by Tamara Scully
Tall grass grazing relies on the relationship between the pasture plants and the soil microbial organisms. This relationship, based on nutrient cycling, is the key to growing nutritious and plentiful pasture. Whether growing warm or cool season grasses – or both, depending on your growing region – tall grass grazing eliminates fertilizer applications while keeping animals healthy and productive.
Dave Scott raises sheep utilizing tall grass grazing, and is a specialist with the National Center for Applied Technology – Appropriate Technology Transfer for Rural Areas (NCAT-ATTRA). He was regularly fertilizing his pastures, and efforts to reduce fertilization midway through the grazing season always resulted in a lack of grass. He never thought that tall grass grazing would work.
“I was a firm believer that if you were going to get good grass production, you were going to have to be fertilizing,” Scott said in a recent webinar. But a chance encounter with veteran grazing specialists, and a need to reduce the amount of money they were spending on nitrogen applications, led Scott to successfully transition the farm to tall grass grazing.
The result? The farm, after a four-year transition to tall grass grazing, has a gross margin per acre of $1,013, up from the $687 when they were fertilizing and grazing with a shorter rest period. They’ve increased their dry matter production from 12,000 pounds/acre to 14,000 pounds, went from applying 160 pounds/acre of nitrogen to zero, and lost a mere 0.03 pounds of average daily gain (ADG) per ewe.
“We gained a lot more financially. Much more, that overcame that” slight loss in ADG, Scott said.
What it means
Grazing tall is all about allowing the natural cycling of nutrients time to occur, and capitalizing on the resulting growth of pasture forages to put on gain. When a plant photosynthesizes, it uses sunlight to capture carbon and churn out sugars which feed the leaves and stems, and these feed the livestock, who then fertilize the land with their excretions.
But it’s often overlooked that plant roots exude sugars and short proteins too, in order to feed the soil microbes. Up to 60% of the sugar a plant produces can leave through the roots and feed the soil bacteria and fungi.
Microbial life depends upon these root exudes. The microbes trap nitrogen and capture in it their cell walls. Soil microbes can capture about 70% of the nitrogen present in the air, and ultimately return it to the soil in useable form as ammonia or nitrates. When these bacteria and fungi are then consumed by protozoa and nematodes, the trapped nitrogen is freed and able to provide nutrients to foster plant growth.
When pasture forages are left alone long enough to recover after a grazing event, the plants can optimally capture sunlight, water and nutrients and use them for growth (and to feed the soil microbes). This recovery takes about 30 days, and there are telltale signs when the plants are ready to be grazed again. The stem of fully recovered grass will have three to five sets of leaves, and the bottom basal leaves will be brown, or a few inches on the tip will be brown.
Another way in which tall grazing completes the nutrient cycling is attributed to the animal impact. As the animals graze in tall pasture, there is more dry matter than they are going to consume. They trample this so the plants are flat on the ground, which allows the soil microbes to digest the sugar and carbon directly, decomposing the plant material.
Tall grass regenerative grazing requires a daily movement to fresh paddocks and a high stocking density. The stocking density ensures that the trampling occurs, while moving the animals daily keeps the residual tall, preventing the animals from grazing too close to the bottom of the plant.
Parasite load is reduced when livestock are moved daily. For sheep, the barber pole worm is a primary concern, and requires three days to climb from the manure and up into the leaves of the grass. Moving animals to fresh ground sooner stops the cycle.
These two routes of nutrient cycle provide all the plant available nutrients needed to grow lush pasture from healthy soil. Healthy soil has a fresh, sweet smell. It’s the color of a Hershey chocolate bar wrapper. The soil aggregates resemble cottage cheese around the plant roots. Water will infiltrate healthy soil quickly, which can be measured using an infiltration ring.
Transitioning to regenerative tall grass grazing is best done slowly, and can be done on only a portion of the land at a time. The first two years, nitrogen applications should be applied at 50% of the normal rate. In year three, that can be cut in half again. In the fourth year and beyond, no nitrogen is utilized.
“It’s easy to bail. Your grass may not grow as you want it to,” at least until your organic matter is increased, Scott said. But a commitment to a tall grass grazing program should be for a minimum of seven years.
His farm’s own organic matter was at 4.7%, except for one paddock which was at about 1%, when he began the transition. At one point during transition, when he was still applying some nitrogen, the equipment was not calibrated correctly and he ended up laying the nitrogen down in 25-foot strips. He saw no difference in grass growth on the fields with higher organic matter content. The only place he saw stripes of darker green was in the paddock that had the very low organic matter content. Scott realized then that nitrogen was not needed once the organic matter was above a certain level.
“It’s not going to take you centuries, like we used to think, to improve organic matter in your pastures,” he said.
To properly graze regeneratively, three things are needed: a high stocking density, long rest periods and managed residuals. The rule of tall grass grazing is to “take half and leave half.” The stocking density (the number of animals per acre at any given time) needs to be high to trample the residual forages. And the paddocks can’t be regrazed until the grass is ready.
Monitoring the forage via forage analysis, measuring forage amounts with a hoop or grazing stick and using Haney soil testing is a part of the job. A forage analysis shows why gain does occur in tall grass grazing systems. The leaves and some of the mature stems are eaten in the 24-hour grazing period, providing the livestock with enough energy and crude protein to gain. If they ate the entire plant instead, the percentage of energy and protein consumed would decrease.
And with high stock densities, there’s a lot of pressure for the animals to eat weeds, trample grass and get the nutrients they need from the pasture.
Moving the animals to fresh pasture requires some time daily, but with electric polywire fencing the job is easy, and the system offers protection from predators too. Because of the high stocking density, paddocks are smaller than in a traditional grazing system, so less fencing is required and less time is needed to move the fencing for each rotation.
The basic tenet of tall grass grazing is “to solve problems with biology, not chemistry,” Scott said. “We’re just mimicking nature.”