Guide to Reduced-Lignin Alfalfa

Farmers have greatly increased the quality of alfalfa fed to their livestock, but primarily through management changes.

In the almost 20 years I’ve been writing for FARMING magazine I’ve never covered the same topic three times in a year – let alone three times in six months. That is, until now because reduced lignin is generating more excitement in the alfalfa seed business than any genetic advance I can remember. It may be a breakthrough in efforts to improve the quality of “the queen of forage crops.” Farmers have greatly increased the quality of alfalfa fed to their livestock, but primarily through management changes: earlier harvest, improved windrow management to dry the crop more quickly and retain more leaves and silage inoculants to better preserve forage quality.

There’s still precious little university data on the relative performance of reduced lignin alfalfa. There are three types of reduced lignin alfalfas on the market: HarvXtra is a genetically modified variety that seems to be attracting the most excitement since it’s up to 20 percent lower in lignin than conventional varieties. All HarvXtra alfalfa varieties (sold by a number of seed companies) are also Roundup Ready, and the combination of this trait plus the reduced lignin one add up to a cost of $300 per bag. That’s just for the traits, not the seed itself. The total price (which varies among seed companies and is before any discounts) is about $600 per bag, or two to four times that of conventional alfalfa varieties. There are also two seed companies, Alforex and Legacy, selling conventionally-bred alfalfa varieties claiming higher digestibility – all without the Roundup Ready trait. According to preliminary data they appear to be higher in lignin than the HarvXtra varieties but lower than conventional alfalfa. It will take time to sort all this out.

There have been previous efforts to genetically improve alfalfa quality, but reduced lignin varieties appear to be the first to accomplish it without sacrificing yield or standability. Standability is a potentially big issue in any crop with reduced lignin levels. I remember one alfalfa variety years ago that was promoted as having superior forage quality. We planted it at Miner Institute (Chazy, New York) and sure enough, what we harvested was higher than normal in quality – but that was because every cutting lodged so badly that we left the bottom half of the plant in the field! (By the way, one way to moderately increase the forage quality of an alfalfa field that is in bloom by the time you get to it is to raise the cutterbar a few inches – perhaps harvesting at 6-inch stubble height instead of the normal 2 to 4 inches. You’ll lose some yield, but will probably find surprisingly little of that leftover stubble in the next crop, assuming it’s mowed at the normal height.

The second reason for this “reduced lignin reprise” is that there’s considerable difference of opinion as to how best to manage reduced-lignin alfalfa on dairy farms. The two commonly recommended harvest strategies are to harvest the crop at the normal stage of maturity – typically late-bud stage – or to harvest it 7 to 10 days later when the crop is in the one-quarter bloom stage. In one case farmers would wind up with perhaps the highest digestibility alfalfa they’ve ever fed; in the other case they’d have higher yields of good (but not “supreme”) quality alfalfa. Let’s look at where these alternative harvest strategies best fit.

Cut at normal harvest date

Reduced-lignin alfalfa doesn’t decline in digestibility any slower than does conventional alfalfa; it’s lower in lignin (and therefore higher in digestibility) at all comparable stages of maturity. Therefore, reduced-lignin alfalfa cut at the bud stage is much lower in neutral detergent fiber (NDF) and higher in digestibility than late-bud stage conventional alfalfa varieties cut on the same day.

This may sound like a great idea and it may be depending on how you feed this “rocket fuel.” It’s entirely possible that this alfalfa could be higher in crude protein than in NDF, something few dairy farmers are used to. Alfalfa with this analysis may feed more like a concentrate than forage. If this alfalfa is fed at a relatively low rate and properly balanced with other forages it may give a quality boost to a dairy ration. It’s certainly a feedstuff that needs to be fed with care and with counsel of a competent dairy nutrition consultant.

Delay harvest

Delay harvest 7 to 10 days and cut at 25 percent bloom. This should result in alfalfa of similar quality as varieties with normal lignin levels, though research is needed to determine exactly how many days harvest can be delayed with each type. I favor this alternative for most farmers since forage quality would be about what they’re accustomed to.

Delaying harvest by a week or more for each cutting would usually result in one fewer harvest per season. When is less more? When one fewer harvest results in higher total yield! Several years of research at the University of Wisconsin with a conventional alfalfa variety confirmed this – higher yields with three vs. four harvests per season. Prior to the advent of reduced-lignin alfalfa delaying harvest by a week or more would result in poor forage quality. Fewer harvests mean less labor and equipment cost and less wheel track damage to alfalfa plants. Delaying harvest by a week also allows the alfalfa plant to store more carbohydrates in its root system. Repeated harvests at the bud stage take their toll on the health of the alfalfa plant. When alfalfa is harvested photosynthesis stops because there are no leaves and thus nothing to transmit nutrients to the taproot. Mowing alfalfa also causes the death of rhizobial nodules and some root hairs. According to Cornell University Forage Agronomist Jerry Cherney, repeated harvests at the bud stage is an “accumulation of insults” that when combined with aggressive fall harvest management can severely deplete stands.

Where harvest of reduced-lignin alfalfa at the bud stage might work well is when a forage grass is seeded with the alfalfa and the alfalfa is harvested in the bud stage. In this case the low fiber level of the alfalfa would be balanced by the higher fiber level of the grass, which often matures a bit sooner than we want it to. Each farm planting reduced-lignin alfalfa will have to decide on which approach they’ll take: “super quality” alfalfa with no change in harvest dates, or delayed harvest, which may result in higher yields and one fewer cut. No one size fits all, but now you know where I stand on this.