Early heading generally means better early spring growth.
Late heading means better late spring pasture quality.
What is heading date?
Heading date describes when a grass cultivar starts showing flower or seed heads in spring.
It is also known as 'ear emergence date', as seen in the photo below.
Heading dates of Barenbrug ryegrasses
Day 0 is typically around 22 October, but this varies by 2-3 weeks from year to year. A cold early spring delays heading, whereas a warm spring can bring it on earlier.
Using ryegrass heading dates on farm
Having paddocks of different heading dates can improve spring growth and late spring quality, and make pasture management easier.
Advantage of early heading
Early heading ryegrasses (up to about +7 days) will continue to be widely used on NZ farms for their excellent late August and September growth, during what is often a critical feed pinch. However this advantage has been superseded by Trojan ryegrass, a late heading ryegrass cultivar which has excellent early spring growth.
Advantage of late heading
As ryegrass heading starts, stems begin to develop, fibre levels rise and metabolisable energy (ME) drops as illustrated below.
Late heading cultivars increase animal intake and performance in November by delaying the drop off in ME over standard heading cultivars.
Farms can benefit from sowing late heading cultivars. To help explain this we’ve drawn a model dairy farm with 14 paddocks below, in November - the most critical month for pasture management as quality falls with heading, coupled with high growth rates. Late heading ryegrasses help feed animals well, as they maintain their feed quality and are preferentially grazed.
With surplus pasture it is also the time for making silage, and this is best done on standard heading paddocks (leaving late heading ryegrass for stock). Standard heading ryegrass can still make excellent silage (ME = 11.5+), if it is cut at a herbage mass below 4000 kg DM/ha.