There is some confused opinion as to the link or otherwise between heading date and early growth in ryegrass. This in fact is relatively straightforward, although some of the things we are hearing seem to be making it complex!
The facts: To get high early spring yield, choose a cultivar with high early spring yield.
You do not need an early heading date for early spring growth. This might have been the case 10 years ago. But the use of Spanish genetics in perennial ryegrasses such as Trojan has allowed us to deliver both early spring growth and a later heading date in the same cultivar.
To illustrate this we’ve graphed what is the best industry-agreed yield data source for ryegrass, the DairyNZ Forage Value Index (FVI). In the FVI there is a rating for ‘Early Spring Performance’ for each cultivar from 1 (=poor) to 5 (= excellent), that comes from all the trials run since 1991.
Dairy FVI early spring growth vs heading date for Upper North Island
Two main points stand out in this data. First, to get the best early growth choose the right cultivar. For example from within the late heading cultivars you can get both excellent early spring yield (e.g. Trojan) and poor early growth (e.g. Abermagic).
Second, there’s no real relationship between early spring DM yield and heading date. If you were asked to draw a trend line on the graph, it might be the green one we’ve sketched suggesting very early cultivars (Day 0) are on average slightly poorer.
Later heading cultivars also hold their quality better in November, as they go to seed later, tend to produce less aftermath heading and overall less total seedhead.