Deciding the best approach to cover crops on your farm is a challenge whether you are considering cover crops for the first time, or you have planted cover crops for 10 years or longer.  

Research backs up the benefits of cover crops, but what makes the practice difficult to adapt is finding ways to make cover crops cost effective where they contribute to the bottom line. Hunter Frame, a conservation agronomist and the Virginia Tech cotton specialist, has conducted extensive research on cover crops and stressed that the approach to cover crops must be both agronomic and practical. 

He drove the point home once again in a panel discussion on cover crops at the North Carolina Commodity Conference Jan. 12 at the Sheraton Imperial Hotel in Durham. Frame stresses that cover crops must produce a short-term economic benefit to row crop producers in order for more of them to adopt the practice. 

“If we can’t have an economic benefit going into this, they’re not going to wait five to six to seven years to see the soil benefits moving forward,” Frame said at the conference. 

In Virginia, a cost-share program administered by the Virginia Department of Conservation and Recreation provides incentives for farmers to plant cover crops. But Frame notes that the program isn’t expected to be around forever. For cover crops to work, they must pay for themselves. 

Cover crop choices 

In his research and work with farmers in managing cover crops, Frame is focusing on multispecies cover crops, mainly utilizing legumes, because they are practical from both an economic and feasibility standpoint. The goal is to select species and varieties within a species that fit Virginia’s cropping systems. 

For example, Frame said legumes in a cover crop can improve potash cycling. “If you grow cotton, you know potash is a critical nutrient during the bloom period, and we deal year in and year out with potash deficiency.” 

Frame noted that legume cover crops can help with potash deficiency and decrease the use of nitrogen fertilizers since legumes bring nitrogen to the soil. Still, Frame stresses that cover crops will never fully replace nitrogen fertilizer. 

“We average anywhere from 160 to over 200 pounds of nitrogen in a legume mix based off of our biomass production. We’ve done that now for about 10 years,” Frame said.  

Cereal rye was part of the mix, but Frame notes they have now switched to oats in the mixture. They also examined crimson clover and hairy vetch. In the past, they looked at tillage radishes, but Frame said they have backed off on the use of tillage radishes for various reasons. 

Frame said the legume mix costs roughly $60 to $70 per acre while the rye plus legume mixes costs roughly $83 per acre. 

“What our guys are doing now is they are planting a rye-legume mix. They’re coming in March 16 and spraying Select (herbicide), killing the rye out then letting the legumes take off and they’re getting that $90 (from the cost share program) plus the benefits of the legume,” Frame said.  

“The total value of a legume cover crop in Virginia, when you take in the value of the nitrogen and the cost share and subtract your seed cost, is about $150. The hurdle to this is how do we make this system fit. It fits well with cotton because we are planting in May in Virginia. How to we make this system work in corn that is planted in early April or maybe in late March?” Frame said. 

Selector tools and calculators 

In North Carolina, Chris Reberg-Horton, North Carolina Plant Sciences Initiative platform director of resilient agricultural systems at North Carolina State University, has developed software to help farmers choose the best cover crops for their production systems. He highlighted the species selector tool and other cover crop management tools at the Durham conference. 

Reberg-Horton said the tools enable farmers to determine the approach they want to take when planting cover crops. The tools help farmers determine their best cover crop strategy for their soil type, geography, and drainage class.  

An important part of the series selector tool is a seed calculator which allows farmers to select their cover crop mixture. “Any of you out there that are into these complex cover crop mixtures know that calculating those mixtures can be a pain, so we developed a work sheet calculator that helps you create these complex mixtures,” Reberg-Horton said. 

The nitrogen calculator aids farmers with decision support regarding cover crop residue persistence as well as the amount and timing of nitrogen availability.  

“How much nitrogen do I have in this field? That’s a challenge. We designed that tool with this in mind. When you’re standing in your field, and you’re on your phone, it will pull up pull your soil type, pull your weather.  The combination of knowing your soils, knowing your weather, and also knowing something about what species you have there, we can predict very well how much nitrogen is released day by day on your farm,” Reberg-Horton said. 

The cover crop economic decision support tool helps farmers better understand the impact of incorporating cover crop species or mixtures into their farm. Reberg-Horton said both the decision of what cover crop species to use and the resulting economic impact are very specific to individual operations, and the tool will help farmers understand individualized conditions and management decisions. 

In the meantime, Ron Heiniger, North Carolina State University Extension corn specialist, stressed that the health of soil depends upon organic matter returning to the soil profile. Most of the microbial biomass in soil relies on organic matter to survive. 

“As organic carbon in our soil declines, so does our bulk density as well as our productivity. One of the things we think about when we think about cover crops is that we need to find a way to improve our soil organic carbon which is difficult.  If we’re going to continue to have productivity, we have to find a way to improve soil organic carbon. Cover crops can do that,” Heiniger said. 

“The other thing that is forcing us to these cover crops is climate change. Whatever your faith is in the future of temperatures here in North Carolina, the consensus is we are probably going to see warmer temperatures and the only way to mitigate that is to reduce carbon dioxide in the atmosphere, sequestering carbon some way.  We need to find a way to keep green cover over these soils if we are going to sequester carbon in agriculture,” Heiniger said.