Editors Note: There is a LOT of great information for farmers and ranchers out there already, and one of the things we like to do at On Pasture is find it, condense it or pull out the parts that we think will get you started, and then give you the link so that you can read more if you like. This piece comes to us from Greg Cuomo, of University of Minnesota’s College of Food Agricultural and Natural Resource Sciences, and Kirby Hettver, a former UMN Extension Educator who now manages his family farm full time. It’s part of the UMN’s home study course for beef producers.
Normally in spring, pasture growth keeps up or keeps ahead of grazing animals. Under continuous grazing or high stocking rates, once summer comes and pastures get grazed down, they never seem to quite recover. This is for a reason. One must remember that half of the pasture is beneath the soil (the roots). When a plant is grazed, the plant tops (leaves) are removed. What we sometimes don’t think about is that those leaves are feeding the whole plant (from the sun by photosynthesis). The plant compensates for top removal by sloughing off roots.
When plant tops get shorter because we graze them, plant roots also get shorter. If plant tops are kept short, plant roots will also be short. A short root system can’t explore very much of the soil for moisture or nutrients. When soil starts to dry, it does not take very long before the dry line in the soil is deeper than the plant roots. Even if fertilizer is applied, once nutrients are out of the relatively small rooting zone, the plant cannot get any more. Even when it rains, these plants are not as vigorous and cannot regrow as quickly.
By letting pastures rest between grazings, plants can grow tops, which will help them grow more roots. This will then help them to explore more of the soil for water and nutrients, allowing the plants to grow more quickly after grazing. These are some of the reasons why rotational grazing helps pastures be more productive. However, even with rotational grazing, cool-season plant growth is slow during summer and pastures generally do not produce adequate supplies of forage. Often in July and August animals are grazing whatever they can find.
How to Provide Roots with R & R
How do we manage to have enough high quality forage available from July through fall? By giving our pastures some rest so they can regrow.
To accomplish this, cool-season pastures need to be destocked after spring (less animals per acre because less forage per acre is being produced). How do we go about destocking? There are several ways to do this. One is to stock pastures lightly. Forage growth will get ahead of grazing animals in spring, but animals will be able to selectively graze and there will be more forage for later in the growing season. This is a viable option for some livestock operations. However, animal production per acre will be below its potential.
Some other approaches to destocking pastures in summer are: 1) for dairy producers, graze heifers behind lactating cows in spring (if not grazing cows, graze dry cows behind heifers), or 2) make hay on some pastureland (or alfalfa stands) in spring and then use those fields for grazing in summer. This results in more acres for grazing during summer (destocking). This system allows for both hay production and for extra pasture during slow growth periods. In beef systems you can over-winter calves, graze them the following spring, and move them to a feedlot or sell them as plant growth slows. This option has to be weighed against the cost of feeding animals over winter.
Perhaps the best way to destock pastures is to remove animals altogether. Using more than one type of forage crop for pastures may give the best chance of supplying adequate amounts of forage season long. Coming up, we’ll discuss several alternatives for additional crops and management strategies for pastures.
Plant roots reduce growth if they are defoliated more than 50%. In Spring, each successive grazing should have higher and higher residual, by summer (with cool seasons forages) we want to leave 5 inches behind this shades the soil from direct sun and keeps soil a more ideal temperature and reduced evaporative losses. Too little residual in summer and soil temps can be 20 degree higher creating more stress on the plants.
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