When the famous statistic that says it takes 1.1 gallons (4.2 liters) of water to grow one almond in drought-stricken California hit the headlines, the nutritious, but water-sucking nut was immediately cast as the villain.
Almond growers were vilified for planting thirsty crops that require year-round watering while the state endured drought, and the agriculture industry as a whole was condemned by people who thought it should suffer the same mandatory cutbacks as urban users.
But California’s farmers were tackling the drought in other ways. Some were leaving fields fallow, increasing groundwater pumping (in some places to unsustainable levels) and experimenting with switching to less water-intensive crops.
One of the biggest gains, though, may come from techniques that make water use far more efficient.
Researchers from the University of California Division of Agricultural and Natural Resources (UCANR) and farmers have been working for years on ways of reducing water use. Techniques include switching from flood to drip irrigation or sprinklers; deploying soil sensors; using deficit irrigation where a crop is subjected to stress from getting less than the required amount of water; or tapping new technology to determine the optimum schedule for watering.
However, progress in water conservation and innovation has been slow but steady.
“Irrigation improvements take time. It’s not like you can throw a switch and convert everything,” explained Doug Parker, director of the California Institute for Water Resources. “And there’s no one ‘bang, bang’ technology.”
How Almonds Have Tightened Their Water Belt
California has about 6,800 almond orchards, mostly in the Central Valley, supplying 80 percent of the global demand for the nut. The industry employs 104,000 people and consumes 9 percent of the state’s agricultural water, according to the Almond Board of California.
The almond industry has been experimenting with giving the trees variable amounts of water, from 70 to 100 percent of the normal feed, to see where it can maximize crop per drop.
“Plants really just trade water for carbon, so they absorb carbon dioxide but need water,” said David Doll, a UCANR farm adviser in Merced County, who is also known as the Almond Doctor. “Every crop needs a set amount of water to produce food. If you increase water, you increase yield, up to a point. That change in the slope is when we start losing water-use efficiency.”
For instance, 100 gallons of water could equal 100 almonds, but for 120 gallons, the grower may get only 105 almonds.
Doll has been working since the drought began on trying to find the highest crop-per-drop ratio.
He added that while the figure of one gallon per almond is about right, it’s not just about the nut (which is 25 percent of the fruit), but also the shell (comprising another 25 percent) which provides bedding for animals and fuel for biomass cogeneration, as well as the hull (50 percent of the fruit) that is used to feed cattle.
“We’ve been using the same amount of water to produce 30 percent more yield,” Doll said, helped by better efficiencies in fertilizer use and the fact that 70 percent of the industry has shifted to drip irrigation (below the surface) or micro-sprinklers (above ground) over the last 20 years.
Another improvement is user-friendly software to interpret soil-sensing data, so growers can better understand their soil’s needs.
Plant stress monitoring technology has also become more user-friendly, making it easier for farmers to identify potential stress before a tree reaches the chronic wilting stage. “It’s like taking the blood pressure of a plant,” Doll explained.
He reckons the almond industry could increase its water saving by a further 10 per cent with more widespread implementation of available technologies and better management of soil variability, which can be significantly different even within the same field.
Forage Crops Tap Technology for Water Savings
Milk is California’s top agricultural commodity, and the state has the largest dairy industry in the nation, so to feed those cattle, a lot of hay has to be grown, mainly alfalfa, but also the Sudan, savanna, Bermuda and dry grasses.
While it is a relatively low-value crop, netting growers only about $1,500 an acre, alfalfa is thirsty. Like the almond, it is a year-round crop in sunny California, using up 10 percent of all agriculture water.
The area devoted to alfalfa has shrunk from about 1 million to roughly 850,000 acres, noted Khaled Bali, irrigation adviser with UCANR in the Imperial Valley’s Desert Research Center. While it was once all flood-irrigated, there has been a slow shift to drip and sprinkler irrigation, which has shown a 20 percent increase in crop yield and a water saving of up to 40 percent, depending on the soil.
Cost has been the main obstacle to larger-scale conversions to more efficient irrigation, but Bali and his colleagues have been working on more feasible ways for farmers to reduce water use, such as using salty water and municipal waste. Recycled water could damage other crops, but alfalfa has shown a tolerance to salinity and other degradation.
Bali’s research has focused on ways to mix regular water with saline or degraded water, and study the crop’s tolerance of such combinations. Like Doll, he highlighted how some of the technology used today by the industry, such as drip and soil moisture sensors, may have existed for a while, but recent advances have made their adoption much more user-friendly.
One such technology he singled out is the California Irrigation Management Information System (CIMIS), a network of weather stations across the state run by the Department of Water Resources, which helps farmers by calculating how much water each crop uses and loses so they can decide when to replace it. “It’s like a health meter for your soil,” Bali said.
Drones, Satellite Imaging and Big Data
A surprising amount of technology is involved in farming – something not always apparent from scenic pictures of farm fields.
“Some of these techniques have been around for years and they have been adapted elsewhere – Israel for instance – but we’ve had to customize it to California’s weather and soil, and figure out what works, which takes time,” explained Parker at the Institute for Water Resources.
He cited the example of processing tomatoes – fruit grown to be made into ketchup and canned tomato paste. When drip irrigation was used in the early 1980s, the yield improved but processors disliked the resulting fruit because it was watery and lacked solid bulk. But since then, researchers have calculated how to grow tomatoes on drip lines and not only get better yield but also good-tasting, dense fruit.
Berries and wine grapes have witnessed the same progress – using less water has led to sweeter fruit – although Parker is careful to point out that these conservation measures may have come about more because growers wanted sweeter fruit than simply to cut down on water.
The biggest technological advances in the last few years have come not just in more user-friendly interfaces, but in using drones equipped with cameras to capture real-time images of soil moisture and quality or crop health.
Drones, NASA-developed satellite imaging, low-altitude airplane imaging, geographic information systems (GIS), big data – together, these technologies enable soil management, from customized rapproaches for a single tree or whole fields.
“We’re doing work on variable rate irrigation – so you look at watering each tree instead of a whole field, with different types of valves, flow meters etc. to adapt to differences in soil across the field,” Parker said. “There’s a cost to this, but it makes better sense when there’s soil diversity and salinity present.”
As for a single technology that will have the most impact, Parker said it comes down to how all of the data is combined and used. “Right now, we’re swimming in data and don’t always know how to deal with it.”
Given that California will continue to face water shortages in the long term, these emerging technologies will help better manage crops on the ground. UCANR will look at how water districts can improve their delivery systems, and water trading will become more prevalent as farmers with ample quantities, but poor soil, decide to sell their water instead of using it, Parker predicted.
Researchers are also looking at innovative ways to recharge depleted groundwater tables, by flooding almond orchards in winter or tapping fallowed farmland to replenish stormwater flows.