KIMBERLY, Idaho—Soil scientist David Tarkalson believes a startling discovery he made while conducting an irrigation study may have implications for farmers who raise corn following sugarbeets.
Tarkalson, with the USDA Agricultural Research Service’s Northwest Irrigation and Soils Laboratory, planted sugarbeets in 2011 while researching the effects of different irrigation rates. Beans were planted in the ground surrounding the plot in the same field.
The following year, he planted the whole field to corn. The corn emerged healthy and green where the beans had been but was stunted and purple where the sugarbeets had grown—clear signs of phosphorus deficiency. As the season progressed, the purple corn seemed to recover.
Also in 2012, David Bjorneberg, research leader at the ARS facility, noticed purple, stunted corn following sugarbeets in a field involved in a long-term rotation study.
Tarkalson said local field agronomists have noticed the phosphorus deficiency but have attributed it to cool spring conditions impeding phosphorus metabolization by young plants.
However, Tarkalson said cool weather can’t explain why only the corn on the former beet plot was stunted.
He intends to research the issue in more depth, first determining if the apparent phosphorus deficiency is adversely impacting corn yields. He also finds it curious that the phosphorus levels were adequate in both of the fields where stunted corn was found.
He hypothesizes the deficiency resulted from a condition referred to in the Midwest as fallow syndrome, caused by a lack of beneficial mycorrhizae fungi in the soil. The fungi develop a symbiotic relationship with the roots of plants such as corn, effectively extending the roots’ reach by 100 times. But some plants such as sugarbeets and canola don’t support mycorrhizae, which can also be impaired by fallow years and flooding.
A fallow syndrome pamphlet published by Channel Seed warns the deficiency can reduce yields and recommends applying phosphorus in bands near seed rows or planting cover crops, such as oats, to supply mycorrhizae.
“(Mycorrhizae) really is something we’re not focusing on. We just noticed it,” Tarkalson said. “We’re trying to play around with it.”
Next season, he intends to plant corn in a field currently in sugarbeets that were treated at a variety of commercial fertilizer rates, and with varying histories of manure application, to see if the deficiency surfaces.
American Falls, Idaho, grower Jim Tiede suspects his use of dairy compost, which is high in phosphorus, may explain why he’s never experienced any problems in corn following sugarbeets, which is a rotational order he likes to avoid planting potatoes in corn cobs and crown roots.
Mike Sato, account manager with Pioneer Seed in Twin Falls, has seen the deficiency often. He suspects manure may help but said banding fertilizer wasn’t effective in University of Idaho research conducted about a decade ago. He said some hybrid corn varieties may also better withstand the deficiency.
“If you’re patient, often corn does just fine after beets,” Sato said. “Would it have done better if it hadn’t followed beets? Probably, but a lot of times the rotation doesn’t work that way.”
USDA estimates Idaho farmers planted 171,000 acres of sugarbeets and 340,000 acres of corn in 2014.
Source: www.capitalpress.com