EAST LANSING, Mich. – Michigan State University (MSU) Extension and the Michigan Soybean Committee are studying how foliar fertilizers (liquid nutrients sprayed on leaves) can boost yields and productivity.

“In our (Michigan Soybean On-Farm Research Program, which began in 2011), we test different farming methods and products of interest to farmers,” Eric Anderson, MSU soybean educator, told Farm World.

“We currently committed to conducting each trial for a minimum of two years, but that was not the case in the earlier years, so there are some products that were only tested, for example, one year in one field,” he added. “Our goal is to collect as much data as possible to run statistical analyses, so we find as many cooperators as possible for a given trial, and run it for at least two years.”

He said, “The current trial we are running with MicroStrike Bean is in its first year, and we have 15 fields currently enlisted.” MicroStrike Bean is manufactured with chelated (chemically combined with amino acids) zinc, manganese, and magnesium, as well as boric acid, to prevent and fix these micronutrient deficiencies in all crops, and is formulated to mix with most fertilizers and pesticides, according to Crop Performance, LLC, in Bluffton, Ind.

He said crops like soybeans obtain the bulk of their nutrients by extracting them from the soil as they take up water.

He added since soybeans are nutrient scavengers, fertilizer applications can be made successfully ahead of the previous crop, depending on the soil type and nutrient applied.

“However, to a lesser extent, plants can also take in some nutrients through their leaves when liquid fertilizers are applied,” he said. “Nutrients can be taken in through stomata (microscopic openings in the leaf surface where oxygen and carbon dioxide are exchanged and water vapor is released) and through micropores in the waxy cuticle (outer protective layer). If the stomata are closed or the cuticle is thickened under water stress to avoid water loss, nutrient uptake will be reduced.”

He said, “Typically, micronutrients (manganese, boron, zinc, iron, etc.) are better suited to foliar feeding as they are required in smaller amounts (e.g., several pounds to under a pound), compared with macronutrients such as potassium or phosphorus (e.g., tens to hundreds of pounds), depending on the nutrient. Foliar feeding can also be useful for ‘rescue treatments’ when deficiency symptoms appear during the growing season.”

Since 2011, MSU’s On-Farm Soybean Research Program has studied foliar fertilizers across 132 sites, he said. The results showed a significant yield increase only 9 percent of the time. However, he added that the yield increase at the responsive sites did not always provide enough revenue to pay for the cost of the product and application.

He said foliar fertilizers are most commonly used to remedy micronutrient deficiencies, with manganese deficiencies in particular that are common on the higher pH soils of Michigan.

“Manganese deficiency symptoms manifest as interveinal chlorosis (e.g., yellow/white leaf tissue between veins that remain green) on new growth,” he said. “Applications of manganese will not easily increase soil test levels due to manganese fixation (the process where manganese becomes unavailable to plants due to chemical reactions in the soil), so if deficiency symptoms occur, foliar applications are the most effective means of getting the nutrient into the plants.

“However, if manganese deficiency symptoms appear, it is likely they will reappear again if soil manganese concentrations are not remedied when manganese-sensitive crops are grown,” he added. “Dry soil conditions can also induce manganese deficiencies, which may dissipate quickly once rainfall returns.”

He said MSU Extension recommends applying 1 to 2 pounds of actual manganese when deficiency symptoms appear, scouting new growth seven to 10 days later, and making a second application, if needed.

Regarding fertilizer efficacy when applied to the foliage versus the soil, he said it depends on what nutrient is deficient.

“For example, manganese is a common micronutrient applied post-emergence when foliar symptoms appear,” he said. “Since manganese is needed in relatively small quantities by the crop, this is an effective treatment to mitigate nutrient deficiency. Since manganese can be essentially immobilized when applied to the soil (under certain soil types, pH levels, etc.), applying as a foliar fertilizer is the most effective option.”

He added, “However, for potassium, soybean requires a little over a pound of potassium for every bushel of grain produced, so the most effective way to supply that nutrient (and other macronutrients) is via application to the soil.”

Overall, he said, “Soybean farmers do a lot of thinking. I won’t say where they do their best thinking, but they do a lot of thinking about many different topics, especially about how to produce a better soybean crop, and how to increase their profitability.

“One of my goals as the MSU Extension soybean educator is to answer farmers’ questions using research-based, practical information,” he said. “That is one of the reasons why the partnership between MSU Extension and Michigan Soybean Committee is so valuable: taking advantage of the intersection between university research (at MSU and nationwide), and ‘boots-on-the-ground’ crop production.”