, whilst continuously improving the productivity of the soil. It is an integrated system of farming based on ecological principles. Organic farming relies on natural ecosystem and technologies for plant nutrition and pest and disease control and therefore reduce the reliance on purchased inputs for crop production. There has been very little research done on organic farming systems. Information on organic production methods appropriate to the circumstances and needs of resource-poor farmers are nonexistent or very limited. This is a somewhat ironic situation, since most of the resource-poor farmers are organic farmers by default, since they usually cannot afford the cost of synthetic input materials. At the moment, however, these farmers would not be able to register as bona fide organic farmers, since they do not maintain appropriate management and control measures stipulated by organic farming regulations. As the leading agricultural research organization in South Africa, ARC-Roodeplaat has initiated research in organic farming systems and to asses the possibility of providing the emerging farmers with appropriate technologies to facilitate their entry into the organic market sector.

• Hydroponic Production Systems

Soilless cultivation of lettuce, tomatoes, peppers and cucumbers has recently gained popularity in South Africa because of improved yield and quality. The majority of vegetables in South Africa are grown in open field systems while a small amount are produced under protection, e.g. shadenet houses and greenhouses. ARC-Roodeplaat mainly utilizes two hydroponic systems i.e. gravel film technique (closed system) and open bag systems for research trials. These two systems are commercially used in South Africa. The Gravel Film Technique (GFT) is the most popular re-circulating hydroponic system in South Africa, commonly used by commercial growers to produce leafy vegetables. In a gravel film system, a well balanced nutrient solution is pumped to the top of hydrolines and flows down a 3% slope by gravity. The nutrient solution is collected in a reservoir at the bottom and is pumped back to the hydrolines (re-circulated). The gravel’s major role is to give support to the plant, cover the root system and prevent the nutrient solution from being exposed to sunlight. Different types of lettuce (figure 1), celery, leafy herbs (e.g. parsely, basil), spinach and swiss chard, leeks, spring onion, chive, different types of cabbage and mustards can be produced in this system.

In an open bag system, plants are grown in a container filled with a growth medium (e.g. sawdust, coir) where nutrient solutions are dripped onto the growth medium and there is a drainage allowance of 10-15%. The system is utilized in shadenet houses and plastic tunnels with or without temperature control.

Tomato and sweet peppers growing in an open bag hydroponic system in a plastic tunnel
The open bag system is well adapted for the production of tomatoes, peppers, cucumbers, strawberries, and beans. General information on Hydroponic production of vegetables

ARC-Roodeplaat’s research is focused on fertigation of lettuce and tomatoes, cultivar evaluation, stem and fruit pruning, and comparative performance of vegetables such as tomato, cucumbers, lettuce and peppers in different production systems. The current research can be summarized as follows:

Production systems for tomatoes
Tomatoes are widely grown in South Africa and rank second after potato as a vegetable commodity. Growers in South Africa are faced with the challenge of producing high yield combined with good quality in order to satisfy the local demand. Very often this demand is not met, mainly due to inadequate plant nutrition, adverse climatic conditions, or pests and disease infestation.

The population increase in South Africa and improvement of the standard of living have resulted in an increased demand for foods of high value and quality. Although the majority of tomato production in South Africa is open field production, a small amount is also produced under protection (greenhouse and shadenet structures). Many vegetable growers in and around South Africa utilizing a variety of soilless production systems, have become interested in the greenhouse cultivation of vegetable crops. Little to no comparative information is available on different production systems for tomatoes under local conditions.

Plant growth manipulation of indeterminate vegetable crops in hydroponic production systems
Tomatoes and sweet peppers are important crops in South Africa and their commercial importance is continuously increasing in South Africa‘s retail markets. However, there is little information on how spacing, fruit and stem pruning influence fruit size and yield. Yield and quality variation might occur due to variation in cultural practices, e.g. plant spacing, stem and fruit pruning. Optimal plant spacing may help in proper utilization of land and for obtaining good quality fruits. Optimum marketable yields per unit area may result from canopy structures created by particular combinations of plant densities and trellising systems. Stem pruning might also influence the yield production. The study will be undertaken to investigate the effect of plant density and standard method of pruning for optimum yield and quality of tomato and sweet peppers.

Fertigation of lettuce
Cultivar evaluation of crisphead lettuce in a soilless condition.
This crop is becoming an increasingly important vegetable in salads in South Africa. Its popularity has led to an increase in production and consumption in urban areas.

New cultivars are introduced each year by seed companies which might not be suitable for year-round production and/or other growing systems (e.g. the gravel-film technique) and seasons. This necessitates cultivar evaluation trials of other growing systems such as the gravel-film technique. Not much information is available on the performance of crisphead lettuce cultivars in a gravel-film cultivation system. This study was conducted to assess summer, autumn, winter and spring crisphead lettuce cultivars, cultivated in a closed system, i.e. the gravel-film technique, with regards to their performance in terms of quality and yield. Wrong selection of cultivars can result in financial loss.  [more]

• Low Input Production Systems

Vegetables are important for food security and poverty alleviation. Nevertheless, in South Africa food insecurity still exist, particularly with resource poor farmers and communities. This can be ascribed to higher costs involved in vegetable production as well as high food retail prices. The introduction of modern technology to address the needs of rural farmers are often not accepted because of several reasons, including management skills, high input costs, etc. However, several low input production systems are implemented by resource poor farmers with variable results and sustainability. The low input production systems refer to those technologies that are aimed at optimizing the on -farm input resources, e.g. crop residues and reduction of farm resources such as chemical fertilizers to reduce input costs. These low input production systems are investigated, documented and evaluated in order to develop improved methods. This necessitates an investigation on low input production systems and the development of improved systems to suit resource poor farmers.

Publications and Presentations

DU PLOOY, C.P. LAURIE, S.M. & VAN DEN BERG, A.A. Optimisation of agronomic practices and production season of new sweet potato cultivars in South Africa. International African Crop Science Conference, Entebbe, Uganda. 5-9/12/2005.

DU PLOOY, C.P. LAURIE, S.M. & VAN DEN BERG, A.A. Optimisation of agronomic practices and production season of new sweet potato cultivars in South Africa. African Crop Science Conference Proceedings. 1: 29-32.

DU PLOOY, C.P. LAURIE, S.M. & VAN DEN BERG, A.A. Optimisation of planting & harvest time for sweet potatoes. SRL Conference, Pretoria. 4-6/07/2006.

DU PLOOY, C.P. LAURIE, S.M. & VAN DEN BERG, A.A. Production systems for Orange flesh sweet potatoes. VITAA Sweet potato symposium, Pretoria. 3/10/2007 (on invitation)

DU PLOOY, C.P. LAURIE, S.M. & VAN DEN BERG, A.A. Intensive sweet potato production in South Africa. Sweet potato Challenge workshop, Addis Ababa, 28-31/07/2008 (on invitation)
Mulandana N. S. 2007. Organic Vegetable Production. Manual. ARC-Roodeplaat, Private Bag x293, Pretoria, 0001

CHILOANE, S. 2008. Hydroponics: A new era for cultivation. Afgriland May/June 52 (3), 64.

MABOKO, M. M. 2006. Blossom –end rot in tomatoes. NuFarmer & African Entrepreneur 11:11, July 2006

MABOKO, M. M. Pruning and trellising of tomato, Undercover Farming Magazine 3: 24-25, August 2006

MABOKO, M. M. Fruit Cracking in Tomatoes causes economic losses, Undercover Farming Magazine 3: 8 & 28. September 2006

MABOKO, M.M. Gravel film technique for leafy vegetable growers, Undercover Farming Magazine 4: 22-27, November 2006

MABOKO, M. M. Leafy lettuce grown in a hydroponics system. Undercover Farming Magazine on March 2007

MABOKO, M. M. AND DU PLOOY, C. P. 2007. Production of crisphead lettuce in a soilless production system, El-Minia, Egypt, African Crop Science Conference Proceedings 8, 319-325

MABOKO, M. M. Physiological disorders in leafy lettuce. Undercover Farming Magazine. January 2008.

MABOKO, M. M. AND DU PLOOY, C. P. 2007. Pruning and trellising of hydroponically grown cherry tomatoes. Combined congress., Forever Resorts, Badplaas, Nelspruit. 22-26 January 2007.

MABOKO, M. M. AND DU PLOOY, C. P. Production of crisphead lettuce in a soilless condition. African Crop Science Conference, El-Minia University, Egypt. 27-31 October 2007.

MABOKO, M. M. AND DU PLOOY, C. P. Evaluation of crisphead lettuce cultivars (Lactuca sativa L.) in a soilless production system. Combined congress. Grahamstown, Rhodes University, 21-25 January 2008.

MABOKO, M. M., DU PLOOY, C P. AND I BERTLING. Comparative performance of tomato grown on soil vs in-soil production systems. International Symposium on Soiless Culture and Hydroponics, Peru, Lima, 23-30 August 2008.

MABOKO M M, S CHILOANE AND E VAN DEN HEEVER. Yield response of hydroponically grown tomato (Lycorpersicon esculentum Mill.) to different environmental conditions. 26th Annual congress of the South African Society of Agricultural Technologists, Shelley Point Country Club and Spa, West Coast, 16-19 September 2008.

MABOKO M M, S ZULU, CP DU PLOOY AND P STORK. 2008. Development of low cost growth media for seedling nursery in rural communities. 26th annual congress of the South African Society of Agricultural Technologists, Shelley Point Country Club and Spa, West Coast, 16-19 September 2008

MABOKO, M M. 2008. ‘Rain check’ in tomatoes in high rainfall areas, Undercover Farming Magazine 5 (3), 14.

MABOKO M M. 2009. Growing plants without soil. NUFARMER & AFRICAN ENTREPRENEUR 14 (1), 14

MABOKO M M. 2009. Importance of growing vegetables from seedlings. NUFARMER & AFRICAN ENTREPRENEUR, 14 (2) 22

MABOKO M M. 2009. Shaping tomato plants. FARMING SA

MABOKO M M. 2009. Growing plants without soil. NUFARMER & AFRICAN ENTREPRENEUR vol 14 (1 )

M MABOKO, 2009. Leafy lettuce in a soilless growing condition’. NUFARMER & AFRICAN ENTREPRENEUR, Volume 14 (3),19.
CHILOANE S AND M M MABOKO. 2009. ‘How structures affect growth’. Farming SA 24, 16-18

MARTIN: you are not consistent in the way you report publications

MABOKO M M AND C P DU PLOOY. 2008. Effect of pruning on yield and quality of hydroponically grown cherry tomato (Lycopersicon esculentum). South African Journal of Plant and Soil 25 (3), 178-181.

MABOKO M M AND C P DU PLOOY. 2008. Evaluation of crisphead lettuce cultivars (Lactuca sativa L.) for winter production in a soilless production system. African Journal of Plant Science 2 (10), 113-117. Available on line www.academicjournals.org/AJPS.

MABOKO M M AND C P DU PLOOY. 2009. Effect of plant spacing on growth and yield of lettuce (Lactuca sativa L.) in a soilless production system. South African Journal of Plant and Soil, 26 (3) 199-201

MABOKO M M., C P DU PLOOY AND I BERTLING. 2009. Comparative Performance of Tomato Cultivars in Soilless vs In-Soil Production systems. Acta Horticulturae 843, 319-326

NELUHENI, K.O AND S ZULU, 2008 . Spinach Production . Published in Farming SA magazine.

NELUHENI, K.O. MODISANE P.; ZULU S. AND DU PLOOY, C.P., 2007. Evaluation of different inorganic and organic fertilizers on spinach yield under low input conditions by Presented during the DOA progress report workshop in November 2007

NELUHENI, KO. MODISANE P.; ZULU S. AND DU PLOOY, C.P. Evaluation of different inorganic and organic fertilizers on spinach yield under low input conditions. Combined Congress January 2008, Rhodes University, Grahamstown

NELUHENI, KO. MODISANE P.; ZULU S. and DU PLOOY, C.P Evaluation of different inorganic and organic fertilizers on spinach yield under low input conditions by. Presented during the Combined Congress January 2008, Rhodes University, Grahamstown.

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