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dal. ca www. dal. ca Chemical Measures of Soil Health A New Look at Some Old Tools David L. Burton Department of Plant, Food and Environment, Dalhousie University
How often is the term ”Soil Health” used?
What is “Soil Health”? Soil Health is a state of a soil meeting its range of ecosystem functions as appropriate to its environment. USDA NRCS (2013)
Relative to the term ”Soil Quality”
What is “Soil Health”? Soil Health is a state of a soil meeting its range of ecosystem functions as appropriate to its environment. USDA NRCS (2013) Soil Health and Soil Quality are often used interchangeably Health refers to the internal state of an entity Quality refers that entities “fitness for purpose” The term health implies a capacity to sustain function… not merely a particular function, but the full range of function.
How about in relation to “Soil Conservation”
And now “Soil Fertility”
What is in a word? We use the terms that resonate with issues of the day Fertility addressed the desire to enhance crop productivity Conservation spoke to our desire to halt soil erosion Quality was about our desire understand the total function of the soil for its intended purpose (most often crop production) Health speaks to a broader concern about the physical, chemical and biological aspects of soil function Each of these concepts represents an
“Soil Fertility” was a largely chemical concept Justus von Liebig - German chemist Developed the mineral theory of plant nutrition. . . “Inorganic nutrients were as effective as organic nutrient sources” From this perspective soil fertility was essentially a problem of chemistry. Chemical determination could provide a measure of the ”fertility” of the soil, essentially its chemical nutrient content.
What does the “Soil Fertility” concept bring to “Soil Health” assessment? It provides an example of how we can “actualize” a soil measurement in terms of management responses Soil Health assessment will only be useful it can inform management and the resulting management addresses the issue The concept of “Soil Fertility” speaks to the fundamental function of soil Measures of Soil Health should ideally based on fundamental functions of soil, not merely statistical indicators
Actualizing the chemical concept of fertility John Bennet Lawes and Joseph Henry Gilbert Founded the Rothamsted Experimental Station Conducted pioneering work in the calibration of chemical soil extractions (soil Helped to establish soil tests) in terms of crop response to nutrient testing and fertilizer addition recommendations as an effective tool in crop management Local calibration Gilbert essential! Lawes
Crop Nutrient Response Trials Soil test ratings are related to local crop response to nutrient addition Defines thresholds of response as a function of soil test responsive vs. non-responsive ranges
Soil fertility assessments (soil tests) are only as good as the calibration data they are based on? The need to calibrate soil measurements in terms of crop response to management (or other intended use) Soil fertility tests calibrated with crop nutrient addition response trials Provides a clear understanding of response thresholds The value of tracking soil test values over time as an assessment of management impacts on soil productivity By the 1970’s soil testing methods and nutrient response tables were established in many jurisdictions for most crops by university, federal and provincial researchers Fertility research was “complete” In the 1980’s many of the soil fertility programs were discontinued
What can the “Soil Health” concept bring to “Soil Fertility” assessment Health is often indicated by the function of homeostatic processes Your body’s temperature regulation Do soils exhibit homeostatic processes? Soil buffering capacity Cation exchange and base saturation Soil structure (soil organic matter) Soil phosphorus content
Chemical aspects of Soil Health p. H & buffering capacity p. H is a fundamental character of soil influencing the availability of many other nutrients. Buffering capacity is the ability to resist change in p. H. Low soil p. H is an issue in many Atlantic Canadian soils. CEC and %base saturation Cation exchange capacity retains nutrients. In humid climates soil fertility is often limited by a low % base saturation.
Chemical aspects of Soil Health Soil organic matter Establishes the structure of soil that imparts the ability of the soil to store water, aeration, tilth, resistance to erosion. An important indicator of soil nitrogen supply One of the critical limitations to soil health in Atlantic Canada Phosphorus and P saturation The soil has the capacity to store large amounts of phosphorus in poorly soluble forms. Represents a potential source of P In Atlantic Canada we have many soils with excessive
Cornell Soil Health Assessment Provides a set of measures of soil physical, chemical, and biological indicators of soil health Uses a statistical approach to develop “scoring functions” Scoring functions should be based on regional datasets
What can the “Soil Health” concept bring to “Soil Fertility” assessment These homeostatic mechanisms are all a result of chemical aspects of the soil They are quantified by current soil testing methods These mechanisms are indicators of “soil health” Greater emphasis should be placed on managing these fundamental processes and less on “band aid” nutrient additions Soil Fertility test reports should provide a more robust assessment of the soils condition or “health” Greater emphasis on change over time individually and regionally
Soil Health – the future of soil fertility With the advent of new crop varieties, new soil management techniques and new nutrient sources there is a need for more current regional crop response studies Opportunity to use the broader concept of soil health As a result of “precision agricultural” tools, producers have much greater capacity to measure soil characteristics, monitor crop yields and deliver soil nutrients. As a result there is the opportunity for landscape level, on-farm calibrations.
Atlantic Soil Health Initiative There is a desire to survey “soil health” in Atlantic Canada and create a database to support the construction of soil health functions Currently partners: Dalhousie University (Burton & Lynch) PEI Department of Agriculture (Stiles & PEI Analytical Lab) Perennia (Sangster, Madden & Haverstock) NS and PEI Federations of Agriculture AAFC Charlottetown (Mills & Nyiraneza) East Prince Agri-Environmental Club PEI Certified Organic Producer’s Cooperative (Murchinson) Collaborators welcome… contact me at [email protected] ca