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Soil Health in Organic Fruit Orchards in the Western Cape
Author: Janina von Diest, Annika Pieterse
Published: 15/05/2017

Farming in the Western Cape has yet to fulfil the huge demand for organically grown produce, even though South Africa is among Africa's largest organic produce exporters. Most farms in the Western Cape utilise traditional farming methods, including the use of chemical pesticides which have a higher negative ecological impact than organic farming. Organic farmers rely on synergies between multiple ecosystem services, which provide natural regulatory processes like biological control by natural predators. This allows farmers to forego chemical pesticides, although management intensity regarding decisions to support the agro-ecosystem health of the crop system, is higher. Management decisions regarding pest control and nutrient management in these crop systems could be influenced by research into organic fruit production, as it remains unknown to what extent individual management practices affect the relationships between multiple above- and belowground ecosystem services.

An international team of research entomologists, nematologists and plant pathologists gathered in Stellenbosch from 12 – 16 September 2016 to initiate a collaborative project entitled:  "Ground cover management in organic orchards in South Africa: Trade-offs between above- and belowground ecosystem services".  The project aims to understand the ecological mechanisms that underlie the simultaneous provision of above- and belowground ecological processes. Organic growers must rely on multiple ecosystem services as they cannot replace these processes with synthetic inputs.  In South Africa, very little scientific information exists for effective organic fruit production, and as a consequence very few certified organic fruit growers exist, particularly in the Western Cape. 

This project is funded by the Ekhaga Foundation in Sweden, and is managed by Dr Klaus Birkhofer, Lund University, Sweden.  Collaborators include Drs. Pia Addison, Antoinette Malan, Nomakholwa Stokwe, Corinna Bazelet, Fisayo Daramola, and Matthew Addison and Caro Kapp (all Department of Conservation Ecology and Entomology, SU); Profs Wijnand Swart and Schalk Louw (University of the Free State); Sheila Storey (Nemlab); Prof Des Conlong (South African Sugarcane Research Institute, and ConsEnt); as well as Drs Jan Bengtsson (SLU, Sweden) and Regina Lindborg (Lund University, Sweden).

The first meeting included field visits to select trial sites, and a workshop to discuss the trial layout and sampling protocols, as well as the contributions of the various researchers.  Certified organic or intensively managed sustainable fruit farms were visited in Stellenbosch, Ceres and Robertson, Western Cape. Discussion sessions with the growers and farm managers on their farms provided invaluable input and information about farming techniques, challenges and successes. In three days of intensive discussions and presentations held at STIAS, the research team assessed the stated needs of the growers, and fine-tuned the study design and research questions to best complement current practices in order to benefit the growers and the overall sustainability of organic fruit farming practices in South Africa.

Tierhoek, an organic farm in Robertson which specializes in plum, apricot, peach and quince production, was selected as the study site. The study will compare the effects of "business as usual" mulching practices with an intensive mulching alternative on a variety of above- and belowground organisms as well as fruit damage and yield. The hypothesis being that mulch reduces evaporation of water from tree systems, and provides detritus and organic material which promote healthy soil, and as a result, healthier trees and ecosystems.

Field work began in November 2016 when a large team of staff and students from the Department of Conservation Ecology and Entomology traveled to Tierhoek to set up the experiment (i.e. to rake grass). A fun day of bonding and hard physical labour was had by all. Two weeks after the setup, the various researchers each made their way to Tierhoek and collected their first round of data – each researcher focussing on the organism of their expertise. For some researchers this meant taking soil samples to evaluate in the lab for bacteria, fungi and nutrients. Others dug traps in the ground to catch beetles and other detritivores and decomposers, searched underneath and in between the trees for spiders and grasshoppers, or hung traps in the trees to catch flying insects.

The project duration is 18 months, during which time there will be several opportunities for the collaborators to meet and work together to gather data. One more session of data collection is planned for June 2017, after which all data will be analyzed and results will be published in a scientific journal. Finally, the collaborative research project will terminate in a final meeting in Robertson to discuss dissemination of results back to the people who will implement them – the growers.

The agricultural industry in the Western Cape stands only to benefit from a greater knowledge base surrounding organic farming and hopefully the Western Cape will see a growth in the number of organic growers, for with a greater knowledge base and more informed industry advisors, comes support for farmers looking to transition from traditional methods to organic farming, with the lowest possible risk.