CHICAGO Two inches of rain over the next two weeks is all that the soybean crop needs to ensure that millions of tiny pink flowers now budding at a near-record pace mature into the small green pods that will help feed the world.
As scattered rain in the north and east of the farm belt this week brought the first significant relief to this summer's drought, the worst in 56 years, agronomists said even a small amount of moisture will help the soybean crop avoid the fate facing corn, which has been decimated by the unrelenting heat.
Not only do soybean plants reach their most critical stage of development -- called pod-setting -- about a month later than corn's reproductive pollination phase, they also can withstand drought a little better because they have a much smaller biomass than corn, and can idle their metabolic activity at night.
"High night-time temperatures make corn plants maintain themselves, which means they are using some of their sugar to maintain cellular function. Soybeans do not have this problem. They are just sitting there waiting to grow," said agronomist Michael Cordonnier of Soybean and Corn Advisor in Chicago.
Corn needs five times as much water as soybeans over the course of its life, and about 1/3 of an inch of rain a day -- more than two inches a week during pollination, experts say.
While most analysts agree it is too late for the rains to salvage much of the corn crop, which analysts reckon will be at least 22 percent smaller than initially estimated this spring, there is hope for the world's largest soybean crop -- potentially tempering the run-up in food prices. Analysts have so far reduced their yield forecasts by only 5 percent.
At the moment, however, even that modest moisture is in doubt. New forecasts on Thursday suggest that drier conditions will return to much of Nebraska, Missouri, Kansas and southern and western Iowa and parts of Illinois over the next 6 to 15 days, according to the Commodity Weather Group.
AN INCH A WEEK
Soy plants need the most moisture as the flowers develop into pods, a process that will occur for most of the crop over the next two weeks. Dry weather causes the plants to channel more of their energy into growing their roots in search of water in the subsoil, while the above-ground activity slows, thus reducing the pace of converting its sugars into pods and beans.
Since a plant typically loses 50 to 60 percent of its flowers, further aborting of the blooms about the size of a thumbnail could mean fewer pods and possibly smaller seeds.
Pods, generally about 3 inches long, may have one or two beans rather than the typical three. Soil quality, moisture, fertilizer and seed type can also effect the size of the beans, which are later crushed to make cooking oil, feed and biofuel.
But agronomists said that the hardy soybean crop, which even under the worst conditions accumulates enough energy to ensure that it produces enough seeds to regenerate itself, can create new flowers over a 40-day period depending on moisture.
"What we really need is about an inch of water a week," said agronomist Jim Beurlein, a consultant with Becker Underwood, an agricultural research company based in Ames, Iowa.
This year, both corn and soy plants are maturing one or two weeks earlier than usual after farmers took advantage of one of the mildest winters on record to plant seeds at a record pace -- only to be met with a sudden turn to dry weather and high heat.
The U.S. crop is also more crucial than usual because a drought earlier in the year devastated crops in Argentina and Brazil, the world's second- and third-largest exporters. The U.S. crop harvested this fall must tide over importers until the South American harvests in early 2013.
USDA data showed that 79 percent of the soybean crop was blooming as of July 22, well ahead of the 60-percent 5-year average but just short of the 81 percent reached in July 2005, the fastest pace since the USDA began recording the data in 1981. It said 36 percent were setting pods, matching 2005 and nearly double the 19-percent average for this time of year.
In a Reuters poll this week, 11 analysts were expecting the average U.S. soybean yield to be 38.6 bushels per acre, down 1 percent from a week ago and down 4.7 from the USDA's current estimate of 40.5 bushels per acre.
NOT A DISASTER...
Rains that fell sporadically over the north and east of the Midwest farm belt this week gave crops a much-needed boost. Early field tours have also helped soothe worries that soybeans too may be shriveled. November futures prices have surged a third over six weeks to hit a record of nearly $17 a bushel on Monday, but have since pulled back to $16.
Beuerlein, a 40-year veteran with Ohio State University before his retirement three years ago, said on his visit to a soybean field about 45 miles north of Columbus, Ohio on Tuesday, he saw a "really good crop" after rains a day earlier.
"The soybeans were heavily flowered, which is pretty typical of central Ohio. The plants had barely begun setting pods, but I did see some very, very small pods starting to form," he said.
"This crop is definitely not a disaster," he added.
The MDA EarthSat crop tour on Thursday saw a vibrant soybean crop in central Iowa, with flowers popping up overnight after showers heavy enough to make the fields wet with moisture.
...BUT STILL NOT GREAT
Which is not to say it's in good shape. Moisture has been scarce in western states like Iowa and Nebraska, which account for 12.5 and 7 percent of soybean plantings, data show.
The U.S. Department of Agriculture rated just 31 percent of the crop in "good to excellent" condition -- the worst rating in about 25 years, but still better than the 20 percent rating at this point in 1988, the most severe drought in recent history.
Another 35 percent of this year's crop was in poor-to-very-poor condition, the worst rating since 1986.
Some agronomists say that this portion of the crop is unlikely to get better even with rains.
"We are going to have some changes but not huge changes," said Charles Hurburg, a professor of agricultural engineering at Iowa State University.
Crop specialist Bill Wiebold of the University of Missouri says heat-stressed plants face an additional risk apart from the pod-setting process: poor soil moisture will cause the plants to close the pores on their leaves, known as stomates, as a way to prevent loss of any moisture already in the plant.
This can lead to the level of carbon dioxide in the leaf dropping rapidly and thereby causing photosynthesis -- the process of turning sunlight and carbon dioxide into sugar in the plant that enables growth -- to halt.
"Soybeans have a built in capacity to stand this stress. They are in some ways less vulnerable than corn," he said.
(Additional reporting by Michael Hirtzer; Editing by Andrew Hay)