Regrowth after grazing

Grazing cows leave behind a mosaic of different grass heights. In one place the grass has been eaten almost to the ground, while further away long remnants of refused grass have remained. And there are also places with all grass heights in between.

Green leaf

The speed at which a grass plant recovers after grazing depends on the presence of the growing point and the amount of green leaves. If the grass has been cut or mowed so short that the growth point has been removed, the regrowth will immediately start with a delay from a newly formed side shoot. The amount of green leaves determines how quickly the grass gets off the starting blocks. Normally, up to a grass height of approximately 15 cm, the more leaves, the faster the regrowth. But this rule does not apply above that, because more older leaves will die. The net growth will then be the same or even slightly lower.

Measure growth rate

In Amazing Grazing, a trial was conducted at Dairy Campus in 2018 to measure the growth rate of grass from an initial situation with different stubble lengths. After the first, second and third cut, fields were mowed at a stubble height of 5, 8, 11, 15 or 18 cm to simulate the influence of grazing as closely as possible. Subsequently, the fields in the second, third or fourth cut were harvested as a mowing cut. With a stubble of 5 centimeters, the grass grew daily at 75 to 125 kilograms of dry matter per hectare. The higher the stubble, the faster the grass grew. With a stubble of 15 or 18 centimeters, the grass growth was 100 to 200 kilograms dry matter per hectare. The results calculated an average extra growth of about half to four percent per centimeter of extra stubble length. This knowledge has been used to improve the prediction of grass growth after grazing.