You've seen the maps and charts displaying the severity of the 2012 drought. Meteorologists pour over weather statistics providing graphs that show number of days over 100 degrees Fahrenheit or number of days without precipitation. Based on those number, they compare this year to past events. Then some weather experts give it a tagline of "worst drought in since 1956."
However, Bill Wiebold, MU soybean specialists said that crop productivity is a good indicator of drought intensity. Wiebold combed through data from over the decades to determine just how well crops performed during the early drought years versus how well they performed this year. He outlined his results in a recent Integrated Pest Management article from the University of Missouri.
What he concluded was that "drought severity, as calculated by corn yield loss, was greater in 2012 than for any year within the past 50 years."
"Crop productivity is also an excellent indicator of drought intensity," he said. "Most grain crops have specific stages of development when their yields are most sensitive to drought stress, so timing of stress also influences the amount of yield loss
According to Wiebold's findings, corn's most sensitive stage is a three-week period centered on R1 or commonly known as "silking." The stress placed on plants at this stage reduced the number of fertilized flowers. Stress after silking, he states, will result in increased kernel abortion, and if the stress has not been relieved, reduced seed size.
During mid-vegetative stages, corn may be so stressed that it reduces ear size, plant height and leaf size.
For soybeans, the most sensitive stage is during pod development. Stress at this time reduces the number of flowers and small pods that are retained on the plant. According to Wiebold, these R3 and R4 stages usually occur in late July and early to mid-August in Missouri. Stress during seed filling can result in additional pod abscission, arrested development of one or more seeds in retained pods, and reduced seed size.