Seeding grasses with alfalfa provides better cover management and reduces erosion, said Tom Cox, University of Wisconsin (UW) ag economist.

“The question is, what does that do to the rest of our farming system?” he added. “Can we make money doing it and improve environmental performance?”

Before making this type of crop management decision, Cox urged growers to consider whole-farm management systems that make use of on-farm and university research and management tools. He spoke at the U.S. Dairy Forage Research Center Forage Tool Box seminars at World Dairy Expo in Madison, WI.

Cox used the example of seeding grasses with alfalfa vs. growing pure alfalfa to show whole-farm management can improve environmental and economic performance.

“We have a big tool kit of things that we can use to allow the individual producer to make a choice about what makes sense for his situation.”

Before adding grass to hay, a producer has to deal with several management issues: which grass to use, when to harvest, at what feed quality and how that crop will affect a ration.

“You're going to have to choose the type, the yield and the maturity,” Cox said. Orchardgrass, for instance, yields about 6 tons/acre/year on average when seeded alone, according to UW field trial information. Timothy yields just over 3 tons; smooth brome, 4 tons and tall fescue, just 2 tons/acre (see Table 1).

Yet don't choose based strictly on yield. You may need to find a grass with a maturity that more closely matches that of the legume, Cox said.

Then look at when your grass will yield and whether that matches your management goals. “What is it going to do during the summer slump? Are you going to get most of it in spring? If you're grazing, that's not going to be overly attractive. Will you have a variety that's going to have a better distribution of yield?”

UW Table 2 shows that orchardgrass and tall fescue yields distribute more consistently through the season than those of smooth brome and timothy, so offer a more-consistent alfalfa-grass hay.

“You can see that tall fescue has about 30% of the total yield available in August and September. If you're a grazier, this is very attractive. This information is available; we need to incorporate it into our whole-farm systems thinking and management tool.”

Research on rust-resistant grass varieties shows that they yield 2-3 tons/acre more than common varieties, and that late-maturing varieties head close to alfalfa harvest timing. Common types, however, head up to two weeks earlier than when alfalfa is ready to be cut. Improved perennial ryegrasses, for example, yield up to 1½ tons/acre more than common varieties.

Additional data about variety yield differences can be utilized before making a seed-buying decision. “There's as much as a 6 ton/acre difference between top- and bottom-performing varieties of ryegrass. You may not want one on the lower end of the distribution because, for the same amount of work and energy, it's giving you a lot less yield.”

Growers and graziers can also match grass and alfalfa maturities using research data. The cutting-date window for orchardgrass is about 30 days, so choose a variety that matches when you think your first-cut alfalfa will be ready.

Orchardgrasses also have a seasonality, so graziers may want a variety with good production during summer slump. Later cuttings can be harvested when the alfalfa is ready.

To measure feeding quality, UW researchers ran nine simulations showing 25:75, 50:50 and 75:25 ratios of corn silage to hay-crop silage, respectively. Within those ratios, differing proportions of hay were tested — straight alfalfa, straight grass and 50:50 alfalfa-grass mixtures (see Table 3).

“It looks like we gave up 2 lbs/day of milk by going to more grass in hay; we gave up yield but lowered cost per unit,” Cox said. Table 4 shows that diets with mostly corn silage brought higher purchased feed costs as compared to the 50:50 and the largely alfalfa-grass silage diets.

“This is not necessarily what's going to happen on your farm and in your situation, but it will give you an idea of the performance across scenarios,” Cox said.

Using whole-farm management is a win-win situation, he added.

“If we look at the science being generated, at the knowledge that's being generated on farms, and if we can then promote this whole-farm management perspective … there are opportunities to identify increasing economic as well as environmental performance. We're trying then to use the science and analytical tools to help devise decision tools to evaluate these tradeoffs,” Cox emphasized.

For his pdf presentation, visit and look under “Presentations.”