Irrigation to aid germination

Irrigation can greatly improve germination and resulting stands in dry soil conditions.

One of the most valuable times to have irrigation available is when the lack of rainfall threatens to cause uneven germination. Most farmers appreciate a nice rainfall the night after they finish planting a field. Producers with irrigation can take advantage of their investment by making sure every irrigated field gets off to a good even start.

Our commonly irrigated sandy loam soils of Indiana and Michigan need about a half inch of irrigation to wet the soil down to 5 inches to 6 inches. This amount most often is enough to encourage germination and carry the crop seedling for a week, hopefully until the next spring rain. Heavier loam soils may need 0.7 inches to 0.9 inches of water to wet the top 6 inches of soil.

One potential challenge to irrigating a crop through emergence is the chance of creating a dry layer of soil to exist beneath the root zone. Leaving a dry layer below the root zone can lead to problems for the seedling to extend roots through dry layers down to natural moisture below. It is not very common for spring rain to be so infrequent to cause this situation but irrigators need to be aware of this potential situation to provide water to prevent seedling stress. Double crop situation often require extensive watering to establish the second planting in the warmer dryer summer weather.

In extremely dry soils, conditions like planting no-till planting into a burn-down rye cover crop, irrigation may better utilized before planting to allow the planter to perform better and even seed germination. Likewise heavy tall cover- cropped fields may benefit from irrigation before tillage if dry soil conditions exist.

The economics of using irrigation to help germinate a crop are potentially good. Most Indiana and Michigan farmers’ cost to irrigate with one inch of water is between $1.50 and $8 per acre. The key is knowing whether the seed zone is unacceptably dry or unevenly dry. Uneven seedling emergence of corn caused by uneven seed zone moisture content can result in yield losses as high as 20%.

One of the excuses most often cited for not taking advantage of the option to irrigate a germinating crop in a dry soil conditions is that the irrigation system was not ready to run. Having the irrigation system ready to run when you plant can makes the difference between looking at a good stand that is primed for maximum yield potential or trying to make the best of a poor stand.

Special thanks to Dr. Robert L. Nielsen, Extension corn specialist, Department of Agronomy at Purdue University, and Bruce MacKellar, MSU Extension educator for their input into this article. 

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