By Kyle Gustafson, WinField United Agronomist
One misconception I often hear in the field is that micronutrients aren’t as important to crop development as the macronutrients, including nitrogen, potassium and phosphorus. The terms “micro” and “macro” refer to the quantity of nutrients that a particular crop requires for development. Deficiencies in micronutrients can be just as detrimental to crop development as a macronutrient deficiency. Don’t let the terminology undercut the importance of micronutrients to your fertilization plan.
Don’t wait to see symptoms
By the time plants show symptoms of micronutrient deficiency, it’s often too late for corrective action. Having a pulse on the nutrient status of your crop throughout the season can allow for fertilization adjustments to mitigate deficiencies. Soil testing, done in conjunction with tissue testing, can provide a comprehensive set of data that can help you better understand nutrient availability to your crops.
Soil testing is a good starting point to determine how much of a specific nutrient is available in the ground. It provides a baseline, but I don’t recommend using soil test results alone as an end-all decision-maker for fertilizer applications. Nutrients in the soil can vary depending on environmental conditions and time of year. The goal of soil testing is to evaluate nutrient availability in soil year-over-year, so plan to test at the same time every year to get the most accurate results. In most areas that’s either in the fall or early spring.
Tissue testing can provide even more specific insights on nutrient availability. You’ll get a real-time snapshot of how plants are taking up nutrients from the soil. By tissue-testing plants in the same location as soil tests were done, you’re able to contrast nutrient availability in the soil with nutrient uptake in the plant.
A guided tissue test is another way to better understand nutrient uptake, specifically in areas of the field that may be showing deficiency. Technology tools like satellite imagery can help you to target areas in a field that appear stressed in order to take a deeper look with tissue sampling.
Why are micronutrients deficient?
You’d think that since micronutrients are only required in small amounts they’d rarely be limiting. The truth is, changes in field conditions and soil composition can impact micronutrient availability to plants. Zinc, boron and manganese are three common nutrients that farmers in the upper-Midwest may find deficient in their crops. Here are some things to keep in mind as you manage these micronutrients.
- Cool, wet springs lead to zinc deficiencies. Zinc assists with chlorophyll production in plants, so it’s an important nutrient for harnessing energy for grain production. Deficiencies are common in cold, wet soils and in soils with high pH, free calcium, and low organic matter. Supplemental zinc can be applied a number of ways, including as a seed treatment, included with starter fertilizer at planting or as a foliar application later in the season.
- Monitor boron levels in alfalfa crops. Alfalfa uses a lot of boron; therefore, it’s important to survey nutrient levels in an alfalfa crop. Like nitrogen, boron is mobile in soil and is prone to leaching, especially in sandy soils with low organic matter. Boron is important for proper nodule development and overall root growth in alfalfa.
- Glyphosate applications can tie up manganese. Glyphosate has the ability to tie-up manganese in the plant leaf (such as soybeans), making it unavailable. This is more common when crops are grown in organic soils with low pH that are deficient in manganese to begin with. Supplemental manganese can be applied as a foliar application along with glyphosate.
No “easy button” for fertilization
Unfortunately, there’s no one fertilizer recommendation that works for every situation. In order to evaluate your crop’s nutrient status, you’ll need to get in the field to soil and tissue sample.
Scout fields and continue to tissue-test throughout the season to understand and mitigate nutrient deficiencies.
Adequate nutrition is required to drive the physiological processes in plants that ultimately lead to grain production. Talk with your agronomist today about how you can continue to tissue test throughout the season to mitigate problems before they lead to yield loss.