Something in the air
Forget the common perception that plants need light, water and soil to grow. Now, all they need is air - well almost. In Peru, the International Potato Centre (CIP) is introducing the technique of aeroponics, which requires only air, water and a nutrient spray, to grow potato seeds. Pioneered by NASA, the technology is environmentally friendly and requires less water than other cultivation techniques, including hydroponics. This, and the fact that aeroponics avoids the use of pesticides, ensures the technique has high-flying potential.
Potato growers attribute maximum importance to the seed potato, as it is the quality of the seed that determines the success of the harvest. In Peru however, they are expensive and often diseased, and the lack of healthy potato seeds affects consumption of what is an important local staple crop. CIP is using aeroponics to improve the production of healthy seed potatoes, and to reduce their cost. The centre has set up experimental stations in La Molina, on the coast of Peru and in Huancayo, located over 3000 metres above sea level in the Andes, to test seed tubers grown in mid air.
The results, says Rosario Falcon from CIP's Germplasm Enhancement and Crop Improvement Division, are amazing. "For example, we obtained an average of 70 seed tubers in 180 days from one plant. Using soil in the greenhouse, we only obtain five to six tubers per plant in 90 days."
In fact, the mid air method has been up to ten times more successful than conventional techniques such as tissue culture, which take longer and are also more labour intensive. In addition, the aeroponically produced seeds can be harvested at any time and size that the grower requires, from five to 30 grams.
Aeroponics allows plants to capture oxygen and carbon dioxide more effectively, exposing the plant to air for most of the time, and only occasionally allowing contact with water and nutrient droplets. The roots of the potato are exposed inside a box covered with black plastic to make it dark enough for the tubers to grow. A timed device sprays the roots every five minutes. At regular intervals the roots are also sprayed with droplets of essential nutrients and fertilisers.
The size of the droplets is carefully calculated. Droplets too large will deprive the roots of oxygen, and those too small will encourage too much root hair, which affects the sustained health and growth of the plant. The method of spraying fertilisers directly onto suspended roots allows plants to grow continuously for up to 180 days. Most importantly, air-rooted plants can be placed directly into field soil without suffering from 'transplant shock', wilting or leaf-loss - characteristics of other soil-less growing techniques, such as hydroponics.
One of the main reasons behind changing the production technique for potato seeds is to avoid use of harmful chemicals, such as methyl bromide. Such chemicals, now banned in an effort to protect the ozone layer, were used to disinfect diseased soil. With aeroponics, if disease develops, the infected roots are removed and prevented from infecting others.
Aeroponic potatoes for poor farmers?
Although the technique has potential for providing poor farmers in Peru with disease free potato seed, the technique itself will not be available to everyone. Falcon notes that "people who are going to conduct this seed production must be well trained. The technique requires the appropriate amount and quality of water for the spray solution, and additional knowledge of crop physiology." Yet the researchers have been keen to stay in close contact with the farmers. "Many come to visit CIP. They are amazed by the technique and they are excited to start working with the seed," says Falcon.
CIP is currently evaluating the cost of installing greenhouses with aeroponic units, using cost-effective and locally sourced materials. It is hoped that, while only a few farmers may be involved in potato-seed production, many others will be able to access improved quality, low-cost seed, ensuring that the technology leads to success in the ground, as well as in the air.
Date published: May 2007
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