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Crop establishment and management

Paludiculture systems are managed so that the above-ground biomass is optimised for use / sales; this distinguishes them from peatland restoration, where biodiversity outcomes are the main target. Paludiculture cropping systems are also differentiated according to the crop that is established. Some paludiculture systems are semi-natural where the crop develops naturally. For example, summer mowing or grazing coupled with rewetting can create wet meadows or wet pastures. Wet meadows or wet pastures usually consist of heterogeneous vegetation and are adapted to the site through their natural development. Reed beds can also be developed in a targeted manner by mowing in winter.

 

Paludiculture systems also include systems where crops are established deliberately in monocultures or simple mixtures to create denser and more homogeneous crops e.g. alders, willows (tree crops) and stem-biomass crops such as reeds and Typha species (also known as bullrushes / cattails). Targeted establishment is recommended to enable a reliable harvest of specific species allowing management of crop quality. Pasture species (grasses and herbs) can also be sown in a targeted manner and, with appropriate management, can form stable vegetation levels with higher forage quality over a longer period. Within such systems, crop evaluation and improvement can take place with selection of desired qualities within existing landraces and the potential to breed new varieties.

 

A distinction should also be made between paludiculture on raised bog and fen soils. Despite major changes due to drainage and utilisation, they have different site conditions (e.g. nutrient availability) that become more pronounced over time, particularly after rewetting. These conditions limit the selection of cultivable plant species. Reeds, Typha, cultivated grasses and alder are primarily suitable for fenland sites, while sphagnum or other special crops such as sundew or berries are more suited for raised bog sites. For more information on site requirements and plant selection, see Site requirements of different paludiculture crops.

 

Here we give some preliminary information that is relevant to all paludiculture systems, before providing crop-specific details on crop establishment and management.

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Crop establishment

Crop establishment

The initial set-up of paludiculture systems may require levelling, gradient profiling or terracing depending on the existing relief and slope.  These major works are likely to take place alongside the implementation of site-specific water management approaches developed to take account of the availability and quality of water, the degree of peat degradation and the requirements of the crop.

Rewetting is an important tool in the weed control strategy for many sites. Experience from pilot sites highlights that weed competition can be a problem in the first year for most paludiculture crops, especially where soils are not wet at establishment. From the second year, weeds are less of a problem as established paludiculture crop stands become more competitive. The main problems at establishment usually arise from annual weeds germinating from the soil seedbank before full rewetting occurs. However, if establishment of paludiculture crops takes place after water levels are raised, adapted low ground pressure technology for seedbed preparation and planting is likely to be required (see Adaptation of land management equipment).

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There are currently few commercial seed or transplant systems for paludiculture crops. Establishment from seed, if practicable, is often cheaper than transplanting. However, both approaches are likely to need some land preparation, e.g. mowing and clearing of existing vegetation, creation of open soil to optimise soil to seed / root contact. Raising transplants or developing plugs for sphagnum (or other crops) in nurseries may require specialist skills / facilities. Seed preparation approaches, such as pelleting, are also likely to be developed together with their associated sowing technologies e.g. sowing by drone, by water drift, or use of typical agricultural seed-drills.

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Experience from pilot sites also highlights the importance of pest control to protect young plants from grazing or disturbance e.g. deer, geese, wild boar.

Challenges

The challenges of managing wet and waterlogged peatland soils

In its natural state, a peat bog retains its structural integrity due to the fibrous nature of the living layer and the underlying peat matrix. The strength of the soil and the resistance of the ground to a load is indicated by measurement of penetration resistance (with a penetrometer). Penetration resistance depends on the bulk density, pore size distribution and structure of the organic matter and reduces rapidly as water content increases. Heavily degraded humified peatland soils also have low cohesion and low shear strength, and this falls further after rewetting so that the land surface is not very stable.  A low shear strength means that little forward force can be loaded onto the surface before component layers move laterally in relation to one another; low shear strength will result in vehicles slipping and sliding. Shear strength increases as the proportion of mineral material increases and water content falls.

 

The combination of penetration resistance and shear strength determines whether the peat can be driven on at all and also how deep machinery sinks into the peat body. The deeper the contact surface (wheel, track) penetrates, the steeper the "hill" that the wheel / track has to "drive up" and the higher the tensile forces acting on the sward. If the acting tensile forces exceed the shear strength, the sward will tear and be broken through.

 

Rooting density in the top 10 cm also plays a key role in how peat soils respond to traffic.  The load-bearing capacity of the vegetated surface increases with the density of the plant population. Hence minimisation of sward damage during cultivation of the area and any on-going operations, such as weed control or harvesting, are essential to enable management of stem-biomass paludiculture crops and wet grassland.

 

Depending on the condition of the sward, the use of adapted agricultural technology or specialised technology is necessary for crop management, harvesting and removal of the harvested crop from the field, and is described in more detailed in the following sections for the various types of paludiculture. Choice of the most appropriate machinery for use on wetted peat depends on the load-bearing capacity of the sward and the stability of the subsoil. Some adaptations can be made to the machinery itself (see Adaptation of land management equipment). Vegetation cover and type, water level and soil condition or the degree of degradation are also major influences.

Adaptation of land management equipment

Adaptation

Paludiculture systems are likely to need machinery for various activities:

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  • Land preparation

  • Crop establishment (sowing or planting)

  • Crop management (weed management e.g. topping, reseeding if necessary)

  • Harvesting including initial processing (cutting, chopping, baling, bundling, etc.)

  • Transport of the harvested crop to the edge of the field or transfer point

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To date, landscape and conservation management have provided the main driver for the development of adapted or specialised technology for use on wet peatland soils. Examples from landscape conservation and reed cutting show that effective management of wet sites is possible.

 

Minimising ground pressure is the primary aim of new and adapted machinery. There are several ways to reduce the ground pressure of the machinery used by reducing overall weight, e.g. by using precision technology or lightweight components, and also increasing the contact area. With conventional agricultural machinery this can be achieved by using tracked machines or with wheeled machines that use double/twin tyres, with rounded shoulders and a large lug contact area, as well as reducing tyre pressures. A guideline ground pressure value of approx. 100 g/cm² is often recommended in order to avoid damaging the sward and the peat body.  Balloon tyres with low pressure have been used in reed cutting to achieve the low level of ground pressure that is required, but the small machines developed for reed cutting currently requires a high level of labour input. Adapted grassland technology has a high area output during mowing, but it’s use is currently dependent on dropping water levels ahead of mowing together with maintenance of good ground cover. Traditionally this approach has been used for hay-cutting in some peatland areas. On modern machinery, tyre pressure control systems can make it easy to regulate tyre pressure, thus reducing diesel consumption, working time and wear on tyres.  However, the customisation options for conventional agricultural machinery are not able to reduce the soil pressure to the low target value of approx. 100 g/cm², which enable peat-preserving water levels.

 

A number of prototype machines are currently in use in pilot areas but it is not yet clear whether these machines will be able to be used in large scale paludiculture systems. For example, machines that can complete all work steps are preferred for harvest of small areas. However, where large areas are to be harvested with economic efficiency then harvesting and transport vehicles can be separate. It is also important to balance the weight of the machine, harvesting attachments and the payload. If harvesting and transport vehicles are used separately, the working width of powerful harvesting machines can be increased, increasing the impact force whilst reducing the proportion of the area that is driven over. Light transport vehicles can then be used to recover the biomass.

 

The technical challenges of harvesting paludiculture crops are increasingly being addressed. This is important as harvesting of the biomass partly determines the downstream logistics chain, such as the transport type, storage options, as well as processing options for biomass products. Specific requirements for the harvested crop must also be taken into account during harvesting. For example. this can relate to the provision of certain fibre and stalk lengths, the separation or cutting off of individual plant parts during harvesting, the type of compression and (residual) moisture required for storage and further distribution. Product quality - such as protein content, cellulose and hemicellulose content, lignin content - are determined by the harvest date, among other things. This in turn may have an impact on the machinery that can be used.

 

Precision technology (hand-guided technology, single-axle tractors, small tractors) can currently only be used on small areas due to the small working width and therefore low output / area covered per operator per day. In the future, the use of lightweight autonomous (swarm) technology may overcome these limitations. e.g. development of swarm mowers for maintenance cuts on sphagnum areas, or transporters to move biomass to a permanent roadway.

 

Tracked machinery may be able to protect the soil with high harvest efficiency. However, use of tracked vehicles can nonetheless cause damage to the sward when travelling around (tight) bends and repeatedly passing over the same areas. These impacts can be reduced by replacing the track made of linked steel plates, with a reinforced rubber belt with chevron treads. Wider tracks increase the contact area, reducing the ground pressure. The width-to-length ratio of the track determines the shear forces when cornering. An optimum ratio of 1:4 to 1:5 has been suggested. However, as tracked machinery has to be transported by low loader, the machine width may need to be limited (< 3 metres) to allow transport on roads.

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As well as adaptation of in-field machinery, adaptation of logistics to move the harvested materials to processing facilities also needs to be considered. This is likely to include consideration of:

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  • Construction of driveways via which the harvest area can be reached.

  • If applicable, filling of ditches to provide flat access from existing roads or tracks.

  • Installation of additional access routes.

  • Consolidation of the apron on crossings or access roads e.g. by filling with mineral soil.

  • Creation of paved areas for storage and handling.

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Whatever machinery and trackway adaptation is carried out, knowledge of the area and driver experience are key to effective land management and harvesting without damage to the peat and its vegetation.

Stem-biomass crops

Stem-biomass

The most common stem biomass crops in paludiculture are currently reed (Phragmites australis), Typha (bulrush, cattail). There is also some exploration of the role that reed canary grass (Phalaris arundinacea) and Miscanthus might play in paludiculture systems in the UK.  

 

Land preparation

Cultivation of reeds and Typha (cattails, bullrush) requires permanently high water levels in the peat. Hence, active water management systems are usually required. The most appropriate construction measures depend heavily on initial conditions (relief, type and condition of any pre-existing vegetation, etc.). Steps are likely to include:

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  • Reprofiling of embankments and dykes

  • If applicable, terracing of undulating terrain

  • Establishment of trackways / additional access roads

  • Water retention: adding dams, weirs and sluices within ditches, possible capping of old drainage pipes.

  • New infrastructure for water management. A range of hydraulic engineering measures may be necessary which may include water storage and increased frequency drainage systems to enable effective sub-surface irrigation.

 

The site design also needs to take account of requirements for on-going maintenance such as the control of vegetation on embankments, and maintenance of water management infrastructure.

 

Sowing and planting,

Depending on the initial situation, a range of measures may be required to prepare the seedbed for planting. Ploughing, harrowing, and other tillage operations have been used ahead of rewetting in the past. However, tillage should ideally be minimised as far as possible, whilst ensuring that plant competition is shifted in favour of the crop to be cultivated. Once stem-biomass crops are established, weed competition is not a major issue; however, weeds can be a major challenge during establishment. When sowing, it may be necessary to at least partially open up the existing sward (slit sowing) or to cause it to fail through deliberate waterlogging. Sowing into the existing sward has been demonstrated successfully (for Typha).

 

Establishment by transplanting pre-grown seedlings is more favourable in terms of land preparation and may be less risky in terms of successful establishment. The planting density of reeds is 0.25 - 4 plants per m2, Typha is usually established with 1.5 - 2 seedlings per m2 . Where there are local reed beds then transplants can be prepared from the existing reed beds; however, methods are quite labour intensive (Flora Locale – reed propagation note). However, in general, transplanting is more cost-intensive than establishment by seed due to the high costs of transplants and increased costs of planting. Seedlings are most commonly planted by hand. Mechanical planting using forestry or vegetable planting machines is possible, but this is often carried out on drained soils, ahead of rewetting and can lead to difficulties in ensuring that the crop is not swamped by dryland weeds before rewetting is complete.

 

Seeding methods using prepared (pelleted) seed, due to the risk of drift, are being developed for Typha. Seeding by water drift is also possible within contained sites, but uniform and even establishment is harder to achieve with water drift than with broadcasting, e.g. from drones, or drilling. Typical sowing rates for reed canary grass are 15 - 25 kg seed per ha often with a row spacing of 12.5 cm.

 

The young plants of most stem biomass crops are particularly vulnerable to grazing or disturbance e.g. deer, geese, wild boar. Hence fencing or other deterrent measures should be implemented.  

 

Crop management

Most stem biomass crops in paludiculture systems currently receive very little management once established. Some nitrogen (N) is continuously replenished by atmospheric deposition (10 – 25 kg N per ha) and further nutrient input occurs laterally through surface and groundwater inflow into the peatland body. If the site has been in agricultural use, then nutrient enrichment in the topsoil ensures a high availability of nitrogen and phosphorus in the first few years after land use change. However, for example, the supply of potassium is more problematic. The biomass yield of Typha and reed increases with higher nutrient availability, with nitrogen in particular being the limiting nutrient. Reed has been shown to have a higher nutrient efficiency and reacts less markedly to reduced nutrient levels than Typha. Even where the supply of nitrogen and phosphorus are sufficient, an unbalanced nutrient ratio has been shown to lead to a decline in yield. In addition, nutrient replenishment from peat mineralisation will slow markedly due to the higher water levels. With a (medium-term) decline in the availability of nitrogen, potassium and phosphorus, reeds can therefore be expected to produce more stable yields in the long term in the absence of additional nutrient supply via water inputs or as fertiliser.

 

Targeted water management can support the supply of nutrients to the crop whilst simultaneously reducing the input of nutrients into downstream water bodies. In particular, nutrient-laden receiving water bodies can be used for irrigation and for additional nutrient supply, provided that the crop can effectively use the nutrients. Especially where sites are being used actively to ‘clean’ water then samples should be taken regularly from both inflows and outflows so that the flow rates and retention times can be optimised and to prevent nutrients from dissolving back out of the soil (if retention times are too long.

 

Water management

Water requirements for in-season irrigation need to be considered carefully as part of the planning process so that appropriate water storage and other infrastructure can be put into place. Irrigation systems have been used widely for field-scale horticulture crops and hence there is a range of materials available to provide guidance e.g. Introduction to irrigation guide for market gardens. Irrigation planning will require consideration of:

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  • Water storage – volumes and sources

  • Site-specific approaches for transferring and applying water

 

Active irrigation by pumping requires an energy source either via the power grid or from a decentralised source (solar, wind energy), together with a monitoring system to determine when and how much water to apply.

 

Harvest

Following an establishment period of 1-3 years, stem biomass crops are usually harvested annually cutting and binding stems, or mowing and chopping biomass before baling for transport and storage.

 

Reed yields range widely 6 - 24 tonnes DM per ha per year when harvested in winter; 3 - 15 tonnes DM per ha per year from summer mowing.

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Harvesting of reed for thatching (known as reed cutting) takes place in winter after leaf fall. This is a traditional industry across the UK and much of northern Europe.  In Germany, Seiga machines from a Danish manufacturer with balloon tyres were primarily used for this purpose, although these are no longer in production. Replicas of this machine are used for reed harvesting in Hungary, Poland and Ukraine – examples of them in operation can be seen online).  Recently, new or converted tracked (caterpillar) vehicles have been used. Loglogic has been the major developer and supplier of machines in the UK over several decades. Reeds can also be harvested by summer mowing in the form of bales. However, summer mowing limits reed regeneration and results in a shift in plant species composition, e.g. towards sedge reeds.

 

Typha biomass yields are similar to those of reed and also vary widely between sites, yields of  4 - 22 tonnes DM per ha per year are typical.

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Cutting and harvesting machines used for reed have been trialled with varying degrees of success as bundles of Typha tend to be conical or pear-shaped compared with parallel reed stems (with a much higher volume near the ground).  Typha biomass can have a high water content (approx. 70 %) and usually needs to be dried (ideally with agitation) before storage. Several approaches to drying have been successful, including a wood chip drying system with solar thermal energy and a trailer drying system using waste heat from a biogas plant. Passive drying is possible with smaller quantities, both in the open air or beneath a roof, or underneath a fleece.

 

A further challenge for mechanised harvesting of Typha is that the seed heads and biomass can be used in different ways. The different parts of the plants may need to be harvested separately or be separated during harvesting or post-harvest processing. For example, for processing into some building materials, leaves and stems need to be harvested in a parallel position. An early first cut of Typha can allow "cob-free" pure leaf mass to be harvested without the pithy stem.

 

Reed canary grass yields are lower than those of the other stem biomass crops usually ranging from 1.5 to 13 tonnes DM per ha per year.

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Pictures 5 and 6: Examples of single-stage harvesting for reed cutting with Seiga and caterpillar technology from Hanze Wetlands on the island of Rügen. Photos: T. Dahms 

Alder

Alder (Alnus glutinosa) and other tree crops e.g. willow

Land preparation

Site selection needs to be made carefully for these long-lived species. Ensure that climate, exposure and site pH are taken into account when selecting appropriate sites for any tree species. The most appropriate construction measures depend heavily on initial conditions (relief, type and condition of any pre-existing vegetation, etc.). Steps are likely to include:

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  • Reprofiling of embankments and dykes

  • Establishment of trackways / additional access roads

  • Creation of water management systems that prevent stagnant water as well as maintenance of high water tables.

 

The site design also needs to take account of requirements for on-going maintenance such as the control of vegetation on embankments, and maintenance of water management infrastructure.

 

Planting

Saplings should be sourced appropriately. Currently little is known about provenance differences but seed from good quality British stands should be preferred within the UK. Planting density is commonly 3,000 - 3,500 saplings per ha with row spacing of 2 x 2 m. Planting designs may create blocks of trees, but may also utilise trees as borders to provide wind breaks or shelter.

 

Depending on the initial site situation, a range of measures may be required to prepare the ground for planting. Mowing of existing vegetation is essential to reduce competition with the young trees. Once trees are established, weed competition is not a major issue. It may be necessary to at least partially open up any existing sward. For small areas, planting with a spade or motorised manual method (one-man earth auger, planting hole drill) is common; for larger areas, planting machines (with integrated tiller, if required) are available but bearing capacity needs to be considered carefully when using machinery designed for forestry (see Adaptation of land management equipment)

 

Crop management

Nutrient supply should be considered carefully. While tree species are less nutrient demanding than stem biomass crops, some nutrient inputs are required. Targeted water management can support the supply of nutrients. Alder is a nitrogen (N)-fixing tree and can supply some additional N to a mixed stand.

 

After 5 - 10 years, thinning will be required. Where the aim is to develop high quality timber, then thinning will target removal of poorly shaped trees and support the development of selected thigh-quality trunks by removing neighbouring trees. It is expect that thinning will take place on 4 – 6 further occasions before a final timber harvest. Accessibility for thinning needs to be considered carefully during the design and due to low soil bearing capacity, it is likely that low intensity methods will need to be used (e.g. cable pulling methods, see harvest information).

 

Water management

Water management should be built into the site design so that appropriate water storage and other infrastructure can be put into place. Few tree species will tolerate stagnant water for any length of time and hence active water management should ensure that flood risk is minimised

 

Harvest

Some tree species will be harvested regularly e.g. willow stems for basketry but where mature timber is the aim then full development will often be attained after 30 - 40 years. In paludiculture system, alder has been estimated to supply 600 – 800 m3 per ha of valuable timber at maturity.

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Selection of a suitable harvesting method for timber on wet sites depends on various site and crop parameters, including groundwater balance, crop size and shape, maximum cutting distances, total cutting volume, average unit mass of the harvested trees and the cutting rate. Logs are almost always cut by hand using a chainsaw. On the most vulnerable sites, or when extracting the very smallest products (like coppice poles) extraction may be carried out using horses. Cable systems are ropeway systems where timber is extracted by means of moving cables, powered by a static tractor- or lorry-powered winch. The timber load can be carried wholly clear of the ground. High lead systems are best suited to small thinnings or shorter extraction distances, and high product density. They have substantial setup time and will require careful planning to ensure that sufficient stacking space is available at roadside.

This information is taken from a translation of the Paludikultur Leitfaden, originally produced in German in 2022.

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With thanks to the Greifswald Moor Centrum and to funding from the Paludiculture Engagement Fund (within the Nature for Climate Fund).

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Pictures 7: Cable crane technology for recovering manually felled logs.

Photo: Peter Röhe.

Wet meadows and pastures

Grassland

Conversion to wet grassland often results in synergies with nature conservation objectives, which means that these systems can also be implemented on, or close to, sites with existing protected status. In many lowland peat regions, this creates the potential for large areas of wet meadows and wet pastures. On-farm conversion to wet meadow or wet pasture is less costly and involves fewer uncertainties compared to conversion to stem biomass or other paludiculture crops. In the short to medium term, there is therefore great potential in switching from drained to wet meadow and wet pasture management.

 

Land preparation

In many circumstances, establishment of wet grassland will occur through succession, i.e. a natural change in vegetation after high water levels have been restored in drained grasslands. Some construction measures may be needed but these will depend on initial conditions (relief, type and condition of any pre-existing vegetation, etc.). Steps are likely to include:

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  • Reprofiling of embankments and dykes

  • If applicable, terracing of undulating terrain

  • Establishment of trackways / additional access roads

  • Water retention: adding dams, weirs and sluices within ditches, possible capping of old drainage pipes.

  • New infrastructure for water management. A range of hydraulic engineering measures may be necessary which may include water storage and increased frequency drainage systems to enable effective sub-surface irrigation.

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The site design also needs to take account of requirements for on-going maintenance of water management infrastructure, together with infrastructure needed for management of livestock in grazed systems. If grazed, issues to consider are:

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  • Fencing with at least double electric fencing that is adapted to wet locations

  • Drinking water supply

  • Livestock shelter to provide protection from the cold and sun

  • Ensure access to a dry part of the area as a retreat, with artificial creation of a paved resting area if required

 

Planting

In drained grassland areas, especially where there a semi-natural wet grasslands nearby, water-tolerant species such as sedges and reed canary grass will establish naturally. Wet meadow species may also be present along ditches and recolonise the wider area from there. The plant population will change following rewetting over the course of a few years. Seeds of wetland-adapted plants can survive in the soil for many years. Many plant species that are adapted to high water levels have buoyant seeds that can enter the area as a result of flooding and ditch damming. However, if there are no local sources of seed, then it may be necessary to transfer mown material from existing wet meadows elsewhere, especially in the case of previously intensively managed drained grassland regions.

 

Where grasslands are being re-established, in predominantly arable areas or intensively managed drained grassland regions, then a range of measures may be required to prepare the seedbed for planting e.g. ploughing, harrowing. However, tillage should ideally be minimised as far as possible, whilst ensuring that plant competition is shifted in favour of the grassland species to be sown. Seed may be drilled directly and wetland pasture mixes can be obtained; some discussion with the seed merchant will be needed to ensure the most appropriate mix for the site is obtained. Bearing capacity will need to be considered carefully when using machinery designed for grassland management (see Adaptation of land management equipment). Alternatively, cut ‘green hay’ materials can be spread over the surface sourced from nearby wet meadows with the intended species composition.

 

Grassland and livestock management

Ongoing management of wet meadows and wet pastures will depend on:

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  • Area size

  • Productivity

  • Accessibility

  • Transport distances

  • Available machinery

  • Stock density

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Some nitrogen (N) is continuously replenished by atmospheric deposition (10 – 25 kg N per ha) and some N-fixing species may be able to be sustained in wet grasslands. Further nutrient input will occur laterally through surface and groundwater inflow into the peatland body. Nutrient release from peat mineralisation will nonetheless slow due to the higher water levels. Hence appropriate management of  potassium, phosphorus as well as other macro- and micronutrients for crop and animal nutrition may be needed, e.g. through targeted supplementary feeding.

 

To establish/maintain a viable sward, mowing may be necessary to maintain grazing quality or weed control. Machinery will need low ground pressure (preferably 100 to 120 g/cm²) to avoid damage to the sward and peat body, see more consideration in Harvest section.

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Extensive grazing of wet and rewetted grasslands has been primarily established as a landscape management measure. Small-framed grazing breeds and water buffalo, which also eat rushes, cattails and reeds, can be considered for (year-round) grazing on wet sites. It may also be possible to establish other alternative grazing systems such as with red deer and geese on wet sites. In order to establish / maintain a robust, tread-resistant sward, it is necessary for grazing systems to be planned carefully. This can be achieved by rotational grazing with a high stocking rate or by a long grazing period.

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Water management

Careful management of drainage to prevent i) prolonged waterlogging and ii) irrigation to prevent drying out of the sites in the growing season need to be considered carefully as part of the planning process so that appropriate water storage and other infrastructure can be put into place. Water management planning will require consideration of:

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  • Water storage – volumes and sources

  • Site-specific approaches for transferring and applying water

 

Active irrigation or drainage by pumping requires an energy source either via the power grid or from a decentralised source (solar, wind energy), together with a monitoring system to determine when and how much water to apply / remove.

 

Harvest

Sedge meadows or mixed wet grasslands can yield 2 - 12 tonnes DM per ha per year.

 

Adapted conventional grassland technology or special (tracked) technology is needed to harvest biomass from rewetted grasslands usually once or twice annually. There is experience of harvesting wet meadows from within landscape management schemes, but this is only designed for maintenance of small areas. Here the focus would be on low contact surface pressure, high area output and optimisation of the logistics chain which will need continued development of harvesting technology for wet meadows. Separation of harvesting and transport vehicles is likely to be needed to achieve the required impact force. Balloon tyres have proven their worth for reed harvesting and have great potential for biomass transport in particular. In pilot projects, converted snow groomers have been used. However, many converted snow groomers are overpowered and have high tare weights. Track-based new technology from various manufacturers is already available, but this has not yet overcome the problem of high tare weight. Use of standard agricultural attachments is possible thanks to front and rear three-point linkages and PTO connections. If it is not possible to dry the crop in the field due to high water levels, fresh biomass, i.e. heavy materials, must be transported to the edge of the field or transfer point in a way that does not damage soil, then dried or preserved away from the field. In the case of downstream drying, this must be carried out using primary energy as efficiently as possible.For multi-stage processes, all the machinery used must be adapted to the soil conditions, e.g. by equipping light balers with a double axle and twin tyres or using caterpillar-based combinations. In the future, advanced autonomous vehicles are likely to be used as part of wet meadow management.

 

The purchase cost of harvesting equipment is a major challenge for farms that aim to rewet grassland without needing to drop water tables to enable harvesting. The estimated costs from European studies suggests costs of around EUR 100,000 to around EUR 450,000 for caterpillar-based harvesting and transport technology. Cooperation with other farmers (e.g. in machinery rings) is therefore more attractive in terms of harvesting costs. The high level of wear and tear on the machinery and auxiliary equipment used must also be taken into account. This is linked to a shortened service life, which for wet surfaces is stated to be approx. 2/3 of the normal service life, resulting in higher lifetime costs for machinery. Harvesting costs of between €52 and €150 per t DM were determined for rewetted grassland biomass in Europe depending on the harvesting and transport technology used, based on a model for calculating labour times for harvesting biomass from paludiculture.

Sphagnum – peat moss

Sphagnum

Inspired by a method developed in Canada where sphagnum vegetation is transferred for restoration of peat extraction sites (so-called 'moss layer transfer technique'), the first pilot area for cultivation of sphagnum was established in 2004 in north-west Germany. Sphagnum is cultivated in order to harvest the biomass and utilise it as a renewable raw material, e.g. for the production of high-quality growing media for horticulture. Sphagnum biomass has a wide range of other potential applications, including as a dressing material, hygiene products (nappies, sanitary towels), as an absorbent material in the event of chemical accidents or as a water filter.

 

Land preparation

Cultivation of sphagnum is particularly suitable for raised bog sites. Drying out of the surface is a major threat to the survival of the establishing Sphagnum and hence active water management systems are usually required. The most appropriate construction measures depend heavily on initial conditions (relief, type and condition of any pre-existing vegetation, etc.). Steps are likely to include:

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  • Removal of any degraded, fertilised topsoil

  • Creation of an even, largely vegetation-free peat surface

  • Establishment of trackways / additional access roads to provide access to the sphagnum beds for maintenance and harvest

  • Water retention: adding dams, weirs and sluices within ditches, possible capping of old drainage pipes.

  • New infrastructure for water management. A range of hydraulic engineering measures may be necessary which may include water storage and increased frequency drainage systems to enable effective surface wetting.

 

The site design also needs to take account of requirements for on-going maintenance such as the control of vegetation on embankments, and maintenance of water management infrastructure.

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Crop establishment

 “Inoculation" i.e. the use of live sphagnum fragments or cuttings is needed to establish new sphagnum crops. However, wild-harvested cuttings are rarely available as active peatland areas are often protected.  The aim of establishment is to form a closed sphagnum turf quickly. Application of 80 m³ of sphagnum cuttings per hectare has proved successful for rapid establishment. Micropropagation of sphagnum has been developed to help meet this demand with a focus on sustainable production (see Beadmoss website). Cultivation of seedstocks also allows selection of targeted provenance, for example, more productive peat moss provenance to reduce the time taken to achieve full groundcover and / or increase yields.

 

Crop management

Sphagnum grows best in comparatively low nutrient, often acidic conditions and can manipulate its environment to further promote these conditions. In agricultural landscapes, input water may need to be filtered to reduce nutrient / basic cation content before it is used for irrigation. The main management needed during cultivation is weed control of vascular plants; this can be through mowing. Use of machinery are limited by the low bearing capacity of the rewetted soils, but also the easily damaged sphagnum plants; in future this may be deliverable by autonomous light equipment carriers

 

Water management

Water management should be built into the site design so that appropriate water storage and other infrastructure can be put into place at the outset. It is likely that field-scale sphagnum cultivation would take place within beds i.e. hydrological units with homogeneous water levels. Active water management in this system would require a network of irrigation ditches / pipes together with installation of automatic pumps including sensors in the irrigation ditches around the sphagnum beds.

Where irrigation was largely provided from surface water then the system would need to be equipped with adjustable culverts and sluices to allow the water level to be raised as the sphagnum grows.  Misting or other surface irrigation systems may also be required.

 

Harvest

Once fully established (1.5 – 3 years) sphagnum beds are harvested every 3 - 5 years. Harvesting takes place when the thickness is optimum for a high value, quality crop and hence will vary from site to site. Expected yield potential is the equivalent of 2 – 8 tonnes DM per hectare per year. The cutting depth will influence the ability and time taken for the moss to regenerate. The world's first mechanical harvest of sphagnum paludiculture was carried out in 2016 using a mowing bucket, which harvested the 10-metre-wide sphagnum beds from a driveway using a long arm excavator.

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The mosses were loaded from the excavator into a tractor-drawn loading trailer (dumper), which stood ready on the driveway and was used to transport the biomass off site for drying and processing .  The driveways were formed from earthen peat and covered a large area; in this system, they continued to be a significant source of greenhouse gas (GHG) emissions. New designs and management approaches to reduce GHG emissions from driveways or to reduce the area of driveway needed per unit of cultivated area are needed for future implementation of sphagnum farming systems. For example, biomass harvesting with track-based machinery is under trial; in the future autonomous light machinery may also be available.

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Pictures 8: Harvesting sphagnum biomass with mowing bucket.

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Pictures 9: Pilot harvesting of sphagnum with a track-based adapted harvesting and collection machine.

Other crops

A range of other crops are being evaluated under wetter farming conditions, for example, celery, blueberry, lettuce. More details about crop establishment and management will be added as they become available.

This information is taken from a translation of the Leitfaden Fur Die Umsetzung Von Paludikultur, originally produced in German in 2022.

Nordt, A., Abel, S., Hirschelmann, S., Lechtape, C. & Neubert, J. (2022) Leitfaden für die Umsetzung von Paludikultur. Greifswald Moor Centrum-Schriftenreihe 05/2022 (Selbstverlag, ISSN 2627–910X), 144 S.

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With thanks to the Greifswald Moor Centrum and to funding from the Paludiculture Engagement Fund (within the Nature for Climate Fund).

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Implementation of paludiculture is currently still very much in the pilot stage. Many farmers are aware of the significant climate impact of their peatlands, but they lack specific practical knowledge for conversion alongside specific economic prospects and commercial exploitation partners. Some pioneering farms are already implementing cultivation at high water levels and paludiculture crops are being further developed and tested in research projects. However, large-scale realisation of paludiculture systems in practice is still in its infancy.

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We therefore expect this guide to grow and develop as farmers and researchers provide new information to update it. If you spot errors or want to add material, please contact us at: paludiculture@niab.com.

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