Why do soybeans look better than corn?
In this year's historic drought conditions, why do soybeans look so good relative to other crops?
Shawn Conley, the University of Wisconsin's soybean and small grain specialist, says that because of the time they were planted on most fields in the state "they've been chasing water all season long" and have roots that have gone nearly straight down in the soil profile.
In a normal year, the roots of the soybean plant are pretty close to the top six inches of soil, but this year they have gone deep - as far as four feet.
Conley said that soybeans can grow a centimeter of roots per day so in 2-½ days they can grow an inch of root, especially if they are reaching for water.
One of the things that has contributed to the relative success of soybeans this year is that they require a little less water than corn.
Soybeans need 18 inches of water to successfully produce a crop, Conley said. By comparison, corn requires 20-24 inches of water.
Because of the symbiotic relationship with the nitrogen-fixing rhizobia in their root nodes, soybeans fix nitrogen out of the air.
Under this year's drought and heat conditions, that nitrogen-fixing ability is limited and Conley predicts that overall the protein content of the U.S. crop is likely to be lower than normal.
But once there is rainfall, as there has been in the last week in parts of the state's drought-stricken region, soybean plants can start fixing nitrogen again within seven days.
He advised farmers not to apply nitrogen to their soybean crops.
Conley joined other experts at a meeting in Waunakee organized by Wisconsin's corn and soybean growers associations and promotion boards in an effort to get timely drought information out to farmers.
There were 250 farmers on hand at the session in Waunakee; in the morning there had been 180 people at an earlier version of the meeting on the same day.
Soybeans may fare better than corn in the drought because the plants have a much wider window for their flowers to form and pollinate, leading to the production of beans.
Conley said the plants begin flowering about July 1 and continue to flower through mid-August.
In an average year, the agronomist said, soybean plants will abort 50-80 percent of their flowers. In stressful growing conditions like this year, the plants have a system for deciding what to let go of.
"They'll abort flowers first, then little pods and then bigger pods. But I think we still have the potential for 40-plus bushel beans out there," he said.
In northern Wisconsin, where farmers experienced five years of severe drought in recent years, soybeans that were 14-16 inches tall on Sept. 1 still produced yields of 10-25 bushels per acre; a surprise with plants that short, he said.
With this year's extreme drought in the southern two-thirds of the state, Conley said he hasn't seen a lot of fungus in the crop that require treatment, but he has noticed that the previous year's crop has a big effect on how fields look in the drought.
"The rotation effect is a big deal this year," he said. "I'm seeing a big yield increase on corn after soybeans. Some of the worst fields out there now are long-term corn fields."
Conley said, in general, the early-planted beans in the drought areas look the best and the late-planted beans look worst.
Some farmers are trying to alleviate drought stress on their beans by spraying foliar fungicides - basing that practice on last year, when such applications produced a 2-½ bushel yield response, he said.
Conley said another concern this year is spider mites. "This is one insect that can take a field to zero. This could take 23-30 bushel beans down to zero."
The product dimethoate can take care of the insect pest, he said, and should be applied even if the soybean yield is likely to be about 20 bushels per acre. With beans trading at $17.50 per bushel and treatment costing $20 per acre, it still pencils out.
"You need to pay attention and scout. They can come in pretty quickly."
Farmers should also remember, he said, that even if mites are taken care of once in a field, they can come back.
Asked about the possibility of using soybeans as a forage crop for livestock, Conley said the best time to harvest is at the R6 stage, generally the end of August, but added that farmers might be better off to harvest the beans for grain and use that money to plant another crop that can feed livestock.
Many farmers are considering planting oats as a feed crop after getting some fields opened up. Conley said they need to consider how crop insurance and previous herbicide carryover will affect those plans. Dual and Lasso programs require 4-½ months before a crop like oats could be planted.
There has been talk of planting milo or sorghum-sudangrass to try to generate some additional feed for cattle, but Conley said that seed availability is part of the problem there.
"The Texas drought put a crimp on sorghum-sudangrass seed production."
Online resources developed by Extension specialists are available at http://fyi.uwex.edu/drought2012/ or by searching for Drought 2012 in any search engine, Conley said.