If you are the sort who takes notice of such things when traveling around the countryside, you’ve probably seen a drastic increase in the amount farm fields displaying greenery in the fall along with a decrease in the amount of farm acreage that is laid bare by fall tillage after the crops which grew in them the previous summer were harvested. These undisked/unplowed fields displaying a coating of green plant life right up to the killing frosts have been planted with cover crops.
The practice is growing in popularity for several reasons - most of which make economic sense to farmers. Healthy soil is a living resource, teaming with life. The better the soil, the better the crops that can be grown on it. Cover crops improve soil health. Fall tillage, devoid of living plants, retards soil health. Bare soil is highly subject to wind and water erosion. Cover crops stop erosion in its tracks.
Plants thrive from a two-part process involving photosynthesis when the above ground in the part of the plant gathers energy from the sun while their underground roots take in soil nutrients below. That’s why farmers use fertilizer, to ensure their crops have ample soil nutrients.
Fertilizer is expensive. The nutrients, once extracted from the soil by living plants, stay in the plants. Nutrients in the soil unused by plants depletes or washes away with time. It can’t be stored in the soil.
Nutrients can be stored in plant material and when that plant dies and decomposes, the nutrients are recycled back into the soil. This is how cover crops provide a direct economic benefit to the grower. Cover crops growing after the crops are harvested take up and store soil nutrients leftover after the main crop is harvested instead of allowing those nutrients to escape. When the cover crop decomposes the following growing season, those stored nutrients become available for the main crop to use. In effect, it becomes fertilizer reducing the amount a farmer needs to purchase and apply to the field for the next crop.
It's not only farmers benefitting from cover crops. A new study finds birds benefit as well. A graduate student at the University of Illinois was one of those people noticing the trend of increasing numbers of farmers planting cover crops. The student knew cover crops produce benefits to the environment, reducing nutrients loss and promoting healthier soils but hadn't seen much research on their effects on wildlife.
As part of the graduate project this student was conducting, she compared corn and soybean fields with and without cover crops to determine which ones best provided habitat for migratory and resident bird species and whether birds of conservation concern used the habitat.
After cold-calling farmers to get permission to monitor their fields, the student compared corn and soybean fields with and without cover crops by walking through the fields, recording which birds were present and the number of individuals.
"It's cold out in early March, but it's beautiful and when it warms up it is really neat to see what birds end up in these fields," said Cassandra Wilcoxen, lead author on the study published recently in Agriculture, Ecosystems and Environment.
She observed a total of 6,133 birds of 52 species. The most common were the red-winged blackbird, common grackle and American robin.
Not all species of birds sought out the fields with cover crops. However, both migratory and resident bird species commonly associated with prairies and grassland were recorded in much greater numbers in cover cropped fields.
"Migratory birds were looking for places they could rest and refuel," Wilcoxen said. "Resident birds are looking for habitat to breed in. They see cover crop fields as this really lush green habitat in the springtime when there isn't much else growing."
Most birds, the researchers found, preferred corn fields and cover crop fields, whose old stalks and litter provided more vegetative structure than soybean fields.
Cover crop fields also hosted birds of higher conservation concern. Species, such as the eastern meadowlark, are of high conservation concern because of population declines in the last half-century associated with declining amounts of available habitat.