Farm and Field

Wet weather pushes soybean planting into cover crops

Posted: Jun. 23, 2019 12:01 am

Cool, wet weather is forcing more farmers to consider how to plant soybeans into tall, mature cover crops this spring.

This might be the year that farmers want to consider "planting into the green," or no-tilling soybean into growing cover crops.

Many growers terminate cover crops early in the season when the cover crop is less than knee-high. This lets cover crop biomass break down quickly before planting.

But University of Missouri Extension nutrient management specialist John Lory, who heads the Missouri Strip Trial Program, says research shows only a small yield loss when planting soybean into the green. Strip trials from the past three years show a 1 to 2 bushel per acre loss at some locations. The yield differences could be attributed to factors such as voles or poor seed-to-soil contact going over terraces, he said.

Many growers are most comfortable with terminating the cover crop early then waiting a couple of weeks before planting. However, in this year's extremely wet field conditions, late termination before planting may result in a mat of tough, dead cover crop residue that will slow drying of the field and might be harder to plant into than the live cover crop.

Planting into thick or tall green cover crops might require some adjustments to the planter and attachments.

MU Extension field specialist in agricultural engineering Charlie Ellis offers some recommendations including:

º Don't get too far ahead of planting with the sprayer. Only spray what you can get planted. If you spray and cannot plant, the dying vegetation does not remove moisture from the ground. It creates a mat on the soil which will prevent sun and wind from drying the soil.

º Check planter disk openers and closing wheels to make sure they are in good condition to no-till into cover crops.

º Planters need to be leveled for good depth control and closing wheel operation.

º Check seeding depth frequently, and plant soybean deep enough to get good seed-to-soil contact and seed slot closure. Ellis suggests a 1.5-inch depth.

Ugly corn

Ugly corn is better than no corn this year.

Corn often looks ragged in early growth stages, University of Missouri Extension corn and small grains specialist Greg Luce said, but this year more fields appear exceptionally ragged.

Extended wet conditions and cold periods left corn uneven, pale, yellow and even purple.

"Don't despair. The corn will be improving soon," Luce said.

Warmer weather will boost corn's appearance. As corn reaches the V5 stage and beyond, the root system grows rapidly. Strong roots support healthy growth above ground.

Corn can become purple-tinted when temperatures drop at night and sunny days follow. This causes early season stress and restricted root growth. When growth slows, sugars produced by photosynthesis accumulate in leaves. This triggers anthocyanin pigment colorization and results in purple corn. Corn usually outgrows the "purpling" condition by V6 stage (12 inches).

Phosphorus deficiency, root injury from insects, fertilizer burn, compaction and herbicides also can cause purple corn. Purpling usually appears in an application pattern or certain soil types.

As soil dries, oxygen returns, and growth rates pick up. Plants green up if there is enough nitrogen, but too much rain and warm soil create the right conditions for denitrification -- and prevented nitrogen application.

"The good news is that corn can recover from a lack of early season nitrogen more than we once thought," Luce said.