Fall rye cover crop reduces erosion, salinity

North Dakota research finds that crop’s fibrous root system helps to build soil aggregates, which improves water infiltration

EDMONTON — Multiple resource issues can be addressed by adding a fall rye cover crop into prairie rotations, says Jay Fuhrer, soil health specialist with the U.S. Department of Agriculture.

“The big ones are salinity, wind erosion, water erosion, and building soil aggregates,” he said after his presentation at FarmTech in Edmonton.

“It also helps from a water quality viewpoint because any residual loose pools of N would be locked into the plant to be released when the plant dies.”

Fuhrer, who studies planting soybeans into a fall rye cover crop for the USDA near Bismarck, North Dakota, said a fall rye cover creates an excellent soil environment for soybeans.

“Agronomically, coming in with a broadleaf into that grass makes for a nice environment for us, and it gives us an easy cover to no-till into,” he said.

“In our region it’s going to be primarily no till options. Very little hair pinning happens going into a standing green crop.”

A grower asked Fuhrer during his presentation if the fall rye cover slows down soil warming in the spring, but he said it has the opposite effect.

“If we have somewhat collapsed soils that are compact, then we are not warming up from below because we don’t have warm air coming up from below through the pore spaces,” Fuhrer said.

“If we have good soil aggregation and good (water) infiltration built into our soils, then we are probably going to warm up from both directions. So a lot of it kind of depends on how healthy are our soils.”

He said the fields on which they grow fall rye covers on didn’t warm up well in the spring when they started their research. However, the soil warmed up faster as the soil aggregates improved.

It’s the fibrous root system of fall rye that helps to build soil aggregates, which improves water infiltration, he said.

Growers have more control over the amount of moisture on their fields when using a fall rye cover crop.

“If it’s a dry year, it’s going to be terminated in advance of seeding,” Fuhrer said.

“So you might be a week or 10 days in advance of seeding that you would be looking at termination. If it’s really wet, it’s probably going to be much closer to your seeding window.”

In wet springs the fall rye will reduce the amount of water evaporated from fields, which can cause salinity issues, because the crop uses up the water.

He said fall rye cover crops are also effective at suppressing weeds in the spring.

“We’re all really concerned with weed tolerance to a lot of our herbicide package,” he said.

“Here we get a lot of help with weed suppression, as well.”

He said using fall rye cover crops also increases soil organic carbon over time.

Seeding rates for fall rye cover crops will depends on whether cattle will graze on the crop.

“If we’re not going to bring livestock in, I might have a fairly light seeding rate. Maybe I’m going to use 40 pounds (per acre) in the fall,” he said.

“If I’m going to bring in livestock, maybe I’m going to bring in 50 to 60 lb., depending on how early or late I seed in the fall.”

Fuhrer has planted only soybeans into fall rye cover crops, but he thinks it’s likely that other broadleaf crops could also be planted into the cover crop.

However, he thinks growers should always start with a small field when incorporating this technique into their operation.

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