By Bruce MacKellar and Eric Anderson
With low corn prices and increasing costs for inputs, irrigated corn growers need to be looking at trimming costs while keeping yield potential high. The following are a few thoughts that hopefully can promote these goals.
The basic truth remains that there are substantial differences among hybrids, even those offered by the same company. Hybrids differ in their ability to perform in high population, high competition environments. Don’t overlook leaf disease ratings in irrigated corn. If you can find information on tar spot tolerance, that could be important this year. With hybrid turnover at such a fast pace, it takes work to keep up to date. Be a student of the game in hybrid selection.
Starter nitrogen and phosphorus (2x2) is the most efficient way of maximizing nutrient uptake while applying a high enough rate to ensure nitrogen availability. Only add phosphorus if the soil test levels suggest it is needed, as excess does not improve yields but does quickly add costs. Check potassium on sand/loamy sand soils regularly, as it has potential to leach through the soil profile. Sulfur is likely to be needed on most of the irrigated sands in the region. Sulfur helps with nitrogen utilization as well as alleviating the yellow striping that can slow down corn growth in the early vegetative stages. Make sure there is adequate magnesium in your soil test (80 pounds per acre, 40 ppm).
Always plan on splitting nitrogen applications on irrigated corn. This provides the best chance to match nutrient application with crop needs while reducing the chance of leaching loss. Applying some nitrogen through irrigation also helps optimize applications by applying nitrogen only where water is being applied and yield potentials are high in the field.
This is a bit tricky. The Michigan State University maximum return to nitrogen (MRTN) system recommends 123-191 pounds per acre depending on your fertilizer and corn prices—see the chart. But irrigated nitrogen management really requires a careful estimate of applied nitrogen losses and the soil’s ability to mineralize nitrogen (texture, organic matter level, manure applications).
Asiatic garden beetle white grubs
Pests like Asiatic garden beetle white grubs are on the rise in southwest Michigan. This is especially a problem on the lightest portions of fields. Effectiveness of control with soil insecticides often varies with the population densities of these pests. There are no rescue treatments though, so early scouting for grubs being turned up by soil tillage is the key to see if soil insecticides, along with seed treatment, is warranted.
Scout for trouble