Farm Industry News first covered the Veris 3100 Soil Electrical Conductivity (EC) Mapping System in the March 2000 issue. That system used six heavy-duty, spring-loaded coulter electrodes mounted on a steel frame sensor cart. Location was tracked and mapped via GPS, and the data were stored in an on-board computer.

Since then, the company has combined EC and pH sensing capabilities in a new product it calls the Mobile Sensor Platform. The on-the-go system is the first of its kind to map changes in both physical structure of the soil and chemical properties. We called on Team FIN's Chuck Myers in Lyons, NE, to test the new capabilities. Here is his report.

As a test field, I used a 160-acre field with variable soil types and yield data. We ran the Veris system over 28 acres of that field and developed maps that show changes in pH and electrical conductivity.

Most agronomists say balancing soil pH with lime is one of the most cost-effective things you can do for your soil. That's because soil pH can affect everything from germination and nutrient uptake to herbicide performance.

For corn and soybeans, I'd like to attain a pH somewhere between 6.3 and 6.7. But that's not easy on this field because it has some lighter soils and some heavier, high-organic-matter soils. The lighter soil requires less lime to correct a 5.6 pH. Heavier, high-organic areas require more lime even if you start at the same pH level. A map that shows both pH and EC should be helpful in making that adjustment.

Zone map uses

Mapping the changes in EC and pH using the Veris system is much more precise than relying on the rough estimates attained by 2.5-acre-grid sampling. The Veris maps show exactly where variability occurs.

In theory, putting exactly the right amount of lime on every part of the field should attain the ideal pH on every part of the field. That would increase yields. I wouldn't necessarily use less lime; it would just be distributed better.

The maps that Veris generates clearly show where the soil granulation changes. In addition to being useful for variable-rate lime, I can see how the maps could allow for better-targeted soil tests for major nutrients. Rather than relying on a grid, we could target our tests by zone for more useful results. We might also save some money by not doing grid sampling, which costs around $10/acre for a half-dozen major nutrients.

I can see a lot of potential for using this kind of data, but I haven't actually acted on it by applying variable-rate lime yet. I'd like to test the whole field first and compare the EC and pH variability to data from my combine yield monitor. It will take some additional work to factor out things like moisture variability on hillsides.

Costs

Ideally, when and if the value of this kind of data is proven, I'd prefer that my local ag retailer conduct the tests and make the appropriate variable-rate application. I wouldn't have to invest in the equipment, which costs between $15,000 and $25,000. Plus I think it would be worth the cost to have a professional interpreting the data.

I need to consider that custom application costs extra too. Most farmers in my area put down about 2 tons/acre when they apply lime. I have our fertilizer supplier apply the lime at a cost between $15 and $17/ton. Having the lime applied at a variable rate costs an additional $2/ton. So I'd need to add that cost to whatever my retailer might charge for testing.

Overall, I'd say this technology looks promising. But will it pay off on my fields? I'm still not sure. Although I know some farmers have already purchased this system and are sold on the results, I'll continue to evaluate the data and take it one step at a time.

Veris system versus grid sampling

An October 1996 Farm Industry News cover story noted the limitations of coarse grid sampling and predicted that sensors would someday be able to map fields more precisely. The updated Veris system seems to fulfill that prediction.

Researcher Viacheslav Adamchuk has evaluated its capabilities at Purdue University and the University of Nebraska. His findings indicate that the system provides pH readings that are accurate and repeatable. On-the-go sampling can take more samples than grid sampling in less time for less expense. But the initial investment in equipment is higher and existing on-the-go systems currently can't test for nutrients such as nitrogen, potassium and phosphorus.