ILSOYADVISOR POST

Agronomy: Is It Planting Time or Just Planting Fever?

There’s no telling how spring 2014 will go. In 2012, beans were planted very early; in 2013, very late. The important lesson learned is that the days of planting by the calendar are over.

While it can be tempting to get in the field early, here are some important points to consider to ensure you’ve prepared the best possible seedbed for your soybeans.

Consider soil temperature

While some researchers will recommend an earlier planting time to help soybeans reach their maximum yield potential, keep in mind that earlier may not be better.

The minimum soil temperature for soybean germination is between 55 and 60 degrees F. Remember that’s the minimum, and germination rates will increase as soil temperature warms. Any time you plant into a cool soil, you’re putting soybean seedlings at risk for diseases or damping off.

Prepare the seedbed

Rapid germination requires moisture and warmth, helping to speed the soybean seedling to emergence. This is a critical time for soybeans, as cool temperatures, crusted soil or an improper planting depth can lead to poor emergence and compromised yields.

Unfortunately, those same things that factor in to make a great seedbed for soybeans also make a great place for weeds to gain a foothold in your fields.

If soil moisture is adequate, soybeans can get off to quick start, helping them to outpace weed seedlings in the race for sunlight. Remember, anything that shades weeds will slow their growth. Using residue to cover the space between planted rows can also discourage weed growth.

How deep is too deep?

Planting depth may vary, and large seeded varieties are better equipped to emerge from greater soil depths than standard varieties. Also, plant deep enough to ensure adequate moisture and temperature for germination, typically 1—1.5 inches. In low moisture conditions, planting depth can be as deep as 2 inches, with 1-inch depths better for cool, moist soil.

Optimize plant population

Select the appropriate plant density based on a combination of management and environmental factors. Plant at too high of a rate and you’ll have increased lodging and reduced branching of the plants. Plant at too low of a plant population and you’ll reduce lodging and branching concerns, but may increase weed competition.

Consider increasing your plant density when growing determinate, semi-dwarf and non-branching varieties. Additionally, the local soil type, environment and seed quality can influence plant density.

While typical populations for wide rows are in the 150,000 range, populations for narrow rows can go up to 175,000. Regardless of the row width, adjust populations so that lodging is minimized and pods are high on the plant.

Is narrower better?

The end game in a well-managed soybean field is a uniform stand. Typically, soybeans will yield more in narrow rows than in wider rows, as long as weeds are controlled. Other benefits from narrower rows will depend on location, soil conditions, weather conditions, planting date and variety. The downside to narrow rows? It’s much harder to cultivate weeds, if needed.

Still, a good rule of thumb is the standard that the canopy should close by flowering, helping to keep late-season weeds at bay. Some growers have also begun standardizing both their corn and soybean crops to 20-inch rows, simplifying equipment needs.

Adapted from information provided from the National Soybean Research Laboratory.


Illinois Soybean Association
The Illinois Soybean Association (ISA) is a statewide organization that strives to enable Illinois soybean producers to be the most knowledgeable and profitable soybean producers around the world. ISA represents more than 43,000 soybean farmers in Illinois through two primary roles; the state soybean checkoff and legislative and regulatory advocacy efforts.


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