Slow Crop Development and Tillage Compaction May Create Need for Early Season Irrigation

Increased use of tillage to help warm soils and the delayed in killing cover crop are two additional reasons we see drier than normal planting condition. “Wet spring conditions forced some producers to work soils wetter than desired resulting compaction and slowed/restricted root growth in some fields” says Lyndon Kelley, Michigan State University Extension and Purdue Extension irrigation educator. Late planting and slowed root growth may result in a greater need for June irrigation for developing crops as we enter into the typical drier weather of summer.

Irrigation water applied at ½ to ¾ inch will wet dry soil down to 6 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 years’ rainfall is plentiful enough to replenish water lost to tillage or cover crop, but a dry layer 6 inches to 8 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 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 inch of water will move activated soil applied 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 visit the Michigan State University Extension Irrigation webpage. Delayed planting, slow root growth and reduced rooting may all increase the need for monitoring soil moisture and June irrigation. Soil probing below the developing root is a good indication of the need for early season irrigation. Soil below the roots should still be able to form and hold if adequate moisture is present. USDA offers an easy to use guide on hand feel method of soil moisture motoring.

Source: Lyndon Kelley, Michigan State University Extension