While of little use to a farmer with a field full of docks, the following, from a new Green MEP letter to the European Commission is worth hearing.
“Evidence suggests that weeds only affect the yields under certain conditions, and that a totally weed-free field is not needed, and indeed that many wild plants offer microhabitats for other beneficial species that protect the crops from pests.
"To prevent too much competition from weeds, there are a number of techniques...”
Weed-free environments is about competition between plants; once the crop dominates, the other plants can carry on in irrelevancy.
This point is supported by studies in Denmark which suggest, “Danish weeds growing in cultivated fields comprise approximately 200 wild plant species, but about 80% of these are so weak in competition with crops that they do not affect yield substantially in any well-run farms”.
It’s the other 20% that are of concern.
When I spoke to organic farmer Pat Lalor recently, he said much the same thing.
“I don’t have a weed problem, because weeds are about competition. So a good dense crop equals fewer weeds. Oats grow taller than weeds, the winter crop is six inches higher than weeds.
"Oats also exude a substance at germination to inhibit weed plants, as does rye.”
He continues, “This all helps. But it’s part of a package of crop rotation, use of legumes, farm yard manure, all increasing e microbiology in the soil which is the key to the whole thing.
“Lots of fungi in the soil gives you less weeds than if you have less fungi.”
Conditions both above and below ground are important.
“I increase the quantity and diversity of micro-organisms in the soil. Worms are good, but I’m talking about the ones you can’t see, the microscopic ones.
It’s a long term soil build over years. In organic systems, phosphorus and potassium levels won’t be as high, neither will nitrogen.
But if you put on a lot of chemical fertilisers, you grow both the weeds and the crops. So if you don’t have the super-high chemical NPK, both yields of weed and crops are down. So, for example, scutch grass is not the same problem in organic at all.
You don’t push the crops in organic, so the weed is starved. There is a happy medium, you can’t starve the soil, but you can manage it so you don’t have weeds of consequence.”
“To explain it is easy, but to achieve this delicate balance is hard!
“Moving from intensive tillage to organic tillage is a difficult transition. It’s possibly easier to go into organic tillage from permanent grassland. But my own beef land isn’t suitable for tillage. And it’s the same for much of the land around here.”
That Green MEP letter to the European Commission points to a number of other approaches to weed control.
These include appropriate crop rotations such as
* Clean fallow against perennial and rhizomal weeds.
* Cover crops doubling as mulch or green manure.
* Following weed-prone crops with those where weeds can easily be controlled before they set seed; rotating between crops planted in different seasons.
* Stale bed techniques to germinate weed seeds before sowing crops combined with mechanical weeding.
* Mulching to suppress weed germination.
* Avoiding bare soil in plantings, for example using intercropping or nurse crops undersown to emerge before the main crop.
* Shallow ploughing to maintain subterranean communities and soil structures, while avoiding bringing up weed seeds.
* Thermal treatment in using steam or grill/hotplate.
* Use of rotary hoes between rows and within rows later in the season.
This column will focus on the latter more mechanical techniques next week.
© Irish Examiner Ltd. All rights reserved