Over the last month black-grass control experiments have been assessed and demonstrated. There is no doubt that the issue is how to control the weed with herbicides in dry autumns. We are now so dependent on the pre-emergence and early post-emergence herbicides and typically they will not work anywhere near their best when seedbeds are dry.
In addition, in many cases we have the legacy of a high seed return this year. The whole industry really knows what to do about it but many are looking for new and quick solutions. A quick solution would be a new and effective herbicide. We have known for years that this would not be the case. Until quite recently many farmers still firmly believed that the chemical companies were holding something back.
I have had queries about alternative approaches. Weed wiping has been suggested but there are severe practicalities in keeping the wick from touching the crop. Some farmers are suggesting that the industry should be allowed to return to straw burning. I do not think that this will provide all the answer, even if it were allowed (which, I am sure it won’t).
I was a technical adviser to MAFF when the ban was being discussed. There is no doubt that in many circumstances straw burning would provide some advantage and this was one of the arguments which was presented to MAFF. However, public sentiment was totally against burning.
What interests me is the current debate on the impact of direct drilling on black-grass populations. The impact of primary cultivation on black-grass numbers was assessed in the LINK funded series of trials on the greater understanding of the agro-ecology of the weed. Adopting the Simba Solo resulted in the highest black-grass numbers and the plough resulted in the lowest numbers. Direct drilling was somewhere in between.
So direct drilling was by no means the disaster that some had predicted. There could be several reasons for this. One is that much of the freshly shed black-grass seed is lost from the soil surface. A few years ago The Chadacre Agricultural Trust and The Morley Agricultural Foundation funded a PhD on losses of grass weed seeds from the soil surface. Losses were very significant in the autumn and winter but it was difficult to gauge the role of the different factors. There was, for the first time, the suspicion that some black-grass seeds were eaten by predators, possibly birds.
I believe that the proponents of a straw rake to encourage losses of seeds have a case. Pot trials show that black-grass seed germinates and establishes much faster if buried at a depth of 1 cm (0.5 inches) rather than lying on the surface. This may increase overall losses despite burying the seeds away from the soil surface where they are vulnerable to some losses.
In terms of chemical control with soil acting herbicides, one potential advantage of direct drilling is that the seedling and secondary roots of black-grass may be closer to the soil surface when compared to other approaches to primary tillage. Such differences could be of greater importance where there is significant resistance to the herbicides and when conditions are marginal for herbicide activity.
Of course, there is direct drilling and direct drilling. There is a huge difference in the level of soil disturbance between the different types of drill. This has resulted in observations that more black-grass survives between the row of some types of drill and along the row with other types of drill. This aspect could be critical in the longer term. Attention to detail is now the order of the day.
There are, of course, possible downsides to direct drilling. By treating only plants from seed shed in the previous crop, the further development of herbicide resistance will be maximised. This is assuming that resistance can get worse! In addition, there could be some unforeseen circumstances. In Australia, millipedes and earwigs have built up to such high levels in long term direct drilling that they are now damaging crop plants. I am not saying that this would occur on the UK, what I am saying is that there could be problems that we would not have predicted.
However, we will get an early warning because some UK farmers have been direct drilling over the last 10 years or more. Let us hope that they will be on the ‘leading edge’ rather than the ‘bleeding edge’.
If you want to get really depressed, listen to the black-grass blues