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Les Henry: A recipe for 65 bushels per acre of canola

Some lessons learned many years later

What we did not  realize  was  canola  had  the  rooting and uptake ability to suck the soil P to very low values.  
A few years of big yields with big N and big water and P becomes the limiting factor.

When cleaning visuals from talks of years gone by, I stumbled on one from 1978 — the year canola was born. It showed what it took to produce 65 bushels per acre of canola in garden patch agriculture (i.e., small plots). In 1978, the highest average RM yield of canola in Saskatchewan was 29 bushels per acre. At that time, canola was considered to be a summerfallow crop, so divide by 2.

In recent years with good rainfall, modern hybrid varieties, proper nutrition and overall good management, many farmers have grown yields of canola in the 50s and beyond. In 2011, it was my pleasure to sit in a combine at Annaheim, Sask., where the yield monitor bounced around between 68 and 72 bushels per acre, and a whole section yielded about that 70 mark — if the combine went less than two miles per hour, slow enough to separate the seed.

I expect that many 60-bushel crops have been grown, but only 50 bushels made it to the bin. In dry conditions, where the straw, etc., breaks up fine, it is often not possible to separate seed from trash if the combine is at full threshing capacity. If you are combining a high-yield canola crop at four to five miles per hour, just slow down to two miles per hour for a while and see what happens. Repeat the little experiment until you have satisfied yourself that you must slow down.

The recipe


The soil was an Elstow dark brown loam with two per cent organic matter located in the Outlook, Sask., irrigation area. The soil test data included the following:

  • Nitrogen — 40 pounds per acre nitrate-N to a depth of two feet
  • Phosphate — Eight pounds Olsen P per acre to a six-inch depth
  • Potassium — 460 pounds K per acre to a six-inch depth
  • Sulphur — 81+ pounds SO4 S to a depth of two feet

Seed and seeding

The plot was ploughed and harrowed with an oscillating harrow. A plough you say — what is that? In the early days of irrigation, ploughing was used to bury weed seeds, such as green foxtail, which were hard to kill with herbicides of the day.

The variety was the first canola variety (Tower) seeded with a knife press drill with seven-inch spacing at seven pounds per acre and treated with Furadan. A seven-pound seeding rate was no problem — seed was not $600 per bushel at that time. Seeding was May 9, 1978, and harvest was August 21.

Weed control was triallate at 1.5 pounds of active per acre plus trifluralin at eight ounces of active per acre as a tank-mix pre-plant and harrow incorporated. No wonder the poor soils of the day had challenges with all that tillage. I recall farmers from the Melfort, Sask., area talking about seven times over the field between the combine and seeder.


Fertilizer included the following:

  • Phosphorus — 20 pounds P2O5 per acre with the seed as monoammonium phosphate.
  • Nitrogen — 100 pounds N per acre applied immediately after seeding as surface broadcast ammonium nitrate (34-0-0).
  • 100 pounds N per acre applied July 10, just before irrigation as surface broadcast ammonium nitrate (34-0-0).

I still mourn the loss of ammonium nitrate. It was the best N fertilizer and we lost it because some clown used it to blow up a big building in Oklahoma.


At seeding time, the soil was moist (at field capacity) to only eight inches, which is only about one inch of available water.

The details of the rain and irrigation schedule are shown in Table 1 below.

With only one inch of water in the ground at seeding and 4.6 inches of rain, a 10-bushel crop would have been “all she wrote.”

During the 1970s, we did dozens of experiments in the irrigation area of the dark brown soil zone during a time when irrigation was really needed. It allowed us to vary both nitrogen and water at the same time. Table 2 shows the average of many such experiments.

If we add up the water and nitrogen alone, the increase is 18 bushels per acre, however, when the two are provided together the increase is 34 bushels per acre. Thus, the interaction effect is 34-18=16 bushels per acre.

That data was instrumental in making interpretations across soil zones for proper nitrogen fertilizer recommendations. In the early days of stubble cropping, our nitrogen recommendations for the brown soil zone were very low. After we learned about the nitrogen-water interaction, we often said our early soil test N recommendations for the dry areas ensured a crop failure whether it rained or not.

I must first credit the above heading to Elston Solberg, a well-known soil fertility consultant from Alberta. When we finished about a decade of soil fertility work at Outlook, it was very clear: pour on the water, pour on the N, give a dash of P and all is well. We grew 65 bushels per acre of canola with only 20 pounds of P2O5 per acre.

On that basis, we had concluded that canola did not need a lot of P. Many times, I would remind folks that we grew 65 bushels per acre of canola in garden patch agriculture with only 20 pounds P2O5 per acre. What we did not realize was canola had the rooting and uptake ability to suck the soil P to very low values. A few years of big yields with big N and big water and P becomes the limiting factor.

By and by, several colleagues showed high rates of broadcast P would increase crop yields for many years. Then along came Renaud Lemke, from Swift Current, Sask., who calculated over the long term 98 per cent of the P that was poured in the ground was hauled away to the elevator in crops.

In recent years, I have seen simple canola P experiments showing visual response just like we saw with N many years ago. John Heard and Don Flaten in Manitoba took the lead in calculating the balance required to keep the soil test P at a level to maintain high crop yields. Thus, a new story emerged about P as a plant nutrient. Maintain the soil test P level and yields will be maintained. As the soil test P level drops too low, so does crop yield.

The new story of P is now common thinking. We must always maintain an open mind and occasionally let go of old concepts and embrace the new.

About the author


Les Henry

J.L.(Les) Henry is a former professor and extension specialist at the University of Saskatchewan. He farms at Dundurn, Sask. He recently finished a second printing of “Henry’s Handbook of Soil and Water,” a book that mixes the basics and practical aspects of soil, fertilizer and farming. Les will cover the shipping and GST for “Grainews” readers. Simply send a cheque for $50 to Henry Perspectives, 143 Tucker Cres., Saskatoon, Sask., S7H 3H7, and he will dispatch a signed book.



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