ISSUE 1 May 10, 2007
Although the State of North Dakota has laws on the books that help screen farmers from products with questionable benefits, the laws have several loopholes. Basically, if a product sounds too good to be true, it is. Fertilizers with special almost magical qualities are especially prominent this season. Unusual fertilizer products are registered based on their guaranteed analysis, then the "magic" is added to the marketing later. The following are important questions to ask when evaluating a product-
Can I see the data from unbiased, non-company related research?
Was any of the research done locally or regionally?
If there is no data from unbiased, non-company related research, or the research was done far away, be extremely skeptical of any testimonials, or company-led research that you see. Not all unusual products are without value. Some have demonstrated efficacy in certain situations. Check the research results to see how often yield or quality improvements have been recorded. Check to see if improvements are related to certain soils or conditions. If your farms fit into the model of when the product works best, then perhaps this product might improve your bottom line as well.
Finally, when testing a product on your farm, donít "test" it on 5,000 acres. Test it on a few strips across the field and be prepared to evaluate the results using a yield monitor (preferred) or weigh wagon at seasonís end. A satellite image of the farm prior to heading/tasselling can also show differences in a field from the strip application of product.
In the end, the law can only protect buyers to a point. The phrase "buyer beware" has never been more applicable than this planting season.
NITROGEN RATES FOR CORN
Nitrogen recommendations across the corn-belt have been changed radically during the past two years based on a reevaluation of hundreds of site-years of corn nitrogen rate trials from Minnesota to Ohio. The recommendations were changed due to the inability of formulas like 1.2 X Yield Goal to predict the economic optimal nitrogen fertilizer rate. Several common themes were observed from compiling the data across these states. One theme was that the rate of N necessary to optimize N rate in a poor-growing year was similar to the optimal N rate in a good year. Another observation was that the northern states (MN, WI) tended to have higher relative check (0 N) yields than more southern states (IA, IL).
Based on these observations and data analysis with N costs we have today, N recommendations have been decoupled to yield goal in several states, including MN. One rate is used for corn following corn, and a rate, usually 30-40 lb/a lower is used for corn following soybean. In NW MN, using a percentage of the residual nitrate determined with a 2-foot soil test is subtracted from the table N rate for the soil.
In North Dakota, our corn N-rate database comes from the 1950's through the late 1960's, with yields from those early varieties/hybrids that are not related to our current hybrid yield capacity. The only current research data that we have is from the Oakes test site under irrigation from the 1990's. These data correspond quite well with the observations from the corn belt state. The growing conditions across North Dakota differ drastically from those of most of the corn belt. We can be wet or we can be dry. Most of our fields are not tiled, so when they are wet, they are wet for a long time. The humidity in dry years is extremely low compared to corn belt states. Yield potential is therefore highly variable, and will probably always be lower the further west one is in the state.
Without a broader database in North Dakota, we will probably not officially change our corn N recommendations for several years. However, given the data that exists in Minnesota and South Dakota, and the data generated at Oakes, I would suggest considering the following:
In the higher yield potential of the moister areas of eastern North Dakota, use of a formula similar to
1 X yield potential, or 1.1 X yield potential, both with previous crop credits and residual soil nitrate subtracted from them, would be a better fit than the current 1.2 X yield potential formula. As in small grains, one would expect better growing years to also result in higher N release from organic matter/residue mineralization by microorganisms.
In the west, where yield potential might not by formula reach 100 lb N/acre, I would still suggest a floor of 100 lb N/acre, since in drier soils, efficiency of N uptake and mineralization from soils would be lower than in the east. The 100 lb N/acre floor would include previous crop N credits and residual soil nitrate from a 2-foot soil test.
Dr. Dave Franzen
NDSU Extension Soil Specialist