Cathcart, A., Hawkins, J. & Williams, C. (2023). Envirocrops: Switchgrass Best Practice Guidelines. [online] Envirocrops. Available at: https://envirocrops.com/

DISCLAIMER This Best Practice Guideline has been collated from various sources based on the most current relevant information available. Much of the research carried out on switchgrass has taken place in North America, where switchgrass is a native grass. Some information also exists from European field trials. Throughout this publication, reference is made to a number of pesticides (herbicides, fungicides and insecticides) which have been used either commercially or experimentally in switchgrass production. It should be emphasised that with any pesticide application the relevant legislation (Health and Safety at Work Act 1974; Poisonous Substances in Agriculture Regulations 1984; Food and Environment Protection Act 1985; Control of Pesticides Regulations 1986; Control of Pollution Act 1974; Plant Protection Products (Sustainable Use) Regulations 2012 etc.) and the Product Label Recommendations must be adhered to.

1. INTRODUCTION

1.1. SWITCHGRASS

Switchgrass (Panicum virgatum) is a species of perennial warm-season grass native to North America. Switchgrass stems grow to between 0.5-2.7 m tall with a root system up to 3 m deep. Two ecotypes of switchgrass exist: upland and lowland. The upland ecotype is shorter and finer-stemmed than the lowland ecotype and is more tolerant to both drier and wetter environments. The upland ecotype shows earlier senescence compared to the lowland ecotype.

Switchgrass displays the C4 photosynthetic pathway making it more efficient at biomass production compared to C3 photosynthetic grasses. C4 grasses can produce 2x more biomass per day using relatively little water and nutrients however high light intensity and temperatures are required and an adequate supply of water and nutrients.

Switchgrass can be grown on a wide range of soil types and climates. Biomass yields are expected to be lower than other biomass crops such as Miscanthus and Willow on mineral soils.

Environmental concerns including climate change, along with a global desire to source alternative energy supplies, have led to interest in the cultivation of bio-energy crops. Perennial herbaceous grasses can play an important role in this and can contribute a number of desirable attributes to cropping systems including:

• reducing soil erosion between rivers and streams in arable fields
• improving water quality by filtration
• creating an ideal nesting habitat and shelter for wildlife, including birds and small, ground-dwelling mammals
• absorbing carbon dioxide, and air-borne/soil-borne pollutants
• having lower agricultural chemical and nutrient requirements, and,
• Increasing the organic matter content of the soil.

1.2. GROWTH CYCLE

Switchgrass can be grown from seed; it produces roots up to 3m deep and can spread by rhizome which is approximately 1 cm thick. The plant height ranges from 50 to 270 cm at maturity.

Once established, switchgrass takes 2-4 years to reach maximum yields depending on soil type, climate, and variety. Switchgrass can be cut twice per year however, a single cut after a killing frost is preferred for biomass production as the biomass quality is better and fertiliser requirement is lower.

Yields in the first year are often too low to harvest in northern ranges. When growing for biomass, the crop is established for 15-20 years before reseeding is required; generally due to reduced yield from stand loss. In general, a single harvest in winter is optimal, following a killing frost. A higher yield may be obtained in a two-cut system (summer and winter) however this will increase the cost of harvesting and fertiliser and reduce biomass combustion quality.

As a warm season grass, switchgrass can be outcompeted during early spring growth in cooler climes by weeds. Cutting of weeds above the height of the switchgrass shoots can help with establishment prior to canopy closure.

2. PRE-PLANTING

2.1. SITE SELECTION

2.1.1. SUITABLE SOILS

Switchgrass is easiest to establish on well drained soils with a neutral pH that have previously been used for annual cropping, which reduces weed pressure.

While its native habitat is along streams, establishment and productivity is best in fields with loam or sandy loam soils. Switchgrass will also grow on lower quality acid soils. Application of lime to increase soil pH is an option however it may not be economically viable.

2.1.2. WATER AVAILABILITY

Annual rainfall and soil water retention will influence yield of switchgrass at any site. The grass is generally not found when precipitation is lower than 300 mm per year. Most varieties can tolerate short periods of waterlogging. As a so-called ‘warm season grass’ switchgrass has good tolerance to heat and drought stress.

2.1.3. TEMPERATURE

Switchgrass is native to North America and widely distributed from Canada to the southern states of the US. Ideal growth temperature, and heat and cold tolerance will vary depending on the latitude of origin of the variety. Typically, switchgrass germinates when soil temperatures exceed 15.5°C. Trials in the Netherlands (at 52° North) showed that the varieties with latitude of origin between 36° and 39° provided the highest yield.

2.1.4. SITE ACCESS

Whether ‘green harvesting’ in autumn or ‘brown harvesting’ in late winter/early spring (See Section 5.1), soils can have high water contents. Irrespective of soil type, it is essential that the soil does not get excessively compacted during any harvesting periods as this may limit accessibility for harvesting machinery and cause damage to the soil structure. Hard access is therefore advisable to support the movement of harvesting machinery and harvest material to and from the site.

2.1.5. SUITABLE LAND AREA

The economically suitable land area for planting switchgrass for biomass production can vary depending on a number of factors, including climate, soil conditions, and market demand for biomass.

Switchgrass can be grown on marginal land that is not well-suited for food crop production. In general, it is recommended that at least 4-5 ha of land be used for switchgrass production to achieve economies of scale and make the investment financially viable.

However, the ideal land area for switchgrass production can vary based on local factors such as rainfall patterns, temperature, soil quality, and proximity to markets. In some areas, as little as 2 ha may be sufficient, while in other regions, 40 ha or more may be necessary to achieve optimal yields and economic viability.

It is important to conduct a thorough feasibility study before deciding on the land area to use for switchgrass production. This should include an analysis of local market conditions, input costs, potential yield, and other factors that can affect the profitability of the project.

2.1.6. LOCATION IN THE LANDSCAPE

Depending on the cultivar of switchgrass grown, the height of the crop can be up to 2.7 m. However, most varieties will grow no higher than a crop of maize (~2.0 m). Hence, visually the crop will be very similar to a standard arable crop and will not cause visual impairment to local environments. In fact, switchgrass has a clumping growth tendency and produces dense stands which can be a visually pleasing addition to an environment. What is more, switchgrass is commonly used in landscaping, soil erosion mitigation and wildlife habitat creation (in America) and is regarded as not only an aesthetically pleasing crop but a useful tool. Hence, depending on opinion, the tall perennial grass could improve landscapes.

2.2. VARIETY SELECTION

Most breeding of switchgrass varieties has occurred in North America, as switchgrass was designated as a model herbaceous energy crop by the US Department of Energy in the early 1990s. The Canadian Resource Efficient Agricultural Production (REAP) has also been working on switchgrass since 1991.

2.2.1. VARIETIES

• Alamo: lowland ecotype, tetraploid, 28°
• Blackwell: upland ecotype, octoploid, 37°
• Caddo: upland ecotype, octoploid, 35°
• Cave-in-Rock: intermediate ecotype, octoploid, 38°
• Dacotah: upland ecotype, tetraploid, 46°
• Forestburg: upland ecotype, tetraploid, 44°
• Kanlow: lowland ecotype, tetraploid, 35°
• Pangburn: lowland ecotype, tetraploid, 34°
• Pathfinder: upland ecotype, octoploid, 40°
• REAP 921: upland ecotype, tetraploid, 41°
• Shelter = NY4006: mixed ecotype, octoploid, 40°
• Summer: upland ecotype, tetraploid, 41°
• Trailblazer: upland ecotype, octoploid, 40°

2.3. SITE PREPERATION

Switchgrass should be established as per other forage (whole crop) grass that has small seed and sluggish seedlings. A firm, smooth seedbed should be prepared to:

• reduce moisture loss from the surface
• enable uniform seeding depth
• facilitate moisture movement to the seed, and,
• ensure the best stands develop.

Rolling, both before and after sowing, is highly recommended.

2.3.1. PRE-PLANTING PEST CONTROL

If growing on a site converted from long-term perennial forage, the site must be cleared of perennial weeds in late summer/early autumn of the previous year. Planting switchgrass in cool areas can be problematic as cool-season weeds may germinate first and out-compete switchgrass, resulting in poor establishment.

A contact herbicide (e.g. glyphosate) should be applied in the autumn before sowing (where permitted) and again several weeks prior to spring sowing. It is recommended that a qualified agronomist is consulted for each specific location and soil type.

For grasslands with heavy weed presence the first step before planting is to spray the site with an appropriate translocated (systemic) herbicide (e.g. glyphosate 360 g/l product at 4-5 l/ha) to control perennial weeds. This should be undertaken in early autumn when weeds are still actively growing before soil tilth preparation the following year, when conditions are correct.

If necessary, the translocated herbicide can be re-applied just prior to planting. A translocated (systemic) herbicide (e.g. Glyphosate - 360 g/l product at 3 l/ha) should be applied in early spring. Best practice recommends that approx. 10 days should be left between herbicide application and planting.

Non-chemical methods of pest control include mechanical fallowing to reduce weed seed reserves. This can be followed by planting a winter annual cover-crop in late summer/autumn prior to planting, similar to traditional farming practices.

For cover cropping, in addition to removing top growth of any existing weeds, seedbed preparation should include chopping-up or otherwise disrupting the rhizomes, rootstocks, and other below ground structures of perennial weeds. It is vital to make sure that weed seeds are not germinating just below the surface when the cover crop is planted to prevent competition. The final shallow tillage to finish the seedbed should take place the same day, or just before, planting.

Legumes or Linseed are particularly good cover crops. Whether there is limited nitrogen, or lots of soluble nitrogen, winter cereal ryes are good as they rapidly take up and out-compete weeds for soluble nitrogen.

If leather jackets (soil-dwelling offspring of crane-fly that eat seed) are an issue, insecticidal control is no longer permitted in the UK. Therefore cultural practices to reduce crane-fly populations in the late summer/autumnal period should be encouraged, for example cutting tussocky fields (if necessary) to try and reduce egg laying habitats.

Additionally, encourage bird populations using bird friendly hedges and crop borders in the headlands (to eat the leatherjackets) before planting. Larvae populations can be reduced through stale seedbed practices.

Again, tillage in early spring before planting can disrupt larvae and expose larvae to feeding bird populations. ###2.3.2. SOIL TESTING AND MANAGEMENT Soil testing should always be undertaken before planting. The pH and Soil Nitrogen Supply (SNS), phosphorous (P), potassium (K) and magnesium (Mg) indices should be screened for and can be adjusted during the site preparation stage if needed. There are multiple soil testing companies which can offer services with in-depth soil analysis and reporting. Even ‘field-level’ analyses can be provided to help carry out targeted nutrient application. It is also worthwhile sampling and asking for carbon report status on the soil. This service is offered by most soil testing laboratories. If the carbon testing is repeated after four years, and on termination of the crop, the soil organic matter and carbon content of the soil may be much higher from perennial management than annual crops.

Baseline soil analysis can be used for predictions of nutrient application based on yields, once the switchgrass has been established.

2.3.3. NUTRITION

Some generally suggested guidelines are detailed below but it is strongly recommended that a qualified agronomist is consulted.

The amount of fertiliser to be given to a crop is an important cost decision and should be based on the cost of fertiliser and the expected gain in yield and quality.

Although switchgrass tolerates slightly acidic soil, soils which test below pH 5.5 could be limed to increase availability of phosphorus, potassium, and several micronutrients, however this will incur additional cost.

Heavy rates or split applications of artificial nitrogen to the aftermath growth is not necessary as later in the season, as days get shorter and soil drier, growth response to fertiliser declines.

2.4. PLANTING MATERIAL

Switchgrass is established by seed making it relatively cheap compared to woody biomass established by cuttings (e.g. poplar, willow) and grasses established by rhizome (e.g. miscanthus). Seeds can be drilled using a common cereals seed drill. Seed dormancy may be an issue therefore germination testing of seeds should be carried out prior to planting to determine germination rate which will inform seeding rate. Approximately 100-200 seedlings emerging per m2 should be sufficient for establishment, although in ideal soils (loam, sandy loam) a lower emergence will suffice. Establishment will require between 5-15 kg of seed per hectare depending on variety and conditions.

2.4.1. SEED QUALITY

Seed germination testing should be carried out prior to planting to determine germination rate which will inform seeding rate. A seeding rate of 200-400 is generally recommended.

2.4.2. SEED DORMANCY

Switchgrass seeds display a high level of dormancy. Breaking dormancy ensures a higher level of germination and better establishment. Dormancy can be broken artificially by soaking seeds in water for 1 month at 5-10°C then re-drying in a process called stratification. This method does however run the risk of causing heat damage to seeds during the drying process, and may not be suitable for high quantities of seeds. Dormancy may also be broken naturally by drilling seeds during the winter where cool soil temperatures encourage stratification however there is a risk of switchgrass being out-competed by cool-season weeds. After-ripening is another method in which seeds are stored in a warm environment for several years to break dormancy. When planted into warm soil, over-ripened seeds germinate quickly, helping stands to more easily out-compete warm-season weeds.

3. PLANTING

3.1 PLANTING MACHINERY

Switchgrass can be established in a number of ways: conventional tillage and drill planting, no-till planting into crop stubble or pasture, and frost seeding.

Conventional seeding and drilling:

• When planting in rows, spacing of 80 cm has been shown to produce productive stands with higher yields than those placed more closely.

No-till planting:

• Seeds can be drilled into crop stubble or grass sod during dormancy in winter. Rollers or press wheels should be used to ensure good contact of the seeds with soil.

Frost seeding:

• Frost seeding is where seeds are broadcast spread on the soil surface during early spring freeze-thaw cycle. The freezing and thawing works seeds into the soil. Low temperatures help to bring switchgrass seeds out of dormancy and improves germination rates. Competition from existing perennial grasses can be severe in frost-seeded stands so herbicide treatment of existing vegetation is recommended.

3.2. TIMING

Switchgrass is typically planted in the spring, after the last frosts. The ideal time to plant switchgrass is when soil temperatures have reached around 10-15°C and air temperatures do not drop below freezing. Planting switchgrass too early in the spring, before soil temperatures have warmed up, can result in poor germination rates and slow growth. Similarly, planting too late in the spring can result in reduced yields and delayed establishment.

3.3. PLANTING DENSITY

Planting density depends on the cultivar planted. Additionally, it is worth considering the intended end use of the biomass crop when planting. However, switchgrass is commonly planted at 7-9 kg/ha which corresponds to an approximate seeding rate of 250,000-300,000 seeds/ha. Seeding density can be dependent on site specifics and cultivar. Therefore, the seed supplier should be consulted on the specific seeding rate for the project.

3.4. PLANTING DEPTH

Switchgrass seeds should be planted very shallow between surface soil contact, down to a maximum seed depth of 2 cm depending on the equipment used.

The seed should be sown no deeper than 2 cm; seeding too deep is a common cause of crop failure. A cultipacker seeder provides excellent depth control for seed placement, whilst press drills with depth control attachments also work well. In high rainfall areas, ‘broadcasting’, then harrowing lightly to cover the seed is also an effective seeding method.

3.5 POST-PLANTING PEST CONTROL

Switchgrass has been found to be highly resistant to pests. Invertebrates such as aphids can affect the crop but usually not significantly. Fungal diseases are more common. These guidelines can only point out the known pests to the crop and, as with establishing any new crop, a complete or partial crop failure should be planned for in any financial assumptions.

Aphids and leaf miners can attack switchgrass, and on occasion, significant yield reductions can be caused by the larvae of various insect species (which kill the stems by feeding inside their base). Additionally, stem damage can be associated with double-lobed moths and fruit flies. Grazing by rabbits and slugs can also be problematic, particularly in the establishment year.

Fungal diseases have been reported on switchgrass, although there is no data from the UK to indicate severity. These include:

• rust
• leaf spot
• smut

4. POST-PLANTING ESTABLISHMENT

4.1. NUTRITION AND FERTILISATION

Switchgrass is highly efficient in the use of nutrients especially if harvested late, after nutrients are translocated to the rhizome and roots in preparation for winter. Provided the soil N, P, and K levels are sufficient, fertiliser application in the first year is not recommended as this will only benefit weeds. Following the establishment year, application of fertiliser equal to nutrient removal from harvest is sufficient to maintain optimal yields. Late harvest of the crop is of benefit as shedding of tops and parts of the leaves return nutrients to the soil-surface, although this will reduce biomass yield.

The large, deep root system of switchgrass is highly efficient at scavenging phosphate, and generally no response to phosphate fertilisation is observed.

Nitrogen fixing legumes can be planted with switchgrass to contribute to nitrogen availability. A legume component of at least 30% is recommended to provide sufficient nitrogen. Alternatively, 2-3 tonnes of manure can be applied in the fall prior to planting, and after each harvest. Chemical fertiliser can also be used however, the cost is likely to be prohibitive.

4.2. PRE-EMERGENCE WEED CONTROL

Weeds will compete with switchgrass for light, water and nutrients, and reduce yield. The level of weed interference will depend on the:

• stage of maturity of the crop,
• degree of weed infestation at the site,
• diversity of the weed species (affected by location, season, climate, and previous land use).

The planting process causes soil disturbance which promotes seed germination. Likewise, the low planting densities which are used results in large unoccupied spaces where weed growth can occur.

Weed control is essential in the establishment phase of the crop because the slow initial growth of switchgrass reduces its ability to compete and infestations can severely inhibit the development of the crop. It’s vital that proposed sites should be cleared of perennial weeds before any planting takes place.

Once the full canopy develops, the germination of new weed seedlings is dramatically reduced; only shade tolerant varieties (such as black-bindweed and chickweed) or particularly mature, deep rooted weeds will survive.

Grass can present problems after crop senescence has occurred in the establishment year and should be monitored. Grass weeds can be suppressed by mechanical mowing just above the switchgrass seedlings.

Before the use of any chemical product, growers should refer to the Off-Label Extension of Authorisation for Minor Uses (EAMU) databases provided by local governing bodies and always adhere to the directions for use on the instruction sheet – it is an offence to use products in a manner that has not been approved.

4.3. POST-EMERGENCE WEED CONTROL

Once shoots have emerged, selective herbicides may be used for the control of vigorous annual dicotyledonous weeds. A weed wiper may be used to apply post-emergence round-up to the taller, more persistent weeds such as thistles. Spring cereal broadleaf weed herbicides can generally be used on switchgrass.

Inter-row cultivators can be used for the removal of weeds between rows. Weeds are most susceptible to damage when in their two to four leaf stage so controlling weeds must occur when weeds are young.

From pre-planting to establishment, fields planted in switchgrass should be walked regularly to check for herbivore and leatherjacket damage. Weed populations must be monitored and remedial action taken when necessary.

The surrounding fields should also be monitored on a regular basis to check for the presence of switchgrass volunteers, which can be controlled via two approaches:

• Herbicides used to control grass weeds in cereal crops or,
• Application of a broad spectrum herbicide after the previous crop has been harvested.

Control in pasture is more difficult; cutting and mowing to prevent flowering is possibly the best strategy to prevent flowering and further spread.

There is little experience to quantify the extent to which switchgrass can be expected to spread. However, as a non-native species, constant monitoring outside the crop boundary is advised.

5. HARVESTING

5.1. TIMING

Switchgrass can be harvested following die-back of the above-ground stand in mid-late October. A moisture content of 15% or less is desirable to facilitate quick baling and transport. The optimum time of harvest is generally decided by the weather conditions during the whole winter period. To maximise biomass quality (for combustion) stands can be harvested in early spring, to ensure low nutrient content of the harvested material. The downside to a spring harvest is a reduced yield, up to 40%, however nutrients contained in the dropped biomass will be recycled for the following growing seasons.

The calorific value of biomass increases with decreasing moisture content and harvested biomass with lower moisture content is easier to store. Harvesting switchgrass in wet conditions (regardless of the season) can produce a product with high moisture and leaf content which will be unsuitable for many applications as it will rot. ##5.2. MACHINERY Switchgrass can be harvested with conventional haying equipment

5.2.1 MOWING AND BALING

The crop is typically mown first before being baled.

The crop can be cut with a conditioner mower. Front mowers tend to work better than towed models to prevent the tyres crushing the crop below the pick-up point on the baler (which need to be fairly high to prevent scalping).

There are a number of different types of balers, each producing different bales (e.g. rectangular, round and compact rolls) suitable for different scales of energy combustion. Large rectangular and round balers can produce bales with a dry matter density of between up to 190 kg/m3 and weighing between 250 and 600 kg. These balers generally have a capacity of 1 ha/hr.

Dry switchgrass must be picked up immediately. If left on the ground, there is a danger of soil moisture and dew/rain entering the dry product.

Bales can potentially be left in the field for up to 48 hours but immediate removal for further processing or storage is strongly recommended as it is usually cut in the winter months. Optimum moisture content for storage is <16%.

5.3. QUALITY

To ensure the best quality of product, it is important that switchgrass is harvested at the correct moisture (<16%) and stored in a suitable manner to keep it dry.

If switchgrass is harvested at >16% moisture content, then it should be stored in a dry shed with air flow to allow further drying to a stable moisture content or force dried immediately preferably using a renewable fuel source, rather than fossil fuels.

Any layers of switchgrass cut below 10cm (‘scalping’) which gathers on the ground under the crop over the winter should not be harvested. This clumpy material is generally excessively wet as it is in direct contact with the soil and doesn’t dry easily. The material will also be decaying, mouldy, and will have a high probability of containing soil or small stones (which do not react well to being processed to pellets). Nesting birds and small mammals might also survive below the blades of the machinery.

Inclusion of this material could lead to an increase in both moisture content and ash content. It could also contribute to higher chlorine levels which are undesirable from a combustion viewpoint within the harvested material.

Additionally, nutrients within this leaf layer provide nutrition for succeeding crops. Consequently, mowing height and the height of the baler pick-up should be set to avoid picking up this material.

Additionally, it is important that mown windrows are not raked together as this will gather any decaying leaf material that will have fallen from the plants over the year and through the winter whilst drying.

If it is possible to rotate areas (even in the same fields) and not harvest everything at once, then biodiversity will be protected for future years. This will appeal to environmental delivery projects and those who support nature, but are in no way mandatory if yield and economics are critical.

6. POST-HARVEST

6.1. YIELD

Yields will vary according to age of the crop and environmental factors specific to the site.

Switchgrass takes 2-4 years to establish and reach full potential yield, and can then remain productive for 15-20 years after which its productivity declines. There is limited yield data for switchgrass plantations in the UK. Four switchgrass varieties were grown from 2002 to 2004 by DTI, achieving yields ranging from 7.57 to 12.72 dry tonnes/ha (see table below). It may not be worth harvesting biomass from the first (establishment) year; allowing it to set seed may thicken the crop for the future.

The varieties grown were:

• Cave-in-rock -- 7.57 dry tonnes/ha
• Kanlow -- 9.01 dry tonnes/ha
• Shelter -- 8.60 dry tonnes/ha
• NL93/2 -- 12.72 dry tonnes/ha

6.2. DRYING

Material harvested at high moisture content should be spread to a depth of one to two metres on a drying floor and dried intermittently with heated air, bringing it down to about 12% moisture content over a two-week period. If whole bales are to be dried, then ensure that air can circulate around all sides of every bale to maximise the drying effect and avoid wet spots forming. It may be necessary to turn bales over during drying if this process is not even.

6.3. STORAGE

The best way to retain the quality of the switchgrass product is to treat it like any other biomass material i.e. wheat, barley and oilseed rape straw. To have the driest material possible (which means higher energy value per tonne, and less moisture penalties or possible rejection) it is best retained by being kept undercover immediately after harvest.

6.3.1. STORAGE OF BALES

Once harvested, bales should be stored inside a shed or outside under cover. Baled switchgrass can be stored in a dry shed for significant periods of time.

Outdoor storage during the drier seasons is possible; however, if moisture levels begin to increase in the bales, quality can reduce drastically and rapidly. Covered storage will ensure that bales will continue to dry whereas bales stored without cover will deteriorate particularly if conditions are poor.

When storing bales, remember to consider:

• Security to satisfy insurance requirements
• Accessibility for lorries
• Distance from power lines
• Free draining ground or ideally a concrete or hardcore pad
• Good level site
• Free from holes, ditches, and other obstacles.

6.3.2. BALE DENSITY

Growers should ensure that the bales are baled to the correct density and shape. When baling is in progress it is important to physically check the bales at the start of the operation and monitor them at intervals throughout the day. Good, tight bales should feel hard when kicked and it should prove difficult to get a hand under the strings and lift the string to any distance. It should not be possible to pull the strings off a bale by hand.

Some of the problems of not having the product baled correctly include:

• More broken bales when clearing fields, loading trailers and trucks etc.
• Increased baling cost (as more bales than needed may be produced).
• Excessive bale damage from handling equipment
• Hard to achieve a tidy stack and build to a sufficient height
• Excessive use of indoor storage space
• Increased haulage costs per tonne of material due to inability to achieve maximum allowable transport weight
• Possible rejection at processing site

6.3.3. BALE HANDLING

Having the correct handling attachment on the telescopic handler or loader will ensure ease of operation and enable efficient loading for the haulage company. Haulage companies generally prefer the bales to be loaded lengthways along the vehicle bed. For this to be achieved when loading the vehicle, at least a two-pronged spike should be used, which can handle at least a couple of bales at a time. The more favourable alternative to this is possible, would be a multi-bale grab. This type of loading grab is generally safer and considerably quicker to use. Plan the bale handling well in advance.

6.4. TRANSPORTATION

Transportation of bales will be subject to restrictions on load dimensions and weight. Weights should not exceed a reasonable weight, having regard to the engine capacity, brakes, tyres, and general construction of the vehicle.

If switchgrass is turned into pellets or briquettes then standard HGV Bulker Lorries or tractor trailer units for shorter deliveries can be used. These are often found on farms or supplied locally by a contractor. Square or round bales are the most common forms in which straw materials are traded on fuel markets. Even so, the bulk volume of bales restricts the trading area.

Briquetting, or pelletising, are ways to further reduce bulk volume if the end user requires it and should be costed in.

The bulk volume reduction from round bales to pellets is ten-fold, and hence, the energy investment associated with the mechanical work involved in the compaction processes may be regained in reduced storage and transportation costs to the end user.

In addition, briquettes, and especially pellets, have advantageous bulk properties and can be handled rationally in transport, storage, loading, feeding systems, etc. The superior bulk properties of pellets compared to wafers and briquettes are probably the main reason why pellets dominate the solid bio energy market and have become a commodity, traded world-wide.

6.5. SITE RESTORATION

When a switchgrass plantation has reached end of life the site will need to be restored to either grass or arable production or replanted with new higher yielding varieties. As a non-native species, care will need to be taken to ensure eradication of switchgrass as its rhizomes may persist and spread to neighbouring fields or sites. It is recommended that a qualified agronomist is consulted for each specific location and soil type. Switchgrass can be effectively removed from an existing site by the application of a post-emergence non-selective herbicide such as glyphosate. When mixed with water at a 2% solution, glyphosate can be applied to switchgrass to kill it actively. Adding a non-ionic surfactant may also help the plant absorb the glyphosate more easily. It’s essential to be aware that glyphosate will also kill any other grasses or plants it comes into contact with, so care should be taken to avoid spraying desired vegetation. When used correctly, glyphosate can be an effective tool for controlling switchgrass.

Under no circumstances should the soil below a depth of 3-5 cm be disturbed for a 12-month period as further flushes of shoots from surviving rhizomes will emerge. Shallow ploughing may not bury any surviving rhizomes and they might re-emerge.

The break crop selected in this destruction phase should allow for maximum use of grass control products (such as graminicides). The crop should be allowed to green-up after harvest or topping, and then, before the new green shoots are 20 cm high (Mid - late May), spray with glyphosate (360 g/l product at 5 l/ha).

Broadleaf crops would be the most sensible break crop in this ‘clean up’ year including Beet, oil seed rape and linseed type crops which are resistant to graminicides, for example.

7. ADVANTAGE & DISADVANTAGES

7.1. ADVANTAGES

• Switchgrass is easier to establish than other bio-energy crops (such as miscanthus and willow) although good seedbed preparation and timely weed control is still necessary during the establishment phase
• Establishment by seed makes switchgrass less expensive compared to woody biomass crops such as poplar or willow, and Miscanthus which is also established by rhizome
• As it can be grown on ‘marginal land’ this minimises competition with food crops. It is possible to make use of non-agricultural land or marginal land that is uneconomic for food production
• Switchgrass may be more suitable as a bio-energy crop in areas where soil conditions are not ideal for Miscanthus or willow
• Switchgrass can out-compete Miscanthus on marginal, brown field, and non-agricultural sites
• When grown to be used as a bioenergy crop, sowing and harvesting can be carried out using typical grass equipment, avoiding the need for specialised equipment
• Minimal agricultural chemical and nutrient requirements lead to: -- improved water quality -- less nitrate leaching -- greater biodiversity -- a reduction in soil erosion between rivers and streams in arable fields and, -- an increase in the organic matter content of the soil.
• Growing switchgrass lessens the effect of climate change for two reasons. First, the crop absorbs carbon dioxide from the atmosphere and stores this carbon in the soil; this reduces the build-up of greenhouse gases in the atmosphere. Carbon storage rates for greenhouse gases exceed those of annual crops by as much as 20-30 times. Second, the use of switchgrass as a fuel avoids the need to use fossil fuels. Burning fossil fuels releases carbon dioxide, a greenhouse gas, into the atmosphere and this has been largely responsible for global warming. Burning bio-energy crops also releases carbon dioxide into the atmosphere but this carbon dioxide is reabsorbed by the plant during the following growing season. Some greenhouse gases are released during the production of switchgrass and during its transportation. However, the use of switchgrass as a source of energy results in substantially lower emissions of greenhouse gases compared to the use of fossil fuels

7.2. DISADVANTAGES

• Seeds of switchgrass are generally rather slow to germinate and weed competition can be a problem in the first year
• On normal agricultural land the dry matter yield from switchgrass is expected to be lower than other biomass at approximately 8-9 t/ha
• Lodging (the displacement of stem and roots of plants from their proper and vertical placement) can be problematic in areas which are unsheltered and/or experience high wind. This can result in wet patches during harvest which can reduce the quality of the crop. Most varieties can recover from mild lodging, with Kanlow and Cave-in-Rock varieties reported to have greater resistance to lodging.
• If winter weather leaves the crop too wet or the soils too wet it may not be possible to harvest switchgrass in a timeframe for high productivity. Equally in a varying climate the same could be said of summer crops.
• Switchgrass is a non-native rhizomatous grass species and therefore its ultimate destruction (if that is the aim) post cropping should be given serious thought prior to planting and given due consideration dependant on land use rules.

8. LEGISLATION

There is currently no legislation relating to planting switchgrass. DEFRA classes Reed Canary Grass (another rhizomatous grass with potential for biomass production) as a ‘permanent crop’ which is technically incorrect as it is a grass, rather than a tree, shrub or bush grown from a stem. Like switchgrass it can also be returned to an arable or annual grassland rotation within 12 months.

This may change as Basic Farm Payment is phased out and Environmental Land Management Systems (ELMS) and sustainable Farm incentive (SFI) are introduced.

9. FLOOD MANAGEMENT REGIME

Switchgrass shows some tolerance to flooding (15-30 days), in comparison to annual crops such as wheat, oats, and barley (3-6 days). Reed Canary Grass is more tolerant, able to cope with flooding greater than 49 days. Switchgrass has also demonstrated the ability to germinate in flooded conditions although the emergence rate is halved compared to control conditions. Generally lowland ecotypes are more tolerant than upland ecotypes.