Abstract: Track 2b: Food sovereignty and sustainable agriculture.Long term comparative organic farming systems research trials have been running for four years, comparing organic and conventional, rotation and mono-cropping,... [ view full abstract ]
Abstract: Track 2b: Food sovereignty and sustainable agriculture.
Long term comparative organic farming systems research trials have been running for four years, comparing organic and conventional, rotation and mono-cropping, biological and chemical pest and disease control and water use efficiency in cabbage, sweet potato and cowpea crops. In Africa the high cost and limited availability of agricultural inputs make agro-ecological approaches attractive, as they are practically possible and improve carbon sequestration and food quality. The research will show whether the improvements which organic farming brings about (higher soil organic matter, lower acidity, better soil biology, aerobic soil conditions, greater water use efficiency, better food quality) make up for the sometimes lower yields of organic farming systems. The trials will run for ten years, and are laid out as a complete randomised block experiment with four replications, split for farming system, with ten treatments. Four studies examine yield components, soil fertility changes, food quality and water use efficiency (using capacitance probes to 1.1 m depth, and theta probes for surface and mulch moisture content determinations). Results from the first three years are presented, showing how the conventional system has raised available soil phosphate levels more than the organic, but caused some acidification of soils. The organic system has raised soil organic matter and dropped acidity and this has made more potassium available in the soil. As with other long term trials, there is still a yield gap, with organic systems yielding twenty to thirty percent less than conventional, largely due to lower available soil phosphate. This problem is now being corrected using rock phosphate. The challenges for viable organic farming systems are thus seen to include: improving soil fertility, controlling pests and diseases and convincing consumers of the quality of organic products. Benefits include: higher soil water retention, sequestration of soil carbon, improved soil micro-biology, better agro-biodiversity and elimination of poisons from the food chain.
Raymond.auerbach@nmmu.ac.za
Keywords:
organic farming systems; soil fertility; water use efficiency.
