In terms of FYM addition, when it is applied is not too critical. You would not want to do it during hay growth & hay making (April-June). It could go on in summer after hay is removed (Aug-Sep) or in the autumn (Oct-Dec) in areas where there is little risk of floodwater washing it away. Applying it in winter (Jan-Mar) would not be a direct problem to the plants, but the soil would be more vulnerable to compaction at this time, and losses to water courses via leaching would be greater too.
Measuring the P-availability at a site is quite straightforward to do and costs perhaps £100 - £200 for the laboratory analysis. Quantifying the deposition of P from sediments is a bit harder. If you know the flood return period and there has been some analysis of sediments in the catchment, then a judgment could be made as to whether excess P deposition was a real threat.
The better thing would be to take a soil sample before and after a flood and look at increase in total P content. Or better still, try to trap sediment using an Astroturf mat.
On another front, analysis of the vegetation itself will indicate how available P is and whether it is likely to be limiting growth. We have studied P budgets across several sites, and hope to expand that in the current work so that we can make more confident generalisations.
The 5 to 15 mg/kg range is based on the inter-quartile range of values from sites with good examples of MG4. That means 25% of such sites have values > 15 mg/kg. I would say that species richness does fall away above 20 mg/kg, and restoration schemes on soils > 30 mg/kg would not develop species rich communities until hay making had started to strip P out of the soil, which would take a few years. If your soil is > 50 mg/kg, then you either should not have species-rich grassland as a restoration target or you need to think about drastic action such as topsoil stripping, deep ploughing to invert profile or chemical amendment.
25 ppm is not so high that it should preclude you trying to restore species rich grassland. It would be best to try to lower the level first however. Is the site currently under arable management? If funds are available and the current farmer is willing, then he could be asked to grow a barley crop to which he adds nitrogen but no phosphorus at all. This is an effective means of stripping P from the soil. IF the site is already grass, then could a hay crop (or better two) be taken from the site this year to strip P before you add other species?
How effective stripping is depends on the soil type. IF it is heavy clay, then it might be necessary to strip for more than one year before P levels start to fall noticeably. Is your project long enough to do that? If instant returns are needed, then you could try to diversify this year but then take an early hay cut in June followed by a second in September for a few years to wear down the more aggressive species. Grazing can also keep aggressive species in check, but it does little to lower the fertility, so double hay cuts are better.
Soluble P from surface waters is rarely an issue as it contributes rather less than any sediment deposition. P in ground water is rarely a threat unless it is significantly polluted. Groundwaters having contact with chalk and limestone tend to have very low P content. We do not currently record P in groundwater.
This research has not yet been published. It is imminent.
No not at the present time, but if local groups have this information it would be very useful to collate.
Seed spreading is best done in autumn because some species have a cold requirement to trigger germination. Others naturally germinate in autumn and are adapted to survive the winter as a seedling; the same species would be susceptible to drought if sown in spring. You would expect more grass and fewer herbs from a spring sowing. Seed being washed out is a risk, but most of it would probably just be re-deposited within the site, so would not be a total loss.
Sonia Newman has recently (2013) completed a PhD study on this topic. She found that a double cut sucessfully controlled both Carex acuta and C. acutiformis. The frequency of the cutting treatment (i.e. cutting twice) was more important than the timing of the additional cut. More information on this study and the recommendations for management can be found in this short summary.
You should try to avoid the unit with nesting birds in and cut as much of the site as you can, returning later in the summer to cut the final bits. Think about developing a cutting pattern that avoids the areas where nesting birds are resident. It is not advisable to delay cutting every year, just in case there are breeding birds as this will change the species composition of the hay and reduce its productivity. There is a fuller discusiojn on this issue in the article on when to cut a meadow.
Our working definition of "Floodplain Meadows," in terms of the Partnership's scope, covers water meadows. Water meadows are a particular kind of floodplain meadow in that they have more intensively managed hydrology. "Water Meadow" and "Floodplain Meadow" are colloquial terms applied to particular vegetation communities, and so there is scope for the two terms to become confused depending on whether you are describing the physical system or the biological community. For our purposes, we use these names to describe the physical systems and we use the National Vegetation Classification to label the biological communities.
We have no specific knowledge of the opico harrow, but anything that results in > 50% bare ground should be OK. Surface sowing is the norm and is recommended by Emorsgate. Attempts to bury the seed are unnecessary and potentially may be counterproductive.
The evidence is based on our own data which has been collected to develop nutrient budgets for individual sites and from some mesocosm work. There is a pattern that the total N (and to lesser extent P) content declines once the seeds are shed - suggesting substantial allocation of resource to seeds. We have not published these data yet as they were not collected systematically, but we are now addressing this. One of our PhD students, Katherine Wotherspoon, is systematically harvesting hay at two-weekly intervals from a replicated block experiment and assessing total nutrient content. She is just entering her second year of study, so hopefully a publication is not too far away.
Several papers show protein yield falls as season progresses (e.g. Mahli et al, 2003, Can J Pl Sci, 83); a recent paper on haylage (Ragnarsson, Livestock Science, 131) suggested protein content almost halved over a period of a month. We have not seen anything quite that marked so far.
Using a spring-time harrow in spring is a fairly normal grassland management procedure and I have known it happen on floodplain grasslands without ill effect. There is no scientific evidence that I am aware of, however, to tell us whether it is beneficial to biodiversity conservation or not. My main concern on floodplain meadows would be whether the soil was firm enough to support the tractor. Any soil compaction due to rutting would offset any good being done by the harrowing. Chain harrows are often used in early April, primarily to knock down molehills. They are used extensively on floodplain meadows and appear to do no harm, whilst facilitating hay making.
My advice would be to say yes to spring-tine harrowing if the grazier is keen to do it and there is a real problem with dead thatch at the base of the sward, but then only if the soil is dry enough.
Molehills, if bad, can be harrowed. A chain harrow is generally used and is not thought to be damaging to the vegetation. Nesting birds are an issue though. Molehills can be a problem even for modern machinery; particularly if a bar cutter is used and for the baler itself. Raking them by hand is the minimum disturbance option, but unfeasible on a large site.
Moles are not a bad thing for the meadow itself. They generally improve soil structure and aeration, and create regeneration sites for seedlings, so are not damaging per se. It is the hills that need to be dealt with and a chain harrow is the simplest means. Some farmers would use a spike harrow if they have a thatch problem too.
In terms of weed control, earlier cutting can help if meadows are cut late. Nettles and reeds are to be expected in meadows that are cut later. See http://www.floodplainmeadows.org.uk/files/floodplain/Cutting%20Article.pdf for more information on cutting times and the impacts on plant species.
We have not looked at meadow communities in this respect and we have rather limited data on MG5, but we do have some. Rodwell gives a fairly full account of MG5's response to surface pH in the relevant section of British Plant Communities. The Rothamsted Park Grass experiment is the best data source for MG5. The team there know that dataset pretty well. Jerry Tallowin has published on the subject.
There is a general trend in European grasslands that the higher the pH the higher the species richness reflecting the fact that calcicoles survived the last ice age in their Mediterranean refuges much better than did calcifuges. Therefore as a rule of thumb addition of lime will assist species diversity. However if there are specific species of interest, their preferences in terms of pH (see Grime or Ellenberg) should be used to inform management.
Keep them in pots for at least a year before planting out, though they can stand outside. Perhaps sink the pots in a larger pot or tray full of sand to help keep the compost cool and moist.
They have been germinated successfully from pots in the past, but have been lost after planting them in to the soil, so best to protect them for as long as feasible. They do make a very small bulb in the first year. The shoot will wither away by late summer, so don't get worried if they have disappeared by August - they should reappear the following March. See our fritillary leaflet here.
A number of organisations including wildlife trusts and individuals cut small sites with scythes. This is fast, low tech, low impact and versatile. The hay can then be raked up and composted. Once mastered, the scythe is a fantastically useful tool, much more adaptable to different situations than a strimmer. And much much quieter! If you don’t have the strength, then the old Allen scythe is motorised and does it for you.
Extreme flooding holds two major risks for floodplain meadows: a) waterlogging of the soil can deplete its oxygen causing plants to suffocate and b) excess sediment dropped by floods can over-supply nutrients. These factors are considered in turn below.
Species-rich floodplain meadows are adapted to cope with winter flooding;the plants are largely below ground and dormant until mid March when the soil warms up enough for biological activity to get going. If the flooding is so prolonged that the soil oxygen is used up, then species will start to die. The length of time this takes to happen is a function of soil temperature. Given the winter has been so mild, there is a risk that flooded soils might start to run out of oxygen in February whereas in a normal, colder year they might have been safe until March.
Historically floodplain meadows have been prized for their fertility and hay quality as a result of regular silt input from floods, so flooding is an important part of the cycle of the meadow. However, if meadows are not regularly cut for hay, then the nutrient levels in the soil build up and the species richness of the plant community declines. If flood events are both large and frequent, then it is possible for too much sediment to be deposited damaging the biodiversity of the meadow, which can take a decade to recover. It is not possible to generalise about how much flooding is too much, because the amount and pattern of sediment deposition is so site specific.
Flood events that occur during the growing season (March-September) are much more damaging because the soils run out of oxygen very quickly when they are warm. Additionally, where a hay cut cannot be taken because a site is too wet, we see a decline in species richness because tall, coarse species tend to smother the finer ones beneath. So summer flooding, especially if regular and prolonged, leads to the demise of the floodplain-meadow plant community and sees itreplaced with swamp communities, in which the species are better adapted to cope with waterlogged soil. For example,species of large sedge, which are not suitable for hay,are becoming more widespread in floodplain meadows, as a result of the increased summer flooding during the past 15 years.
It is difficult to put a figure on the amount of flooding a site can tolerate during the growing season before plants are impacted, as it depends on site-specific factors such as the soil type and local hydrology.
There is much more detail available on the tolerance of different plant species to flooding in the following article http://www.floodplainmeadows.org.uk/files/floodplain/Ecohydrology%20in%2...
Sward lifters can be useful in relieving compaction where it is severe, because the mechanical loosening can allow oxygen back into the profile, thereby kick starting the natural processes that allow a soil to regain its structure (i.e. root and hyphal growth, invertebrate burrowing etc.) It does have its drawbacks however, so it needs to be used with care and should not be used routinely but only to address a particular one-off problem . If it is undertaken when the soil is dry, then the root breakage can cause patches of the sward to die. Conversely, if done when the soil is too wet, little positive benefit is achieved (because the lifted soil fails to crack) and further damage could be done by the vehicle pulling the implement.
In terms of floodplain soils in particular, good structure is important for high biodiversity, therefore areas with damaged structure should be considered for remediation. If the alluvium is shallow (<30 cm) over gravel, then there is probably no need to consider sward lifting. Natural processes (dry/wet cycles and freeze/thaw) should allow natural processes to restructure a damaged soil in the medium term. On deeper soils, where evidence of compaction has been observed in soil pits, then a sward lifter used at an appropriate depth and under appropriate soil-moisture conditions can be useful. Generally it is best done in the autumn such that plants have the winter to recover from any root breakage before they are exposed to moisture stress.
Criteria to help decide if sward lifitng is appropriate should be:
there is evidence that the soil does have a clearly compacted layer, the loosening is done in autumn when the soil-moisture conditions are appropriate, the effects of the loosening are assessed in the following summer, both in terms of its effectiveness in relieving the compaction and the absence of any negative effect (i.e desiccation or species loss) on the sward.
Undertaking a small trial on an area of soil, or one field might be worth considering; assessing the results the following year, before more widespread lifting.
It is worth noting that flooding per se does not compact soils (unless it is saline!) so any argument that sward lifting is required simply because an area has been exposed to prolonged flooding is not valid. It is the action of vehicles or stock on the soil whilst it is flooded or waterlogged that causes the problem and, as prevention is better than cure, it is worth checking why the soil has been compacted. In a case where arable soils are being brought into grassland, then it could be that the compaction is a legacy of former management and therefore a single mechanical loosening to relieve it may be justified. Ideally this would be done prior to any green hay or seed being spread.
Increases in curled dock R. crispus are common after floods, which also result in death of other more typical meadow species due to prolonged soil anoxia. This, combined with an increase in soil fertility resulting from flood deposition of fine sediments (and probably also resulting in seed inoculation as dock seeds float and are often deposited in their hundreds at the margins of a flood) increases the prevalence of curled dock.
Successful seed germination of curled dock is promoted by light exposure and its seedlings are initially slow to grow upward, suggesting a substantial area of bare ground is required to avoid shading from competitors. So infestations tend only to occur following pro-longed flooding which results in death of less tolerant species or soil disturbance by grazing or trafficking whilst the soil is wet. Curled dock is capable of surviving in anoxic conditions through various adaptations including aerenchyma (tissue that can supply atmospheric oxygen to below ground tissues if soil becomes anoxic), and by having accelerated upward growth when submerged, allowing the upper leaves access to the atmosphere and oxygen. It is also favoured by high phosphorus availability, which is often the case in depressions where floodwaters have deposited their fine sediments when retained after the main flood has receded.
Over time, curled dock will decline under meadow management as it does not tolerate a regular cutting and grazing regime, provided the drainage infrastructure functions effectively in order to prevent flood waters sitting on the meadow for long periods. After a few years of heavy infestation the population of dock beetle typically builds to a point where the docks are completely defoliated by the insect reducing their vigour and causing them to be out-competed by the grass.
Recommendations to control docks are: