13 August 2001
Should I adjust seed rates?
Should I adjust my seed rates of winter wheat and oats for a lo-till system?
The issue of seed rates is tricky because it depends on so many variables. I make my decisions by looking at drilling conditions on the day and tweak up or down accordingly.
You need to consider what your target plant population is going to be, then consider how conditions will reduce the numbers of seedlings emerging.
Slugs are the main threat, but if you can ensure precise and deep placement (around 4cm, so this will depend on your drill), good consolidation and are prepared to mix pellets with the seed you probably dont need to up your seed rate.
The other consideration in a lo-till seed bed is that of available nitrogen. Lo-till, particularly where crop residues are chopped and incorporated, have much lower Soil mineral N levels than ploughed seedbeds.
This can very much effect the number of tillers per plant. A lo-till seedbed after beans, for instance, should not be a problem. But after chopped barley straw it is likely to be.
If you intend to apply a little autumn N, there is no need to up the seed rate. If not I suggest you go a little higher, unless you are growing hybrids, which appear to scavenge N well in lo-till seed beds.