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Interested in cover crops? Here are four things to consider to get started.

Tyler Harris, Editor

October 28, 2015

6 Min Read

Whether for grazing, fixing and sequestering nitrogen, suppressing weeds, improving infiltration, building organic matter, or just to keep the ground covered, cover crops are being grown on more acres these days. Cover crop acreage reported by survey respondents in the Sustainable Agriculture Research and Education (SARE) program's annual Cover Crop Survey increased 30% from 2010 to 2014.

But before delving into cover cropping, here are a few tips:

1. Know your goals; consider what's in the mix. This will differ depending on the location and crop rotation. It also plays a role in almost all other cover crop considerations.

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Some growers prefer simply to plant a winter-hardy cover crop like cereal rye to overwinter, put on green growth in spring and hold the soil during the wetter months of early spring.

Cattle producers that can establish them early enough often plant brassicas like turnips or radishes. However, brassicas are low in fiber and typically high sulfur. So, it's usually best to mix in a grass to dilute sulfur toxicity and balance out the high-energy brassica diet.

Those who plant cover crops on chem fallow acres might be interested in cover crops with extensive root systems to compete with weed pressure, but in a drier climate, should also consider cover crops that put on a lot of biomass to reduce moisture evaporation.

In a high-moisture region, some growers plant nitrogen-sequestering cover crops like cereal rye or daikon forage radish to use up any excess nitrogen and prevent loss from leaching, runoff, or denitrification.

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"At the end of the day, there isn't a one-size fits all for cover crops. It really depends on where you're at and what you're doing," says Chris Proctor, University of Nebraska Weed Management Extension Educator. "Growers are pretty innovative. There are a lot of ways to use cover crops."

2. Timing is everything. The optimum time for establishment is different depending on what cover crops are being seeded and what they're being used for.

Whatever the situation, Paul Jasa, UNL Extension research engineer notes, "The best day to plant a cover crop is the day the combine leaves the field."

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Warm seasons like sorghum sudangrass and pearl millet usually put on the most biomass when planted before the first of August, and work well planted after winter wheat. For growers planting cover crops on fallow acres, Jasa says it's best to get them established right after wheat harvest. If cover crops aren't planted until later the following spring, soil moisture will have already evaporated.

Winter sensitive cool seasons like turnips and radishes provide the most biomass for fall cover and forage when planted before mid-September, while winter-hardy species like cereal rye and triticale overwinter and provide more cover and forage in spring. So, some growers interseed winter-sensitive species into standing corn or soybeans for extra growth. But there's an optimum time to do it to ensure there's enough sunlight penetrating the canopy for the cover crop to germinate – for soybeans, usually just before leaf drop as leaves are turning yellow. For corn, usually when the plant is dry up to the ear.

When it comes to termination, there are some restrictions to consider. In Nebraska, cover crops must be terminated before they reach a critical stage of maturity so the cover crop doesn't negatively affect the following cash crop – a stage which is different for the western and eastern parts of Nebraska.

3. Read the label. However, when establishing a cover crop right after harvesting cash crops, growers always have to keep in mind plant back restrictions on the herbicide label. "The issue is most cover crops aren't going to be on the label," Proctor says. "They usually fall under the 'other crop' category, and due to lack of data get pegged under the maximum plant back restriction window."

This also goes back to what the goals are for the cover crop. When it comes to grazing, the plant back restrictions must be followed to prevent toxicity issues in livestock. However, graziers can always plant a cash crop with a defined plant back restriction as a cover crop and graze it sooner. "For example, wheat is often on the label because it's a potential cash crop," says Mary Drewnoski, UNL Beef Systems Specialist. "You can plant spring wheat in the late summer or early fall for fall grazing."

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When using cover crops primarily for soil health, there's a little more flexibility. It all depends on the herbicide being used, and how sensitive the cover crop is. "Check what your product is and whether your cover crop is sensitive to it, and pay attention to how much that product will reduce the stand, and you can reduce that component in your cocktail," Jasa says. I'm using atrazine on corn and planting cover crops in the fall, so I avoid cover crops that are sensitive to atrazine."

4. Put a number on it. When it comes to the tangible benefits of cover crops, almost everyone has a different opinion. While most have a general sense of the soil health benefits of cover crops, there isn't a lot of data that shows the return on investment unless grazing cover crops.

Producers can see a return on investment by putting on some extra pounds on calves grazing cover crops – depending on the time of grazing and amount of biomass available. With enough forage available by planting cover crops early enough for fall grazing, UNL research has shown lightweight spring calves can put on enough weight to see returns of up to $200 per acre.

"Can we afford to do it? Yeah," Drewnoski says. "If you've got spring-calving cows, it might be a way to put on some more pounds on lightweight calves in the fall and make some more money."

"The easy answer is if you graze it you will make your money back. But if you aren't grazing, how do you assign a cost to reducing soil erosion or increasing organic matter?" Proctor adds. That's why it takes a systems approach. "If growers recognize they're reducing soil loss, can benefit nutrient cycling and organic matter, and are willing to invest now without a quantifiable return, they will realize those benefits five or ten years down the road, though they can't put a number on it now."

About the Author(s)

Tyler Harris

Editor, Wallaces Farmer

Tyler Harris is the editor for Wallaces Farmer. He started at Farm Progress as a field editor, covering Missouri, Kansas and Iowa. Before joining Farm Progress, Tyler got his feet wet covering agriculture and rural issues while attending the University of Iowa, taking any chance he could to get outside the city limits and get on to the farm. This included working for Kalona News, south of Iowa City in the town of Kalona, followed by an internship at Wallaces Farmer in Des Moines after graduation.

Coming from a farm family in southwest Iowa, Tyler is largely interested in how issues impact people at the producer level. True to the reason he started reporting, he loves getting out of town and meeting with producers on the farm, which also gives him a firsthand look at how agriculture and urban interact.

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