At this writing (August 28), the forecast is for rain next week. However, how much water does it take to finish the corn and soybean crop since we have had dry weather? The corn kernel milk line is a way to examine the kernels and determine the time to maturity. The milk line is easiest viewed from the back of the kernel or the side opposite the embryo or germ.

A general rule of thumb is corn kernels at half milk line requires about 3.75 inches of water which is supplied by stored water in the soil or additional rainfall or irrigation. At three quarter milk line, the corn plant only needs about one-inch of water to carry to maturity. Full maturity of the corn ears will occur at black layer which is typically 32% moisture.

Soybeans are in seed fill. This stage is known as R-6 which is identified as a pod containing a green seed that fills the pod cavity at one of the four uppermost nodes on the main stem. This stage will require about 3.5 inches of water to finish the crop. There are many different sizes of soybeans on the plant. When leaves start to yellow, this will require 1.9 inches of water.

As soybeans move toward the next maturity stage R-7, one pod on the main stem has reached mature pod color of brown or tan. Seeds are approximately 60% moisture at this stage.

For more information, contact Wayne Flanary, Field Specialist in Agronomy at 816-279-1691, University of Missouri Extension.