LATE SUMMER ALFALFA HARVEST DECISIONS

Alfalfa is a perennial legume, but because it’s typically managed for high forage quality it’s often not a long-lived one. Most dairy farmers in this region are satisfied to get 4 or 5 productive years from a stand of alfalfa or alfalfa grass — and they should be, for several reasons.

First, alfalfa has a number of insect pests. The ones that can be controlled with insecticides include alfalfa weevils and potato leafhoppers. There are now “friendly” nematodes commercially available that are effective on alfalfa snout beetles, but there’s no registered insecticide to control root curculio larvae. The larvae of both these insects feed on alfalfa’s tap roots, eventually killing the plant.

Second, there are several diseases of alfalfa that also take their toll, including Verticillium wilt, Brown Root Rot and Phytophthora Root Rot. Alfalfa varieties have varying amounts of genetic resistance to these diseases; check with company seed guides or your seed company rep for more information.

Finally, there’s the impact of harvesting alfalfa before it’s fully replenished its root reserves. The fewer days between harvests, the more pressure on the plant. Farmers ask me why their alfalfa dies after several years of intensive harvest, and I tell them: “It doesn’t die; you kill it. You kill it by harvesting every cut prior to bloom, sometimes you don’t apply enough fertilizer (especially potassium), and then you cut it during the fall when good root reserves are most important.”

I’m not suggesting that farmers alter their summer harvest management of alfalfa since high quality forage is a key to good milk production. One option is planting HarvXtra alfalfa varieties, but HarvXtra alfalfa has two traits: delayed lignin formation and glyphosate resistance, making the seed very expensive. High seed cost plus the common practice in the Northeastern U.S. of planting alfalfa-grass has limited the use of HarvXtra varieties in this region. Reduced-lignin alfalfa has great potential because it allows harvest to be delayed by up to 10 days while maintaining high forage quality, but so far most farmers in this region have apparently decided that it’s not a great fit for their forage management systems.

What you should be considering now is how you’ll manage your better alfalfa fields this fall — those you plan to rely on next year. Harvesting alfalfa this fall will probably result in lower first cut yield next year — a prediction based on research data. However, the earlier in September you harvest (providing your alfalfa has had at least 6 weeks to recover root reserves), the better your chances of good yields in 2027. The very worst management is to take a fall harvest, then the crop regrows a foot or more before a killing frost. This would result in the alfalfa heading into a long North Country winter with low root reserves. For many alfalfa plants it would be their last winter. This is not a theoretical concept; it’s based on farmer experience. My recommendation: Unless you really need the forage, don’t take a fall harvest. And if you do need the forage wait until soon after a killing frost — the day after is OK.

— Ev Thomas

ethomas@oakpointny.com