Nutrient and Growth Cycles for Grasses
The Opportunity Cost of Not Grazing Intensively
There's a fairly significant opportunity cost when cattle aren’t managed intensively and with a vision to build healthy soil. It comes in the form of nutrients, but also in carrying capacity and soil health. These are linked in a way that some producers aren’t aware of.
The specifics will depend on each context, but there are some good generalities we can rely on. Every situation is different, so it pays to watch what’s happening on your own ground.
The Three Stages of Grass Growth
Grasses tend to have a three stage growing cycle. They start in the vegetative stage, where the roots are getting much of the energy and the grass grows very slowly. This might be up to only a few inches tall.
The second, or elongation, stage is when the grass takes off and grows rapidly. The leaf area increases and photosynthesis increases rapidly. It’s also at this stage that the nutrients garnered from the sun are most palatable, and that nutritional value is at its highest in the early afternoon.
As the grass gets close to the end of the elongation stage, the roots dig more deeply as well, gathering nutrients for the reproductive stage. This is when the energy goes into creating seeds.
Grazing to Keep Grasses in the Elongation Stage
The goal is to capture as much nutrients for your grazers as possible while keeping the grasses in the second, elongation stage. By grazing them towards the end of this stage, the grasses will continue to put energy into growing, sort of resetting rather than going to the reproductive stage.
This is where intensive rotational grazing shines, because we move our grazers off the grass quickly. Ideally, they eat less than 50% of the stalks before we move them.
How Grazing Intensity Affects Roots and Soil
If less than 50% of the height is grazed, the roots remain unaffected. In fact, they’ll keep growing. With some perennial grasses these roots can grow more than 8 feet in depth, adding incredible resilience to the pasture as well as a massively increased water carrying capacity.
If much more than 50% is grazed, the root production will either stop or the roots will die back. If it’s 90% grazed, the dieback is dramatic. And if the grass is continuously grazed, then the roots will die back to a bare minimum.
In contrast, when we use a more casual grazing schedule the effects are negative: roots stay shallow, soil is exposed to erosion and baking, water carrying capacity decreases, and animal carrying capacity drops.
Benefits of Moving Often and Figuring Rest Periods
By moving our animals intensively we gain the highest nutritional value from our foliage, capitalize on the growth cycle of our grasses, continue building deeper and stronger root bases, keep our soil covered, increase water carrying capacity, extend available annual grazing days, have calmer cattle, move them away from dung resulting in less parasite exposure and fewer flies, and increase animal carrying capacity.
Parasites will start being a concern at about 12 days after the dung has been dropped. Most who embrace regenerative intensive grazing will move them once a day, sometimes even more often.
How often a given pasture is grazed is likewise dependent upon context. But even in areas where there’s abundant rain, for both the growth cycle and to avoid parasites, the minimum rest would be about 30 days. In an area where it’s more arid, a 90 day rest would be in order. Watching the grass with a goal to graze before it goes to seed is part of the equation as well.
Learning to Leave Forage Behind
One aspect of this that is hard for many to embrace is when they move their cattle to the next pasture and there’s so much forage still available. It rankles because they feel like they’re wasting an opportunity and resource.
It’s only after they grasp the benefits of keeping the soil covered and capitalizing on the growth cycle for nutrients and root health that they are able to embrace intensive rotational grazing and gain a vision for the greater benefits.