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Call yourself a solar energy manager

Concentrating on your task of capturing and cultivating solar energy could make you a better livestock producer.

Walt Davis 1

March 18, 2020

4 Min Read
Cows grazing under sunny sky
Cows turn captured solar energy (forage) into a saleable item.BIN-WANG-iStock-GettyImages

Ask a cattle producer what he does and likely the answer will be, “I’m a cow-calf producer,” or “I run stockers,” or maybe, “I’m an Angus breeder.” We tend to describe ourselves with the end product we produce.

I don’t think it will catch on, but I would like to suggest a title that more accurately describes what we do: Good grazing managers might do well to think of themselves as “solar energy managers.”

We all manage solar energy: It is what makes grass grow. However, some manage it better than others. We cannot change the amount of solar energy the sun puts out, but there are wide differences in how effectively we make use of the energy it makes available. Effectiveness of energy management is a prime factor in the success or failure of any grazing operation. We have one opportunity to capture sunlight so we would be wise to make use of every sunbeam before it arrives.

In that vein, public enemy number one is bare ground. As with water capture and storage, the most effective solar collector – over time – is a diverse vegetation sward grazed in a way that maximizes soil health, plant health and animal health. This translates to grazing plants, both in timing and degree, so that all members of the soil-plant-animal complex benefit. This is not as hard as it sounds, because all members of the complex evolved together and are dependent on each other.

The importance of solar energy makes it worthwhile to examine the processes by which this energy can best be put to valuable use. To begin with:

  1. Solar energy is captured and converted to biological energy when sunlight falls on green leaves.

  2. The plant takes in carbon dioxide from the air, and by the process of photosynthesis converts it to carbohydrates.

  3. The plant uses carbohydrates for its life functions and to trade with soil life in return for mineral nutrients.

This conversion of sunlight to biological energy is most effective when the leaf is growing and fully functional. As a leaf ages, it becomes less and less efficient until it turns senescent (reproductive) and unable to capture energy. These ineffective leaves intercept sunlight with the same effect as if it had fallen on bare ground; it is lost to the local ecosystem rather than being used to grow forage.

On the other hand, the leaf that is in early stages of regrowth, using previously stored energy, will not be highly effective in capturing and converting energy until the new leaf becomes fully functional. The excess of protein in relationship to energy in very immature plants is the reason animals bloat when grazing such forage. Give the forage a little more growing time, and animal performance will improve as the energy-to-protein ratio gets closer to what the animals need.

Timing the forage harvest to maximize energy capture is one way to increase forage value. Work done in Louisiana found that moving yearlings midafternoon, after forage had received several hours of sunshine, rather than in the morning caused the cattle to gain an extra quarter pound per head per day. This was with once-daily moves. There was no difference in the amount of sunshine that fell, but a lot of difference in the amount of energy taken in by the animals.

Improving the capture, conversion and beneficial distribution of solar energy is the low-hanging fruit of grazing management. Since green leaves close to physiological maturity (early stage two) is most effective at capturing sunlight, management should be designed and managed to have green, growing forage in the pasture for as much of the time as is feasible – by this I mean as much as practical not as much as possible.

For this reason, and others, the forage sward should be made up of multiple kinds of plants. Various types of plants have different growth habits and needs: Some prefer the warm season, some the cool season, some wet soil, some full sun, some partial shade, for example. When given the chance, nature will fill all ecological niches with adapted plants.

There is no single plant that can function effectively in all types of growing conditions. That’s why having a variety of forage plants present and functional at all times – climatically adapted with leaf area and root mass present when growth is possible – is a tremendous benefit for grazing animals and also for soil health.

The opinions of the author are not necessarily those of Beef Producer or Farm Progress.

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