Finn
Arable weeds are species associated with agricultural habitats, including cropland. As well as native species, there are also many non-native arable species: ‘archaeophytes’ are species introduced long ago, now thoroughly naturalised in the UK. Archaeophytic arable weeds are thought to have spread widely from the Near East, having adapted alongside agriculture throughout history, and likely arrived in the UK with human migration. Surprisingly, the classic common poppy (Papaver rhoeas, Fig. 2) falls into this category. Some species are ‘neophytes,’ which are more recently introduced (within the last few hundred years).
B. Lamb’s-succory (Arnoseris minima). Extinct. Archaeophyte. Image credit: A.S. Kers via The Species Recovery Trust website.
C. Scentless mayweed (Tripleurospermum inodorum). Least concern. Archaeophyte. Image credit: Barbara Cooper via NatureSpot website.
These species tend to be small (E.g. Fig. 1A: fingered speedwell), and they use the crops they grow amongst as protection against weather and competition from other weeds. The regular upturning (cultivation) of soil for seed laying on farms is also important for arable weeds, as this allows their seed to germinate, where soil is usually difficult to penetrate.
What happened to arable weeds?
As agriculture has become intensified in the last century, arable weeds have become a less common sight around farmland in the UK. These are thought to be some of the major factors involved:
- Agricultural intensification means that less land is left fallow (not sown or harvested for a season), and often there is also less semi-natural habitat surrounding fields, that would once have provided space for arable weeds
- Increased fertilizer usage means that nutrient levels in agricultural soils are higher, and less suitable for many arable plant species.
- Herbicides are commonly used on crops, to prevent weed growth.
- Seeds from crops are cleaned better, meaning the seeds of arable weeds are less likely to spread.
While some arable weeds were once considered serious weeds of farmland, now seven species of arable plant have already been declared extinct in the UK (Fig. 1B), with others threatened or endangered (Fig. 1A), due to huge decreases in frequency over several decades. From my experience, one arable plant you can spot in and around fields is scentless mayweed (Fig. 1C, Fig. 2), which is tall, with daisy-like flowers and feathery leaves, so it sticks out quite well. The bright red flowers of the common poppy (Fig. 2) are also not difficult to see in arable fields, but are also common in other places, such as roadside verges!
Figure 2. Wildflowers in a cereal field, in North Norfolk, including common poppy (Papaver rhoeas) and scentless mayweed (Tripleurospermum inodorum). Image credit: Me.
How can we manage to benefit arable weeds?
If arable weeds are to make any kind of come back, change is required in the management of agricultural land.
- Margin strips of wildflowers or grass around fields may provide some habitat, but these plants are specially adapted to survival amongst crops, so this type of habitat is likely to be more beneficial to grassland species. A margin of cereal (e.g. wheat, rye, or barley) can be planted surrounding a field, providing a crop specifically for arable weeds to grow within, without the need to harvest and remove the habitat. Increased space between rows may also reduce competition between arable weeds and the crop.
- Farming using less fertilizers could help, as many species prefer to grow in soil with lower nutrient levels, and there is evidence to suggest that fertilizers are used very inefficiently anyway. This change could be a win-win situation in terms of diversity, money and fertilizer run-off.
- Using fewer herbicides could also allow more non-crop growth within fields, letting arable weeds establish amongst wheat plants, for example. This could also increase diversity in land surrounding the fields, including arable plant diversity
- Seed mixes could also be laid into and around farmland to help establish communities of arable weeds.
Some of these changes could help revive arable weeds in the UK, allowing them to once again fulfil ecosystem services and functions that would benefit humans and the natural world alike: providing soil stabilisation, reduced nutrient leeching through soil, nectar for pollinators, food for small mammals, insects and, in turn, birds.
Read more:
Arable fields | The Wildlife Trusts
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