Les Henry: Soil productivity, quality and health

Nature and nurture

Soil health is a prominent topic in current scientific and farm management literature. It is good to see attention being paid to the soil resource our industry depends on. In this piece, we will try to unravel some of the principles and the practical application of those principles.

From the get-go, we must realize farming that started in the early 1900s was essentially a “mining exercise” for the first 60-plus years. Our grandfathers broke the rich Prairie sod and extracted the productive juices (nutrients) and we shipped them all over the world. That is the nature part of the equation.

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It has been my good fortune to have crawled off the combine August 31, 1960, to take on the grand experiment of scientific agriculture at the University of Saskatchewan. It was a very scary leap for a very raw farm kid, but it worked.

Canada Land Inventory

In the 1970s, the Feds and provinces started a venture known as the Canada Land Inventory, with the objective to get a handle on the size of land resource and its capability for agriculture, forestry, recreation and wildlife. We will come back to the agriculture capability part at the end, after we show you how it has evolved.

Soil productivity, the nature part of the equation

Soil surveys started in Saskatchewan in the early 1920s and wound down in 1994. My first few years at U of S were with soil survey and then switched to soil productivity (fertility). In trying to establish the nature part of the equation, we used long-term records from the cereal variety trials at the various Fed Ag research stations. Those records were based on a consistent management practice in small plots with good weed control, and the results mostly reflected the soil (and climate) of the individual sites.

At that time, we were still mostly a one-trick pony (wheat) and summerfallow was still a hallowed practice, despite its destructive nature. The soil zones are really soil climatic zones. Soil organic matter and native fertility are related to climate. The nature part (Figure 1 below) showed clearly soil organic matter and the climate that went along with it were responsible for yield.

Figure 1: A 20-year average wheat yield of 44 bushels per acre may seem high for that time period, but we must remember those are summerfallow yields, so we must divide by two to relate to what we now do. For those kids who do not know, summerfallow was the practice of leaving the soil idle for a year. The soil was cultivated regularly to kill weeds, meanwhile leaving it bare naked and hugely susceptible to wind and water erosion. photo: Supplied

The transition from nature to nurture

The transition started about 1960. The opening of provincial soil testing labs in all three provinces was a big part of the transition. The Saskatchewan Soil Testing Lab provided some of the best data to document the nature part of the equation.

There was huge pent-up demand for the service, so many thousands of fields were sampled each year. All fields were sampled at standard depths of 0-15 centimetres, 15-30 cm and 30-60 cm, and all received the same test in the lab.

Thanks to the foresight of the first director (Ed Halstead, a Nokomis, Sask., farm boy), the very first report was printed from, and all data stored on, a computer. It was easy to spit out soil test summaries in various forms. Each field was assigned a legal location, and from that the soil association and texture was also recorded. Figure 2 (below) shows a summary of nitrogen on a soil zone basis.

When the land was first broken, the first plant nutrient to become deficient was phosphorus. Starting in the 1950s, phosphorus fertilizer was used, so the nitrogen account was further depleted.

Figure 2: This graph shows soil test nitrogen by soil zone. It summarizes many thousands of fields — and drives home in spades the nature part of the equation. It also explains why summerfallow died so hard. Soil moisture storage was widely touted as the reason for much better crops on fallow but data did not always back that up. The soil test data proved that we were juicing up the nitrogen withdrawal from soil big time by allowing a summer of nitrogen mineralization under warm, moist conditions. When the soil microbiologist of the day (the famous Eldor Paul) saw that graph, he called it a province-wide mineralization experiment. photo: Supplied

Nurture

With the help of soil testing, nitrogen fertilization became the norm and nurture took over big time. We were lucky to have the South Saskatchewan Irrigation District start up about that time. Field experiments were established where both nitrogen and water could be varied over huge ranges all in one place. The nitrogen-water interaction effect was huge.

This data was a major game changer for me. As we were struggling with establishing soil productivity for mapped soil units, this made me question what soil productivity really meant. In 1977, that data was presented at a national soil science conference in Guelph, Ont. The point was, this data showed that nurture was a huge factor in soil productivity. My comments made the local press, which stirred up a bit of fuss.

There are countless examples to show the nurture factor to soil productivity. Serious potassium deficiencies in the Carrot River area in northeast Saskatchewan, almost fatal sulphur deficiencies in canola and copper deficiencies in peaty soils are but a few examples of the nurture part of the equation.

Figure 3: Canola response to nitrogen fertilizer — irrigated and dryland averages of many site years. (Keeners can check out the details at Canadian Journal of Soil Science, volume 58, 1978, page 305.) photo: Supplied

Soil quality, the buzzword of the 1990s

As I was rooting around in my old soil productivity files at U of S, I stumbled on a Fed report entitled, “Soil Quality Benchmark Site Documentation 20-NB,” June 1993. The NB was for New Brunswick. It was an excellent report with information that allowed me to fly over via Google Earth and find the exact field.

The report provided a detailed soil survey and the protocols to document various aspects of soil quality. The concept was to have a protocol that could be applied Canada-wide. One aspect of the soil quality to be documented was earthworm counts. It stated, “Earthworm counts should be done on all benchmark sites except for the sites on the Prairies that have no earthworms.”

Long-time Grainews readers will remember the earthworm articles of October 2012 and March 2013. Earthworms were indeed very rare in the cultivated fields of the Prairies in the mid-1990s. Our old farming methods left them with nothing to eat and tillage finished them off. However, with the rapid adoption of zero till farming and proper crop rotation with cereals, oilseeds and pulses, we were soon running into earthworms when inspecting seed placement.

Farmers reported copious earthworms hanging from the openers as the drill was pulled out of the ground. In our environment, earthworms definitely have to be placed in the nurture column. The new soil management allowed earthworms to thrive and they gladly paid us back by further improving the soil.

Soil quality carried on as a research item through the 1990s. There were 10 benchmark sites established in the agricultural parts of the Prairie provinces. Fact sheets and other publications have provided useful data but soil quality as a topic quickly waned.

In recent years, we hear much more about soil health.

Soil health

The soil health initiative has been advanced in no small measure by the Soil Health Institute established in 2015, with headquarters in North Carolina. It is well funded and many useful studies have resulted in much useful data. But, there is no one size fits all. To turn data into information, it must be brought down to the farm gate and make a positive impact on the bottom line.

Soil health includes topics such as intercropping, cover cropping, diverse crops and rotations and intensive grazing. Livestock play a big part in many projects. Intercropping has potential widespread use — but it requires special separating equipment and logistics to pull it off. The South East Research Farm at Redvers, Sask., has done great work to advance the project (thanks, Lana Shaw), and a few farmers are doing very well with the concept.

Cover cropping is great in moist climates with long seasons where soil is bare for a long fall period. I think it is a non-starter for the Palliser Triangle. The fall period after harvest is when we hope for system rains that we can store in the soil for next year’s crop.

Much soil health work deals with soil biology, which is crucial. The role of special fungi is important in phosphorus availability to annual crops. Diversity of organisms is a main part of the current research work. However, no one is looking at the top of the food chain in the soil — earthworms.

The Canada Land Inventory, Soil Capability Classification of Agriculture

We started this piece talking about the Canada Land Inventory. For land inventory purposes, the Soil Capability Classification of Agriculture has been most useful. It is simple in concept and without any special jargon. It works this way —

Classes, degree of limitation

  • Classes 1 to 3 are our annual crop-producing lands. Class 1 is rare on the Prairies because of overall climate limitations.
  • Class 4 is marginal for annual crop production. It fits in the swing category — maybe yes, maybe no.
  • Class 5 is suited for grasses and legumes for improved pasture.
  • Class 6 is suited only for native pasture.
  • Class 7 is unsuited for agriculture (i.e. permanent sloughs, lakes, roads, railways).

Subclasses, kind of limitation

  • Climate: too dry or too cold
  • Soil: too sandy, poor structure (hard), low nutrient supply, too salty
  • Landscape: too hilly, too wet, too stony, erosion, flooding

As new crops come along, the subclass may change. For example, for lentil production, stones take on a whole new meaning.

This simple classification has stood the test of time and is useful for inventory purposes and a first look at a piece of ground. The basic limitations dictate much of the nature. Nurture to overcome nature may be easy to fix (fertility), difficult (salinity) or not feasible (landscape).

Large scale (1:1,000,000) soil capability maps are available online. The Saskatchewan map can be found here.

In Saskatchewan, soil capability maps were prepared for each RM and First Nation (in ag area) but they are not yet available online.

About the author

Columnist

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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