Pre-Season Alfalfa Irrigation May be Advisable
With low soil moisture levels in many areas of the state, now is a good time to irrigate your alfalfa with a goal of having at least six feet of soil at field capacity at first cutting.
Early spring irrigation also provides an opportunity to build a reserve water source for summer use. The biggest advantage of this reserve water comes after each mid-summer cutting.
Alfalfa can develop roots that will use water more than eight feet deep, but it will only do this when surface moisture does not meet crop needs and moisture is available at deeper 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 one-half inch per day. Typical shallow watering during summer encourages only shallow rooting.
Shallow summer watering can also cause other problems. 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 when alfalfa plants are not very competitive. Both problems are reduced when reserve water is available for use by deep alfalfa roots. Then the top several inches of soil can remain dry for a couple days until alfalfa regrowth is well underway.