Early season irrigation

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

How to achieve the most agronomical and economical start from irrigation during planting season is important. Achieving the maximum uniform germination and emergence can be assured through proper early season water management. Irrigating fields prior to or just after planting, can keep the planter moving and still meet the “plant into moisture” requirement.

Irrigation water applied at ½ to ¾ inch will wet dry soil down to six inches to replace water loss to tillage. An inch of irrigation will often be needed in a field that has not received rainfall since the cover crop was destroyed. Monitoring newly emerged crops that were “irrigated up” is essential. It is important to water enough to keep roots growing down into the moisture. Most year rainfall is plentiful enough to replenish water lost to tillage or cover crop, but a dry layer six inches to eight inches down can greatly hinder crops development, and needs to be replenished by rain or irrigation.

Early season irrigation can be both the cause and solution to soil crusting and emergence problems. Depending on soil type, crop residue, and irrigation application equipment early season irrigation can create some soil crusting accelerated by rapid surface drying. Small applications of water 0.2 to 0.3 of an inch may help to allow emergence of seed through the crust.

Many herbicide options can be assisted by a timely rain or irrigation. Applications of 0.3 to 0.5 of an inch of water will move activated herbicides if rainfall does not occur within two days after herbicide application. Irrigating in herbicides can also create the problem of different levels of weed control between the dry corners and the irrigated portion of the field. Timely and directed scouting for weeds in dry corners will be needed later in the season.

Early season irrigation can be more accurately scheduled from monitoring soil moisture in the root zone rather than checkbook irrigation scheduling system for newly emerged crops. Later in the season, checkbook irrigation scheduling will show its advantages over scheduling by soil moisture in the root zone alone. To learn more about checkbook irrigation scheduling click on the following link: http://www.msue.msu.edu/portal/default.cfm?pageset_id=28706&page_id=361029&msue_portal_id=25643 and see the irrigation scheduling tool fact sheet.

For more information on irrigating, contact Lyndon Kelley, Extension Educator Purdue/MSU, Irrigation at 269/467-5511

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