Corn Water Needs and the Value of Rain

Posted: July 15, 2014

Rapid growth stages of corn requires a lot of rain and the value adds up quickly too.

Recent rains have been welcome as the earliest corn is now beginning to tassel. A corn crop uses around 2” of water per week from V12 through tassel and up to R3(milk). So even though corn uses around 22” of water to produce a good crop around 10” of water is needed over the 2 week period prior to corn silking and 2 week after silking.

A high yielding corn crop of 200 bushels per acre requires about 22” of water. One inch of water per acre is about 27,000 gallons per acre, so a 200 bushel corn crop uses about 22 x 27,000 = 594,000 gallons of water per acre. That means that the crop uses almost 3,000 gallons of water for each bushel of yield. So each inch of rain produces about 9 bushels of grain on average, but the rain that falls during the time around silking is the most critical since the crop is using about 0.3” per day and requires over 2” a week.

So what’s an inch of rain worth in this summer for corn?

9 bushel x $4.00/bushel = $36 per acre (rain was worth twice as much a couple years ago when corn was $8)

If you have 500 acres of corn at $4/bu it is still $18,000 an inch!

Source: eXtension

Contact Information

Andrew Frankenfield
  • Extension Educator, Agronomy
Phone: 610-489-4315