Corn ‘greatly impacted with use of cover crops’

PAINTER, Va. — A multi-year study by agronomists at Virginia Tech of various crop and cover-crop rotations has shown corn yield is “greatly impacted by the use of cover crops, especially low C:N cover crops prior to corn.”
Agronomy doctoral student Joseph Haymaker briefly discussed the cover crop studies during the virtual Virginia Eastern Shore Agricultural Conference.
Two other presenters discussed corn emergence dates and fungal treatments.
Haymaker reported, “The cover crop treatments had significantly higher yields compared to the non-cover crop treatments” at both zero and 150 pounds per acre of nitrogen.
Cover crops, Haymaker noted, offer potential solutions to problems faced by corn growers on the Eastern Shore including sandy soils with low organic matter, a warm climate that speeds breakdown of organic matter, plenty of moisture for microbes, nutrient leaching and hardpans.
Cover crops prevent erosion, scavenge excess nutrients, fix nitrogen, relieve compaction, increase filtration, suppress weeds, conserve soil moisture, feed soil microorganisms and increase soil organic matter, he said.
The research examined the effect of three groups of cover crops: grasses like rye, triticale and sorghum; legumes including clover and hairy vetch; Brassicas such as radish and rapeseed; and multispecies mixes of the three groups.
Corn yields with mixed cover crops were “significantly higher” than with rye cover crops at zero pounds of nitrogen, but not at 150 pounds per acre, Haymaker reported. The vetch cover crop was higher yielding than the mixes at both zero and 150 pounds of nitrogen.
In addition, he said, “There is no additional benefit to side dressing” corn under several of the cover cropping regimens studied.
Dr. Wade Thomason, grain crops Extension specialist for Virginia, explained how corn plant emergence dates affect productivity and discussed how to improve consistency of emergence.
He said more uniform emergence may require only simple planter maintenance. He recommended assuring opening disks are not worn and fit smoothly, making sure closing wheels are working effectively and setting down-pressure springs properly.
He said higher yields were achieved by plants that emerged on day one. Plants that emerged on day 3 or later had much weaker ears and much fewer kernels than those emerging on day 1 or even day 2.
Thompson pointed to the “immediate, dramatic decrease in yield potential” from plants emerging after day 1.
He said he believes the later plants are “noncompetitive. They are shaded out. Other plants’ root systems and leaves are developing faster so they just don’t have access to the sunlight and water and nutrients. In fact, they are probably negatively competing against the plants nearby.” He said plants emerging after day 1 suffer poor pollination and poor kernel set.
Thompson noted one study in which day 1 plants yielded 148 bushels per acre while day 2 plants yielded 107 bushels and day 3 only 71 bushels per acre. Plants that emerged after day 3 yielded just 17 bushels per acre.
Dr. David Langston, plant pathologist, briefly discussed gray leaf spot and recommended applying fungicides at the tasseling VT/R1 stage.
He also encouraged rotating corn with non-grass crops and planting disease-resistant corn varieties to control the disease.