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Sign-up Now For Soil Nutrient Benchmarking

Sign-up Now For Soil Nutrient Benchmarking

Iowa Soybean Association's On-Farm Network announces new program for growers.

The Iowa Soybean Association's On-Farm Network is now enrolling Iowa growers for a statewide project this summer to evaluate the current status of soil and plant nutrients in their fields.

The intent is to collect soil and plant tissue for analysis from at least 500 corn and 500 soybean fields. This information will be used by participating growers to manage their nutrient use and also will become the basis for a new soil and plant nutrient database for the state, forming a benchmark from which to measure future changes in soil nutrient status.

Growers will use current aerial imagery of the enrolled fields to select locations to pull samples from at least two points in each field. "Additionally, the same information will be collected from fields enrolled in On-Farm Network replicated strip trials," explains Tracy Blackmer, director of research for the On-Farm Network. "Besides nitrogen, phosphate and potash, we'll also analyze samples for sulfur and additional micronutrients."

You must enroll before July 14, 2011 to participate in this program

After harvest, small local group meetings will be conducted around the state to discuss and compare results. A statewide summary will be posted at Information will also be presented at the 2012 On-Farm Network Conference in February. Participating growers will receive free admission to the 2012 conference.

Click here for more details, or call Christine Borton at 1-800-383-1423 to enroll. Blackmer says you need to act now because the sign-up deadline is July 14 if you want to participate.

While this program is funded in part by the soybean checkoff, there will be a small cost to participating growers, he notes, amounting to less than the price of a bushel of corn or soybeans per acre for the enrolled fields.

Economic and environmental concerns are driving application rates

"Economic and environmental concerns have made all of us—farmers, crop consultants and agronomists--more aware of the amount of crop nutrients we apply and it has often meant cutting back on those amounts to the point that applications may not meet the crop's needs," says Blackmer. "As evidence of this, we have recently begun to see signs of nutrient deficiency in corn and soybeans in some fields."

If you are wondering about the nutrient status of your crops, you are not alone, he says. Blackmer and his colleagues have been getting a lot of questions from farmers this year, prompted largely by what they are seeing in their fields.

The concept is to get an aerial image of the field and use it to guide the collection of soil and plant samples shortly afterward. The goal is to get a minimum of 500 corn and 500 soybean fields, with a proportionate amount from each of Iowa's 99 counties. This broader database will result in not only feedback for a given field, but also a relative comparison to other fields in your area and across the state. So while the tests will tell you the nutrient status in your field, the biggest benefit of the program is the ability to compare your results to the larger database.

Many problems identified in aerial imagery aren't visible in yield maps

As part of the larger program, the same type of soil and plant tissue samples will also be collected from On-Farm Network replicated strip trials to help with comparisons and interpretations. All samples will be collected at roughly the same time and sent to the same testing lab. Analyses will include N, P, K and S but will include testing for micronutrients, too.

Some farmers may say, "I already have yield mapping and I use it to help me make my fertilizer application decisions. And I also sample and test my soil. Why is using aerial imagery better than yield mapping?"

"Using aerial imagery in this way is a newer technique that has interested many agronomists and growers," answers Blackmer. "The imagery we're providing for this is collected at a 1-meter resolution. This allows us to see differences as small as a single row. Many of the problems identified in aerial imagery are not visible in yield maps created at harvest because of the difference in resolution and because not all field issues follow the crop rows. The imagery we will use in this new project will be both color and color-infrared and will be geo-referenced so it can be used in mapping software. With these images as a guide, you can better select the sampling locations for both the soil and plant tissue samples."

You'll able to compare your results with those of other growers

The small group meetings will be held around the state over the winter to discuss the data and answer questions. This will allow participants to compare their results with those of others locally and across the state, he notes.

"We are offering this program for the cost of the services, and have negotiated prices below those you would pay as an individual," says Blackmer. For a field of up to 80 acres, with two soil and two tissue samples, the cost will be $195. Larger fields and more samples will be incrementally adjusted. "The cost of this evaluation translates to the equivalent value of less than one bushel per acre. For many growers, this would be a good investment to give a direct evaluation of their own field as well as a relative evaluation when compared to other fields."

The On-Farm Network is a trademarked program of the Iowa Soybean Association, with approved affiliated programs in Iowa, Indiana, Ohio, Pennsylvania, Delaware, Virginia, North Carolina, Missouri, Minnesota and Illinois. For information go to or

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