Will a fine stale seedbed slump?
I have been using heavy discs for 10 years but have just started using a sterile seedbed system. Does it matter if, after double discing and pressing, I end up with a fine tilth? Or will it slump if it turns wet?
If possible we would try an avoid a situation where the stale seed bed slumped – mainly because if we get yet another wet autumn it takes much longer to dry out.
To avoid a stale seed bed that slumps we try to do all our discing when it is dry, although I am well aware that it is not always possible for you, especially since you are farming further north than us.
If you can disc when it is drier the stale seed bed will generally be coarser and less likely to slump. A coarse tilth will dry out quicker when it comes wet due to a larger surface area.
Pressing or re-consolidation of some form is absolutely essential, to preserve moisture and to re establish the soils natural structure so if it does come wet it will dry out again (eventually).
A neighbour of mine has a Simba disc press which does a first class job: it leaves a fairly coarse surface, but firms the stale seedbed very well. You get a good germination of weeds and volunteers yet it will dry out again if it does come wet.
Discing shallower also seems to help, we used to have a very heavy set of parallel discs which needed to work at a minimum of 10-12 cm deep in order to move all the soil. These discs required a lot of power – 180-200hp on a 3.8 metre set, then we had to run over with a press to re-consolidate the soil.
We have since changed to a set of Kuhn 4.5 metre tandem discs, which move all the soil in one pass at 5-7.5 cm (handled easily by a 150 hp Fastrac). Working shallower we re-consolidated with a set of 6 metre Cambridge rolls, about 2-3 hours after discing.
Having moved far less soil we do not get such a problem from the soil slumping or what we call the porridge effect.
As an aside, we are now harrowing much of our land with the Bullock Mulch Harrow (two or three times) then direct drilling. We get fewer weeds in the crop and no slumping at all, but you do need a direct-drill and the nerve to do it!