Go wide
By Shirley Roenfeldt  |  Sunday, April 01, 2007

Want to make high-quality alfalfa silage in less time?

Go wide.

That’s the recommendation of researchers at Cornell University. When harvesting alfalfa for silage, cutting it in a wide swath allows the hay to dry quickly, and that, in turn, allows you to chop and ensile it in just one day. It also gives you more milk per ton than alfalfa silage harvested in a traditional narrow swath.

Go wide this spring for alfalfa silage — it pays.

Saves time

Traditionally, alfalfa is cut and laid into a narrow windrow. But, depending on weather conditions, it can take two to three days for it to dry enough to be ensiled. And unless you rake it to promote uniform drying, you end up with a windrow that is as dry as baled hay on the outside and wet as fresh mowed hay on the inside, explains Tom Kilcer, regional field crop and dairy extension specialist at Cornell University. However, given what researchers have learned about how hay dries — the plant goes through three distinct phases for drying — harvesting alfalfa for silage in a wide swath makes sense.

During phase-one drying, moisture exits the plant by evapotranspiration in the leaves. So, when alfalfa is cut into a wide swath — at least 85 percent of cutterbar width — and a conditioner not used, you can double the drying rate to 2 percent moisture loss per hour. (In a narrow windrow, the drying rate is 1 percent per hour.) With the wide windrow, three times more sunlight hits the windrow as compared to a narrow windrow, explains Kilcer. This allows the hay to actually heat above ambient temperature and reach the target moisture level of 65 percent for chopping and ensiling in two to four hours. Wide-swath harvesting speeds things up, which means you can cut, chop and ensile alfalfa in one day — and perhaps avoid having the hay rained upon.

Saves nutrients

When cut, alfalfa plants respire until they reach about 30 percent dry matter or the pH falls below 5.5. During respiration, the plant converts carbohydrates into carbon dioxide and water. As long as the plant continues to respire, it will burn these highly digestible and valuable nutrients. So, the longer it takes the plant to dry, the longer you have nutrient losses from plant respiration.

When alfalfa is cut into a wide swath, sunlight hits all of the plants so photosynthesis continues. This photosynthesis — even after the plant is cut — allows the plant to increase its level of carbohydrates at a rate that surpasses the losses from respiration. (In a narrow swath, the plants in the middle of the windrow are shaded, so photosynthesis stops.)  With a wide swath, you actually get a net gain of about 4 percent in starch as compared to a 17 percent loss of starch in narrow windrows. And you even save plant sugars with wide-swath. In just 24 hours, you can lose about 17.7 percent of plant sugars in narrow swath compared to 5 percent for wide-swath.  Research shows that a net energy of lactation of 0.63 to 0.65 can be easily obtained in alfalfa silage harvested using the wide-swath method.

Saving the plant sugars is also important for proper fermentation, adds Loren Bailey, dairy specialist for Agri-King in West Bend, Wis. During fermentation, bacterial organisms or “bugs” use the sugars for fuel and the creation of lactic acid.

Bailey has done some of his own wide-swath research. He worked with one producer to harvest part of the alfalfa in a wide swath and then part in a traditional narrow windrow. The alfalfa was cut at 2 p.m., and by noon the next day the wide swath was at 70 percent moisture and ready to chop. Meanwhile, the narrow windrow was still at 80 percent moisture and required another 24 hours to dry down for ensiling.

But the biggest difference, says Bailey, was the sugar content of the plants. Sugar content in the wide-swath alfalfa was 7.5 percent compared to just 3.5 percent in the narrow-alfalfa windrow. Less energy in the forage means having to feed more corn to meet the energy needs of lactating cows. With corn prices increasing, it would be better to improve the forages instead. 

More milk per ton 

Using the Milk 2000 computer model, researchers at Cornell University found that width-swath-initiated alfalfa silage routinely delivers 300 pounds more milk per ton of dry matter than alfalfa harvested in traditional narrow windrows and ensiled. The chart below shows the impact on potential milk per ton. (Research with grass silage has yielded similar results.) 

 

	First-cutting alfalfa
Narrow windrow fresh-cut	2,652 lbs milk/ton dry matter
Wide swath fresh-cut	2,731 lbs milk/ton dry matter
Narrow-windrow ensiled	2,279 lbs milk/ton dry matter
Wide-swath ensiled	2,574 lbs milk/ton dry matter
Additional milk per ton	294.9 lbs

 

 

 

 

 

 

 

Source: Tom Kilcer, Cornell  University

New York producers who have tried wide-swath are sold on the results, says Kilcer. They have altered their equipment to achieve a wide swath of 85 percent of cutterbar width, or else bought new equipment to achieve those same results. Now, they can cut, chop and ensile in one day. And the
result has been consistently higher-quality alfalfa silage and more milk.

---

Wide vs. narrow

Width: Wide swath is three times as wide as narrow.

Density: Narrow is 5.5 times more dense that wide swath.

---

Wide-swath Web site

To learn more about the wide-swath research done in New York, follow this link.

Printer-friendly version

Email a friend