Late Dry Weather is Hurting Corn and Soybean Yields

Chad Lee, Extension Agronomist, University of Kentucky

The USDA NASS lowered their estimates for Kentucky corn yields by 10 bushels per acre and soybean yields by 2 percent in their latest report. The negative numbers reflect calls and comments we are receiving from producers across the state.

In August, most of our corn and soybean fields looked great. The foliage was lush, canopies were closed and the crop looked to be in excellent condition. Now, farmers are getting surprised about low yields in some fields. Just to clarify, these reports do not reflect all fields. There are some really good yields being reported. But, there are some really bad yields as well and these fields were the surprise. I think the biggest contributor to these bad surprises is the weather. Most of Kentucky was wet early and dry late. The wet weather encouraged shallow root systems. The dry weather late penalized crops with shallow roots.

Yellow Soybeans Need Sun

Chad Lee, Extension Professor and Agronomist, University of Kentucky

Numerous fields of soybeans appear yellow or bright green right now. The symptoms mimic nitrogen deficiency, but the plants are really starving for air to the roots and sun on the leaves. Everyone is thinking about applying some nitrogen to help make the plants greener. But what these plants really need is for sunshine to help partially dry the soils.

Estimating Nitrogen Losses from Wet Soils, 2011

Lloyd Murdock, Extension Soils Specialist, University of Kentucky

Wet soils cause nitrogen losses, and determining how much nitrogen is lost is necessary to choose the proper management options.  In cases where high intensity rain results in high runoff, leaching losses will probably be low.  The primary nitrogen loss mechanism in saturated soils in Kentucky is denitrification, which occurs when soil nitrate nitrogen (NO₃-N) is converted to nitrogen gas by soil bacteria.  Two to three days of soil saturation is required for bacteria to begin the denitrification process.  Well-drained upland soils that have been wet from a series of rains probably have not experienced much denitrification.  Soils in lower landscape positions that stay saturated longer will likely lose more N.  Losses can be calculated by estimating 3 to 4 percent loss of fertilizer NO₃-N for each day of saturation.  Use the Table below to determine how much fertilizer NO₃-N was in the soil.

Wet April, 2011

Chad Lee, Grain Crops Extension, University of Kentucky

Tom Priddy, with the University of Kentucky Ag Weather Center sent out the following link for April rainfall history. With six days left to report, Lexington and Frankfort both have the wettest April in history. Louisville is less than an inch from beating its record totals for rainfall. Bowling Green is fairing much better with 'only' 6.82 inches so far.