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What’s the value of straw?

The demand for crop residues is no longer confined to agronomic or livestock
uses. The increasing interest in bioproducts is driving the demand for crop
residues as potential biomass for various applications. When the next straw
board plant or ethanol plant comes to an area, how do growers decide if they
can afford to part with their straw?

Stripper header straw can be windrowed after harvest for marketing. Photo Courtesy Of PAMI.

Aside from the 'cash' value, some of the considerations include cropping systems,
soil and crop management, fertilizer replacement for exported nutrients, cost
of residue management and timeliness of operations. Mark Stumborg, head of applied
science at Agriculture and Agri-Food Canada's (AAFC) Research Centre at Swift
Current, in collaboration with several other researchers, growers and industry,
have been trying to answer the many questions over the past few years.

Growers and researchers have always focussed on crop residue management as
a key component of direct seeding and no-till cropping systems. "We've
had plots at the Indian Head AAFC Research Centre for more than 40 years where
we've been collecting crop residues," says Stumborg. "Up to 1990,
the research was focussed primarily on conventional tillage systems, but with
the trend to reduced tillage systems, we changed our focus." The research
looked at the accumulation of carbon, nitrogen and phosphorus in crop residues
and the soil. The results so far have shown that growers will need to replace
some but not all of the nutrients lost when the straw is removed by applying
fertilizer.

"No-till systems change the whole dynamics of nutrient cycling, how residues
get into the soil and the fate of the more volatile nutrients. Although the
assumption was a lot of the N would leach out of the nutrients and be captured
in the soil, recent research in Canada and the US suggests much of the N in
crop residues is lost before it can be captured in the soil, with only about
11 to 19 percent being returned to the soil under conditions in the US.

Snow trapped by barrier strips. Photo Courtesy Of AAFC.

"The residues may generate a bit of carbon back into the soil and some
microbial activity that is good for the soil, but you don't get all the N back,"
explains Stumborg. The majority of the nutrients left behind are found in the
crop root residues and standing stubble. As long as fertilizers are applied
to compensate for nutrients removed, and reduced or no-till systems are used,
then the system is fine.

What is the value of straw?
Determining the economics of straw being exported off the field can be challenging.
"We've worked with researchers, companies collecting biomass and growers
to come up with a value that is comfortable and reflects their individual business
cases," explains Stumborg. Some of the companies include Iogen and a plant
near Winnipeg. "Growers can expect to get between $10 and $15 per acre
cash back in their pocket, without doing anything else besides dropping the
residue behind the combine or leaving it standing after a stripper header operation.
It is up to everyone else to do whatever has to be done to get it off."

The economic calculations have built in custom rates for everything except
the windrowing operation. "Therefore, growers may want to make an agreement
to do the custom work for the company, providing another source of income,"
says Stumborg. "Growers who already have highway tractors may want to look
at offering straw hauling services as well. The other benefit of a plant located
in a local area can mean employment for local growers and their families."

Because every company has its own specifications, growers should make agreements
with companies before going out and doing any preparation for baling or baling
on spec. "Some companies can only use square bales because of how the plant
is set up, others can only use large round bales," explains Hill. "Companies
often prefer straw with a certain moisture content, or straw that is clean,
with the chaff removed and no unthreshed grain. Plants generally don't want
straw that is badly shattered or broken."

Snow trapped in full height stubble. Photo Courtesy Of AAFC.

Hill reminds growers to carefully assess their operation and think through
their whole system before making any changes. "It's important to understand
that any time you start to make changes in an operation, it is going to affect
the total system. There are no quick fixes. New equipment may work well for
some crops but not others, so assess your whole system first to make sure that
any new opportunities will really work for you." Hill believes more research
needs to be done on alternative harvesting technologies.

Stumborg believes that within 10 years, many growers who want to be involved
in the biomass industry will have an opportunity. "The demand for natural
fibres is increasing rapidly, particularly for flax and hemp, but also for wheat
straw." Stumborg sees opportunities in straw board and OSB plants, ethanol
and combined agriculture and forestry feeds for pulp and paper interests, among
others.

With emerging technologies and new research, Stumborg expects to see advances.
"We've shown, through our flax research, that we can actually use a stripper
header, leave the flax straw over the winter and bale it in the spring. Surprisingly,
the warmer drier prairie conditions allow for rhetting the fibre in the field,
improving the processing and quality of the end product." In terms of economics,
if plants can access biomass feedstocks around $50 per tonne, then they should
be able to have viable operations. Transportation is the biggest cost and largest
drawback.

What about erosion risk?
"The recommendations developed several years ago for safe residue removal
still stand," says Stumborg. "Wheat straw can be removed off the field
as long as a minimum of 750kg/ha is left behind in standing stubble to prevent
erosion in a no-till cropping system, and the straw is only removed once every
four years from a field." That is basically leaving a six to eight inch
stubble height behind and in most years this will leave behind much higher amounts
than the minimum. "We feel very confident with this recommendation."

Another consideration is stubble height management that maximizes agronomic
performance. In some cropping systems the benefits of leaving the crop residue
in the system may outweigh any returns from removal. Stumborg has research projects
in both Swift Current and Kamsack areas, and in southeast Saskatchewan, comparing
conventional and stripper headers on rotary and conventional combines, yields
and losses, baling operations, fuel usage and work rates in a variety of crops
with an emphasis on wheat and flax. Results from the research are expected this
year.

In the south, where snow trapping isa very important part of cropping systems,
leaving standing stubble or stubble trap strips can be very important for reducing
erosion and improving soil moisture. "One of our co-operators used a stripper
header to combine flax, followed by a windrowing and baling operation,"
explains Stumborg. "We found that by cutting the straw at four to six inches,
but leaving a trap strip every 18 feet, the field will accumulate almost the
same amount of snow as if all the straw had been left behind."

In wetter areas, such as the Black soil zones in Manitoba and Saskatchewan
where the fall of 2006 was extremely wet with some areas receiving upwards of
eight inches of rainfall in September, removing the residue may be a good idea.
Cutting the straw at four inches when baling will leave enough winter cover
without accumulating additional moisture. Baling the straw means there is no
need for a heavy harrow or other tillage operation, or burning. It also removes
any straw bunches left behind, making the spring operation much easier.

Factor in the cost of residue management
The cost of residue management is another factor that must be considered. "Essentially
it's a 'pay me now or pay me later' situation, there is no freebie out there,"
says Les Hill, manager of business development with PAMI in Humbolt. "There
is no magic 'no cost' way to deal with crop residue, there are machinery, labour
and other costs for any operation."

Straw chopping and spreading can become fairly significant, and power requirements
can get as high as 80 horsepower. "Chopping the straw with the combine
can limit the potential capacity of the machine, requiring either a combine
with more power or slowing down the operation," says Hill. During the critical
operating window at harvest, limited capacity can have a big impact. The combine's
chopping operation can be substituted with a follow-up mowing or cutting and
baling operation, but overall the energy requirements will be the same.

In flax crops, producers often resort to burning as a way to get rid of the
residue. "The cost to collect, bunch and burn flax straw is likely between
$5.00 and $8.00 per acre," says Stumborg. If there is potential to leave
the biomass to someone else who wants to collect it, there could be savings
for growers.

One of the considerations for growers is ensuring the straw is removed in a
timely manner to allow time to complete whatever their next operation may be.
For some, that may be fall weed control or fertilizer applications, for others
it may not matter until spring seeding. "We've tried to address this question
with our research to some extent," says Stumborg. "For example, in
the south where we left flax straw from a stripper header combining operation
in the barrier strips until the following spring, the producer was able to direct
seed into it. We found that by using single shoot knife openers there was no
problem with the seeding operation as long as the seeding operation was done
at an angle to the rows of flax seeded the year before."

Stumborg adds that the stripper header appears to have some time and cost saving
advantages as well. "We had co operators report that in their own experience,
using the stripper header has cut down their fuel costs by more than 40 percent,
plus they can get over the field up to 40 percent faster. Wear and tear is also
reduced by a substantial amount because less straw is taken in by the combine,
impacting longevity and capital replacement requirements." This means for
very large operators, they may be able to get away with fewer combines, fewer
operators and truck drivers, and still cover the same harvest in the same amount
of time. And they can leave the straw standing for someone else to come in and
remove.

In the end, determining the value of straw becomes an individual exercise based
on agronomic and environmental needs. And perhaps, innovations like stripper
headers will become part of the mainstream.

"However, we need to do more research, more demonstrations with growers
and get a better economic evaluation of all aspects of the stripper header and
the resulting harvest system to get ready for this change," cautions Stumborg.
"The last thing I would want is growers to invest scarce dollars based
on the limited information we have available to-date. By working with PAMI,
producers, manufacturers and Flax 2015 participants, we hope to get much better
data and a higher level of confidence in the results before we make recommendations."