Irrigation expenses are usually the biggest energy cost on the farm. On dry years, they become even higher. So how does one know when the system must be started and when it can be turned off? How should the low commodity prices this year affect these decisions? University of Nebraska Extension explains.

Elwyn Taylor, Iowa State University climatologist, reported that 200-bushel corn needs 19 to 23 inches of water during the growing season. For 200-bushel corn at 75 degree F (soil temperature), corn needs 1-acre inch of water per week, doubling to 2 inches at 85 degrees F, and doubling again to 4 inches at 95 degrees F. Read more in this article from Ohio's Country Journal.

Kansas State University Extension discusses the results of research investigating the effects of irrigation timing on cotton lint yield and also corn yield when the two crops are grown with a shared water supply.

University of Nebraska Extension discusses how much irrigation water will the corn need during the vegetative growth stage to produce optimal yields.

Water quality regulations in the 1990s led to a surprise increase of herbicides in waterways, despite decreased use of the target chemical. Turns out drainage tile — so useful in no-till fields — is speeding the compounds from field to stream.