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Food for thought for organic pastures

Brittany Olson for Progressive Dairyman Published on 18 January 2019

Many principles when managing organic pastures are the same as when managing conventional pastures, albeit with some special considerations.

In a webinar hosted by Penn State in October 2018, Dairy Extension educator Mat Haan and forage and field crops educator Dave Wilson presented best management practices organic dairy producers should adhere to regarding pasture management.

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“The fundamentals are similar to conventional dairy pasture systems, but there are some caveats that apply to organic systems,” Wilson said. “Pasture grazing is an important part of the system on an organic farm because it’s required; we need the pasture grazing. In a conventional system, we may or may not have some pasture grazing.”

Play by the rules

Because organic dairies must have 30 percent or more of dry matter intake coming from grass or residual forage, according to the National Organic Program Pasture Rule, there are certain rules and management practices they must abide by in order to keep their certification, including – but certainly not limited to – management of pasture to provide sufficient forage quantity and quality to graze throughout the grazing season, description of all feeds (pasture included) and detailed recordkeeping, and a region-specific minimum grazing season of 120 days.

One strategy that may boost forage quality in a grazing system involves clipping pastures a day or two before moving cattle into the paddocks and grazing the windrows.

“On some organic farms, we see them cutting ahead and leaving it lay in the pasture if they see heavy spring growth or heavy fall growth. We cut ahead at a certain quality so the plant doesn’t get too lignified,” Wilson said. “The plants are still alive and have exposure to the sun, so they’re still carrying on photosynthesis, and sugar content is being boosted.”

Pasture management plans on organic farms should also include the types of pasture being grazed (annual or perennial pasture, as well as plant species in said pastures), the grazing system being utilized (rotational, high-density, rest-rotation, etc.), locations and types of fencing, shade, water and soil fertility plans.

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“Management is dependent on their market. We see more variability on organic farms as far as the types of grazing systems used,” Wilson said. “In a grass-only system, we tend to see more high-density grazing of more mature pastures because they aren’t getting any starch in the barn. That additional fiber will slow things down in the rumen.”

What lies beneath

Wilson said it all begins with the soil. Tilth impacts crop quality, which affects animal health and productivity and, in turn, has a direct effect on a dairy farmer’s bottom line, no matter what type of operation they run. While soil fertility, or nutrient levels within the soil, can affect yield more than it does quality, low soil fertility can and does hamper forage quality.

For example, proper potash and phosphorus levels aid in maintaining the desired level of legumes in a pasture mix while reducing pressure from weeds such as thistles.

“Soil fertility is needed for high forage yields and quality, to ensure a good grass and legume stand, maintaining pasture productivity and maximizing disease resistance,” Wilson said. “It is also necessary to balance soil fertility to avoid nutritional imbalances in ruminants.”

Before placing an order for potash or phosphorus, Wilson recommends taking a soil test about four to six months before establishing a crop and submitting the samples to a lab. He suggests sending in 10 to 20 soil cores, taken from 3 to 4 inches below the soil surface, over the entire area to overcome variability – but cautioned against using one sample to cover a broad piece of ground.

“One sample should not represent more than 10 to 20 acres,” Wilson said. “Also, send them to the same lab every time at the same time of year. Record your results per field to determine nutrient and soil acidity changes.”

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If a field is at or above optimum levels of a certain nutrient, there is a smaller chance of having a profitable response to nutrient application. However, if levels of potash, phosphorus or nitrogen are below optimum, the likelihood of a profitable yield bump is far higher.

Soil pH, too, can either enhance or endanger pasture quality. As soils become more acidic, desirable crop nutrients can become less available, while other less-desirable compounds can reach toxic levels. The most common remedy for pH neutralization is applying lime.

“Hydrogen activity is expressed as a negative logarithm, and a one-unit decrease in pH implies a 10-time increase in acidity. A soil pH of 5.0 is 10 times more acidic than a pH of 6.0 and 100 times more acidic than a pH of 7.0,” Wilson said. “Liming is a long-term investment that pays in many ways. It moves very little in the soil and is slow to change soil pH, and the rate of limestone required should be determined by a soil test that includes pH and a lime requirement test.”

Know your plants

Selecting a good grass variety to incorporate into a new or existing pasture can be tricky because, from aspects such as winter hardiness to digestibility to protein content, differences in grasses are more pronounced than differences in corn or soybean hybrids. Grass also contains fewer nonfibrous carbohydrates than silage corn or alfalfa, as well.

When selecting grasses, persistence needs to be taken into consideration as well as winter hardiness because the two traits appear to go hand-in-hand. Smooth bromegrass and meadow bromegrass are the most persistent and winter hardy, with a persistence of 15 or more years after seeding, followed by tall fescues and orchardgrass with persistence up to seven years.

Timothy has an expected persistence of two to four years, while Italian or perennial ryegrass – which also has the poorest winter hardiness of the main forage grasses – must be reseeded every one to three years. Disease resistance varies from variety to variety, as well.

For optimum pasture quality, a stand should contain more than 35 percent legumes including, but not limited to alfalfa, clovers or hairy vetch. Another upside to having a solid mix of grasses and legumes in a pasture is: In a pasture with legume content greater than 25 percent, applications of nitrogen are not needed.

Diversity of species also keeps plants competitive, as well as in the vegetative stage of growth, where they are most nutritious and palatable to the cow.

“When mixing legumes and grasses, plant a late-maturity grass with alfalfa, an early maturity to mix with clovers and late-maturity orchardgrasses to mix with other grasses,” Wilson said. “There is a two- to three-week difference in maturity of orchardgrasses but little to no difference in smooth or meadow bromegrass.”

For more detailed information, speak with a fellow grazier from a local grazing network or resource conservation and development council, as well as an agronomist with experience in organic agriculture and a nutritionist who understands grazing.  end mark

Brittany Olson is a freelance writer and dairy farmer in Chetek, Wisconsin.

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