Irrigated pastures are often the most abused and neglected areas in Idaho. Thousands of acres of irrigated pasture are simultaneously over- and under- grazed, resulting in loss of feed quality and productivity, and causing erosion and weed invasion. Applying five principles of pasture management can improve pasture productivity and animal performance. Proper application of these principles should improve nutrient cycling, specie diversity and survival, water retention and infiltration, productivity and profitability.
Carrying capacity (CC), or the amount of forage produced, varies during the growing season and from year to year. Stocking rate (SR) is the feed demand by livestock. Effective grazing managers keep these components in balance. If SR exceeds carrying capacity, the extra demand is met from body fat, from hay, from stockpiled feed or by de-stocking. When CC exceeds SR, we can increase stocking rate, stockpile forage in the pasture, cut hay, or permit the forage to be “wasted” or returned to the soil without passing through our livestock.
Plants are solar collectors. Grazers use the captured solar energy in plant tissue, and convert it into salable livestock products. When we graze pastures very short there is not enough leaf area and re-growth is slow. This is “Phase I.” When plants become mature, growth slows as lower leaves are shaded and older leaves die. This is “Phase III.” In between is “Phase II,” where energy capture is most effective. Phase I has low quantity and high quality. Phase III has high quantity and low quality. Keeping plants in phase II keeps forage high quality and high quantity!
Livestock are gourmets, but do a poor job of forage allocation. Overgrazing occurs from re-grazing a plant before it has recovered from the previous grazing. This can happen by leaving livestock in a pasture long enough that re-growth is re-grazed or by returning to a grazed pasture too soon. During rapid growth, recently grazed plants will initiate new shoots in 4 or 5 days. During slower growth, this can be from 6-10 days. While these new shoots are low energy, they are the tastiest tidbits in the pasture. Livestock return to the new shoots, overgrazing these plants, while ignoring more mature forage.
To reduce over- and under-grazing in the same pasture, use the highest number of animals possible in the smallest feasible area for the shortest reasonable amount of time. This increases uniformity of grazing so that we can manage time for the whole pasture, rather than trying to manage individual plants. In well-managed irrigated pastures, stocking may be more than 50,000 pounds of live weight per acre!
With only one pasture, plants never get any rest, or they are rested all the time. Both situations are undesirable. By controlling when and how long animals have access to plants we improve feed quality and permit adequate rest. Feed quality decreases every day livestock are in a pasture as the highest quality feed is consumed first. In addition, more and more feed is trampled and defiled by urine and manure. We can prevent “over-grazing” with at least 8 paddocks, when SR=CC. More paddocks are required to maintain high feed quality. More paddocks also provide greater flexibility. How many are right for you depends on your situation!
By combining animals and reducing herds, you can increase the number of paddocks in your system. This means that each paddock will spend more time resting! While this is not a comprehensive treatment of irrigated pasture management, proper application of these principles should improve nutrient cycling, specie diversity and survival, water retention and infiltration and profitability in your pasture.
For more information on Management-Intensive Grazing contact Charles Cheyney at 527-8587 or send an email message.
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