Massey University professor Danny Donaghy gave farmers an insight to ryegrass leaf assessment and its value for grazing decision making at the field day in Bay of PLenty in February. With research experience that spans the tropics, down to South America and across to Tasmania, he’s developed a leaf-based assessment method for farmers that has proved to be effective in all grass systems.
The key is identifying that the optimal window for grazing time is between the two to three leaf development stage in ryegrass.
“If you take your ryegrass plant, the one leaf stage has the plant only generating enough energy to supply the root system. Coming in to graze at less than two leaves on your rotation more than once, you will damage that pasture. You may get away with it once, but do it again and you will affect that plant’s ability to continue growing well in the future.”
The “two leaf” stage is the lower limit of grazing, and the three leaf stage the upper.
“There’s no benefit in grazing above that, as at that point every emerging leaf is simply replacing a dying leaf. You are only increasing the thatch at the pasture base, and lowering the light that can come in, and providing nothing more than worm food, of which there is already plenty.”
There were two visual cues farmers could look to when making a decision based on leaf assessment.
“Firstly, when you walk into a paddock, if the blunt tops of grass leaves are looking up, it’s not ready to graze. Secondly if you have the full three leaves, it means leaves are falling onto the ground and dying, and you are wasting the feed you are looking at.”
Winter was a period when that “three leaf” status was often reached, and with cows wintered off, farmers ended up facing a feed block on their return, with thatched dying grass matter blocking light.
“This is when you have to ask if you can keep some cows on and graze these pastures earlier.”
A farmer had compared the assessment to baking a cake – “you always take it out at the right time regardless of how many people you have to feed it to”.
“Ready” was between leaf two and three’s emergence, and it sometimes involved feeding a paddock off sooner than if straightforward drymatter amount were the only means of assessing it.
Donaghy acknowledged the “leap of faith” farmers would undertake with such an assessment and advised them to do a comparative trial alongside a traditionally assessed paddock. The assessment and grazing timing went hand in hand with good clover development.
“It is good for the tillering of the rye plant, and good for clover root development.”
