From the October December 2018 Beef Newsletter
What this really means is—double the forage production on the number of acres of pasture you have right now. It does not mean buying supplements all summer and hay all winter which is in part a result of mediocre grass yields from permanent pasture.
Pasturing is not automatically Grazing
In dairy, the difference between a productive conventional (confinement housing and stored feed supply) and a profitable grass dairy (seasonal grazing with harvested forage needed in winter) is one less acre per cow. Grazing is optimized when you utilize cows as haybines (moving from field to field as each “cutting” is harvested, with a rest period in between to regrow the forage—just as you manage alfalfa fields) rather than just turning them loose to wander the entire area.
Dairymen quit pasturing because they perceived they grew more feed per acre with row crops, and the negativity toward pasturage spilled over to become a negativity toward grass. This is in spite of forage test data indicating vegetative high energy grasses can produce 4000 pounds milk per ton—higher than either alfalfa haylage, dry hay, or corn silage.
For those who learned to rotate pastures as “fields”, allowing the grass some rest time (just like you manage an alfalfa field) – productivity could be sustained and seedings remained perennial.
Most people that pasture think rotation of paddocks too time consuming. The result is a waste of productivity as well as forfeited feed quality. Grazing rotationally solves those losses.
The science of grass as a plant (it is different from alfalfa)
Grass, small grains, and corn are all variants of the same zhea plant species. They all grow from a root mass, they all go through a vegetative stage with a goal of pushing out a seed head, and once the seed head is fully formed, the stalk and leaves dry up. Energy captured during growth (from the sun primarily) gets concentrated in the seed head at plant maturity, but until then, is basically stored in the cellulosic (plant fiber) structures of stalk and leaf. All of them are highly responsive to nitrogen, and all are dependent on finding water and minerals within their root zone. They tolerate a wider range of soil pH. Rumens were designed for grasses.
Visualize the grass plant below the ground level
Corn breeders like to show off root balls from hybrid varieties, to demonstrate how important a good root system is to crop yield. A corn plant grows mostly undisturbed until the seed head matures and then you harvest. You can predict your yield from the rainfall patterns along the growing season and the days of sunlight.
When it comes to managing grass pastures however, we need to perceive pasture as a “field” growing a “crop” and harvest it as “cuttings” (like hay) – and there is no doubt that rotated pastures produce at least twice as much feed as open pastures where animals wander about. There is an easy explanation of this; when you harvest your crop, the roots die. Eat the grass too low, and you have more dying roots than new shoots. The pasture withers. Leaves must remain for photosynthetic capture of sunlight energy and roots must absorb rainfall.
COMPARING ROOT RETENTION (NRCS simulations from digging up plants)
Grazed to 6” and rested Grazed to 4” before rest Continuous pasturage
Alfalfa [not a grass, but a legume] has a tap root or branch root system that feeds a crown, from which forage stems grow. You cut the stems every 28-35 days but the crown still lives, so sends up new stems for the next harvest. (Of course we also rarely cut alfalfa below 4 inches, so it should be no surprise grasses would need similar care). For grasses, each blade of grass has a corresponding root; when that blade is cut, the root may die; what insures it will die is when the grass blade is cut below the flag leaf as it can no longer do photosynthesis to regrow.
With continuous overgrazing, the most palatable grass gets exterminated (eaten too close to the ground) and future growth that season is inhibited. It is not the fault of your seeding or of grass as a forage plant. (If you cut the top off a green corn plant, would it regrow and produce feed? This is no different— all grasses work the same way. We must manage for yields.)
Rotation grazing is a practice that allows your grass paddocks time to regrow, and that growth becomes exponential when the grass is above 6 inches tall. If companion clover is also seeded, nitrogen from the clover nodules underground will feed this grass growth, to keep it vigorous. Cows do like clover, however, so when overgrazed, a pasture will lose its clover (extra source of nitrogen) alongside all the grass it would have “fed”. Most loss of productivity in a pasture system is a result of the compounded effects of continuous (“over”) grazing.
Grass responds to sunlight, rain and nitrogen
Lake City Experiment Station has confirmed from recent trials that adding 5-8 pounds of clover seed by frost seeding produces 150-200 pounds of nitrogen annually for the next two years. In turn, this bumps up forage yields in pastures in the same way it bumps wheat or corn yields. If we expect to get yield from pasture, we need to feed it like a crop and clover is the cheaper way.
Dealing with “summer slump”
The best perennial forage grasses are “cool season” varieties. Grass is the first thing to grow in the spring because it likes cool weather (and has root masses that can tolerate wet soil). Spring grass is so vigorous that you could rotate back every week and not overgraze. However, as soon as temps rise to 80 degrees F (and it also quits raining) grass slows down, so your rest periods must go longer. A small field of summer annuals [eg, Sudangrass] can feed the cattle until fall rains and cooler nights return. Paddock rotation can provide feed all the way into winter.