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Dave Wilson, a Penn State Extension educator, holds brassica leaves as he speaks about grazing.

LEOLA, Pa. — Cool-season grasses are the mainstay of many Pennsylvania farmers’ grazing strategies, but they generally aren’t enough to meet feed needs year-round.

Species often used as cover crops can help fill that gap, particularly during the summer slump, when hot weather slows the growth of cool-season forages, said Sjoerd Duiker, a Penn State soil management professor.

Duiker spoke about grazing cover crops during an Aug. 2 field day at the Eli Weaver farm in Lancaster County.

Cover crops can be economically justified as a way to improve the soil, but grazing gives them the added value of livestock feed. As a result, farmers have an extra incentive to fight weeds and get fertility right, Duiker said.

Growing cover crops tall also helps the soil. Large plants develop larger root systems than plants that are cut short all the time.

Cattle won’t eat all of that lush vegetation, though. Some of it they will trample into the soil. “It’s not a waste. It is also feed for the earthworms,” Duiker said.

The flattened plants protect the soil from erosion too.

And if the alternative to grazing cover crops is feeding hay, keeping the cows on pasture can cut labor costs by roughly half. When they aren’t in the barn, the cows harvest the feed and distribute the manure themselves, Duiker said.

Weaver, the host farmer, has always liked grazing, and it’s become more attractive as the price of grain has increased.

With grazing, “you can make a decent amount of milk at very low cost,” he said.

But there are potential downsides to grazing cover crops.

Cattle can cause some compaction, especially if the ground is wet. Farmers need to have a sacrifice lot or concrete pad for days when the pasture is too soggy to graze.

Fortunately, if the pasture is managed properly and the soil has a healthy microbial and root community, the ground can withstand compaction fairly well, Duiker said.

Weaver tries to plant his summer annuals so they are ready to graze when his other pastures have slowed down, but it can be hard to get that timing right, he said.

A lot of cover crops can fit into a grazing program.

Dave Wilson, a Penn State Extension educator, showed attendees an all-brassica demonstration plot featuring turnips, radishes, rapeseed and the like.

Brassicas give livestock a lot of protein, but a grazier would not normally plant them on their own. In large doses, brassicas give cattle thunderously loose bowels, though dry hay can offset that somewhat.

In a pasture mix, brassicas only need to be seeded at a few pounds per acre. Otherwise, they overwhelm the other crops, Wilson said.

For some reason, cows take a while to warm up to brassicas when they are first offered them. “Once they try them, boy, then they go nuts,” Wilson said.

The brassica plot was lush, but some redroot pigweed and marestail had managed to get ahead of the brassicas.

Nearby, Wilson pointed out mixed cover crop plots with species like sorghum sudangrass, cowpea, fava bean and Japanese millet. They had grown a little higher than their ideal grazing height, but Wilson wanted them to still be standing for the field day.

From this plot Wilson pulled out a sunn hemp plant that was just starting to lignify in the stem.

When sunn hemp is knee high or shorter, the cattle will eat the leaves and the stem. If the crop grows taller, the cattle will eat the leaves and skip the toughening stem, Wilson said.

Buckwheat, another crop in the mix, grows quickly and is very digestible before bloom. It has been used as a forage in emergencies and makes phosphorus more available in the soil, but it can cause a rash in light-colored animals if it makes up more than 30 percent of their diet.

Buckwheat yields are relatively low, so “it’s been out of favor,” Wilson said.

Warm-season annuals like pearl millet and sudangrass are easy choices for grazing this time of year. They grow quickly and thrive when cool-season grasses are on their summer break.

Corn can even be grazed late in the summer, though dry corn has a diminished feed value. “It stands up very nicely. That’s the advantage,” Duiker said.

Forage quality is a particular issue on Weaver’s farm because he has dairy cattle. Beef animals can use lower quality crops like switchgrass, indiangrass and big bluestem, but those won’t meet milk cows’ needs, Duiker said.

Using alternative forages can reduce the risk of overgrazing cool-season grasses, which can send pastures into decline.

Orchardgrass and similar species store their nutrients for regrowth in their first 1 to 3 inches above ground. If the grasses are mowed or grazed to the ground, regrowth is set back, Wilson said.

Legumes, Kentucky bluegrass and timothy don’t have quite the same problems because they can store more nutrients where cows can’t get to them, he said.

To add some protein to a cool-season grass diet, farmers can seed clover during the winter.

Clover seed is small and heavy, so it falls into the cracks created by the freeze-thaw cycle. “The cows like clover in their diet,” Wilson said.

Clovers are good suppliers of soil nitrogen too, so farmers sometimes do not need to fertilize a pasture that is at least one-third clover.

Weaver said he usually gives his pastures a shot of nitrogen early in the season to get them going. If there is enough clover, that’s usually all the fertilizing he needs to do.10

Photo by Philip Gruber

Dave Wilson, a Penn State Extension educator, holds brassica leaves as he speaks about grazing.

Photos by Philip Gruber


Sjoerd Duiker, left, a Penn State soil management professor, shows a chunk of soil from a pasture plot as Extension educator Dave Wilson observes.


The mixed brassica plot at the Eli Weaver farm was planted for demonstration. Brassicas contribute protein to a cow’s diet, but they cause loose bowels when they make up a large percentage of the ration.