Start Post-Harvest with a Good Soil Test
Foundational to your cropping plan and to next year’s outstanding yields is your fertility program. AgVenture encourages growers to take soil samples every three years. Grid samples are preferred. Don’t skimp on this investment. A high-quality soil test provides valuable information you need to make critical decisions. This includes factors such as buffer pH and base saturation information on potassium, magnesium, calcium and hydrogen.
Pay Special Attention to Soil pH
Review soil test results carefully to assure that pH is in the desired range for the crops you’re growing. For corn and soybean that is typically 6.5-6.8. Proper pH is essential and allows other soil nutrients to do their jobs well. Applying limestone or other liming products in the fall may help maintain ideal pH levels. Fall is an ideal time for application as limestone takes roughly six months to react and correct soil acidity. It provides a relatively inexpensive source for Ca2+ and Mg2+ when those nutrients are deficient at low pH and reduces the likelihood of Mn2- and Al3+ toxicity.
Correcting pH by liming improves effective activity of certain herbicides while providing a desirable environment for organic materials to decompose, enhancing soil structure and tilth.
Fall Applied Nitrogen
Soil temperature and soil moisture levels make a significance difference when applying anhydrous ammonia. The rule of thumb is to apply anhydrous ammonia after soil temperatures fall below 50 degrees at a 4-inch depth and the projected trend is for continued cool conditions.
The reason is that when the soil is cool, it slows the bacterial conversion of ammonium nitrogen (NH4) to nitrate nitrogen (NO3). Slowing this reaction down allows efficient use of ammonia as it retains NH4 in the soil. NO3 is easily lost through leaching or denitrification into the air. Soil moisture also influences nitrogen (N) efficiency. Extremely dry soils can be too dry to create a proper seal to capture the ammonia applied. AgVenture suggests protecting your investment, using a N stabilizer to slow conversion, and by only applying a portion of your N needs in the fall. This helps ensure the crop has the necessary N available when it needs it most.
(Graph) Effect of soil temperature on nitrate formation (Adapted from Frederick, L.R. and F.E. Broadbent).