Is it time to stop irrigating corn?

It’s extremely important to know when to stop irrigating corn crop while considering the best kernel development, quality, and yield.

Corn plants in a field at Milan Research and Education Research Center (MREC) in 2024

The first thing to keep in mind when deciding to stop the irrigation is ‘not hurting our crop yield with early termination of irrigation right at dent corn’. Cut-off at dent is a no-no decision! Cutting off irrigation at that stage can impact and reduce grain yield and quality.

One thing that can help to make a better decision on cut-off time for the irrigation is monitoring the kernels milk-line. The observation will help to see the development of the milk-line, shortly after the corn reaches the dent stage. The milk-line will start at the top of the kernel and then make its way down to the corn cob in the center.

½ milk-line (left) to almost no milk-line/maturity (right)

Corn plants need to be irrigated until the crop reaches maturity/no milk-line. In corn that means when the black layer is appearing at the very base of the corn kernels (see figure below). A kernel at ½ milk-line may take about 10 to 14 days to reach the no milk-line/black layer. Usually, it will take corn plants 75-77 days after silking to reach the maturity stage/ black layer.

Black layer at the base of a kernel where attaches to the cob

If you are using soil water loggers and sensors in your irrigated field then you can use the soil water content information to estimate when the corn crop will reach to physiological maturity too. Having access to soil water loggers and sensors will help with:

-Water saving

-Understanding the crop root development and

-Being aware of time to cut off irrigation

I would recommend reading other colleagues Extension publications on this topic if you are interested in learning more about how to make the best irrigation termination timing for your irrigated corn crop.