Identifying Deficiencies and Benefits of Foliar Applications

Fertilizer programs are not always foolproof, and a lot of the time, nutrients need to be supplemented throughout the growing season to ensure a healthy, high-yielding crop. 

There are a few different tips and tricks that could help you make the corrections you need now and fine-tune your fertility program for the upcoming season. Understanding what the plant needs just by a glance could help you make the necessary adjustments to be successful this year. 
Here are some tips for diagnosing corn deficiencies visually by Tom J Bechman, editor of Indiana Prairie Farmer.
Nitrogen. Younger plants with nitrogen deficiency may be stunted and spindly, with light-green or yellowish-green color. Older plants show traditional V-shaped yellowing on older leaves. It starts at the leaf tip and progresses down the midrib.”
Phosphorus. Low levels in the soil is an obvious cause of phosphorus deficiency, but cold soils, wet soils, or dry and compacted soils can limit how much phosphorus roots can find, producing a deficiency in the plant. Early symptoms include stunted, dark green to bluish-green plants with purpling or reddening of tips and leaf margins.”
“Potassium. Yellowing leaf margins on lower leaves, beginning at the tip and running around the margin, is a symptom of potassium deficiency. Plants may wilt easily, especially in full sunlight.”

“Sulfur. Young plants deficient in sulfur will be stunted, spindly and light green in color. Upper leaves will become light green first. Interveinal yellowing or leaf striping is a key symptom.”

“Magnesium. Symptoms for magnesium deficiency are most likely to appear on sandy, acidic soils in high rainfall areas, where soil tests are less than 100 pounds per acre for magnesium, where soil exchangeable potassium levels are high, and where a high rate of ammonia was applied on soils with low magnesium levels.”
“Look for yellow to white interveinal striping in young plants. Beaded streaking of dead, round spots may appear. Older leaves become reddish purple. Actual symptoms expressed for this deficiency — or any deficiency — are heavily tied to weather conditions. Confirm suspected deficiencies with tissue tests.”
“Manganese. Light-green or olive-green leaves may indicate a problem with manganese. Look for a slight yellowish stripe on upper leaves. Manganese deficiency is most common where manganese soil test levels are low and soil pH and/or organic matter levels are high, in low areas of fields, and in organic sands, peats and mucks.”
“Zinc. Low soil levels combined with high pH or high phosphorus levels may produce symptoms of zinc deficiency. You may also see problems with zinc on cool, wet soils with low organic matter, when it’s cloudy early in the season, and if soil compaction affects rooting.”
“Classical symptoms are white, interveinal strips extending from leaf base to leaf tip. Leaf edges, tips and midribs stay green.”

Although this can be an effective method, it is still not as concrete as performing a tissue sample. From a nutrient perspective, tissue sampling is the best way to understand your plant’s needs. It is best practice to have a schedule and routine when pulling tissue samples. Doing it early in the week will help turnaround and ensure your tissue sample isn’t sitting in the mail over the weekend. Regular tissue sampling will help with adjusting your fertilization plan in the following years and give you the chance to adjust with foliar applications on the current crop.

Tom J Bechman interviewed Betsy Bower, an agronomist with Ceres Solutions in west-central Indiana. She explains the three times best for pulling samples—the first time being the five-leaf stage. Bower states, “Pull 25 leaves at random within the designated sampling area. At V5, pull the uppermost leaf with a collar. It’s important to wait until V5 to pull the first sample because then permanent roots are functioning.” The next time you should pull a sample is at V9 to V12. The third sample should be pulled in the reproductive phase. Bower explains, “That sample provides information on what the plant sees at the beginning of grain fill.”  

Now that mid-season deficiencies have been diagnosed, how do we make the corrections? Foliar applications are the preferred way to address the lack of nutrients you may find in your tissue sampling.

What are the benefits of foliar applications?

This application style provides an array of benefits you cannot get from standard granular fertilizer applications. This is the most efficient way to provide nutrients mid-season and early on. When applying through foliar applications, the nutrients will work through the plant’s leaf and stimulate root growth, giving the plant what it needs overnight. 

According to the ICL Specialty Fertilizer’s Agronomist team, “Foliar feeding can be very instrumental under all above-mentioned cases of necessary intensive mineral nutrition. The big advantage of foliar feeding is that they can address an urgent need within a relatively short time. They are therefore, especially efficient as a preventive and in some cases curative treatments.” 
“Foliar fertilization of crops offers specific advantages over soil-applied fertilizers, because the nutrients are applied and taken-up directly by their target organs, providing a specific and rapid response.”
“Foliar applications can also fight low pH soils and the negative affects you will have from a buildup of hydrogen in the soil. Ground applications on low pH soil will significantly hurt availability and lead to lost fertilizer. The amount of fertilizer wasted on a soil with a 4.5pH is up to 71%. When performing this style of application there are some rules to follow.”
Applying mid-day in 100-degree weather is not the preferred time; this could lead to lost nutrients and or burn the plant depending on the chemical you are applying. These applications should be applied early in the morning or late in the afternoon for optimal results. Farmers in America should be given all the best possible solutions to ensure they will have a healthy, successful crop. At AgriTec, we constantly look for new and innovative ways to best serve American farmers