On my drive to work this morning the temperature was 47 degrees, and I noticed more and more of the leaves on beans and of corn are beginning to mature, fall is coming fast. And as fall comes fast, so too does fall spreading of fertilizer and soil sampling. Variable rate spreading of fertilizer is one of the biggest misconceptions that I find growers have.
Many people believe that Variable rate spreading is way more expensive, calls for a lot more fertilizer, and has to be done forever once started. All of these misconception can be true, but all of them usually deem false to most growers. In an example today I will walk you through a 40 acre piece of land. Soil type is a loamy sand, and rotation is two years of corn followed by one year of soybeans. Tillage is done after the first year of corn. Otherwise it is run as no till. After sampling on 2.5 acre grids (to produce good data for variable rate spreading) we found potassium levels to vary from 38 – 118 ppm, with an average of 63 ppm. This large variance in levels is not uncommon in Wisconsin fields. For this particular field the grower shoots for 200 bushel on the first year of corn. This being said a flat rate recommendation would be for 200 lbs of Potash. Using flat rate spreading, the field would cost the grower $1,310. With the increase in cost for variable rate application and a 200 bushel yield goal, the cost for the field is $1,271, this decrease in cost can help justify the cost of sampling the field and still provides the needed fertilizer for all the plants in the field. The application prescription varies from 121 lbs- 219 lbs of product with an average amount of 177 lbs. This use of variable rate spreading will be utilized until the levels of potassium in the field reach an equilibrium allowing us to return to flat rate spreading.
As we move closer to fall harvest keep this bit of information in mind, and if you may be interested in variable rate spreading and soil sampling feel free to contact your local agronomist or YieldPoint Specialist. If you would like to receive more information on this price comparison and the data behind it, feel free to contact me.
By: Alex Yost, YieldPoint Program Specialist