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A hay dilemma

"A hay dilemma"

Keith Porter  01/04/1994
 
Hay meadows are one of our most spectacular and easily maintained wildlife habitats. But as their numbers dwindle there is a dilemma. Should farmers harvest and sell wild flower seeds from their hay meadows or will the long term effects be detrimental to the creatures that live there, asks Keith Porter.

For a few brief months a traditionally managed hay meadow is a riot of colour as early - flowering perennials and annuals strive to flower and set seed before the hay cut. The plants and animals of such meadows are in tune with the traditional cycle of spring flush, total removal of standing crop, followed by a period of grazing. Provided this cycle is maintained without the additional stimulus of artificial fertiliser of reseeding, this rich and colourful habitat is easily maintained.
 
Recent history has dealt with these flower rich meadows, for around 95% have been lost in the past forty years. Perhaps even more alarming is the evidence that such meadows continue to disappear at the rate of something like 10% per year. Change in agriculture are the cause, particularly the shift from hay to silage feed for overwintered livestock.
 
One of the options available to farmers since the late 1970s has been to add value to the hay by taking a crop of wild flower sees, then cutting the standing hay as usual. This seed harvesting option has presented conversation organisations with a dilemma: we want to encourage traditional hay systems and recognise the potential benefits of producing native seed mixtures, but fear that we may be killing the goose that laid the golden egg.
 
Many conservationists see seed collection as a break from tradition because the timing and frequency of harvesting and the ultimate "hay cut" have been altered. At best, a phased rotational harvest has been agreed but at worst consent for harvesting on SSSIs or nature reserves has been refused. This dilemma must be resolved in order to take advantage of schemes and incentives to extend non intensive grasslands throughout the countryside.
 
In converting modern arable to grassland we commonly find that the seed bank is largely destroyed, adjacent meadows are absent and wild flower seed mixtures are very expensive. The source of the wild flower seed is a problem because non-native races of plants may create unexpected results. 

Seed Harvesting

 
The first machines designed for the process was essentially large "Hoovers" which sucked up the loose seed from the crop along with both living and dead "debris". The efficiency of these machines depends on the weight and shape of the seed and operators rarely claim more than 20% of available seed is harvested. The seed mixtures collected contain a high proportion of common "weedy" plants. These mixtures will not instantly recreate a Cricklade meadow or a Pixey Mead, but they will form the starting point for reasonably natural swards of native species if managed correctly.
 
Seed harvesting can change the rate and timing of seed deposition into the meadow. Some of the plants of our hay meadows, such as yellow rattle rely on a annual recharge of the seed bank to produce next years plants, while others rarely, if ever produce mature seed before the hay cut (Jones, 1989).
 
In order to maximise yield, seed harvesting usually continues after the hay would have been cut to allow seed to mature. Bearing in mind the relatively low efficiency of harvesting, this means that more seed of later flowering species will be deposited than would traditionally be the case. This is particularly true of species such as knapweed, saw-wort and sneezewort, but may be less significance in these perennial species than for annuals. Changes in the amount of seed could alter the sward composition over a few seasons.
 
Later hay cuts, extra movement of machinery on the meadow and knock-on effects to grazing will eventually affect the composition on the flora if consistently carried out on site. Most conservationist are happy that limiting seed harvesting to a fifth or a quarter of the site and rotating the section harvested each year should reduce the risk of damaging the botanical value of the meadow. This forms the basis on which seed harvests are collected.
 
Very little is known about the smaller animals of hay meadows: the flies, beetles, moths and related groups. A common misconception is that the hay cut is a catastrophic event. The buzzing and biting throng that populates the hay meadow in June consists largely of "tourist" species; visitors in the meadow to feed on flowers on their insect visitors (Kirby, 1992).
 
In among the invertebrate community of these uncut hay meadows is a much smaller sub-community of meadow species. These are spring and autumn species which survive the barren months in resistant stages. A good example is a common hay meadow hoverfly Cheilosia albitarsis, which lays its eggs down among the buttercups in spring (Rotheray, 1990). These eggs produce inactive larvae which begin to feed in the roots of buttercups in the autumn. Although not restricted to hay meadows, this hoverfly is clearly capable of coping with traditional hay meadow management.
 
A truly specialised group of insects which use hay meadows are the gall flies (Tephritidae) whose larvae generally develop inside seed heads, stems or roots. Many hay meadow plants are particularly favoured by this family of flies, especially knapweeds, saw-wort and related species.
 
Waring (1990) considered the impact of a suction harvester on the moth and butterfly fauna of a site in Buckinghamshire, concluding that many individuals and species were extracted with the seed and damaged particularly the winged adults.
 
This may be overcome when brush harvesters are used (Payne pers. comm.), but they still collect more burnet moths than a suction machine. Estimates of the overall compact of the suction harvester on the populations of flying moths and butterflies suggest that harvesting has great impact on relatively sedentary species, such as a forester or burnet moths, which rest high on flower heads.
 
A more comprehensive attempt to define the invertebrate fauna of hay meadows was made by the author. A serious of four meadows in Oxfordshire were sampled by placing two types of trap in the centre of the meadow from early may until the end of June when the hay was cut. The picture that emerged confirms the view that hay meadows are populated by large numbers of relatively few, common species (Kirby, 1990). This sample though biased towards flying insects, provides a more comprehensive picture of the species that may be at risk from seed harvesting.
 
The species can be roughly divided into three types: those that are widespread and clearly "tourists"; those that breed in habitats immediately adjacent to the hay meadow; and those that breed on the hay meadow itself.
 
The point to be taken from these brief studies is that there are some important invertebrates which use hay meadows for breeding. Such species are completely secure provided that the traditional hay management continues. Some of these species are affected by the physical act of harvesting, particularly if their larval or pupal stages are within seed heads which are disturbed before the usual hay cut time. Cut hay is turned and dried on site allowing larvae or adults to leave the hay.
 
If these animals were evenly distributed across the hay meadow then the botanists compromise could be applied. In reality, the invertebrate populations are usually grouped in particular areas. Rotational harvesting of the block could easily affect the whole breeding area of critical invertebrate species. This is not a risk that should be taken with a rapidly -diminishing resource.
 
What can be done? The brief observations of Waring (1990) provide a series of guidelines for seed harvesting. Central to these suggestions is the need for more information on specific sites to direct seed harvesting to non-contentious parts of any meadow.
 
Waring suggests that the fall back position, where we are ignorant of the fauna of particular sites, is to harvest only a proportion of any meadow, and to harvest the same block every year. In view of the shifting nature of invertebrate populations this might not best serve the needs of critical species.
 
An ideal position is to use the principle of rotational patches in the meadow but to spread the risk of local extinction by reducing the size of the plots to an acceptable, pragmatic level. Harvesting in strips is recommended with one strip in every five being harvested for seed, each strip the width of a standard harvester or mower. The experience tractor operator should even be capable of taking hay from four out of every five strips in advance of the completion of seed harvesting, thereby maintaining traditional practice over most of the site while allowing minimal impact seed harvesting to optimise the extraction of mature seeds.
 
The issues set out above and the ideal solution given can help conservationists to be positive about wild flower seed harvesting. We all wish to see the threatened core resource of our meadow expand. These long standing habitats cannot be recreated within the same time scales available, but we can encourage non-intensive "friendly" grasslands, which help buffer the core resource and having a growing value in their own right. The provision of a relatively cheap, locally derived seed stock can only assist this process.
 
This article has focused on hay meadows but the arguments and suggested solution are equally relevant to chalk grassland and other permanent grassland where the potential for impact is far greater. The advantages are clear; the problems are being faced. Now we need experience of practice.

At the time this document was written Keith Porter was Team Manager for English Nature's Environment Audit Standards Team
 
FACTS
  • Potential benefits of wild flower seed harvesting from hay meadows.
  • Locally derived seeds can be used to re-seed new grasslands.
  • Seed mixtures from hay meadows are much cheaper than commercial mixes.
  • Using seed from hay is closest to the traditional way of restoring grasslands on arable land

 

Page last modified on Friday 22 of June, 2012 23:21:17 BST