Fine roots provide pathways for nutrients, improve soil heath over winter
COLUMBUS - There was still frost in the ground when area farmers walked out into the Roche family’s field last week to see the root and earthworm activity in a field that had been inter-seeded with a cover crop last summer.
“Any time we are managing soils – tilling – we will end up with some compaction. We see it when roots go horizontally,” says Dr. Jamie Patton, UW-Extension ag agent from Shawano County, speaking from the soil pit on a Dodge County Healthy Soil-Healthy Water field tour at the Roche farm at Columbus.
She illustrated why she likes cover crops, pointing out how they put roots down into the system to create pore channels.
“If you don’t have living plants after harvest, the channels will close up,” she states. “If you do covers year after year the root channels help to make the soil crumbling.”
She urged the participants of the field tour to take a look at the soil down deep in the pit to notice the very fine roots that spread throughout the soil. Patton points out that it isn’t just the large roots like radishes that push their way down.
It is more beneficial to establish covers that have many fine roots that spread out in all directions and hold soil and create passages for water, Patton added.
“Many fine roots mean more opportunities for the established crop to take on nutrients,” she states.
Deep-rooted plants can help to break through compacted layers in the soil such as a hard pan, or as it is sometimes known, plow pan. This will improve drainage.
The penetrating roots of the cover crops make channels through which soil water can move after the root system decomposes.
These winter cover crops with large tap roots or massive root systems can help to alleviate some of the effects of soil compaction by penetrating the compacted layer when the soil is wet and relatively soft during winter.
Field day host Bob Roche says they wanted to establish a cover on the field because silage is harvested earlier than corn for grain, allowing more growing time for the cover.
Once the sun hits the ground after harvest the cover begins to grow, sending down roots that continue to grow even after the surface of the plant freezes.
While the growth of the cover was slow because of weather conditions in fall and winter, an examination of the soil in the pit revealed living roots below the surface.
Regarding the deep roots of covers, Patton says, “If you start a crop early and get more root growth before freezing the roots will continue to grow over the winter so it is important to get into the field early. Once the roots get below the frost line they stay alive and continue to feed the life in the soil throughout the winter.”
Patton stresses the importance of providing a blanket on the soil to prevent surface erosion, especially in spring.
She says seventy-five percent cover is important. That cover can be in the form of a cover crop or residue but a cover provides the additional benefits beneath the soil.
“Spring is when the soil is most vulnerable and it is also the time when we generally get heavy spring rains,” Patton said.
“Because of the economics and current grain prices I believe there are a lot of farmers who plan to plant soybeans into (a field that had been) soybeans this year," she said. "That’s not good for soil health.”
Because there is little residue on a harvested soybean field, if there is no cover crop to protect it there will likely be a soil loss.
“Just because you don’t see a gully doesn’t mean you are not losing soil to erosion,” she pointed out.
Due to the lack of snow this winter, Patton said there has been a lot of wind erosion on fields that are not protected with plenty of residue or cover.
“It is evident on the fields where there was fall tillage,” she reports.