“Early spring irrigation provides an opportunity to build a reserve water source for summer use,” says Bruce Anderson, University of Nebraska extension forage specialist. “This offers a big advantage for each midsummer cutting.”
In areas where soil moisture is currently low, Anderson says now is a good time to irrigate with a goal of having at least 6 feet of soil depth at field capacity by first cutting.
In a recent issue of Nebraska extension’s CropWatch newsletter, Anderson explains that alfalfa can develop roots that will use water more than 8 feet deep, but this only occurs when surface moisture does not meet crop needs and there is water available at the deeper soil depths.
“If you have deep roots and deep reserve moisture, it will make your summer irrigating much easier by providing extra moisture when plants use as much as 1/2 inch per day,” Anderson says. “Typical shallow watering during summer encourages only shallow rooting,” he adds.
Another problem with shallow summer watering is that alfalfa roots need oxygen in the soil for fast regrowth. Watering immediately after cutting suffocates roots and slows regrowth, Anderson explains. Immediate watering also encourages shallow rooted or sprouting weeds.
These problems are negated when water is available for use at lower depths in the soil profile. Such a condition provides an option to let alfalfa initiate regrowth before applying water.