Just a Fraction of a Bushel!

Higher prices for corn and beans have subjected Iowa growers to a record number of sales pitches from ag suppliers promoting the idea that with higher prices, it takes only a fraction of a bushel of yield increase to pay for their product or practice. 

Trying all these new products and practices may be tempting, because the higher grain prices are producing higher income. Higher income gives you the option to invest more in products that increase yields. When considering this, growers typically target their higher yielding fields, because with higher yields there is more grain to sell for more money. 

But this often causes people to lose sight of an important metric: the yield response to the added product/practice. If a product costs $5/acre and increases soybean yield by 1 bu./acre, with  soybean prices at $12/bu., it increases profit by $7/acre. If the yield response is the same whether you’re growing 40 bu. beans or 70 bu. beans, this product is equally as profitable on all fields. Clearly, higher yielding ground tends to be more profitable because the higher yields generate more revenue per acre.

However, not all products or practices affect yields the same on both higher and lower yielding ground.  So, you may be willing to spend more money for inputs on high yielding fields because they potentially have more revenue to work with. This does not mean the products work better on higher yielding fields than on lower yielding fields! This concept, though, has been used by a number of data processing services to show a trend in which fields where a specific product was used had higher yields than fields where it wasn’t. Such a correlation can often be made legitimately. However, you can’t stop with just this correlation, since it does not actually show that the fields yielded higher because of the product. If the results being cited are from actual grower fields, it could simply mean that growers were more willing to pay for the product on their higher yielding ground. Of course, it could also be because the product increased the yield. 

Extensive nitrogen fertilizer rate studies in corn have shown that in many areas of Iowa, the higher yielding fields don’t need higher N rates. This is because the higher yielding areas of a field often have better rooting depth and higher organic matter content, giving the plant easier access to the extra N needed for higher yields.

Another example is the use of fungicides on soybeans. Hundreds of On-Farm Network^® fungicide trials in Iowa have shown the yield increase from using them is about the same regardless of yield level of the soybean fields. In other words, you would expect the same yield increase whether in a high- or low-yielding environment.

Many different factors can affect how a product will perform in a given environment. In today’s economic climate, it is tempting to say why not use the product? After all, a fraction of a bushel will cover the cost. When making this determination, make sure you realize that the change in yield because of a management practice is yield response and should be the basis of agronomic decisions, not the field potential. Ask yourself these questions: 

1. Is the product or practice actually responsible for the yield difference? 
2. Will it work the same on lower yielding fields? 
3. Or might the yield response to the product be greater on the lower yielding field? 
4. Does the product correct a problem that exists on the lower yielding field, but not the higher yielding field?

For examples of Iowa data measuring the yield response to different agronomic practices, go to www.isafarmnet.com.