Look Out for Alfalfa Winter Kill

As I’m writing this on Jan. 18, the temperature in downtown Hartwick is 37º F with a light mist falling. Most of our recent meager snowfall has evaporated or melted into the ground. Without adequate snow cover, alfalfa stands – particularly clear alfalfa stands – on less than ideally drained soils are prone to heaving, due to the freezing/thawing stress of expanding/contracting soils.

Years back, Cornell Field Crops Professor Bob Seaney explained how a companion grass protected alfalfa from heaving damage. Seaney showed that the fibrous root systems of grasses (particularly timothy) provided a shock absorber benefit to counter expanding soils as they yanked against the nodule-laden alfalfa roots.

I’ll tap into the wisdom of Certified Crop Advisor Tom Kilcer, who for decades oversaw field research at the Cornell Valatie Research Farm in Columbia County. In his online advancedagsys.com, Kilcer wrote that in 2020 he conducted experiments assessing winter-killed alfalfa damage. The original concept was that as soon as it was determined that the stand was dead or nearly dead, growers could no-till red clover or red clover with oats to re-establish a forage legume for the next three years.

Alfalfa allelopathy had no effect on either crop. One simple definition of allelopathy reads “the chemical inhibition of one plant or other organism by another, due to the release into the environment of substances acting as germination or growth inhibitors.”

Into this dead alfalfa sod, in 2020, they planted oats followed by sorghum. Quoting Kilcer, “This approach was a spectacular failure: the sorghum did not grow well, if at all. We speculated that the oats had an allelopathic effect on the sorghum. We strongly suggested not to try this practice. A farmer subsequently told me they had the same failure.

“To determine if this was a fluke of weather or a real issue, we repeated the study in 2021. We added another variable to the test. After harvesting the oats, for part of the oat plot, we lightly tilled (one to two inches deep) with a disk to break up and incorporate the top inch or two of soil.” Next they planted the brown-midrib (BMR) sorghum/sudan (SS). The SS in the fallow ground grew fine. The sorghum no-tilled into oat stubble did not grow at all, thanks to allelopathy.

However, in lightly tilled ground – whether in fallow or oat stubble – SS grew very well with no issues from oat allelopathy. Kilcer stressed, “This solves two problems in one pass with the disk. First and most important, it breaks the allelopathy to allow sorghum to grow. Second, it is a perfect time to add manure to meet the NPK needs without purchasing more expensive fertilizer. Spreading manure and immediately incorporating will more than triple the amount of nitrogen your crop can get from the manure. It does this without adding excessive phosphorous.” This allows growers to empty manure storage in early June so they’re not pressured to spread on hay ground during growing season.

Sorghum is handily followed by no-till winter forage triticale. Both crops regrow in autumn, until the first frost kills sorghum. Triticale continues growing, protected from harsh winter by dead sorghum trash, usually flattened by snow. Come spring, expect two to four tons of dry matter/acre of high-quality forage (better than BMR/SS) as the first cutting. This practice leaves the field in ideal condition to no-till seed alfalfa or red clover in early June after harvesting triticale haylage. Kilcer said they have consistently gotten much better seedings by planting them at this date, using stubble to keep the small seedlings growing optimally.

Alfalfa particularly clear-seeded is susceptible to leafhopper damage. With minute hairs on its leaves, medium red clover is naturally protected from potato leafhopper. Leafhoppers hate those tiny hairs. Three years ago, a demonstration was performed at Valatie where a seeder was loaded with alfalfa in one hopper, and red clover in the other hopper. Result: alternating yellow and green stripes covered the meadow. Yellow was hopper-hammered alfalfa; green was medium red clover. As a non-chemical control, hairy clover saves the cost and time of spraying.

Clover has slightly less crude protein (17.07%) than alfalfa (19.02%). Total amount is only part of the story. According to Michael Flythe, Ph.D., Agricultural Research Service (USDA), “Clover has compounds that inhibit hyper-ammonia rumen bacteria from breaking protein to inefficiently utilized ammonia, (thus) increasing the metabolizable energy for milk.”

Flythe also found that “clover contains polyphenol oxidase enzymes that inhibit protein breakdown for more bypass protein (25% – 35%) than alfalfa (15% – 25%), thus enabling lower cost rations as they have less added very expensive bypass protein. If it is not rumen degraded, then it is bypass protein. Alfalfa had 72% rumen degraded while the clover was 68% (alfalfa bypass 28%, clover bypass 32%.” (Rumen-degradable protein and rumen-bypass protein total 100%.)

It’s important how photosynthetic energy is stored in plants. In alfalfa, energy is stored in cellular starch. Alfalfa had 92% more starch than clover. Clover has much higher sugar than alfalfa – 87% more. This means two things. First, with a proper inoculant, clover provides a medium for rapid fermentation. Second, it is even more critical to utilize wide swath same-day haylage with clover to preserve sugar energy to the cow’s mouth.

According to Kilcer, “Occasional reports of cows not wanting to eat red clover may be due to narrow row, multi-day drying systems that respire most, if not all the readily available sugar in the plant. But clover also stores considerable energy in pectin. There is not a direct test for pectin, but it shows as non-fiber carbohydrate (NFC) levels. Clover consistently had higher NFC (13%) than alfalfa. Clover can be a superior forage on farms that are affected by cloudy cool conditions downwind from the Great Lakes and in high cool elevations and any less-than-ideal drained soil. A critical key is to use modern red clover varieties as in these trials, not some cheap ‘Variety Not Stated’ junk with no disease resistance or improved productivity.”

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