Derk VanKonynenburg used to think measuring the soil moisture every 15 minutes on his 1,500-acre fruit and almond orchard was as precise as he could possibly need. He gets the data from probes that measure moisture in the soil and send readings over a wireless link to a collection station. From there, it's relayed to a data center, and VanKonynenburg accesses the data online from a PC, helping him decide when and how much to water the trees.

Once VanKonynenburg and his partners got accustomed to the feed, however, they wanted even more data, and they wanted it better. "We decided we needed a measurement every minute," he says.

That's right. On this one midsize farm around Modesto, Calif., a farmer is measuring the soil moisture every single minute of the day to make irrigation decisions. Understand, VanKonynenburg isn't looking at that moisture count minute-by-minute like a stock ticker, waiting to hit the water switch. He looks about once a day to create an irrigation plan. But because the farm irrigates in bursts--say, seven minutes on and 14 minutes off--collecting readings every 15 minutes wasn't accurate enough. With better understanding of moisture needs, "we think it may allow us to lower our water use another 10%," says VanKonynenburg, "and 10% is a huge number."

The breakthrough here isn't the sensors, which farmers have had for decades. It's wireless. In the past, a farmer had to collect the readings by hand with a meter, since running wires to a sensor is impractical in a farm field. A farmer might get to a sensor every few days.

VanKonynenburg and his water-conscious peers show the potential for information technology to help with a major environmental issue: how to feed the masses without exhausting fresh water resources. For the sense of urgency, look no further than California, where several years of drought amid growing demand for water spurred lawmakers this month to pass the most significant water-use reform in three decades.

A number of emerging technologies promise to cut water use. Wireless sensors that allow for more precise water use are one. Some farmers are applying GPS controls to their center pivot irrigation systems, so that as the automated rigs move across a field, they know to turn off or lessen the flow in areas that need less water. Web-based data services are available to help farmers calculate when to water even if they're using low-tech techniques, such as flooding a field.

But the problem of reducing irrigation doesn't come with a tidy technology solution, given the obstacles to adoption.

Agriculture uses about 80% of all water consumed in the United States, according to the U.S. Department of Agriculture, and more than 90% in some Western states. Irrigated fields produce just 16% of all crops, yet they generate nearly half of the value of all crops sold. Increased use of biofuels such as ethanol could add to the pressure, if such demand prompts farmers to grow corn instead of less water-intensive crops.

However, the USDA estimates that in 2006, the last year for which data is available, less than 8% of irrigated farms used "smart" irrigation--soil or plant moisture-sensing devices, irrigation scheduling services, or computer simulation models. California farmers could cut water use by 17% by using local climate and soil data to make decisions, abandoning flood irrigation in favor of sprinklers, and other techniques, concludes the nonprofit Pacific Institute in a report this year.

Economics can be a barrier to water-saving technology. In some areas, water's just not expensive enough to justify investment in technology to conserve it, says Guy Fipps, director of the Irrigation Technology Center at Texas A&M University. It's why drought-plagued developed countries such as Australia and Israel are leaders in water-saving irrigation.

Politics can make the economics more complicated. In the Western United States, in particular, water's a major public policy issue. In California, water shortages led to tens of thousands of farmland acres left unplanted last year. That kind of uncertainty makes it dodgy to invest in water-saving technologies.

For farmers to invest in such technologies, they need long-term assurances of a water supply--even if it's for less water than they're currently allocated or used to having access to, says David Zoldoske, director of the Center for Irrigation Technology at Fresno State University. "You can't go to the banker and borrow if you have water this year and you might not next year," he says. "You can invest with less water, but you can't invest with no water."

Tom Rogers considers both the economic and political issues as he considers investing in high-tech irrigation. Rogers and his brother work a 170- acre almond farm in central California, about 30 miles north of Fresno, that their father ran before them. Rogers has access to water, from wells on his land and surface water he pumps in, but the rate he had to pay for surface water shot up 40% recently, driving up his operating costs. "That hurt," he says.

By reducing water costs and maximizing crop yields, Rogers figures his investment in a wireless soil moisture sensor network paid for itself in three years. The risks of trying to minimize water use, however, are significant. Underwatering during the peak May, June, or July growing season can cut crop size 20% to 30%, he says.

Politically, Rogers thinks that the data he collects will be increasingly important in helping farmers justify their water use. He has watched farmers on the drier, west side of the valley lose almost all water to urban use in recent seasons. "There isn't an unending supply of water," Rogers says. "I have to show that I use water responsibly, or why should I have it?"

That thinking applies to everything Rogers does on the farm, because of both cost and environmental pressures. For instance, he'd like similar tools as he has for irrigation to help him monitor and manage how much fertilizer to give crops at a given time.