St(RAW) deal

Don’t rob our Prairie croplands — help rejuvenate them by working in all crop residues

St(RAW) deal

Here we go again. “Alberta May Get Straw Plant” was a headline that appeared last summer in an agricultural publication. Why the concern? How many of you remember those massive piles of straw on the Trans-Canada Highway near Elie, Man., just east of Winnipeg? There were stacks and stacks of big, round straw bales — perhaps a few hundred thousand in all.

This was a strawboard plant that opened around 1998, some 23 years ago. The straw plant, with help from the provincial government, offered job creation and a value-added promise for farmers. Round and square bale sizes vary considerably, so farmers were able to market their straw for $10 a tonne. Selling their straw for the incredibly low price of $10 a tonne, not including the cost of a baler and baling, perhaps along with some transport, was a value-added potential? This price per tonne even some 20 years ago was more like a charitable donation, qualifying cereal growers for a tax rebate.

This Manitoba strawboard plant then ran into financial and technical problems and closed its doors around 2001. Dow Chemical Canada generously took over the plant but it kept running at a loss until its final closure in 2005.

During these early years, Dow met with more than 20 interested purchasers, all of whom lacked either the funding or technical ability for the plant machinery to operate the plant and consume the straw. The plant was finally shut down and some 150,000 bales were gradually removed from the site.

Nutrient value of wheat straw, an analysis

In my very many visits to grain farms across the Canadian and U.S. Prairies over the last 45 years, it seemed to me many, if not most, farmers considered cereal straw to be a somewhat useless by-product. Many failed to understand the vital role grain straw played in cropland regeneration.

In the mid-70s and later, Manitoba grain farmers, in particular, would often burn the grain crop’s residual straw. Many individuals, and even crop specialists, said straw burning controlled cereal crop diseases, since there was always a yield bump on a burned field. As a plant disease specialist, I can say no that is not the reason. Removal of the straw did not tie up 50 to 60 pounds of nitrogen in the following crop.

Let’s get down to brass tacks and we will specifically deal with wheat straw. Growing a 50- to 80-bushel crop of wheat on the Prairies results in a variable amount of residual straw after combine harvest. The amount of straw produced per acre will vary from dry southern soils to good, moist northern soils — variations of 1.25 tonnes to 2.5 tonnes per acre. To make this analysis uniform, let’s look at a 60-bushel crop of wheat that produces two tonnes of straw.

In the straw and grain analysis, we will assume the grain was 12 per cent protein and we will only discuss nitrogen (N), phosphate (P), potash (K) and sulphur (S). Magnesium, calcium and all micronutrients are not included so as not to confuse the major issues.

When you remove an acre of grain (the 60 bushels per acre of wheat you remove from your cropland, in this example), the nutrient amounts you take from your soil bank per acre are 75 pounds of N, 39 pounds of P, 24 pounds of K and five pounds of S (the P is P2O5 and the K is K2O).

Now for the two tonnes of straw — that would make about 2.5 bales per acre at 800 pounds each. The amount of nutrients in these two tonnes of straw is on average 30 pounds of N, nine pounds of P, 60 pounds of K and seven pounds of S. If instead of baling this straw you followed the old practice of burning, you would lose 30 pounds of N and seven pounds of S per acre, with some P and K blown away in the smoke.

What is the nutrient value of these two tonnes of wheat straw based on relatively current fertilizer prices per acre?

The nutrient total value not including calcium, magnesium and micronutrients is $67.80.

Based on fairly current fertilizer prices, your two tonnes of straw per acre contains about $68 worth of N, P, K and S, not including micronutrients such as boron, zinc and copper in the straw.

Since we have 800-pound round bales, that makes for 2.5 bales per acre, so a single bale would give you $27.20 of nutrients per bale ($68 divided by the 2.5 bales).

Now with variable costs, you can assume each bale of straw (800 pounds) is worth $27.20 in nutrients (fertilizers).

Look at your baled straw. Every bale is worth $27.20 in fertilizer alone. Also, consider the following:

  • Your cost of baling — $3 per bale or custom baling?
  • Was it wet in the field when you baled?
  • Did you have a contract and the bales were still on the field in April?
  • What did the baler cost, including its maintenance and the cost of baling?
  • How were the bales transported?

The actual cost to you as a grain grower is now around 30 to 35 dollars per bale. That’s your cost recovery alone, not including any profit. If you sell for less, you could qualify for a charitable donation.

Eighteen reasons never to sell crop residues

In the June 2 issue of Grainews last year, I wrote an article called “Sixteen reasons why grain growers should never sell crop residues.” Read it. I could expand those 16 reasons to 18 by stating that tracking straw bales off your cropland, especially by contract, is a very good way to spread clubroot and aphanomyces pea rot from field to field. In addition, in a wet fall or spring, consider the compaction on your cropland by the 20- to 30-ton bale truck.

Remember, when you buy nitrogen (N) as urea it’s only 46 per cent nitrogen. Potash (K) is only 60 per cent as K2O.

Consider the fact that we all talk about soil rejuvenation, moisture retention, feeding the microbes and worms, improving soil tilth and so on. What better way than leaving the crop residue on your cropland unless it really pays you to sell your straw.

Think of a straw chopper or stripper header. Leaving the stubble high or straw on the ground traps snow on the field instead of filling up your ditches and roadways.

You may need more power to chop your straw and maintain the equipment but the benefit to your cropland is immense. You are building up soil organic matter and rejuvenating your soil, leaving money in your pockets.

Do not rob our Prairie croplands, help rejuvenate them by working in all crop residues.

Knowledge is knowing a tomato is a fruit. Wisdom is not putting it into a fruit salad.

Finally, let’s think in terms of quarter sections when every two tonnes of straw is worth $68 in fertilizer (nutrients) N, P, K and S. That’s $68 x 160 acres, which equals $10,880 of fertilizer taken away (removed) in the 320 tonnes of straw.

This calculation of $10,880 of fertilizer in every section of straw applies to barley, oats, rye, wheat and, perhaps, pea straw — give or take a few thousand dollars.

What did it cost to bale the straw and how much did your baler cost, including baler maintenance and fuel costs? We are perhaps looking at $12,000 to $14,000 per section of straw just as a break even. Think about it and read my feature in Grainews from last June about why you should never sell a bale of straw again.

About the author


Dr. Ieuan Evans is a forensic plant pathologist based in Edmonton, Alta. He can be reached at [email protected]

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