The approach — known as planting green — could help no-till farmers counter a range of problems like soil erosion, nutrient losses, soils holding too much moisture and causing a delay in the planting of main crops, and main-crop damage from slugs.
With climate change bringing more extreme precipitation events and an increase in total precipitation, no-till farmers need a way of dealing with wet springs. Penn State researchers conducted a three-year study of planting green to see if farmers could get more out of their cover crops by letting them grow longer in the spring.
As cover crops continue to grow, they draw moisture from the soil, creating desired drier conditions in wet springs for planting corn and soybeans. With planting green, after those main crops are planted into the cover crops, the cover crops are typically terminated by farmers with an herbicide. The decomposing cover crop residues then preserve soil moisture for the corn and soybean crops through the growing season.
During the study at five sites, researchers compared the results of planting green to the traditional practice of terminating cover crops 10 days to two weeks before planting the main crops of corn and soybeans.Cover crops included in the study were primarily rye and triticale, as well as a mixture of triticale, Austrian winter pea, hairy vetch and radish in one location.
Findings were mixed. Planting green appeared to benefit soybean crops more than corn. Cover crop biomass increased by 94 percent in corn and by 94 to 181 percent in soybeans. However, because planting green results in more cover crop residues acting as mulch on the surface, it also cooled soils from 1.3 to 4.3 degrees Fahrenheit at planting.
At several of the sites during the study years, main-crop plant populations were reduced when planted green, possibly due to the cooler temperatures slowing crop emergence and nutrient cycling, and/or from cover crop residue interference with the planter. In corn, crop damage by slugs also increased when corn was planted green.
No-till farmers struggle with slugs damaging corn and soybean seeds and seedlings because no-till doesn't disturb the soil and kill slugs or bury their eggs the way tillage does. No-till with cover crop residues also provides habitat for some crop pests and keeps the soil moist — so no-till cover crop systems tend to be great slug habitat.
Researchers had hoped that letting cover crops grow longer in the spring would supply alternative forage for the slugs, as well as habitat for slug predators such as beetles — and these factors would reduce slug damage of the main crop seedlings. But they did not see a consistent reduction in slug
damage on main crops.
When researchers compared crop-yield stability between the two cover crop termination times across the multiple locations and years, corn yield was less stable and reduced by planting green in high-yielding environments; soybean yield was not influenced by planting green.
They concluded that corn was more vulnerable to yield losses from conditions created by planting green than soybeans. Since soybean yield was stable across all locations, and not affected by cover crop termination date, they suggest that growers who want to extend cover crop benefits and avoid the risk of crop-yield reduction from planting green should consider trying it first with soybean.
Source:
Heather Karsten, associate professor of crop production ecology, Penn State College of Agricultural
Artwork: Buckwheat Cover Crop Seed
