Profits and Black Grass
After a break crop, a first wheat can perform well, even with some black-grass present, achieving yields of 4t/acre. However, some farms are getting nearer 5t/acre and 4t/acre in second and third wheat.
Yet, if black-grass is present in the first wheat, then second and third wheats can become unviable. Spring crops may then be introduced into the rotations with limited herbicide options which, again, fill up with black-grass. The profitability of a farm with these issues can take a rapid downward spiral making a return to full profitability almost impossible unless the drilling system is changed allowing for late drilling of crops in all conditions.
Late drilling is highly profitable if you can get the seed set securely. Residual herbicide is more effective in late-sown damp conditions. Take-all will have subsided, and £120 herbicide stacks can be reduced as low as £20/ha.
Only about 40% of black-grass seed will germinate in a one-pass false seed bed. If the grass is then destroyed and a second false seed bed is made it might take 3 weeks for the auxins to subside and the next flush of grass weeds to emerge. This time a higher percentage of the remaining grass seed will germinate because most seeds will be less densely spaced within the range of other plants auxins.
When a third false seed bed is made often 90% of the final seed bank will germinate as almost no seed is near enough to other seedlings to be halted by auxins.
| false seed bed 1 | 100 grass seeds | 40% control | 60 seeds remain |
| false seed bed 2 | 60 grass seeds | 60% control | 24 seeds remain |
| false seed bed 3 | 24 grass seeds | 90% control | 2 seeds remain |
Three false seed beds can give significantly better cultural grass-weed control than one false seed bed.