If your soil profile is dry, you might be wise to irrigate your alfalfa this spring, suggests Bruce Anderson, University of Nebraska Extension forage specialist.
Early spring often is the best time to irrigate alfalfa because it builds a reserve water source for summer use, he says. Alfalfa can develop roots more than 8’ deep, but only when surface moisture doesn’t meet crop needs and moisture is available all the way down to those depths.
“Deep roots and deep moisture will make your summer irrigating much easier by providing extra moisture when plants use as much as half an inch per day,” says Anderson. “Unfortunately, typical shallow watering during summer encourages only shallow rooting.”
The biggest advantage of reserve water comes after each summer cutting. Alfalfa roots need oxygen in the soil if plants are to regrow rapidly. Watering right after cutting suffocates roots, slowing regrowth. Immediate watering also stimulates shallow-rooted or sprouting weeds, especially at a time when alfalfa plants are not very competitive. Both problems are reduced when water is available for deep alfalfa roots while the top several inches of soil remain dry.
Early spring irrigation also tends to help warm up the soil, helping to speed early alfalfa growth, since irrigation water usually is about 55°, says Anderson.
“So improve your alfalfa irrigation by watering early, with a goal of 6-8’ of soil at field capacity at first cutting,” he advises.