Variable rates offer variable results

Jul 11, 2001 12:00 PM, Wayne Wenzel

As profit margins on chemicals, seed and fertilizer get tighter, co-ops have adapted by selling their expertise in variable-rate technology as a per acre service. Will their services pay off for you? We asked Growmark Precision Farming Manager, Sid Parks some key questions about variable rate profitability.

What’s the typical return on a precision ag investment?
Every situation is different, and because of the vast variability in soils and individual farm practices, there are no profitability guarantees. From universities, private companies and experience with our own GREEN PLAN/gis crop recommendation program, there’s been a lot of excellent data collected using precision agriculture. It is important to consider both potential increases in yield and reductions in inputs weighed against the extra costs. For the customers we serve, our data typically shows a $2 to $6 net gain per acre per year from variable application of phosphorus and potassium fertilizers, with 2 fields in 3 benefiting from variable application. This is influenced by the variability and range of the soil test nutrients, cost of gathering information and implementing actions, as well as the crop price and field productivity levels. The benefit of variable-rate lime application to correct pH is on top of that.

How do you know if a particular field will respond well to precision applications?
You don’t, therefore you first need to collect some information. For farmers considering a precision ag program, I’d recommend starting in fields where the topography or soil type varies significantly, where past management practices differ, or where you see dramatic changes in yield as you go through a field. Many farmers look closely at local success stories to convince themselves that precision ag will work in their area and then start with a field on their farm. After they see positive results demonstrated on their field, they usually enroll more acres each year.

Which types of precision applications have the best payback?
Again, it depends on your field. Most often though, because of the effect pH has on crop growth and herbicide efficacy, we find that you’ll get the best payback from balancing a field’s pH level using a variable-rate lime application. Variable-rate phosphorus and potassium applications are next. Field mapping is also useful in spot treatment of problem weed areas and determining whether or not to apply other nutrients to specific areas of the field.

What about variable-rate nitrogen?
Agronomists who understand the complexity of the nitrogen cycle will tell you it’s harder to determine the value of applying variable-rate N. Unlike P and K, N is not strongly held by soil particles. It is subject to movement in the soil and loss through nitrification, leaching, and denitrification. The opportunity to accurately measure soil nitrogen or variably apply product based on crop needs is limited because of the inability to predict nitrogen availability. The best nitrogen strategy is to take all credits from previous crops, manure or fertilizer applications, and then apply the recommended rate to meet your yield goal. We have some customers who variably apply nitrogen to take advantage of nitrogen supplied from variable-rate phosphorus applications of diammonium phosphate (DAP). DAP contains 18% N and 46% P, giving you a significant nitrogen credit.

Does precision agriculture make sense with today’s low grain prices?
Actually, when profit margins are tight, it makes even more sense to monitor your inputs closely, and that’s exactly what site-specific management provides farmers. Many times, you put about the same amount of product on your field, you simply redistribute the inputs to where they’ll give you the biggest potential yield response. Additionally, we’ve found in some fields VRT isn’t justified. A uniform-rate is recommended that is less than might have been traditionally used because past applications may have been done without a producer testing fields frequently, if at all. Grid sampling provided the additional information from which we could base the nutrient recommendation.

Are a lot of farmers in your area using precision ag services?
The rate of technology adoption varies by area. Here in central Illinois, we started helping farmers integrate site-specific practices earlier than some other regions, making significant inroads as early as 1994 with continued growth since then. Adoption in these areas has slowed because significant portions of the acres are already done. Areas which started more slowly are seeing continued growth of precision ag services. Overall, we expect to see peaks and valleys in the adoption curve. I’ve heard ag economists report new technologies may take 20 to 30 years before they are fully integrated. As this technology improves and farmers become more familiar with it, we expect our business to continue growing. In the future, I believe site-specific management will become the standard used by most farmers.

Are some farms too small to make precision ag pay?
Actually, if you’re farming to make a profit, no farm is too small to take advantage of grid sampling and variable-rate applications. Many of our smaller customers can’t afford to buy precision ag tools themselves, but they can still benefit from grid sampling, variable-rate application or data mapping services provided through their FS co-op. It really doesn’t matter if the farm is 40 acres or 4000. Many farmers own just a yield monitor and use that in tandem with our services. While spending $7,000 for a yield monitor is a significant investment, I’ve never talked to a farmer who really used it who said he wished he’d never bought one. However, the fewer acres you have to spread the investment over will impact how soon you feel the investment paid for itself.

Don’t all farmers want to make a profit?
Everyone wants a profit, but some people aren’t willing to make tough choices that precision ag tools might point out. Those individuals may not be the best candidates for adopting precision farming. Look at it this way—the tools of precision agriculture can provide management advice like an accountant or a banker. Some individuals are so production-oriented that they’d keep farming a certain way even if their advisor told them they’d be losing money at it. Likewise, long-term yield maps might show a certain field, or a part of it, would be better off taken out of production. That can be frustrating, but instead of row crops you might be better off to put in filter strips or grass waterways in those less-productive areas. And if you’re renting the ground, you might be advised to let the land go, or at least try to negotiate reduced cash rents for less productive acres. The power in collecting and using the information is to make smarter management decisions.

FS/GROWMARK offers grid sampling and mapping, variable-rate application, data mining and data management services in six Midwest states and Ontario. For more information:

GROWMARK Inc. 1701 Towanda Ave. P.O. Box 2500, Bloomington, IL 61702. 309/557-6247. www.growmark.com.