DES MOINES, Iowa - Fall provides growers a chance to get a head start on soil testing and nutrient applications, say experts at Pioneer Hi-Bred, a DuPont business.
"With harvest ending, now is an optimum time for soil testing to reveal any potential nutrient deficiencies," says Keith Diedrick, Pioneer area agronomist in west central Indiana. "Growers can work to increase the nutrient profiles of their fields, spread the workload and prepare for spring."
When agronomists assess poor-growing crops, the first questions usually revolve around basic nutrient availability, especially nitrogen, phosphorous and potassium. Knowing which nutrients are out of balance is the first step in improving conditions for crops.
"Soil tests are a good tool to measure existing nutrient levels available to crops," says Diedrick. "The results provide you with a good idea of what may be going on in your fields."
To maximize profitability, using the right combination of fertilizers is important. "Results from consistent soil tests are critical for growers making those decisions," says Diedrick.
A standard soil test provides a measurement of macronutrients such as phosphate, potassium, magnesium, etc. Knowing the current levels of these nutrients allows you to plan for any necessary applications to prepare fields before spring planting.
Fall soil tests for nutrients such as nitrogen (N) and sulfur (S) may not be as valuable because the nutrient status may change before the crop can take them up. Some growers use soil nitrate tests to fine-tune nitrogen rates in-season, but most N recommendations are based on the previous crop, the N-to-corn price ratio and each grower's personal comfort level for risk.
In-season soil tests also tend to work well for diagnostic purposes - to find out what may be causing a current issue. "If you want to plan ahead, it's important to test at the same time every year for comparability reasons," says Diedrick.
"It's important to understand the results of the soil test," says Diedrick. "Make sure you know what the lab is basing its results and recommendations on." Verify that the recommendations you're getting match your crop needs. Crop plans for the upcoming year will influence your utilization of the results.
"Critical nutrient levels are different for every crop," says Diedrick. If you're unsure of typical nutrient levels in your area, he suggests checking regional agronomy resources such as your local Extension office.
"Regular soil tests, taken every three to four years, allow you to react to changes and reverse negative trends," says Diedrick. "Shorter test intervals tend not to show any significant benefits. If you wait longer than four years, you don't get a consistent benchmark of soil nutrients."
For accurate results, representative samples from a proper depth throughout a grower's fields are necessary. Sampling methods depend on cropping and fertility management practices. Check with your local Pioneer expert for more information on correct sampling methods.
Soil test results can alter a grower's nutrient application rates. For cost-effective application in the fall, Diedrick suggests using a granular, dry fertilizer.
"Dry fertilizers will dissolve and react with the soil similarly to liquid fertilizers," says Diedrick. "Most dry applications can be soluble with little rainfall, and are easier and more economical to handle in large quantities."
However, N application is generally more efficient in the spring. "Fall and winter applications can result in potential losses of significant amounts of nitrogen," says Diedrick.
Whether you decide to apply nutrients in the fall, winter or spring, consistent testing from year to year is one of the best ways to ensure a balance between economic and environmental factors.
For more information on interpreting soil test results or understanding critical nutrient levels in your area, contact your local Pioneer sales professional or visit the soil fertility page on pioneer.com.