– Jeff McCutcheon, Extension Educator, Knox County
With the stretch of warmer weather I have started to notice a greener color to the pasture fields. I have even noticed livestock grazing in fields you would swear there was nothing to graze. Soon it will be time for the question ‘When should you start grazing cool-season pastures in the spring?’
The recommendation to graze a field is usually given in forage height. Depending on the forage species and the animals used to graze, the general recommendation is to turn animals into a field when the forage height is between six and ten inches.
The six to ten inch recommendation is based on the grass growth curve during the growing season. Remember how forages grow. First they break dormancy in the spring and start to grow leaves. Cool-season grasses can do this when the temperature reaches 40 degrees Fahrenheit. This growth is fueled by reserves stored in the roots or crowns of the plant. This growth is slow.
Once enough leaf area is produced, the plant really takes off. This is the second stage. Growth is now fueled by energy produced from photosynthesis with some replacing what was used earlier from the reserves. The six to ten inch grazing recommendation should catch plants in this stage before they get to the reproductive stage when growth slows down.
Waiting until forages reach this second phase of growth puts the grazier behind. They will never be able to keep up with the ‘spring flush’. ‘Spring Flush’ describes the fact that our cool season grasses produce 40-60% of their annual growth in the months of April, May and June.
The explosion of growth in the spring is hard to manage. If a grazier gets behind the ‘spring flush’, the forage will quickly get ahead of them and will lose quality. It is also difficult to get the staggered regrowth needed to make the following rotations of grazing go smoothly. The first grazing needs to start earlier than the recommended 6 to 8-inch height.
In a survey of attendees from the “Pastures for Profit” or beginning grazing schools we asked if they had been able to extend the grazing season by managing grazing. It was not surprising that the majority of respondents said they were able to extend the grazing season. One way producers said they extended the grazing season was by starting an average of 23 days earlier than usual.
But don’t start grazing too early. If you do, you risk reducing yields or even killing the stand. Remember that the first growth is fueled by the reserves stored in the roots and crown. Depending on the previous fall those reserves could be low, so the reserves could have been used up keeping the plants alive through winter. The reserves may be just enough to fuel two to three days of growth. Cutting off those first leaves may mean no more growth from that plant.
When should you start grazing to stay ahead of the spring flush but not damage the plants? For spring turnout the general recommendation is to graze when the forages are about three inches tall. The first grazing should be light. Rotate the livestock through quickly. You do not want to remove half of the dry matter on this rotation. Remember those new leaves are needed to fuel the next growth. One additional problem graziers face is that the fields in springtime are usually wet. The soil can be too moist to support the animals when the forage is ready to graze. At those times, plan to graze on well-drained, accessible paddocks first. If soil conditions continue to be less than ideal, you may want to start grazing in a sacrifice area first. A sacrifice area may be a field you are planning to renovate soon.
Another option if field conditions are too wet is to wait until the forage is six inches tall. The extra growth will help support the animals. Graze for short periods, and only allow them to lightly graze the stand down to three to four inches. Just keep in mind that waiting this long could put you behind the ‘spring flush’. If forage growth gets beyond the ideal stage before you can start grazing, offer the animals larger areas for shorter periods. Let them top off the fields.
When to graze is always based on the forage growth. For the initial turn out in the spring, the plants should be about 3 inches tall and the soil should be dry enough to support the animals without damaging the plants.
This article was originally published by Farm & Dairy and is used with permission.