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Forage specialist reviews alfalfa production practices

July 17, 2014 | 0 comments


The introduction of low lignin alfalfa, how the width of swaths affects forage drying, ideas for establishing new alfalfa stands, and the latest research on fiber digestibility by dairy cows.


Those were the major topics that University of Wisconsin Extension Service forage specialist Dan Undersander discussed in a presentation at the summer twilight meeting of the Calumet County Forage Council on July 14.


Meowing Alfalfa


Undersander described the pending introduction of low lignin alfalfa as a “cat's meow” for alfalfa growers. That observation was based on his experiences in evaluating alfalfa with that new genetically-modified trait in research plots at Arlington, where annual yields have been 6 to 8 dry matter tons per acre (about double the typical on-farm averages in Wisconsin).


Several hundred tons of low lignin alfalfa are being harvested at four research sites this year, Undersander reported. He said he pushed for feeding trials as one aspect of the evaluation of the trait.


Presuming that production of low lignin alfalfa receives approval from the Animal and Plant Health Service (a division of the U.S. Department of Agriculture) within the next 6 to 8 months, Undersander said supplies of seed would become available to growers by 2016. He said there was virtually no objection to such an approval during a public comment period that recently closed.


Lowdown on Lignin


Undersander, who noted that he had studied the low-lignin trait as a graduate student decades ago, explained that alfalfa with that trait doesn't have less lignin overall. The difference is the location of the lignin in the plant, he indicated.


A major advantage of the trait, which relates to the fiber digestibility of the forage, is that low-lignin alfalfa can be harvested up to 10 days later than conventional varieties without sacrificing quality, Undersander stated.


This not only results in higher yields but can also reduce the number of cuttings per year by one – from 4 to 3 in the Upper Midwest, for example – without a loss and probably even an increase in yield, Undersander observed. “You can harvest it later with more yield and the same quality.”


Ready for Roundup


There will not be alfalfa varieties with a low-lignin trait only, Undersander reported. All of them will be combined with those already having the Roundup Ready trait for tolerance to glyphosate herbicide, he stated.


With that associated ability to improve control of weeds, Undersander suggested the possibility of better persistence of the alfalfa stand. He also noted that no problems have been seen with lodging of alfalfa that will be standing longer nor is there any difference on nutrient requirements.


To a question about seed cost, Undersander agreed in general that the new combination would “cost a lot.” He said there are no firm numbers yet but he remarked that that questioner's suggestion of as much as a 70-percent increase might not be out of line.


Roundup Ready (RR) accounts for 15 to 17 percent of alfalfa seed sales today, Undersander stated. He said it is most popular in the West where control of weeds in alfalfa stands is a more common practice for the commercial production of dry hay but suggested RR is a good choice in Wisconsin, especially for establishing stands during abnormal conditions such as the cold and wet spring that prevailed this year.


Widening Windrow Widths


Regardless of the variety of alfalfa being grown, “I'd like to challenge you” to widen the forage swaths both for harvesting haylage and hay, Undersander continued. With the exposure of a larger portion of the forage to sunlight, this quickens the drying and allows an earlier harvest, he stated.


Undersander is calling for a swath wide of at least 70 percent of the mower width. Narrower swaths slow the drying rate and lead to a loss of dry matter and the sugars and starches that are crucial to the nutritional value of the forage for livestock, he emphasized.


Based on 13 University of Wisconsin Extension Service trials with the wider swaths, haylage was dry enough for ensiling by an average of 11 hours earlier in 70 percent of the cases, Undersander reported. He acknowledged, however, that growers would have to fit such schedule changes into their operating timetable.


To a question about the best time of day to cut alfalfa, Undersander said the notion about doing so in the afternoon because of the daily buildup of sugars and starches is applicable mainly in the West because of the low humidity and rapid drying in that region. In areas of higher humidity, research shows no increase at the time of harvest in forage that was cut in the afternoon because of losses incurred during the extra drying that is required, he said.


Moisture Timetable


What's most crucial, Undersander emphasized, is to reduce the moisture content of the alfalfa from approximately 75 percent to 60 percent within a few hours after the crop is cut. That is not possible if a large portion of the portion of the forage is not exposed to sunlight or wind, he pointed out.


Forage on the bottom of the swath continues to respire for many hours, resulting in the loss of nutrients, Undersander indicated. He also cited research which showed that the humidity can jump to over 90 percent in the forage at the bottom of deep and narrow swaths.


Mower conditioners help by quickening the drydown in alfalfa stems but they do not address the leaves, Undersander observed. “The leaves close when they are in the dark.”


By placing the forage in swaths as wide as the equipment and harvesting conditions allow, it might be possible to not use the conditioner in some cases, Undersander suggested. In general, it's better to drive over cut forage than to drop it in narrow swaths, he remarked.


A related problem, especially on wet soils, is that narrow swaths will also absorb moisture from the soil surface, Undersander warned. Narrow swaths are also more prone to rest on the soil rather than on the plant stubble, he added.


That phenomenon, along with the saturation in many fields this spring, has resulted in a lot more ash in forage samples being tested in laboratories, Undersander noted. He said that number is running at 14 to 16 percent in many cases compared to the 10 percent of ash that he considers to be acceptable.


Establishing New Stands


Given the large number of non-planted fields and large sections of crop drownout in other ones, Undersander said this presents an opportunity for the establishment of new alfalfa stands. With sufficient moisture and relatively cool temperatures, he said this can done in any month during the major portion of the growing season.


With the weather prevailing so far this summer, Undersander didn't rule out a July planting of alfalfa with an oats cover crop. He would also consider using Italian ryegrass as a cover crop for alfalfa but at a per seeding rate maximum of two pounds per acre for the ryegrass.


In the cases where a portion of the alfalfa planted this year perished, Undersander would disk the soil and then reseed. For older alfalfa stands, he mentioned red clover and grasses as possibilities but cautioned that they present drying challenges when harvesting for haylage or dry hay.


For the spring establishment of alfalfa, Undersander has changed his outlook on whether to include a cover crop such as oats. In wet conditions such as were prevalent this year, he explained that the presence of a cover crop takes up some of the excess water that would otherwise contribute to the development of diseases in alfalfa seedlings. Another benefit, he added, is the additional feed tonnage from the cover crop.


Total Tract Fiber


Referring to research by Extension Service colleague Dave Combs, who is a dairy nutrition specialist, Undersander reviewed the new process that is titled Total Tract Neutral Detergent Fiber Digestibility (TNDFD). It pertains to predicting how well the fiber digestion compares in vitro and in viva (in cow digestive systems) analyses.


The Combs research considers both the neutral detergent fiber and TTNDFD values for determining forage quality, Undersander explained. It also allows comparisons of the TTNDFD values derived in laboratory tests of corn silage, alfalfa, and grasses, he added.


Improving the prediction of the in vivo fiber digestion is the goal of this new formula, Undersander stated. He said this applies to the 24, 30, and the now largely discarded 48-hour windows for determining how much of the fiber is digested.


Digestibility Exception


This revised formula might be particularly useful this year, Undersander commented. That's because the first cutting of much of the alfalfa in the state has relatively low fiber digestibility, he noted.


It's typical that the first cutting of alfalfa has the top digestibility of the several cuttings during the season but that might not be true this year, Undersander remarked. He attributed that to the relatively low portion of leaves on the first crop, probably due to the prevalence of cool and wet weather during most of the time when it grew.


The overall digestibility and protein value of alfalfa depend greatly on the portion of leaves, Undersander explained. He also noted that this year's early season weather conditions were ideal for the development of leaf diseases. Applying a fungicide such as Headline probably would have been a good choice in many cases this year, he observed.

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