The rancher watches which kind and how much grass the cows are eating and measures how much they have eaten. When the cattle have eaten just the right amount, the cowboy moves the cattle to a new pasture. Now the grass they had been grazing on can rest and grown more leaves and roots.

When the grass is healthy above ground, the roots are healthy too. Grasses need healthy roots to store energy and help make the soil healthier. Healthy soil has many insects, worms and small organisms in it. The roots of plants help to keep the soil from becoming hard and compacted.

If a rancher overgrazes the grass, the soil and the grasses deteriorate. The grass plants get smaller and more bare soil begins to show. When a hard rain comes, the soil will wash away or erode. When there is less grass, the bare patches of ground are not shaded from the sun so the soil dries up quickly. The roots of the plants then get smaller. The soil gets harder. Soon there will be fewer organisms in the soil. This causes the grasses that are left to be less healthy. The cattle then don't have as much to eat. When mistakes like overgrazing are made, it takes quite a while to restore the range plants and soil to a healthy condition. That is why taking care of the grass is the rancher's most important job.