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What's VRT worth?

Studies explore economics, build knowledge base to support best strategies

Posted: November 1, 2012

Solving the 'VRT payback puzzle' is a key target for the early but growing research effort into the opportunity variable rate technology (VRT) represents for Alberta farmers.

More resources are becoming available to producers, but the lack of available data to fuel strategies and evaluate benefits remains a key limiting factor, says Ty Faechner, Executive Director of the Agricultural Research and Extension Council of Alberta (ARECA) This is why ARECA has supported field trials over 2009 and 2010 to better understand the economics of VRT.

The approach used in the ARECA-supported studies is to analyze the difference between VRT and corresponding constant-rate check strips, in a variety of fields. For now, this effort has focused on fertilizer application only. The latest results were analyzed in early 2011 and have yielded mixed findings, says agricultural economist Dennis Dey, a consultant on the project.

"There is no clear cut evidence to make the case that a farm business will be better off implementing VRT compared to their current practice of applying a constant, single rate application of fertilizer," says Dey. "However, the data and the economic analysis do provide a better understanding of the constraints to be overcome and the opportunities that variable rate applications of fertilizer might provide in the future."

Field knowledge is major factor

Right now, the indications are that whether VRT pays or not depends largely on the specifics of the field, the knowledge that producers have available on that field and how well they use that knowledge to their advantage. "For variable rate fertilizer applications, the key is having good knowledge of the fertilizer response pattern for each zone within a field," says Dey.

In the short run, the potential economic benefits from VRT could be constrained by a limited knowledge of crop response patterns to levels of fertilizer, the availability of data, the reliability of data, as well as the costs associated with establishing the different zones, soil testing and developing fertility strategies, he says.

However, in the long run there is potential to overcome these hurdles. "This will come from continuously improving knowledge of how fertilizer performance varies across a given field, including under different environmental conditions, and developing capabilities to reliably define multiple zones and varying crop inputs according to the specific needs of each unique zone."

New large scale Alberta project

ARD has its own major project, recently underway on a broad basis in Alberta, to further help address the economic question as well as support strategies on best methodologies. Mike Bevans, project engineer with the Alberta Agriculture and Rural Development (ARD) AgTech Centre plays a key role in the multi-level, multi-institutional project, which is headed by ARD agronomy research scientist Ross McKenzie.

"The big focus of this study is to look at what is happening on the ground under a wide variety of field conditions, with the idea of using this information to design methodologies for using VRT for fertilizer application," says Bevans. "Research and knowledge to develop variable rate fertilizer prescription maps is lacking for the Canadian prairies. This project will help remove that barrier."

Yield maps are easily generated from yield monitors available on most new combines, notes Bevans. However, crop yield alone is not always correlated with N fertilizer response. Optimizing N rates in spatially variable fields requires knowledge of how crops respond to N fertilizer changes across the landscape, understanding soil factors controlling yield potential and understanding the consistency of responses from year to year. The five year study started in 2010.

"Ultimately, we want to be able to correlate crop yield response to N fertilizer rates with various physical and chemical soil and topographic factors." The researchers can then use this information to develop simple, cost effective methods of preparing variable rate fertilizer prescription maps to utilize VRT.

AgTech Innovator: Harnessing the power of VRT

New knowledge aims to put more of the variable rate opportunity in farmers' hands.

There's no doubt it's an attractive concept. New variable rate technology (VRT) approaches have the potential to optimize nitrogen fertilizer application, seed placement and even herbicide application. That means more efficiency, along with the promise of cost savings and environmental benefits. But in practice, VRT is an area where progress with the technology has been far ahead of farmers' ability to put it to good use.

A 2011 edition of the AgTech Innovator – the newsletter for farmers from ARD's AgTech Centre – provides a snapshot of the potential, progress and challenges, in an article titled, "Harnessing the power of VRT." Visit www.agric.gov.ab.ca and search "AgTech Innovator" to find this and other editions.

The equipment, for most part, is there to perform a range of variable rate applications, says project engineer Mike Bevans of the AgTech Centre. But often the solid depth of field-specific information needed to make prescription maps for it is lacking. At the same time, there's a knowledge gap where many producers are in the early stages of learning about VRT and haven't seen a whole lot of data to give them a clear idea of the best approaches and the economics potential those approaches represent.

Now new efforts on several fronts in Alberta are aiming to help fill those gaps. What they all share is an on-the-ground focus.

"The high tech side of VRT approaches is one thing," says Bevans. "But the other part is a thorough understanding of the land where you plan to use it. That means getting down to the soil level and understanding all the factors involved, including responses under different environmental conditions. The more information you can get, the better your opportunity for success."


Meristem is a Calgary-based communications firm that specializes in writing about western agriculture, food and land use. More articles at www.meristem.com.

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