Plant & Soil Health: Starter Fertilizer on Soybeans

Do soybeans respond to starter? When should a grower apply starter on soybeans? Is there a risk?

There are growers who are successfully using starter on beans and will swear by its benefit. There are soil fertility specialists who say soybeans do not benefit from starter and there is a risk that nitrogen and potash could burn the seedling if placed with the seed.

So, should growers use starter or not? It all depends on whether they are already using starter with corn. If their planter is not set up to use starter on corn, they will probably not add it to soybeans. If they apply starter to corn and plant beans with row units, it is easier to apply starter when planting beans than if they drill beans.

Whether a grower uses starter on beans also depends on whether they believe soybeans will respond to fertilizer. Some growers fertilize only for corn, others fertilize for corn and beans, but apply the fertilizer before the corn crop only. Then there is a trend to apply fertilizer for each crop before it is planted.

Starter fertilizer is the placement of small quantities of nutrients in a concentrated zone in close proximity to seed at planting. The primary reason to use a starter fertilizer is to stimulate rapid early growth of seedlings, particularly in cool soils. A second reason is to concentrate some of the fertilizer in a band near the row in situations where the soil’s chemistry would tie up nutrients that are broadcast.

Adding starter on beans is a good way to add some phosphate, zinc, iron and manganese in soils with high pH or calcareous soils that tie up these nutrients. Adding starter with phosphate is especially important for soils testing low in phosphate. Starters are often slightly acid since the nutrients in the starter will be more soluble once applied to the soil.

It is important to add manganese to soybeans because they are sensitive to manganese deficiency. Research at Purdue University showed that the glyphosate-tolerant gene imparts a susceptibility to Mn deficiency in soils that are deficient or unable to supply sufficient manganese to the crop.Manganese deficiencies can occur on soils that test low for extractable manganese such as sandy soils, poorly drained soils and soils with a high pH. Calcareous soil may also tie up manganese as it does phosphate and zinc.

Manganese can be broadcast on the soil or applied with the starter. If broadcast on the soil, the little applied can be easily tied up. It is better to apply with starter when it is banded in a higher concentration. When manganese fertilizer is broadcast, 10 to 15 pounds per acre is needed. When banded, only 3 to 4 pounds per acre is needed.

Manganese tank mixed with glyphosate will reduce the effectiveness of glyphosate, as research in Michigan and Virginia has shown that it can reduce weed control by upo to 50%. Addition of adjuvants like AMS and chelates lessens the reductions in weed control depending on the manganese source. Manganese salts should never be used with glyphosate whole chelated organic forms can.

Using a few gallons of starter with N, P and K may boost soybean growth and help the crop establish itself quicker if conditions are cool and damp, or if the crop is no-tilled. Using starter on beans does work in some situations and may serve as a good risk management tool helping the crop get established more quickly, just as with corn.

Let us know in the comments if you apply starter on soybeans, how many gallons, what the formulation is, and if you realize a growth spurt and yield benefit.

Agronomist Dr. Daniel Davidson posts blogs on agronomy-related topics. Feel free to contact him at djdavidson@agwrite.com.