ARS interseeds cover crops into grain corn

MANDAN, ND - Scientists at the Northern Great Plains Research Laboratory (NGPRL) in Mandan, N.D., will be conducting further research on interseeding cover crops into grain corn this summer, so producers will want to tune in.

For the past three years, Mark Liebig, USDA-ARS research soil scientist at NGPRL, and other scientists, have been studying interseeding a cover crop mix into grain corn at specific growth stages.

The premise of the study is: Can producers come out ahead and in good shape in terms of soil health by interseeding cover crops into grain corn without losing yield on the commodity crop?

“Our central question is if we do this interseeding in a drier part of North Dakota, is there going to be a yield penalty to the commodity crop?” Liebig said.

In 2020, the ARS farm crew will be interseeding the cover crops into the corn in a larger field than they used during the previous two years of the study.

“What is really exciting is we are going to be doing the interseeding on a larger field – a 50-acre field – this year,” he said.

The larger field will allow ARS scientists to do additional studies, in real-time, as part of the Long-Term Agroecosystem Research Network (LTAR).

“We are going to be able to see what is happening in fine detail in a cornfield that has the intercrop and in a cornfield that doesn’t,” Liebig said. “It will be a fantastic comparison to see how that intercrop affects these other things that are important for us to understand crop performance in the crop rotation.”

ARS has an instrument tower, which measures carbon dioxide and water fluxes in real-time on fields with and without the cover crops in corn.

In addition, there are soil moisture sensors, which are able to see the differences in soil moisture depletion down to about 6 feet, along with other measurements.

Producers and scientists will be able to check on the crop as it develops through the LTAR PhenoCam Network, a camera system that is set up and pointed at the crop canopy, where a photo is taken every 30 minutes.

“Producers can watch the crops grow in real-time over the season,” Liebig said.

Interseeding study

Liebig explained the importance for interseeding cover crops into a commodity crop.

“Interseeding is a way to increase the soil cover, and the biomass (from the cover crops) can be utilized as a forage resource after the commodity crop is harvested,” Liebig said.

Soil cover is “important” to the study.

“Covering the soil reduces the potential risk of erosion from the field, but cover crops are widely recognized to provide multiple benefits to the soil in cropping systems,” he said. “Cover crop biomass is also effective at taking up any excess nutrients in the soil.”

Later, the biomass can slowly decompose and be available for the following crop, allowing for a more efficient use of nutrients.

Planting with no-till interseeder

Using a specially-made no-till interseeder, the ARS farm crew seeded cover crops in corn in 2018 for the first time. According to the website, the no-till interseeder can sow three rows of standing cover crops, and it also works as a multi-function no-till grain drill.

“We have had good subsoil moisture this spring, although it has been a little dry like most places in southwestern to south central North Dakota,” he said. “All the corn is in and we will be interseeding the cover crops soon.”

In 2019, the crews weren’t able to interseed the cover crops until July.

“Seeding was late last year, as we had persistent wet conditions in the field early in the growing season,” Liebig said. “The corn really didn’t start to take off until the first week in July.”

The ARS farm crew targets the interseeding when the corn is at the V4, V6, and V8 vegetative stages.

The cover crop seed mix the farm team interseeds includes: 17.8 pounds per acre of rye, 3.2 pounds per acre of triticale, 18.9 pounds per acre of cowpea and 2.1 pounds per acre of purple-top turnips.

“The different seeding times allow us to evaluate potential tradeoffs from earlier establishment,” Liebig said. “To me, success would be getting good biomass early and not suffering from a yield penalty.”

Cover crop biomass, corn yields

In 2019, cover crop biomass from the first seeding time (about 600 pounds per acre) was significantly greater than cover crop biomass from the second and third seeding times (averaging about 355 pounds per acre).

Cover crop biomass was on average 81 percent greater in 2019 compared to 2018.

The grain yields did not differ across treatments, with yields ranging from about 120-130 bushels per acre.

“We didn’t finish harvesting the corn until this spring because of the snowstorm we had last October,” he said.

While the third year is not finished and there are no official results, Liebig said the study looks promising.

“The preliminary results point toward this being a promising practice in drier parts of the state,” he said. “We haven’t observed a yield penalty from intercropping and the cover crops over the first two years, but we’ll have to see how the third year shakes out,” he said.

Roberto Luciano, who works for NRCS as an agronomist, works as a liaison between the NRCS state office and ARS in Mandan. He helps document the growth of the cover crop throughout the season.

“Luciano has cameras set up in each treatment to see how the cover crop develops over time,” he said. Luciano also does several measurements on the farm related to soil health.

Commodity crop: Sunflower

While grain corn is not bringing a high price in the current market, the ARS team is planning to run the treatment in 2020 with sunflowers. Sunflowers may bring a better commodity price.

“Some of the same issues with corn may exist with sunflowers, but there are different root and canopy attributes with sunflower,” Liebig said. “We may minimize competition with sunflower because it is a taproot species, but there could be more shading with sunflower. We don’t know how the cover crops could handle that.”

After harvesting sunflowers, biomass tends to decompose quickly, and that residue could partially disappear. That could create issues with soil conservation efforts.

But after harvesting sunflowers, Liebig is hoping biomass left by the cover crops will be a good soil cover for the field. Soil health is one of the main parameters to the study.

Would the study encourage more producers to grow more sunflowers?

“If we could show that cover crops could be incorporated without a yield penalty in sunflowers, then it would be a win-win,” he said.

Cover crops are gaining in importance in the drier parts of the state. The Mandan ARS station has been raising and researching cover crops for about 15 years.

“It is our role to do research on cover crops and help producers understand the trade-offs associated with their use,” Liebig said.