WHAT IS YOUR PLAN FOR MICRONUTRIENT APPLICATIONS THIS YEAR?

Chances are it may include some zinc on your corn, some boron on your alfalfa, and maybe some copper in your wheat fields.

WHAT ABOUT SOYBEANS?

While micronutrients are essential nutrients for every single crop you raise, the focus is often placed on just one micronutrient in each crop. When it comes to soybeans, they often get left off the micronutrient plan completely.

HERE ARE SOME OF THE KEY MICROS FOR SOYBEANS AND WHAT THEY DO IN PLANTS…

ZINC

Zinc gets the focus in corn, but adding one quart of zinc sulfate to your 200-bushel-per-acre corn crop provides only enough zinc for that season. None will be left over! While soybeans don’t “remove” a lot of zinc, a 60-70 bushel soybean crop pulls the equivalent of two quarts of zinc sulfate out of the soil to use during the growing season. This really shows up on drought years as zinc is important in water efficiency. We shoot for zinc to be around a 10:1 ratio with phosphorus. Zinc doesn’t move in soil very well, so it’s best to either till it in or apply it in a 2 X 2 (or otherwise inject it into the soil) in no-till.

BORON

Calcium helps nutrients get into the plant. Boron helps calcium get into the plant. While boron is critical in sufficient quantities later in the season due to its role in pollen viability and reproduction in general, this nutrient is needed throughout the season, as it is important in cell and seed wall formation. The challenge with boron compared to the other nutrients on this list is that it is the micronutrient we worry most about leaching through the soil. Boron levels can be built up to 2 pmm or even 3 ppm in heavier soils with good calcium levels (1000:1 ratio of Ca:B is the target) with pre-season fertility additions. In sandy soils and higher rainfall areas, keeping boron around 1 ppm can be a challenge and in-season applications become critical.

COPPER

Copper is important in the chlorophyll process and in seed production. It’s also a catalyst in a number of plant reactions and enzyme activations. One interesting observation we’ve heard but haven’t witnessed yet is about copper’s role in fighting sudden death syndrome. The comment was that in soils with high copper levels (5-6 ppm or more), SDS has not been an issue. While I’m not recommending applying copper to get to that level everywhere just yet, if you’re grid or zone soil sampling and notice some higher copper zones, this is certainly something to watch for.

IRON

Of all the micronutrients, iron is taken in by soybeans in the highest quantity. For example, 60-70 bushel soybeans pull in nearly two pounds of iron! Beans want that to be in the ferrous form (2+ charge), so if your soil pH is above 7 and especially above 7.4, you may need to supplement iron in the ortho-ortho chelate form to ensure plenty is of the ferrous form is available. Iron is super important, as it’s required for the formation of chlorophyll. Iron is also involved in respiration, nitrogen fixation, and energy transfer, among other things.

MANGANESE

Higher levels of soil manganese have been believed to reduce sclerotinia white mold incidence, as well as help the plants fight off other diseases. Manganese is an activator for enzymes involved in plant growth processes. It is needed for uptake of magnesium and phosphorus and helps with nitrogen utilization. Manganese also helps with photosynthesis.

MOLYBDENUM

One of the cool things about soybeans is they can produce much of their own nitrogen through nodulation. Of all the things molybdenum does, one of the key functions impacting soybeans is that molybdenum helps with nodulation and the whole process of nitrogen production. Soybeans short in molybdenum may exhibit leaf cupping and overall stunting.

APPLYING MICRONUTRIENTS IN SOYBEANS

On our farm, we focus on building levels in the soil with less expensive dry broadcast fertilizer applications. Then we maintain levels and feed the crop with readily available (often banded) liquid applications. As soybeans are less tolerant to in-furrow fertilizer than crops like corn, we like broadcasting dry fertilizers and banding liquid micros away from the seed (in a 2 x 2 or similar) for safety. Foliar feeding can also be done to supplement a good soil fertility program.