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The green, green grass of a dairy pasture

Dennis Johnson

Published in Dairy Star April 23, 2005

There are many factors influencing pasture growth and quality – soil fertility, forage species, weeds, temperature, rain fall and management of grazing pressure to name the main factors. Many pastures are less productive than they might be if they have been continuously grazed over the years. But those pastures can often be turned into higher yielding acres with a few inexpensive changes in management.

Grazing at the proper stage of growth

Figure 1. Grazing at the proper stage of growth.

Pastures should be grazed before the forages head out, and then be given time to rest and recover between grazings. Figure 1 shows the balance to seek between yield and forage quality. Young lush rapidly growing forage is of the very highest digestibility and protein content but yield is low. Mature forage has maximum yield but quality is low. The compromise for the dairy producer is to graze the pasture when the plants have achieved most of their growth. Once the area is grazed, the cows should be removed to another paddock that is at the same stage. One of the challenges of a grazing system is to sequence pasture growth so the herd always has pasture that is at the right stage. Preferably, the cows will graze one paddock for a day, and then move to the next paddock. Moving cows rapidly through the pasture system in the spring helps to establish a sequence of growth. A rough rule of thumb for a typical legume-grass pasture would be to allow 2-3 week intervals between grazings in the spring, 3 to 4 weeks through most of the summer, and 4-6 weeks in the fall when growth is slow.

Existing boundary fence

Figure 2. Organizing a pasture system.

A method for organizing a pasture system is illustrated in Figure 2. A series of 8 paddocks have been arranged according to topography and species. If cows were moved from one paddock to the next every 3-4 days, the herd would get through the sequence every 28-32 days. Daily allowances of fresh forage can be offered by strip grazing each paddock. This means placing a temporary fence at the 1/3 mark of a paddock on day one, at the 2/3 point for day two, and allow access to the entire paddock on day three.

It’s a fact of life that the strongest pasture growth usually occurs during late May and June in much of Minnesota. Northern Minnesota may lag 2-3 weeks behind the south before hitting rapid growth. One strategy for matching supply of forage to herd requirements could be to hold a portion of the pasture out of rotation for hay crop early in the summer, then fit that portion into the grazing plan for July and August.

Pasture growth rate over time chart

Figure 3. Seasonal differences in pasture growth.

Is there an economic gain from investing in pasture renovation? A pasture renovation experiment was conducted at the West Central Research and Outreach Center, Morris. A bluegrass and brome grass pasture that had been not been fertilized or rotationally grazed was selected for the study. When the grass had grown to 6 inches in the spring, it was sprayed with a half dose of glyphosate – enough to brown the grass but not kill it. A no-till seeder was used to plant strips that included alfalfa, or red clover trefoil mix, or a mixture of 13 grasses and legumes, or left unseeded as a control. The investment in renovation was approximately $50/ acre. Forage was clipped and weighed before each grazing. The results in Table 1 show that all renovation treatments led to significant increases in high quality pasture yield (as compared to the control strip). The cost of renovation was depreciated over three years. The cost of the additional high quality pasture attributable to renovation was only $10/ton.

A recent study has showed that pastures rotationally grazed by heifers can be more profitable than corn, soybeans or hay. In conclusion, grazing is a traditional system that can be reintroduced to the economic, environmental and social benefit of the dairy farm family.

Table 1. Performance of grazed forage for four pasture renovation treatments
Pasture renovation treatment Year
1 2 3
  --- Ton/Acre/Season ---
Alfalfa 5.2 7.9 5.4
Red clover/trefoil 4.4 6.4 4.3
Graziers mix 5.7 6.4 4.9
Control 3.1 5.0 3.4

> LSD (0.05=0.48 ton/ac) is suitable for comparisons within and between columns.

Data source: FINBIN

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