Managing High-Biomass Sorghum 

as a Dedicated Energy Crop
2 2010 | Blade Energy Crops

CONTENTS

ABOUT SORGHUM . . . . . . . . . . . . . . . . . . . . 4

High-biomass characteristics

HYBRIDS AND TRAITS . . . . . . . . . . . . . . . . . . 5

Types and selection considerations

STAND ESTABLISHMENT . . . . . . . . . . . . . . . . 9

Land preparation, weed control, input 

requirements and planting rates

STAND MANAGEMENT . . . . . . . . . . . . . . . . 13

Diseases, pest control and water needs

HARVEST . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Timing, common methods and biomass moisture 

GOVERNMENT INCENTIVES . . . . . . . . . . . . . 17

Biomass Crop Assistance Program (BCAP)
Managing High-Biomass Sorghum | 2010 3

FOREWORD

This guide was developed to provide agricultural producers and biomass procurers with the most 

current information on the establishment, management and harvest of high-biomass sorghum as a 

dedicated energy crop for biopower and biofuels. While sorghum has been widely planted for grain and 

forage production, and even syrup, its use as a biomass crop is still evolving.

Due to the broad geographical range and environments where sorghum can be planted for bioenergy, 

we will address more general recommendations as well as considerations unique to managing highbiomass sorghum types as a raw material for power generation and cellulosic biofuels. Management 

practices for the use of sweet sorghum as an energy crop will be discussed separately in a future guide.

In preparing this publication, we have drawn from our collective experience with sorghum as well 

as our collaborative partners at Texas AgriLife of the Texas A&M University System, among others. 

Because we foresee upcoming innovations in genetics, seed technology and farm equipment – as well 

as developments in the biomass markets – we expect to update this guide frequently, as these forces 

necessitate changes to crop management practices.

Blade has established the largest trial network of energy crops in 

the world, including leading universities and institutes. 
4 2010 | Blade Energy Crops

GS I High Biomass Sorghum

GS I

Grain and Forage Sorghum

GS II

Grain and Forage Sorghum

GS III

High Biomass Sorghum

GS II

first leaf

third leaf

leaf sheath

seed

flag leaf

flag leaf

sheath

leaf 

blade

head

peduncle

second leaf

leaf collar

SORGHUM AS A DEDICATED ENERGY CROP

As a quick-growing annual, high-biomass sorghum fits well into the mix of dedicated energy crops. It 

adds flexibility to feedstock production and can be rotated as part of an annual cropping system using 

existing production equipment.

Like other energy grasses, sorghum uses water and other inputs very efficiently, and thus tends to 

perform well on lands or in conditions considered marginal for other crops. And unlike perennial energy 

grasses, which are generally not harvested during the first season, sorghum has robust establishment 

characteristics and can produce high yields of biomass in as few as 90 to 100 days in many areas.

Agronomic practices for growing sorghum as a forage or grain crop are relatively well defined—and 

many of these practices can be employed when planting and establishing high-biomass sorghum—

however, managing sorghum as a bioenergy crop requires distinct considerations:

• Availability: Extension of the harvest/supply window—through the use of single harvest, multicut harvests and staggered plantings—minimizes storage requirements for bioenergy facilities, 

which need year-round supplies.

• Moisture content: Optimal feedstock moisture content ranges will vary according to bioenergy 

conversion technologies and storage systems.

• Biomass composition and quality: Relative amounts of carbohydrates, compounds including 

ash or sulfur and debris collected during harvest will likely impact the quality of biomass.

GROWTH STAGES

Sorghum development is typically divided into three growth stages (GS): GS I, GS II and GS III. GS I refers to the vegetative stage 

between emergence and initiation of the reproductive stage, and is characterized by the development of structures such as leaves 

and tillers. GS II refers to the plant’s reproductive phase, which includes panicle initiation, booting and heading. GS III refers to the 

grain-filling stage, beginning with flowering and continuing through grain development and final maturity. 

Due to photoperiod sensitivity or long maturities, many high-biomass sorghums reach GS II very late in the season, if at all. Most 

never complete the GS III stage.
Managing High-Biomass Sorghum | 2010 5

HIGH-BIOMASS CHARACTERISTICS

High-biomass sorghums are typically late or nonheading, photoperiod-sensitive (delayed flowering) hybrids. 

They are similar to forage types, but with greatly enhanced biomass yield potential. When planted in 

nontropical latitudes and during periods with appropriate day length, high-biomass types are highly 

productive and can reach upwards of 20 feet in height under favorable conditions. This is 

due to the plant’s prolonged vegetative growth stage. (See Growth Stages sidebar.)

Growth stage I (GS I) lengths for these types of sorghums vary greatly from 

typical grain sorghums. Many high-biomass hybrids are able to grow 

continually for more than 200 days in southern areas such as Texas. By 

comparison, a typical grain sorghum plant remains relatively small and 

completes its lifecycle in 60 to 90 days. 

Many of the photoperiod-sensitive sorghums grown in North America 

today have photoperiod triggers of about 12 hours and 20 minutes of 

daylight, meaning that a day length of 12 hours and 20 minutes or less 

is required to induce flowering. As such, these sorghums should be sown 

after daylight hours exceed this duration. For most areas of North America, 

this dictates an early April planting date – or later, depending on the specific 

latitude. Planting before the day length has reached a sufficient photoperiod will trigger early 

flowering, premature crop “cutout,” and result in a very low biomass yield. For varieties that ratoon (regrow) 

well, this issue can be mitigated by a cut and subsequent regrowth during a period of appropriate day length. 

Due to photoperiod sensitivity, high-biomass hybrids generally do not produce grain heads until very late 

in the season, if at all. Therefore, if provided sufficient inputs, they continue growing and producing more 

biomass (i.e., stems, stalks and leaves) until the fall, when shorter day lengths trigger flowering, or plants 

experience the first killing frost. 

(Note: Since high-biomass sorghum hybrids were selected for bioenergy production, and not for 

consumption by livestock, they may not have the same nutritive value as forage types. Contact your local 

cooperative extension agent or veterinarian prior to feeding to ensure the fitness of biomass as a feedstuff 

for a particular livestock species.)

HYBRID TYPES

Producers have a number of different hybrid types and traits to choose from: 

Sorghum x sorghum – These hybrids result from the cross of two sorghum parents. They show the 

highest biomass yield potential and represent the latest in high-biomass plant breeding and trait 

development. Sorghum x sorghum hybrids are designed for single-harvest production systems that 

endeavor to maximize per-acre yields while minimizing crop input and management expenditures. 

Moreover, currently available hybrids were generally not selected for ratooning, and are therefore not suited 

to multi-cut harvest systems. Two of the newest hybrids in this class are ES 5200 and ES 5201, from Blade. 

ES 5200 and ES 5201 

from Blade should 

be planted after day 

lengths exceed 12 hours 

and 20 minutes — early 

April in most latitudes 

of North America.
6 2010 | Blade Energy Crops

Sorghum x sudangrass hybrids – Sorghum x sudangrass hybrids result from the cross of a grain 

sorghum female parent and a sudangrass male parent. These hybrids have been used for many years in 

the livestock industry for grazing and hay production, but also have application in bioenergy, since their 

finer stems and enhanced ratooning quality allows for multiple cuts throughout the season. For end-use 

processes requiring dry biomass material, the thinner stems of these hybrids have been shown to dry 

down more easily than sorghum x sorghum hybrids. ES 5140 and ES 5150, available from Blade, are two 

sorghum x sudan hybrids suited to bioenergy production.

Sudangrass – Although not a sorghum, sudangrass has been proposed as a potential biomass source, 

and has historically been used in forage and hay operations alongside forage sorghums. The very thin 

stems of sudangrasses lend to easy drydown and baling. Straight sudans also tend to ratoon well and 

can be cut for biomass throughout the season. However, most sudangrasses have been developed for 

feed applications and tend to have quite low biomass yields when compared to high-biomass sorghums. 

For this reason, pure sudangrass varieties are not generally recommended for bioenergy production.

HYBRID SELECTION CONSIDERATIONS

As with other crops, appropriate hybrid selection is one of the most important elements of successful 

sorghum biomass production. Key considerations for evaluating sorghums include adaptation, 

maturity, harvest timing, 

drydown ability and end-use 

requirements.

Adaptation – While biomass 

sorghums are generally 

broadly adapted, it is essential 

that a given hybrid has 

appropriate tolerances to 

disease, temperature, soil conditions and other environmental factors likely present at your planting 

site. Choosing an ill-adapted hybrid may result in a substantial reduction in performance and yield.

Thick-stemmed hybrids (right) offer comparative yield advantages and other assets. 

They can benefit from stem-crushing harvest systems to speed drydown.
Managing High-Biomass Sorghum | 2010 7

Maturity – Sorghum maturity can be regulated by photoperiod (day length), as described previously, 

or thermal time (heat units). Thermal-time regulated hybrids will reach maturity following exposure to 

a specified accumulation of heat units, as calculated by average daytime and nighttime temperatures. 

Hybrids that are regulated entirely by thermal time are referred to as photoperiod insensitive. Many 

sorghum hybrids have a combination of maturity-determining mechanisms, and are regulated to 

varying degrees by both thermal time and by photoperiod.

Harvest timing – Selecting hybrids according to their appropriate harvest time is the key to influencing 

both biomass availability and quality. 

• For once-over harvest systems, full-season hybrids that maximize biomass production are preferred. 

• For multi-cut harvest systems, hybrids that show strong ratooning ability should be selected. 

Note that hybrids intended for single-cut systems should not be used for multi-cut systems 

unless regrowth potential is specified in the product description.

Producers may consider using a combination of sorghum maturity types to extend the supply window 

for a particular bioenergy process.

• Harvest can be extended by planting blocks of photoperiod-insensitive hybrids (such as ES 

5140 and ES 5150) early in the season, followed by blocks of photoperiod-sensitive varieties 

(such as ES 5200 and ES 5201) later in the season. 

• Staggered planting, as part of a rotation with other crops, is another method to optimize 

biomass supply.

Drydown ability – Full-season maturities maximize biomass production potential. However, they also 

increase the likelihood that sorghum biomass will be green at harvest time. Moisture content and levels 

of extractives (e.g., starch and sugars) in the harvested biomass can be higher later-maturing varieties 

than in lower-yielding and typically earlier maturing hybrids that senesce (dry) before harvest. Longer 

maturity times also tend to produce a crop with larger and thicker stems that may require different 

drydown steps. (See Harvest section.)
8 2010 | Blade Energy Crops

Selecting sorghum varieties that will flower and mature in your region prior to harvest time can help 

lower the moisture content of the biomass. This benefit comes at a cost, however. Flowering, production 

of grain and crop senescence before the end of the growing season will potentially reduce total biomass 

yield, as well as alter the compositional makeup of the biomass harvested. 

If delaying harvest for drydown purposes, it is important to note that newer sorghum x sorghum 

hybrids have been bred for late-season standability. In contrast, many forage sorghums used historically 

for biomass production were developed for harvest earlier in their growth cycles — a trait that may lead 

to a greater risk of lodging with later harvest dates. 

Biomass composition and quality – Distinct compositional differences among sorghum varieties 

influence the efficiency by which sorghum biomass is converted to biofuel or biopower. This is an area 

of intense study, and significant improvements are expected as “lock-and-key” systems are developed 

between customized seed varieties and bioenergy conversion processes.

TRAITS

Several traits exist for biomass sorghums that can influence hybrid selection.

High-biomass traits – The latest high-biomass hybrids offer growers a new trait named Skyscraper, 

which provides a significant boost to overall biomass yield potential. Since it was developed through 

genomics-based plant breeding, there are no additional stewardship requirements. Hybrids ES 5200 and 

5201 both feature the Skyscraper trait. 

Brown midrib traits – Many forage sorghums in use today contain traits for 

altered lignin, a tough, fibrous compound that plants use to build their cell 

walls. Referred to as brown midrib (BMR), for the characteristic brown 

color in the plant’s leaf ribs and the pith of the stalk, this trait has 

been shown to improve the digestibility of feed. Biofuel process 

developers have speculated that BMR traits may be similarly 

beneficial to conversion processes that employ enzymes to break 

down and convert biomass to liquid fuels. However, current 

research shows that lignin content and enzymatic digestibility 

are not necessarily linked. Furthermore, sorghums with BMR traits 

tend to have a higher risk of lodging due to weakened cell walls, 

which leads to reduced yield—particularly under adverse weather 

conditions. Additional research is necessary to determine if the brown 

midrib trait conveys enough added value to offset its potential for harvest 

losses due to lodging.

Biotech traits – Currently, there are no commercially available sorghum hybrids with traits developed 

through biotechnology. However, greater resources have been applied to improving sorghum, and 

rapid advances are expected. Initial advances will be realized through marker-assisted plant breeding, 

where important characteristics are tracked at the DNA level. Biotech traits are expected to follow soon after. 
Managing High-Biomass Sorghum | 2010 9

SEED TREATMENTS

 A wide range of seed treatments are marketed to bolster 

performance and stand establishment. Maxim and Apron are 

newer fungicides; longstanding options include the fungicide 

Captan and Lorsban, an insecticide. Systemic seed treatments 

that protect sorghum from certain insects during establishment 

and herbicide safeners, which allow a wider range of preplant 

herbicides to be used, are also available. 

Many of these products are standard treatments provided 

when seed is commercially prepared and sold, while others are 

provided upon request. Consult your seed supplier about available 

treatments, and always follow the manufacturer’s directions. 

STAND ESTABLISHMENT

Successful stand establishment involves several critical considerations. As discussed previously, the 

agronomic practices required vary greatly by region, local cultural practices, equipment and existing 

cropping systems. While the following guidance will help with general planting requirements, 

consultation with an agronomist or crop consultant who has location-relevant expertise is critical for 

successful stand establishment and maximum biomass production potential.

Location selection – Sorghum is relatively drought tolerant compared to many other row crops, and 

performs well on a wide range of soils, from clay to sandy types. It prefers well-drained soils, as excessive 

moisture or waterlogging leads to reduced germination or plant death. Sorghum also fares best in 

deeper soils that support its extensive root system.

Land preparation – Land preparation options vary greatly by location, 

condition of the field and equipment available. For conservation purposes, 

the following tillage practices are recommended for high-biomass 

sorghum, when appropriate:

• No till (on suitable soils)

• Strip till

• Conservation tillage

Conventional tillage should be carefully considered for bioenergy 

crops. Excessive tillage can result in topsoil erosion, additional weed 

pressure and the release of greenhouse gases. 

Agronomists generally advise that high-biomass hybrids be planted 

on a 20-inch or 30-inch row spacing to maintain compatibility with most 

production systems. Narrower row spacing is being evaluated, since denser stubble 

tends to keep windrowed biomass off the ground. This may facilitate drying and reduce ash content 

Common Seed Treatments 

for Sorghum

 Captan – Fungicide

 Lorsban® – Insecticide

 Maxim® – Fungicide

 Apron® – Fungicide

 Concep® – Herbicide safener

 Poncho® – Systemic insecticide

20-inch or 30-inch 

row spacings are 

most commonly used 

for bioenergy crop 

production. 
10 2010 | Blade Energy Crops

of the harvested biomass. It is important to note that optimal row 

and plant spacing is dependent upon both plant variety and the 

agronomic systems employed. Regardless of the preparation 

techniques, good seed spacing (singulation) and seed-to-soil 

contact are essential.

Weed control – Herbicide options for establishing and managing 

sorghum are somewhat limited compared to other crops. Thus, it is 

essential to eliminate or reduce weed pressure before planting. If sown 

into weed-free soil under good conditions, high-biomass sorghum hybrids 

will typically outcompete most weeds because of their rapid germination 

and growth. Excessive weed pressure can create stand-establishment problems and 

subsequently reduce final biomass yield. Controlling weeds as early as possible can help soil retain fertility 

and moisture, an important factor in water-constrained areas. 

The optimal weed management program for a given location must factor in planting history, previous 

crop rotations, soil type and climate conditions. While weed pressures can potentially be managed 

through repeated tillage prior to planting, consideration should be given to reducing soil erosion and 

input costs associated with land preparation, as well as potential bioenergy qualification requirements.

If sowing into fallow cropland, or if weed pressures are expected to be high, one or several preplant 

burndowns, using a broad-spectrum herbicide, should be considered.

A few examples of herbicides labeled for sorghum include Bicep, Dual and Expert. Always check with 

your local extension agent or the herbicide manufacturer before use. Care must be taken during 

herbicide application to prevent damage to the crop. 

Agronomists often recommend the use of pre-emergent herbicides during planting and establishment, 

as the pre-emergent herbicide provides a window of opportunity for sorghums to grow in a period of 

reduced weed pressure. Consult an agronomist or crop consultant to determine whether a seed safener is 

necessary for your intended herbicide program.

One example week management strategy that has been effective for many growers establishing forage 

sorghum involves a preplanting weed burndown using a glyphosate-based herbicide. Seed is then 

treated with an appropriate seed safener before planting, followed by a pre-emergent application of 

atrazine and s-metalochlor herbicides.

With regard to labeled herbicide and pesticide use, sorghum grown for bioenergy is generally 

considered the same as sorghum grown for forage, although some ambiguity still exists. Always consult 

your local extension office for optimal herbicide application regimes for sorghum in your area. Always 

read and follow all label directions for herbicides. 

Rotation – As with all crops, growing multiple crops of sorghum back to back in the same location 

is not recommended due to crop-specific nutrient depletion and the buildup of disease and pest 

pressures. Sorghum crops should be rotated with alternate winter crops and/or summer crops to 

Reducing or 

eliminating 

weed pressure 

before planting 

is essential.
Managing High-Biomass Sorghum | 2010 11

mitigate these risks. Several good choices for rotation exist (including soybean, cotton and corn), 

depending on your geographic location.

Nutrient requirements – Removal of green plant material depletes nitrogen (N), phosphate (P) and 

potassium (K). Soils should be tested for pH, P, K and N before planting, and pH should be adjusted to 

between 6.0 and 6.5, if possible. 

A typical fertilizer starting recommendation for a sorghum crop is 120 pounds of N, 65 pounds of P2

05

and 120 pounds of K2O. Required levels for these nutrients vary by soil type and local environmental 

conditions. Consultation with an agronomist or crop consultant familiar with the biomass production area 

will be important. If deficiencies of P and K exist, these nutrients can be applied to the soil before planting. 

Nitrogen deficiency is the most common soil issue faced by growers who produce sorghum for biomass 

yield. A standard recommendation frequently cited for biomass production is 10 pounds of nitrogen 

per dry ton of biomass removed. The optimal rate is highly influenced by sorghum variety, environment 

and management practices. For example, sorghum yields in good soils under favorable conditions have 

shown high performance with nitrogen application rates of less than 10 pounds per dry ton of material 

removed per acre. Conversely, sandy soils and/or fields that receive excessive rainfall early in the season 

can exhibit diminished levels of available nitrogen, regardless of initial application rate. This results in 

an apparent increase in the nitrogen needs per unit ton of biomass harvested. Other examples include 

the use of leafier forage sorghums or multi-cut systems, where the removal of higher leaf-to-stem ratio 

material can increase the nitrogen removed from the fields, resulting in nitrogen requirements reported 

to exceed 15 pounds per ton. 
12 2010 | Blade Energy Crops

(Note: Nitrogen recommendations for sorghum silage production range from 10 to 20 pounds of 

nitrogen per ton of dry matter removed. High biomass sorghums are not developed or evaluated for 

their feed value. They are grown on lower nitrogen input levels per ton of biomass harvested than have 

typically been used for sorghum in forage applications. Further research is being conducted in this area.)

Planting time – Sorghum seed germination requires a minimum soil temperature of 60°F – 65°F 

(16°C – 18°C). Optimal soil temperatures for germination and growth are between 70 and 75°F (21 

to 74°C). Planting should commence only after any risk of freezing temperatures has passed, as 

sorghums are highly frost sensitive. 

Photoperiod-sensitive hybrids should be planted after day lengths exceed 12 hours and 20 minutes. 

Planting before the day length has reached a sufficient photoperiod will trigger early flowering and 

premature crop cutout, resulting in a very low biomass yield. 

Planting method – Energy sorghum is generally planted in rows, using either a row-crop planter or 

a conventional or no-till drill. Planters should be equipped with press wheels for good singulation 

and seed-to-soil contact. It is important to note that average sorghum seed sizes are in the 16,000- to 

18,000-seed-per-pound range. However, sorghums can have seed as large as 12,000 seeds per pound, 

and as small as 35,000 seeds per pound. 

A proper match between planting equipment (plates and/or air settings) 

and seed size is important for successful stand establishment. Preferred 

planting depth is typically 3⁄4 to 11⁄4 inches for heaver to medium 

soils. Lighter, sandy soils permit planting to depths of up to 2 

inches (5 cm). Planting into moisture is encouraged, and care 

must be taken to ensure enough moisture is present to allow 

for imbibition (absorption of water), germination and growth. 

Sufficient moisture reduces the risk of stand failure due to drying 

out and subsequent seed/seedling death. Avoid soil crusting and 

planter disk opener sidewall compaction, since both can reduce the 

plant’s ability to emerge.

Seeding rate – Experience has shown that sorghum biomass yields 

vary across a range of seeding rates, and yield potential can be maximized 

with optimum plant density. The average seeding rate for sorghum grown for biomass 

Purchasing seed by count rather than by weight 

will help growers avoid overbuying to cover 

variations among seed varieties and lots.
Managing High-Biomass Sorghum | 2010 13

is 100,000 seeds per acre. Seeding rates influence space availability for plants to grow and directly 

influence stem thickness and ratooning properties. 

Seeding rates in locations with better resource availability can be higher as the inputs are more likely to 

support the stand. Planting density can be as high as 120,000 seeds per acre or as low as 75,000 seeds 

per acre, depending on input and management scenarios. 

Irrigation during establishment – Sorghum is generally a drought-tolerant crop traditionally grown 

in hot, dry conditions. However, the crop is most vulnerable to drought stress during establishment. 

Limited irrigation at this time can be useful to ensure good stand establishment and improve 

flexibility in planting time, if sufficient moisture is not available through rainfall. 

STAND MANAGEMENT

Insect pests and diseases – 

Sorghum can be affected by 

a number of different insect 

pests throughout its life cycle. 

Insect pressure depends on 

location, weather and the 

growth stage of the crop. 

Common examples of pests that 

can severely damage a sorghum 

crop include cutworms on seedlings, nematodes on roots, greenbugs or fall armyworm on leaves and 

panicles and sugarcane borers in the stalks. 

Sorghum may also be affected by a number of diseases that are geographically and managementsystem dependent. Examples include anthracnose, downy mildew and Fusarium. Sorghum diseases 

commonly encountered in a given growing location should be identified prior to planting so that 

appropriate management practices can be employed.

Several standard agricultural practices exist for mitigating disease and insect pressures in a sorghum 

crop, including seed treatments, crop rotation and the application of crop protection products. 

Consult your local agronomist, crop consultant or extension service before planting for information on 

mitigating pest and disease risks in your area.

Rainfall, irrigation and yield – Sorghum typically does not require irrigation in most environments. 

However, there is a strong correlation between water availability and yield. Sorghum will do best in areas 

with at least 30 inches of rainfall per year. While sufficient soil moisture is critical at establishment and in 

the early stages of growth, overall water use by the crop is low in the early stages of development. 

Water use increases later in the crop cycle, as the sorghum enters its rapid, or logarithmic, growth phase 

—typically 80 to 90 days after emergence. This is the time when substantial biomass accumulation occurs. 

Water needs taper off substantially when the plant initiates its reproductive phase (GS II) as biomass 

accumulation declines rapidly and eventually stops. 

Fungal diseases can limit biomass yields. The impact on conversion has 

yet to be determined. 
14 2010 | Blade Energy Crops

During periods of drought, well-established sorghum stands 

tend to enter a dormant phase while waiting for additional 

moisture. Once conditions improve, the sorghum stand will 

rapidly recover and continue growing. However, prolonged 

periods of drought can adversely affect sorghum yields. In 

periods of prolonged drought, supplemental irrigation—

even in small amounts—may minimize crop loss and 

maintain high yield potential. 

HARVEST

Harvest timing is dependent on when biomass is needed, 

variety type, season length, time of planting and desired 

moisture parameters. Several options exist for harvesting 

sorghum using currently available equipment. While many 

of the high-biomass sorghum hybrids favor a single cut in 

the later stages of the season to achieve maximum biomass 

production, hybrids specifically developed with ratooning 

qualities may be cut repeatedly throughout the season to 

ensure continuous biomass supply. 

The issue of harvest frequency and timing for dedicated 

energy crops depends on the agronomic system used to 

deliver the most continuous supply of biomass possible to a 

biorefinery or biopower facility. Thus, management practices 

must be optimized to achieve maximum sustainable yields, 

while recognizing the needs of end users at the biorefinery or 

biopower facility.

Common harvest methods – The two most common 

methods for harvesting sorghums for biomass are 1) swathing 

followed by baling or chopping of windrows, and 2) direct 

forage chopping of the standing crop. A key consideration 

in choosing between the two methods is the optimum final 

moisture content of biomass for the desired end use, as well as 

what level of subsequent drying is needed to achieve it. 

Arguably, the most convenient method for harvesting 

sorghum is to direct chop the standing material into a truck as 

it passes through the field. This method minimizes dirt in the 

harvested material. However, it also requires rapid processing 

of the harvested biomass because the sugars present in the 

freshly chopped material will contribute to its degradation.

Top: Existing equipment is capable 

of harvesting high-biomass types. 

However, equipment manufacturers are 

studying optimizations. Middle: Swather 

systems with built-in single or double 

conditioning systems have been used 

successfully. Photo courtesy of Dave 

Jordan, MacDon, Inc. Bottom: Large, 

square bales are a storage option when 

moisture content is below 20%. Photo 

courtesy of Brian Olander, AGCO.
Managing High-Biomass Sorghum | 2010 15

Using a swather to cut and windrow for later pickup is another way to harvest and dry sorghum for 

biomass. This method also allows the biomass to be field dried before final pickup, when drier material 

is required or field storage is preferred. 

While existing swather technology is able to handle the harvest of biomass sorghums, several wellknown companies are developing customized swather technology that can more efficiently handle 

the higher yields associated with biomass sorghums. Once ready for pickup, the windrow can be 

baled directly or run through a forage chopper and put into a trailer. Care should be taken to avoid 

picking up soil when collecting the windrow, as excess dirt can have a negative effect on biomass 

quality and end-use processes.

Lodging – Like many crops, high-biomass sorghum can experience lodging. Sorghum’s susceptibility 

to lodging may increase at later stages of its growth cycle, particularly in locations prone to high wind 

or heavy rain. In many cases, the large amount of material produced in a given field results in the crop 

leaning against itself, rather than completely falling over. 

Despite some of these challenges, it is usually possible to get beneath the crop and successfully harvest 

the material. Certain types of harvesting heads are known to be more successful in collecting lodged 

crops. While optimal harvest time for sorghum in the Southeastern U.S. is typically July through October, 

high-biomass sorghum has been harvested from stands in North America as late as March, despite the 

lodging issues associated with the crop at that time of year. It is important to note that soil contact 

during lodging can increase grit and potentially reduce biomass quality.
16 2010 | Blade Energy Crops

Managing moisture – Sorghum’s moisture content at harvest can be as high as 80%, and is directly 

related to hybrid variety, growing conditions, harvest timing and harvest method. However, with proper 

management, and in the right environment, moisture can be reduced to the maximum 15 to 20% range 

required for baling. When moisture content is immaterial to the end-use, then forage chopping is likely 

the most convenient means of harvest. 

When end uses (storage, handling or conversion processes) require dry biomass, several techniques can 

be used to enhance drydown of the material. 

In some environments, sorghum stands can be left in the field to allow natural senescing or exposure to 

a killing frost, which will also aid drying. 

Research is under way to determine if broad-spectrum herbicides can be applied to the stand to 

terminate growth and encourage drydown in advance of desired harvest time. This method would 

be best suited for situations where a harvest time is desired before field senescence can occur, or 

the length of the season prohibits waiting. Early results of this research are encouraging. However, 

regardless of the preharvest drying method used, it is important to note that later harvests increase the 

likelihood of complications caused by lodging.

Following preharvest drying, motorized swather systems with built-in single or double conditioning 

systems can break apart the stalks and allow further field drying in windrows. Additional drying can be 

achieved through the use of raking or tedder systems to turn or spread out the windrow and allow sun 

Moisture content at harvest can be as high as 80%. However, with proper management, levels can be reduced to the 15-20% range for 

bioenergy uses requiring drier biomass.
Managing High-Biomass Sorghum | 2010 17

and wind to evenly reduce moisture content. Moisture contents below 

10% have been achieved with these methods, though the minimum 

achievable moisture is highly dependent on relative moisture (rain 

and humidity) in the production area. For example, 30 – 40% 

moisture content would be typical in the high rain and humidity of 

the Southeast U.S. Achievable moisture levels will vary significantly 

based on harvest time and weather conditions during the drying 

process. Adverse weather conditions, such as rain during the 

drying process, will also reduce overall biomass yields because the 

extractives present in the biomass will be washed out as the material 

lies in the field. Bales stored in the field may also see weathering 

effects, such as the loss of extractives, depending on how they are stored.

Stubble height – For multi-cut hybrids, a stubble height of 4 to 6 inches 

(10 to 15 cm) is generally recommended to promote regrowth.  A clean 

cut can be equally or even more important than stubble height. Cutting 

too quickly (ground speed) or using a dull cutting mechanism (e.g., 

rotating blade or sickle) can shatter the base of the stalk, resulting in greater open area for disease 

entry, drying out from ambient temperature and other damage. Be especially careful of ground speed 

in stands with heavier stalks.

Storage – Although just-in-time harvest and delivery to a biorefinery is preferred, there are very few 

locations where this will be feasible year round. 

Storage of biomass will be necessary for two reasons: 1) to provide for year round operation, and 2) to 

ensure operation during inclement times (when using just-in-time harvest). 

Several different storage options are being developed by equipment manufacturers and university 

programs such as Texas AgriLife Research (Texas A&M System). 

One option is large, square bales, which can be used when moisture content is below 20% (some 

research has shown that moisture levels approaching 40% may be acceptable). Note that higher 

moisture content, depending on the conversion technology, may not be as concerning as it is for 

hay because forage quality may not be as important. Storage of biomass at elevated moisture 

levels should only be undertaken with suitable facilities and equipment to prevent overheating and 

spontaneous combustion. 

Large, round bales are also a possibility. However, they are less efficient to transport and store. 

Another option under evaluation is using the cotton module builder to receive cured, chopped 

sorghum in module form.

Lastly, ensiling processes are also being considered. 

Windrowed sorghum is blown directly into a 

semitrailer for immediate shipment to a nearby 

power generation facility, which co-fires the 

sorghum biomass for electricity production.
18 2010 | Blade Energy Crops

GOVERNMENT INCENTIVES

The U.S. departments of energy and agriculture as well as many state governments are supporting 

demonstration and commercial-scale activities for energy crops. The 2008 Farm Bill contains a program 

known as the Biomass Crop Assistance Program (BCAP) to help growers seeking experience with 

nonfood, low-carbon crops, such as high-biomass sorghum. 

The first phase of the program provides dollar-for-dollar matching payments for collection, harvest, 

storage and transportation of qualified biomass, up to $45 per dry ton. More than 400 facilities have 

qualified for the program to date. Phase 2 of the BCAP program will support the establishment and 

production of certain biomass crops for conversion to bioenergy. Final rules and funding for Phase 2 

are expected in 2010. Contact your local Farm Service Agency office for more information about BCAP. A 

reference guide on BCAP may also be downloaded at www.BladeEnergy.com.

ENERGY CONVERSION

There are three major types of biomass conversion processes: combustion, thermochemical and 

biochemical. These processes can be used to produce energy in the form of liquid transportation fuels 

(e.g., ethanol, butanol, gasoline, diesel and jet fuel), heat and power (electricity), as well as provide the 

chemical building blocks for industrial processes. 

10000

9000

8000

7000

6000

BTU / pound

11000

The average BTUs per pound for sorghum compares very favorably with grasses and also overlaps the range of values for 

woody feedstocks. 

Comparison of Energy Content

BTU/lb Comparison of Feedstocks

 Other Grasses* Sorghum** Hardwoods* Softwoods*
Managing High-Biomass Sorghum | 2010 19

Other

Lignin

Fermentable

Sugars

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

0%

The content and accessibility of sorghum sugars compare well with corn stover and other grasses as well as woody crops.

Chemical Composition of Biomass Feedstocks

Comparison of Feedstocks

 Pine Corn Stover Sugar Cane Bagasse Sorghum

For combustion and thermochemical conversion, a key measure of expected performance is BTU (British 

Thermal Units) per pound. At an average 7,750 BTU/lb., sorghum compares very favorably with grasses, 

and also overlaps the range of values for woody feedstocks. By comparison, Powder River Basin coal, a 

common fuel for electricity generation, averages 8,800 BTU/lb.

As with many other features of biomass, many of the key compositional features that influence the 

performance of herbaceous crops in biopower applications—including energy (HHV) and ash content—

are influenced by both agronomic practices and genetics. It is generally accepted that biomass can 

be cofired in coal-fired facilities at up to 15% without requiring significant boiler retrofit. Sorghum has 

shown to compare favorably against multiple other biomass feedstocks in these areas, and projects are 

currently underway to conduct larger-scale evaluations. 

Biochemical conversion of biomass to biofuel utilizes a process that involves a thermochemical 

pretreatment of the biomass, which is usually followed by enzymatic treatment to break down the 

complex of structural carbohydrate chains found there. The resulting sugars can then be fermented to 

biofuels. Some of the challenges of this technology involve the complexity of converting the biomass 

into a form that is efficient for conversion, as well as the diversity of compounds present in biomass. 

The efficiency of this conversion process is dependent on a host of factors that can make the sugar 

chains more or less accessible to enzymes and/or fermenting organisms. Understanding those factors 
20 2010 | Blade Energy Crops

and modifying them to increase the accessibility of convertible sugars is an active area of research. 

However, it is generally understood that higher content and easier accessibility of these complex chains 

of sugars are important, since they establish the maximum theoretical biofuel yield. In this regard, 

sorghum compares well with corn stover and other herbaceous and woody species.

FURTHER READING

Sorghum Growth and Development, Gerik, Bean and Vanderlip.

Grain Sorghum Production Handbook, Kansas State University, February 1998.

Forage Sorghum, Roth G. and Harper J., 1995
Managing High-Biomass Sorghum | 2010 21

LEGAL NOTICES

This guide is intended to serve as an informational tool for growers to use in the production of highbiomass sorghum as an energy crop. The information contained in this guide is based on public and 

private research that is currently available. Successful farming of any crop requires a high degree 

of skill. Seed and crop performance are heavily dependent on environmental conditions such as 

sunlight, moisture, temperature and soil composition, all of which are beyond the control of any 

individual. The authors and collaborators who prepared this guide do not guarantee crop yield or 

performance. In order to maximize a crop’s potential, growers must actively manage the crop according 

to environmental conditions, pests and diseases as they occur. While no farming guide can predict 

or address every farming situation, this guide will provide a strong foundation on which to build 

techniques for producing a high-biomass energy crop.

This guide is not part of the labeling of any seed or pesticide. Growers must always read and follow 

all instructions in the product labels of seed and pesticide products. Contact the pesticide product 

manufacturers or local extension agents to confirm that pesticide products are labeled for an intended 

use. Contact the seed producers to confirm instructions and intended uses on seed. Always read and 

follow all labels and instructions for pesticide and seed products. 

Skyscraper is a trademark of Ceres, Inc.

Apron, Bicep, Concep, Dual, Expert and Maxim are trademarks of Syngenta.

Poncho is a registered trademark of Bayer

Lorsban is a trademark of Dow AgroSciences.
22 2010 | Blade Energy Crops

NOTES
Blade Energy Crops® is a brand of Ceres, Inc. 

© 2010 Ceres, Inc. All Rights Reserved 

1006.1
Visit us online at www.BladeEnergy.com

Blade Energy Crops Thousand Oaks, California College Station, Texas

Toll-free 877.498.SEED International + 1.805.376.1208

info@bladeenergy.com

BLADE ENERGY CROPS is a brand of Ceres, Inc.