| | AESA’s Soil Quality Benchmark Study is poised for progress. As one of a handful of long-term soil quality monitoring programs in North America, it is providing a unique, comprehensive dataset for understanding soil quality changes in Alberta’s agricultural soils.“
"It’s an exciting time because we’re on that event horizon of being able to start picking up more trends out of the data,” says Dr. Jason Cathcart, the AESA Soil Quality Program Coordinator.
The study, which began in 1997, has several major objectives: to create a dataset for use in testing and validating models for predicting changes in soil quality; to provide baseline soil quality information; and to monitor changes in soil quality.
The 42 benchmark sites cover all agricultural ecoregions in Alberta. Each site has been selected to be representative of the soils, landscape, climate and agricultural practices in the area. Samples are taken annually and analyzed for a wide range of soil characteristics, such as various forms of organic matter, nutrients and pH, as well as crop yield and biomass.
At each site, samples are taken at three locations – the upper, middle and lower positions along a slope. This approach adds a valuable dimension because landscape processes can influence soil quality. Cathcart explains, “A classic example is removal of the upper soil layers on the crests of hills by water erosion, and the accumulation of that material in the lower depressional areas. That can result in quite different responses in crop yield or nutrient requirements with only about a metre of elevation change [across a field].”
Data from the study’s first five years have been analyzed, but most soil characteristics did not yet show statistically significant trends. The main exception was the pattern of soil characteristics along a slope, which had significant results for quite a few soil properties. The trends were as expected, with lower slope positions tending to have higher levels of organic matter and nutrients like potassium, phosphorus and sulphur, than middle or upper slope positions.
This spring, the study will be entering its eighth year. That may sound like a long time, but in terms of the statistics of soil sampling, it’s just the beginning. Cathcart explains, “Unlike small plot research, we don’t do repeated measurements at a given site. So we have to essentially assign the repeats over a number of years. Other scientists have said we are just moving into an area where we may be able to start picking up trends in some of the results after seven years.”
Another major factor is that, unlike small plot research, the benchmark study does not apply any specific treatments to the sites. Cathcart says, “The producers go about their normal management practices. That allows us to more easily grasp how current production practices are really being used and how they are affecting soil properties.” But it also means that more years of data collection are needed to sort out the effects on soil quality of the different crops and practices used in each year of the producer’s crop rotation.
In fact, one of the study’s most complex considerations is analyzing the effects of agricultural management. Cathcart is looking forward to the challenge of finding the best way to present and analyze the long list of data collected each year on such things as tillage and tillage dates, crop rotations, fertilizer products, rates and timing, and herbicide products, rates and dates.
Cathcart says, “We have a very strong baseline dataset – and an increasingly strong one as each year goes by – that will allow us to move forward into different areas, to validate pretty much anything we want to look at. ...It’s exciting in that it allows a lot of future opportunities, including opportunities to work in partnership with other academic and government institutions.” For more information on this study, visit www.agric.gov.ab.ca/soilquality.
On-farm soil quality assessment made easy
Along with just a pencil, a spade and the Alberta Soil Quality Card, you can evaluate soil quality in your fields. Checking soil quality every few years can help in assessing the effects of various management practices and in targeting potential problem areas for special attention. The card is available at www.agric.gov.ab.ca/soilquality or by calling 1-800-292-5697. |
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