Soil Health
What is Soil Health?
Soil has various components - organic matter, nutrients, water-holding capability, and amount of carbon - all of which need to be in balance in order to maintain soil health and sustainably produce crops.
Soil health represents the capacity of soil to respond to agricultural intervention so that it can continue to support both agricultural production and support its ecosystem. Healthy soils can maintain their structure, cycle nutrients, transform and store carbon by decomposing plant and animal materials, and support a wide range of bacterial, fungal, and insect populations. However, certain agricultural practices such as tillage, replacement of natural fertilization and pest management with synthetic alternatives, and reduction in crop diversity have stripped the soil of organic matter and have increased soil erosion and contamination.
Current farming practices in Canada are negatively impacting indicators of the above major soil functions, impacting crop growth and ultimately crop yield. Primary factors impacting these indicators to be discussed further in this document include monoculture; erosion due to wind, water, and tillage; use of inorganic fertilizers; and use of certain pesticides.
Conservation Agriculture
The Food and Agriculture Organization of the United Nations (UN FAO) promote the practice of conservation agriculture for increasing water and nutrient use efficiency and contributing to sustainable crop production. Conservation agriculture relies on three principles:
- Minimal soil disturbance, i.e. no-till practices
- Maintaining soil cover using crop residues or cover crops
- Crop rotation involving at least three different crops
Maintaining soil health is vital to reducing the carbon footprint and environmental impact of farming, nourishing a growing population, and creating a sustainable economic sector for future generations.
Read more about conservation agriculture:
- Alternative Management Practices Improve Soil Health Indices in Intensive Vegetable Cropping Systems: A Review (Norris and Congreves, 2018)
- Beware the glitz of neo-industrial agriculture (Ryan Katz-Rosene, 2017)
- Misunderstanding conservation agriculture: Challenges in promoting, monitoring and evaluating sustainable farming (Findlater et al., 2019)
Soil Organic Matter and Healthy Soils
What is Soil Organic Matter?
Soil organic matter, or soil carbon, is a critical indicator of soil health. The loss of soil carbon not only represents the transfer of CO2 into the atmosphere, contributing to climate change, but also a critical decline in the function of the soil resulting in a decline in productivity.
Soil organic carbon can be retained by increasing biodiversity (crop rotation), ground cover, and incorporating crop-livestock interactions.
Nutrient Content of Crops
Soil health, including factors such as fertilizer and pesticide use, can impact the nutritional content of crops.
For example, one study showed that synthetically fertilized soil contains 5-9 µg (micrograms) of vitamin B12 per 1000 g soil, while soil that has been treated with organic fertilizer once every 5 years contains 10-14 µg B12/1000 g.
Greenhouse Gas Emissions
A study found that no-till operations resulted in 33% lower N2O emissions in western Canada (a slight increase was observed for eastern Canada due to higher soil moisture causing denitrification) caused by less decomposition of organic matter. The same study found that eliminating summerfallow reduced emissions and that both increasing and decreasing N-fertilizer resulted in combined emissions. Evidence suggests that climate change will in turn impact soil organic carbon content; researchers in Germany predict that SOC will decrease 11-16% under and mean temperature increase of 3.3 °C.
Monoculture
Monoculture refers to growing one variety at a time in a given space or to growing clones of a single plant. Continuous monoculture (year after year) is called monocropping.
Benefits
|
Consequences
|
Alternatives to Monoculture
The alternatives to monoculture are polyculture (many crops) or oligoculture (few crops), these are the practice of planting several crops together. For best results, farmers should find the proper mix of plants and animals that complement, protect and improve the environment around them.
Cover crops are planted specifically to provide what are now called ecosystem services: benefits like controlling erosion, attracting pollinators, increasing grazing potential, suppressing weeds, recycling nutrients, and supplying nitrogen.
Tilling and Erosion
Ploughing, disc-tillage and vegetation burning accelerate the decomposition of soil organic matter and leave the soil susceptible to erosion. Tilling is a way of mechanically preparing seed beds for planting by breaking the ground which may have become dense and compact.
Tillage of any form exposes the organic matter to air and will resulting in losses due to increased mineralization rates and erosion.
One study of 34 farms in the Maritimes linked lower-intensity management, manure application, and low tillage to higher soil respiration, water-stable aggregates, fungi, mycorrhizae, Gram negative bacteria, and lower phosphorus.
Soil erosion is the cumulative effect of erosion due to different sources or phenomena, namely wind erosion, water erosion, and tillage erosion. Water and wind erosion are largely caused by mismanaged runoff due to structural management failures such as excessive slopes or agronomic issues such as tillage.
Solutions
No-till farming is already the status quo in the prairies and is gaining popularity in the rest of Canada. No-till practices result in better pore connectivity but can result in lower root biomass, while reduced-till systems had higher accrual of labile carbon and other long-term benefits, but conventional methods provided other short-term benefits to crop production.
Basin tillage, small dams created between rows of crops, can enhance infiltration, reduce runoff, reduce contaminant loads, and increase yields.
Water erosion can be mitigated by reducing or eliminating tillage, maintain crop cover, maintain organic matter content, grassed waterways to carry runoff, terracing, lined channels, or drop structures.
Wind erosion can be mitigated by maintaining vegetative cover, reducing or eliminating tillage, avoiding overgrazing, planting shelterbelts (tree-lined perimeter of field).
Nutrients and Fertilizers
Nutrient Content of Crops
Nitrogen, phosphorus, and potassium (N-P-K) are the primary nutrients needed by plants. A fertilizer labeled as 20-10-6 contains 20% nitrogen, 10% phosphorus, and 6% potassium. Fertilizers in which the quantity of nutrients is equal, or where nitrogen is slightly higher are considered general purpose fertilizers.
There are two groups of fertilizers, organic and inorganic, with reference to the way they are produced. Plants can’t distinguish whether a fertilizer is organic or inorganic.
Organic, or natural fertilizers are derived from decomposing animal or plant waste and can include compost, aged manure, bone meal, and kelp. Because decomposition is gradual, nutrients are released over time, reducing the risk of burning the plant.
Inorganic, or mineral fertilizers typically contain higher levels of nutrients than organic fertilizers and can be tailored to specific types of plants.
Friable Soil, or Loam, is characterized by a crumbly texture and is beneficial for root growth, uniform development of root vegetables, and drainage. Clayey soils are not friable and can therefore be problematic for plant growth.
In 2017, 58% of crop fields were fertilized with manure at least once per year, while 20% of field crops have never been fertilized with manure.
Repeated use of inorganic fertilizers can permanently destabilize soil pH, which in turn may negatively impact soil microorganism populations.
A 13-year study compared the impacts of manure and inorganic fertilizer on soil health. The researchers found that manure, when compared to inorganic fertilizers better maintained soil pH, resulted in more substantial increases in organic matter content, total nitrogen, electrical conductivity, and water stable aggregates.
Solutions
Use of organic fertilizers alone may not sufficiently replenish specific nutrients which have been removed in each harvest over several growing seasons. In this case, mineral fertilizers containing custom amount of mined phosphorus and potassium could be applied prudently.
Pesticide Use
The term pesticide covers a range of compounds the most common of which are herbicides, insecticides, and fungicides. 93%, 38%, and 26% of crops produced in Canada benefited from the use of herbicides, fungicides, and insecticides respectively. In 2017, 73% of pesticide sales in Canada were for the agricultural sector.
Typically, pesticides are selected and regulated based on their persistence in soil. Though, heavy treatment with pesticides can negatively impact soil microorganisms which are essential for the conversion of nutrients and organic matter.
A 2015 study showed that microbial richness was responsible for between 49% and 77% of organic matter mineralization intensity. Soil microbes modify soil structure by aggregating both mineral and organic constituents via production of extracellular compounds with adhesive properties. Such compounds are produced by bacteria and fungi as a feeding mechanism, to aid colony cohesion, as protective coatings against moisture loss and as a means of adhesion.
In a 2002 to 2004 survey, growers reported horticultural oils and phosphoric acid to be the most common active ingredients, accounting for 27.7% and 18.4% of all pesticide active ingredients.
Pesticides must be registered under the federal Pest Control Products Act. In Ontario, they must be registered with the Ontario Ministry of Health under the, which distinguishes between 12 different classes.
Integrated Pest Management (IPM), reportedly practiced by over 70% of Canadian growers, is defined as “a dynamic decision-making process that emphasizes the use of non-chemical management techniques to prevent or manage pest problems”.
Farming in Canada
Farms in Canada
The number of farms in Canada peaked in 1941 and has since decreased by 73%. Ontario has the most farms - more than Manitoba, BC, and the Maritime Provinces combined - followed by Alberta and Saskatchewan. There are, on average, 1.4 farm operators per farm, with an average age of 55 (up from 47.5 in 1991).
Regarding quality of agricultural land in Canada, Ontario contains over half (56%) of Canada’s Class 1 agricultural land, while Saskatchewan has the most (39%) total dependable agricultural land (total of class 1, 2, and 3 agricultural land) of each province. Maritime provinces have no class 1 land at all and possess the least amount (6.4%) of all dependable agricultural land.
Canadian Farm Size
The average farm size in Saskatchewan is 7 times larger than that of Ontario (1724 vs 249 acres of farmland per farm). Surprisingly, the total amount of farmland has been relatively stable over the last century (+/- 5%), peaking in 1966 and having decreased by 9% since then. In 2011, cropland was the greatest component of farm land use, comprising 54.6% of the total farm area. Pasture followed in second place at 31.2% of the total.
Farmland is defined by Statistics Canada to include “cropland, summerfallow, improved and unimproved pasture, woodlands and wetlands, all other land (including idle land, and land on which farm buildings are located)”. An alternative base measure is cropland, which is defined as the total area of all census crops used for producing crops including hay field crops, tree fruits or nuts, berries or grapes, vegetables, seed…”
In today’s climate of corporate irresponsibility, it may seem intuitive that larger farms tend to be less sustainable than smaller farms, however, a 2016 meta-analysis showed that in fact farm size does not predict sustainability, but that mixed crop-livestock farms are more indicative of sustainable practices.
A group of researchers found that small farms, those less than 2 ha, represent 84% percent of farms and occupy about 12% of the world’s agricultural land. They also note that average farm size is increasing in high-income countries and decreasing in low- and medium-income countries.
Crop Variety
Varieties of wheat represent the plurality of crop production and of crop acreage in Canada.
Current Initiatives
The Canadian Agricultural Partnership is a five-year, $3 billion investment by federal and provincial/territorial governments to support programs aimed at strengthening the agri-food sector. The partnership focusses on growing trade and expanding markets; innovative and sustainable growth; and supporting diversity, dynamism, and evolution.
For example, through the Canadian Agricultural Partnership, Ontario’s ONFARM Project allocated $5.75 million over four years towards their stated goals of :
- oping a comprehensive, science-based method to measure soil health in Ontario.
- Measuring the effectiveness and impact of agricultural best management practices aimed at reducing nutrient run-off on farms.
- Working with farmers to gain evidence and awareness of how to improve productivity, soil health and water quality.
- Establishing applied research and monitoring sites to facilitate peer-to-peer knowledge transfer and capacity-building among industry professionals. Additionally, the Ontario Ministry of Agriculture, Food and Rural Affairs published a soil conservation strategy titled New Horizons: Ontario's Agricultural Soil Health and Conservation Strategy. This strategy spans from 2018 to 2030 and is summarized below.
Other Provinces
- The Research and Development Institute for the Agri-Environment, in partnership with Ministère de l'Agriculture, des Pêcheries et de l'Alimentation du Québec (MAPAQ), will complete a five-year study on the health of agricultural soils in 2022.
- The Saskatchewan Soil Conservation Association 's Carbon Advisory Committee published a soil carbon position paper establishing the role of science, addressing the role of soil health in climate change, and the proposal of a soil carbon credit.
- British Columbia just updated their Agricultural Environmental Management Code in 2019 to better reflect vulnerabilities in high-risk areas such as areas with high rainfall.
- Several provinces have map-based agriculture tools and records such as Alberta’s Soil Information Viewer, BC’s Soil Information Finder Tool (SIFT), and Ontario’s Agricultural Information Atlas.
- The Agricultural Research & Extension Council of Alberta, an industry organization, began the Alberta Soil Health Initiative in 2015, but it has since disappeared without much of a trace.
- Manitoba hosted the Soil Conservation Council of Canada’s (which is also based out of MB) Summit on Canadian Soil Health in October 2019
Summary and Recommendations
In Canada, the absolute number of farms is decreasing while average farm size is increasing, implying industrialization of the once independent farmer-dominated sector. Monoculture is increasing as demand for cash crops such as soy and wheat increase.
Tillage, and to a lesser degree monoculture, mineral fertilizers, and synthetic pesticides currently threaten crop yields on agricultural lands in Canada. Soil organic carbon, the primary indicator of agricultural soil health has historical declined; dropping 21.7% between 1910 and 1990. The decline, however, has slowed due largely to an increase in no-till practices and fertilizer use. Soil health can also be maintained and enhanced by employing conservation agriculture techniques other best management practices such as cover crops, precision nutrient application, and enhanced irrigation efficiency.
Areas Requiring More Attention
|
|