It’s all about managing on the knife-edge. One of the ways of ensuring this is to make sure that leaf stage and round length complement each other.
Many factors influence the time between the appearances of each new leaf in ryegrass pastures. One of the major factors is thermal time. During the peak growing season, October to December, a new leaf emerges about every eight days, resulting in a round length of 24 days.
If it goes much faster than this (18-20 days) quantity could be compromised because plants will be just past the two-leaf stage where 40% of potential yield per grazing could be lost. In times of rapid growth and where herd demand doesn’t need this feed, grazing can happen closer to the two-leaf stage.
Conversely, if it goes much slower than 24 days, under ideal conditions quality will be compromised as growth pushes past the three-leaf stage. After the three-leaf stage, yield will begin to plateau as the first leaf dies and is replaced by a new leaf. Therefore the statement that leaf stage should set round length stands true, and this should be considered as changes are made during the season.
Along with leaf stage and round length, ensuring target post-grazing residuals (1500kg DM/ha in spring) are achieved remains non-negotiable. We can do all we like to get the leaf stage right but if residuals aren’t hit subsequent pasture growth and quality won’t be there.
The key to great results in pasture management is planning and monitoring, knowing exactly where you are and where you’re likely to be in the near future.
This information allows you to stay ahead of the game or get back on track if needed. In terms of tools for monitoring, there are many. It’s about finding a set of tools that works well for you and allows accurate pasture management. This could include a platemeter, feed wedges, feed budgeting or using DairyNZ’s new resource – The Perennial Ryegrass Grazing Management in Spring Pocket Guide.
The pocket guide contains photos and descriptors of leaf stage, pre-grazing yields and post-grazing residuals and is excellent for calibrating your pasture assessment, helping you drive the most out of your system. Not getting feed management right has a cost. The difference between poor and top managers is about $333/ha at $3.85/kg MS. How much are you missing out on?
Pasture management is one of the topics regularly covered at DairyNZ discussion groups. For a list of discussion groups visit dairynz.co.nz/events.
