Imagine, or just push the fast-forward button: You activate your sensor network to take soil, root and leaf readings and report data. You receive temperature, moisture, plant hormone levels and more from georeferenced points. Your computer integrates them with already-identified and mapped organic matter (OM), pH and electrical conductivity (EC) zones in those fields, with the specific variety planted.

You output an application map with recommended rates varied by zones for selected herbicides. Download the map to the crop-reflectance-camera-equipped applicator for more refinement on the go. As it crosses the same field, ratio and volume vary according to crop and weed biomass levels and reflectance values. The end result is maximum weed control, minimal crop impact and least-cost application.

Much of this data is already available. Some of the sensors and the network to power and operate them are still under development. Some are still being envisioned by ag researchers studying the fast-changing world of field and crop sensor technologies.

Other scenarios include in-crop sensing of available nitrate forms and conditions such as temperature and soil moisture likely to impact near-term conversion, as well as uptake. Adjusting application rates accordingly would offer maximum yield at least cost per additional unit of input.

"The goal is a complete picture of what's happening in the field," says Chad Fick, OptRx product specialist, Ag Leader Technology. "Right now optical sensors can ask a plant if it is healthy or not relative to nitrogen utilization. However, this is a more complex question than simply N, and this is where the technology is going, not just to the major elements, but to a bigger picture of what is happening in the field to help growers make decisions based on what's available to them at the time."

Fusion is the key

"The main issue today is sensor fusion and data integration," says Viacheslav Adamchuk, associate professor, Bioresource Engineering Department, McGill University and adjunct associate professor, Biological Systems Engineering Department, University of Nebraska-Lincoln.

He sees Fick's "complete field picture" coming together by defining specific agronomic strategies for different cropping applications and combining appropriate data to fulfill the strategy.For example, variable-rate irrigation could tap a combination of conventional EC, elevation mapping and wireless networks to assess water-stressed areas at any given time, Adamchuk says.

How the different types of data are integrated and managed will depend on the technology, with some carried out by growers, some by consultants and some by retailers, suggests Adamchuk. Paul Drummond, Veris Technologies, Salina, Kan., says growers and their service providers are recognizing added data’s value and the new technologies providing it.

He points to the slow but steady adoption of EC mapping, with users in different areas finding value differently. Veris first introduced the technology in 1997. Some fertilizer supply companies, like Helena, CPS and Wilbur Ellis, use EC maps as a zone delineation tool to improve soil sampling and nutrient management, he says.

"In the Delta and southern cotton markets, variable-rate nematicide applications are increasing. Electrical conductivity is the best indicator of where to apply, as low conductivity, sandy soils are more susceptible to root-knot nematode pressure, while higher EC, heavier soils require a lower nematicide rate.”

EC mapping correlates residual nitrate with slope and soil textures in the northern Great Plains and Canadian provinces, Drummond says. The recently introduced Veris MSP3 adds on-the-go, organic matter and soil-pH mapping to the mix. The OM mapping in particular is something Drummond is confident is at the right time and right place for corn producers, and he sees increased interest in the Midwest.

"Growers are looking for the next step in managing things like population," Drummond says. "They can use yield maps if they have good data, but many don't. Or they can use soil surveys, but they know transition zones aren't accurate. EC maps are good, but EC and OM maps are better."

While EC and organic matter sensors can better match plant population rates to a field, in-crop optical sensors can better match N applications to soil moisture and crop-use potential.

Tim Norris is an OptRx user and reseller in central Ohio. The past couple of years, with adequate soil moisture, he relied on Ag Leader’s optical sensing system to match plant needs to application, based on an N-rich strip and multiple in-season applications. Denitrification was high during these wet years, facilitating sensor payback with in-season applications.

"We had an average benefit of $49/acre with sensor-driven applications across three farms and 1,500 acres of corn over the past two years," says Norris. "We also had a customer use his sensors on a haybine to map high and low biomass production zones across fields, while another mapped biomass yields for corn silage."

In the face of this past season's drought, he completely cut out his last N application, saving input costs that otherwise would have already been invested...and wasted. While he doesn't think the N-rich strips did much good this year, Norris looks forward to seeing how the data comes back.

Norris looks forward to the potential for the data integration Adamchuk suggests. He sees added value if his crop sensor readings were used with yield, soil, topography maps and more for a more complete picture of his fields and cropping potential. "Soil types are simply not a good indicator," he says. "There are other, better tools."

Those better tools may be closer than Norris expects. "We need not only real-time, on-the-go canopy sensing," says Adamchuk. "We also need to integrate these sensor measurements with other field data, whether soil, yield or remote imagery. Different people are pursuing different ideas here, looking for a more systematic approach."

Adamchuk references the broad array of sensor work underway, including gamma ray spectroscopy for measuring soil textures, ground penetrating radars for water management, X-ray, etc. "The issue is if you have the data, what do you do with it?" he asks. "Our old rules were good, but based on stationary conditions. Perhaps we will need to redefine our rules using these new technologies."

Stuart Birrell, associate professor, Agriculture and Biosystems Engineering, Iowa State University, and colleagues in electrical engineering are among those working on new sensor technologies. One such system involves sensors the size of iPods placed a foot deep in the soil and in a grid 80-160 ft. apart. The sensors measure moisture and temperature, transmitting the data to a central computer.

"We started with moisture and hope to add analysis of additional nutrients in the future," says Birrell. "Even if you just understand moisture flow along with temperature, you can predict if denitrification or leaching will become an issue."

A research team at Purdue, headed by Marshall Porterfield, professor, Agricultural and Biological Engineering and Biomedical Engineering, is using black platinum and carbon nanotubes to evaluate the plant hormone auxin and how it regulates root growth and seedling establishment. The sensor oscillates, taking concentration readings at different points along the plant root. An algorithm shows whether the hormone is moving into or out of cells.

The auxin research was a follow-up to earlier diagnostic work using a nanosensor for oxygen diagnostics. Similar microsensor research is underway to diagnose nutrient utilization, N form and oxygen availability, as well as water stress and soil conditions. A scaled up auxin sensor assess plant hormone levels in crude plant tissue extracts may make herbicide applications more crop safe and effective.

"It would be part of a field diagnostic kit to dial herbicide rates up or down to match field stress," says Porterfield. "There is always a delicate balance, especially with those herbicides that mimic auxin, to balance minimal impact on crop and yield with maximum impact on weeds."

Porterfield looks beyond his team's current efforts to developing live, disposable "on-the-chip" sensors to get real time assessment of nutrient bioavailability.

Now on leave from Purdue, Porterfield's full-time assignment is as division director, NASA Space Life and Physical Sciences Research and Applications Division, overseeing and managing fundamental space biology, physical sciences and all NASA human research.  He is also lead interagency contact between NASA, the National Institute of Health, the National Science Foundation and USDA. He credits cross-pollination between different research fields as sparking much of the new sensor research and application to agriculture, along with the Internet.

Collaboration across disciplines squares your output, he says.

The question, as Adamchuk poses, remains, What will we do with the data produced? The optimistic answer is "More than we could ever do without it." The realistic answer is "We have just begun to find out."