As the world population climbs and water stress spreads around the globe, finding ways of getting more crop per drop to meet our food needs is among the most urgent of challenges.
One answer to this call is drip irrigation, which delivers water directly to the roots of plants in just the right amounts. It can double or triple water productivity – boosting crop per drop – and it appears to be taking off worldwide.
Over the last twenty years, the area under drip and other “micro” irrigation methods has risen at least 6.4-fold, from 1.6 million hectares to more than 10.3 million. (One hectare is about 2.5 acres. The latest figures from the International Commission on Irrigation and Drainage include countries accounting for only three-quarters of the world’s irrigated area, so the 10.3 million figure is low.)
The most dramatic gains have occurred in China and India, the world’s top two irrigators, where the area under micro-irrigation expanded 88-fold and 111-fold, respectively, over the last two decades. India now leads the world, with nearly 2 million hectares (about 5 million acres) under micro-irrigation methods.
Amazingly, most farmers today still irrigate the way their predecessors did thousands of years ago — by flooding their fields or running water down furrows between their rows of crops. Often less than half the water applied to the field actually benefits a crop.
The rest isn’t necessarily wasted. Some of it makes its way back to a river or groundwater source where it can be used again. But the excessive diversions can deplete rivers and streams, pollute water supplies with pesticides and salts, and result in large losses to evaporation.
Drip irrigation, commercialized by Israeli engineers in the 1950s, delivers water directly to crops’ roots through porous or perforated tubing installed on or below the soil surface. Compared with conventional flood or furrow irrigation, drip methods can reduce the volume of water applied to fields by up to 70 percent, while increasing crop yields by 20-90 percent.
Today, as throughout modern history, irrigation is crucial to the global food supply: the 18 percent of the world’s farmland that’s irrigated yields 40 percent of the world’s food. Yet less than 4 percent of the world’s irrigated land is equipped with micro-irrigation systems. Clearly, the irrigation revolution has a long way to go.
To date, farmers have adopted micro-irrigation mainly for fruits, vegetables and other high-value crops that can provide a good return on the investment. California is the king of drip in the United States, in large part because it is the nation’s fruit and vegetable bowl. It accounts for 62 percent of the nation’s area under micro-irrigation; Florida and Texas come in a distant second and third.
Netafim, the global market leader in drip irrigation, has expanded drip’s use on cotton in Australia, Egypt, Israel, the United States and elsewhere. In the Philippines the installation of a subsurface drip system on a sugar cane farm resulted in a 90% increase in yield compared with a conventional (center-pivot) sprinkler, and a 70% reduction in water use– resulting in a dramatic increase in water productivity. Netafim reports that the cane’s sucrose content increased by 5%, an added bonus.
Anil Jain, the managing director of Jain Irrigation – the second biggest global micro-irrigation company – expects the drip irrigation market in his native India to expand by 1 million hectares (nearly 2.5 million acres) per year during the coming years and to soon become a $1 billion market in India alone. Between 2003 and 2010, Jain’s drip business grew 20-fold.
But what really caught my attention was Jain’s endeavor to expand drip irrigation to rice, a notoriously thirsty crop and the food staple for nearly half of humanity. India alone has some 43 million hectares of rice under cultivation, so saving even 10 percent of the water now used to grow the crop could free up a great deal of water for other purposes and help slow the depletion of India’s aquifers.
Jain is collaborating with the International Rice Research Institute and other agricultural centers on research and field trials for drip-irrigated rice.
At its R&D farm in the state of Tamil Nadu, Jain has reportedly gotten some promising early results: drip-irrigated fields yielded 22 percent more rice per hectare and required only a third as much water.
For drip-irrigated rice to catch on commercially, however, Indian officials will need to reduce the heavy subsidies to water and energy, which discourage farmers from investing in more-efficient practices.
Over the last decade, low-cost drip systems tailored to the needs of poor farmers have begun to spread, as well. iDE (formerly International Development Enterprises), which successfully introduced the treadle pump to poor farmers in Bangladesh, has also pioneered the development of low-cost drip systems for poor farmers.
iDE’s suite of systems ranges from $5 bucket kits for home gardens to $25 drum kits for 100-square meter plots (about 400 plants) to $100 shiftable drip systems that can irrigate 0.2 hectares (half an acre), including plots on terraced hillsides. More than 600,000 of iDE’s low-cost drip systems have been sold in India, Nepal, Zambia and Zimbabwe.
So will there be enough water to grow the food we need while still keeping our rivers and freshwater ecosystems healthy?
The answer depends in large part on whether farmers will find it profitable to invest in more efficient technologies. Reducing water subsidies, for example, would help expand the drip market.
Drip irrigation is clearly on a roll, but its potential has barely been tapped.
Sandra Postel is director of the Global Water Policy Project and lead water expert for National Geographic’s Freshwater Initiative. She is the author of several acclaimed books, including the award-winning Last Oasis, a Pew Scholar in Conservation and the Environment, and one of the “Scientific American 50.”