Practical Farmers of Iowa studies benefits of cover crops

Livestock farmers are discovering that using cover crops not only boosts soil nutrient levels, but also cuts input costs because the cover crops can be used as a feed replacement for grazing cattle. 

Meghan Filbert, livestock coordinator with Practical Farmers of Iowa (PFI), said a project studying this subject is taking place on land in the North Raccoon River watershed, specifically in Sac, Buena Vista, Calhoun, Carroll and Greene counties. 

 "This project is significant, because this is Des Moines’ watershed," Filbert said. 

The grant project is in its second year and is funded by the Iowa Department of Agriculture and Land Stewardship’s water quality initiative project. Called "Don’t Farm Naked: Integration of Ruminant Livestock on Cover Crops," the project is designed to help farmers meet Iowa’s nutrient reduction loss goals. The project involves farmers planting cover crops in their corn and soybean fields, then letting their cattle graze those cover crops after the cash crop has been harvested.

"What we’re primarily doing is to try to estimate and calculate the economic benefits of that cover crop when used as forage," Filbert said. "Those cover crops include primarily cereal rye, but some producers are planting oats, turnips, rapeseed, radishes and forage kale. They aren’t traditional Iowa crops."  

Another goal of planting these particular cover crops for grazing is to hold the soil in place after the corn and soybeans have been harvested. 

"We’re wanting to add nutrients to the soil and reap soil health benefits," Filbert said. "Planting these cover crops is in turn leading to water quality benefits because there’s less runoff."

Fertilizer value

A side benefit of allowing ruminant animals to graze the cover crops is that the animals are putting nutrients back into the soil with their manure deposited directly on the field.

"We are receiving fertilizer from the manure, so we’re able to deliver nutrients through the grazing animal instead of spreading with equipment or purchasing fertilizer, so it helps to cut costs," Filbert said. "This doesn’t even take into account all of the soil health benefits from the manure."

The soil also is benefitting from the action of grazing.

"The way the cow’s tongue pulls that plant stimulates the roots of the plant to exude nutrients and help it grow," Filbert said. "It’s what bison did on their prairie before we intervened. That’s why our lands would flourish if properly managed ruminants grazed throughout the land."  

Economic benefits

The economic benefits reaped from planting cover crops for grazing have impressed farmers so far, too, Filbert said. There are six farmers involved in this particular study, and the grant money helps pay for the cover crops.

"Farmers are shy about planting cover crops, especially when they’re not making money on corn and beans. Cover crops cost money," she said. "We know there are long-term benefits to cover crops in terms of soil health benefits, but they’re hard to see in the short term. But we’re seeing a return investment on the cover crops. One of our farmers recently stated at a conference that he had seen a $73 per acre return on investments because their cattle were grazing cover crops. Winter feeding of cattle is the largest cost in any animal operation, so they’re also saving money on buying or making hay."  

At a field day held last November at one of the farms included in the study, the farmer said he plans to continue the practice even after the grant project ends.

"He said he’s learned the value and benefits of grazing cover crops and will do so out of his own pocket because he could calculate those savings and now has a more precise idea of his savings," Filbert said. "Farmers need numbers. It’s how they make decisions. Not a lot of studies have done this. We can talk in practical, real terms."

Improving soil health

While this study doesn’t measure soil health or water quality, another project Filbert is guiding does that. It’s similar to this study in the North Raccoon River watershed but studies soil samples to gauge the impact on water quality.

"We are seeing more soil microbial activity where animals are present. We have a control and a treatment field next to each other and they both have cover crops; one is grazed and one is not," she said. "The overall goal is to increase organic matter faster than it normally would. When the cover crops and cattle are not present, the organic matter would continue to decrease if it’s just farmed conventionally without cover crops or livestock." 

There’s also an increase in water filtration with fields that have cover crops, meaning there’s less runoff of nutrients, added fertilizer or chemicals, Filbert said.

"That’s a huge immediate benefit to water quality," Filbert said.