Pasture and Grazing Management
Improved pasture and grazing management offers a means of holding production costs to a minimum by efficient production of high quality forage. Pasture and grazing management often seems like an art but is really based on scientific knowledge. Over the years, the study of pastures, how they grow, and how they are utilized by cattle and sheep has provided us with the knowledge needed to manage pastures for most efficient production.
Developing a pasture and grazing management system for livestock requires an understanding of the following processes:
- Establishing and maintaining good pastures
- Plant nutrient needs and a balanced fertilizer program
- How plants grow most efficiently
- Sheep and cattle feeding habits
- Interaction of plant growth and livestock use of pastures
Establish and Maintain High-Producing Pastures
Pasture reseeding is usually done to correct a problem with weeds or low producing pasture species. Minimum or no tillage can be used if we need only to introduce a grass to a clover dominant pasture or a clover to a grass dominant pasture. Tillage of the soil is necessary when a pasture lacks productive species or has weed problems that are too great to be handled by minimum tillage or selective weed control practices. When you reseed a pasture, it's very important to prepare a fine, firm seedbed; use a roller after cultivation and seeding. Avoid working the soil any deeper than is necessary to get a fine seedbed. It is important to roll the seedbed before and after seeding, if possible. To omit rolling the pasture will result in poor establishment of the seed and a spongy pasture which will be more susceptible to pugging or treading damage by livestock.
Seeds should be broadcast evenly over the ground and not drilled in rows, which leave large areas open to weed establishment. A seeding rate of 28 pounds of perennial ryegrass per acre provides one seed per square inch if broadcast evenly. The same amount of seed drilled in rows would leave 6 to 8 inches between rows with no plants. Seeding on non-irrigated pastures in the fall should be done in time to catch the first fall rains which can arrive as early as mid-September.
Develop a Balanced Fertilizer Program
Plan a well-balanced fertilizer program to meet the needs of your newly seeded pasture. Nitrogen (N) is the most limiting nutrient for pasture production. Because legumes not only fix nitrogen but also produce high-quality forage, clovers are included in pasture mixes.
White clover has the ability to fix 125 lb. of nitrogen from the atmosphere when soil temperatures are above 52°F. Soil temperatures below 52°F greatly reduce the soil bacteria's ability to fix nitrogen or to break down the organic matter that provides nitrogen for pasture growth.
Grass plants will produce 8-25 lb. of dry matter per acre per day at soil temperatures between 41°F and 50°F, if adequate nitrogen is available as ammonia or nitrate in the soil.
Because of lower soil temperatures early and late in the pasture season, using nitrogen fertilizer will supplement the nitrogen produced by soil organisms. The nitrogen fixed by clover isn't directly available to grass plants. To become available, the increased growth by clover plants caused by nitrogen fixation must first be broken down by animal digestion or decomposed in the soil.
Winter growth rates of 12-30 lbs. of dry matter per day at a cost of less than $30.00 per ton of dry matter are achieved during the October-March period when adequate nitrogen is available.
On pasture grazed year-round, 50-60 lbs. per acre of nitrogen applied in late September, early October and in January will increase production 1200-1500 lbs. DM per acre in the form of high quality pasture.
Monitor the grass in the pasture stand for symptoms of nitrogen deficiency (slow growth, yellowish color). New seedings or pastures cut for greenchop, silage, or hay may require nitrogen, either as animal manure or commercial fertilizer, to keep the grass component of the pasture healthy.
In addition, potassium requirements are about 20% higher for harvested pastures over those grazed.
Maintain the levels of phosphorus, potassium, soil pH, calcium, magnesium, and sulfur on any pasture, based on periodic soil tests.
- Nitrogen applied 6 weeks before turning animals on pasture in the spring can increase spring pasture production sharply.
- Nitrogen applied in August, with adequate soil moisture, will correct late summer pasture shortages.
How Plants Grow Most Efficiently
Clover and grass pastures grow most efficiently if you hold them at 1 1/2 to 5 inch height. Pastures in Phase 1 (1 inch high, 450 lb. dry matter per acre) grow very slowly because they lack leaf area for photosynthesis.
In Phase 2 (1 1/2 - 5 inches, 900-2200 lb. dry matter per acre), the plants make the most rapid and efficient growth; their leaf area is great enough to use all the sunlight falling on the area.
Pasture growth slows in Phase 3 (5-12 inches high) as lower leaves become shaded and die.
Allowing dry matter per acre to exceed 3500 lb. before grazing, or grazing below 900 lb. of dry matter per acre, will seriously reduce the pasture regrowth and, thus, the efficiency of pasture production. This pattern of growth will be influenced by soil temperature, soil moisture, and day length.
Livestock Feeding Habits
Cows prefer grazing grasses over legumes and will graze those species that are most palatable. For example, they'll graze ryegrass before tall fescue. Their pasture intake is directly affected by the amount of feed that you allocate in the pasture.
Cattle on pasture will graze a maximum of 8-10 hours a day and spend an additional 3-4 hours ruminating the feed they've gathered while grazing. A cow's pasture intake is controlled by her biting rate.
Research studies show a cow will take about 36,000 bites per day consuming a maximum of about 24 lb. of dry matter if conditions are ideal. Under less than ideal conditions, the amount of pasture dry matter consumed will be considerably less.
The ease with which the animals can tear off and consume the pasture plants, and the quality or maturity of the pasture, greatly influence biting rate. In addition, feed intake is reduced if you don't control livestock's tendency to walk considerable distances while grazing.
Sheep tend to graze selectively, preferring clover, grass and short lush feed to tall coarse plants. They graze for up to 8 hours per day and even when feed supplies are short, will not graze much over 10 hours per day. Young and aged sheep don't compete well with mature ewes for pasture and should be run in separate flocks. Continuous grazing of the pasture by sheep will result in selective grazing or patch grazing.
You allocate feed when you control the height of the pasture presented to the animal, the size of the grazing area they're given, and the percentage of the pasture allowance they're forced to use.
In "residual dry matter" grazing management, you control feed intake and animal production by adjusting the amount of forage dry matter (DM) that remains when you move the livestock to the next pasture. If you maintain forage quality, the height of the pasture determines how much feed the animal can consume and how much milk or weight gain is produced.
Pasture allowances for high-producing livestock need to be generous if they're to consume the 20 plus pounds of pasture dry matter they need daily. High production from pasture requires low use at any one grazing, which means consumption of 60% or less of the pasture allocation or available forage.
Grazing Management Systems
In developing a grazing management system for a farm, the following principles need to be considered:
- At low stocking rates, set stocking gives better production per head than does rotational grazing
- Rotational grazing gives better per head production at high stocking rates
- In determining whether your stocking rate is high or low, periods of feed excesses on a farm can be considered as low stocking and periods of feed deficiencies can be considered as high stocking
- Rotational grazing is the method used to build up feed supplies in the pasture and of controlling feed intakes.
Generally a controlled grazing system will rotationally graze when feed supply is short or animal production targets are not very high and when pasture feed levels need to be rebuilt. Set stocking will be used when feed supplies are high and high performance per head is required. A controlled grazing system on the farm will be a combination of rotational grazing and set stocking, based on the pasture growth conditions and the livestock requirements as they vary from season to season and year to year.
The pasture production profile is a means of identifying feed production shortage and surplus periods. A curve illustrating the pasture growth profile in western Oregon shows that shortages of feed occur in southwestern Oregon during the period from November to March and August through September. Feed surpluses occur during the period from March to July.
A generalized grazing management system for southwestern Oregon based on this curve would include fall rotational grazing to build pasture levels to an average of 900 to 1100 lbs. dry matter per acre at lambing or calving time. This would include the use of nitrogen fertilizer in the fall for most efficient winter growth or early winter and late fall supplemental feeding to save pasture for lambing.
Use set stocking at lambing followed by a slow rotation to give the best feed to the lambs and ewes and promote pasture growth. Following the weaning of the lambs, a summer slow rotation of the ewe flock would be used to clean up pastures in preparation for fall growth.
- Fall and winter pasture production can be made more efficient and increased by the application of nitrogen fertilizer.
- High producing forage varieties help to balance the feed production during the traditional low production periods such as late fall and winter.
- High livestock gains or production from pastures requires low utilization in any one grazing. Not more than 60% of the forage offered on a daily basis is recommended if top gains are expected.
- Allowing pasture levels to exceed 3,000 lbs. of dry matter per acre before grazing or grazing below 900 lbs. dry matter per acre will reduce pasture regrowth.
- To maintain adequate intake, a residual dry matter grazing level of 1,100 to 1,400 lbs. dry matter per acre is recommended for cattle and 900 lbs. RDM for sheep.
- Leaving more than 1,600 lbs. dry matter per acre after grazing will reduce quality for later grazing.
- A minimum of 25 paddocks is required in most sheep farms to provide the flexibility to manage the different classes of sheep and control grazing for optimum and most efficient livestock and pasture growth.
- You can increase production of early spring and late summer clover-grass pasture by applying nitrogen fertilizer.
- High-producing forage varieties have the ability to use high levels of soil N, and newer clover varieties can compete with grasses and continue to fix nitrogen.
Seeding Recommendations - Minimum Seeding Rates in Pounds per Acre on Well-Prepared Seedbeds
One pound of big trefoil may be added to the hill land mixtures
Poorly Drained Lands
Add 1 to 2 pounds of white clover if field is spotted with well-drained areas.
Well Drained Lands
4 to 6 pounds of red clover can be substituted for white clover in mixture #2 if a short term pasture is desired.