Wednesday, 18 September 2019 12:55

Getting spring pasture covers right

Written by  Staff Reporters
Tim Russell, Ravensdown. Tim Russell, Ravensdown.

Managing pasture surpluses or deficits in spring is the key to maintaining quality and persistence going into summer, says Ravensdown agronomist Tim Russell.

The trick is to get pre-grazing and post-grazing covers right, he says.

“Don’t let your pre-graze covers get above 3200kgDM/ha and aim to leave consistent post-grazing residuals of 1500kgDM/ha. 

“For perennial ryegrass pastures, it’s important to understand what’s happening and how the individual plants are reacting to grazing management.” 

Perennial ryegrass plants are made up of individual tillers of which each tiller can only have three leaves at any one time. Once a tiller starts producing a fourth leaf, the first leaf starts to die away – sacrificing both pasture yield and quality. 

The value of 3000-3200kgDM/ha is used because it typically represents the 2.5 to 3-leaf stage for ryegrass and is optimum for maximising quality and yield, with the oldest leaf providing 50% of the total tiller yield.

“Ryegrass tillers only have a life expectancy of one year, so establishing strong new tillers in the spring is essential for ryegrass survival through the summer. 

“This ensures the plant is set up to successfully re-establish itself come autumn.” 

During spring and autumn, perennial ryegrass plants produce daughter tillers which need to be looked after and provided with enough light and nutrients to strongly establish. During late winter and early spring, you may run into a pasture deficit. 

“Depending on your situation, strategic nitrogen applications -- with gibberellic acid -- can be a great way to turn a deficit around. Several factors are important to ensure the best pasture response to gibberellic acid, so follow the label instructions and/or discuss with your agri manager.”

On the other hand, Russell says, it’s equally important to identify and manage pasture surpluses early.

“If pasture covers are too high, subsequent growth rates can be significantly reduced. If covers do get away, consider topping to reset, grazing with dry cows or closing the paddock for silage.   

“Spring pasture covers exceeding 3200kgDM/ha can mean that daughter tillers are starved of light, causing them to die out. This can lead to poorer persistence of the ryegrass plant. 

“So, if faced with a surplus, only select established paddocks with good plant numbers to shut up. If young or open pastures are selected, this will inevitably mean these pastures may be up for renewal sooner than expected.”

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