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Questions and Answers
What is the result of over-application of fertilizers in soils?
What is the main difference between inorganic and organic fertilizers?
What is the result of nitrogen and phosphorous runoff from farms?
What is the primary source of soil contamination from industrial activity?
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What is the result of overgrazing in certain regions?
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What is the primary purpose of contour farming?
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How long does it take to produce 1 cm of natural topsoil?
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What is produced when decomposers break down organic matter?
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What is the main objective of sustainable soil management?
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What is the primary function of shelterbelts?
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What is the primary function of soil in food production?
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What is intercropping?
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What is the term for the process of breaking down rocks to form soil?
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What is the term for a dark, spongy, crumbly mass of material formed by partial decomposition?
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What is the main benefit of terracing?
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What is the term for the dislodging and movement of soil by wind or water?
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What is the primary goal of reducing tillage?
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What is the term for each layer of soil in a soil profile?
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What is alley cropping?
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What is the primary benefit of crop rotation?
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What is the primary factor that influences soil pH?
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What is the term for the decline in soil quality caused by its improper use?
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What is the term for the process of dissolved particles moving down through soil horizons?
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What is the term for the unaltered parent material at the bottom of a soil profile?
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What is soil degradation?
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What percentage of global grain production has been reduced due to soil degradation over the past 50 years?
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What is the primary cause of erosion?
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What is the estimated on-farm cost of agricultural land degradation in Canada per year?
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What is desertification?
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What is the estimated area of land affected by desertification?
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What was the result of the widespread cultivation of wheat and grazing of many cattle in North America from 1879-1929?
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What is the purpose of the Soil Conservation Council of Canada?
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What is the Universal Soil Loss Equation (USLE) used for?
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What is deposition in the context of soil erosion?
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Study Notes
Soil Degradation: A Global Concern
- Soil degradation is a serious global environmental problem that may be exacerbated by climate change.
- Soil degradation encompasses physical, chemical, and biological deterioration.
- Examples of soil degradation include:
- Loss of organic matter
- Decline in soil fertility
- Decline in structural condition
- Erosion
- Adverse changes in salinity, acidity or alkalinity
- Effects of toxic chemicals, pollutants or excessive flooding
- Soil degradation results from deforestation, agriculture, and overgrazing.
- Over the past 50 years, soil degradation has reduced global grain production by 13%.
Erosion and Its Effects
- Erosion occurs faster than new soil is formed.
- Erosion increases through overcultivating fields, overgrazing rangelands, and clearing forested areas.
- Flowing water deposits sediment in river valleys and deltas, making floodplains excellent for farming.
- Wind and water erosion can degrade ecosystems and agriculture.
Soil Erosion Mechanisms
- Wind (aeolian) erosion
- Water erosion (splash, sheet, rill, gully)
- Rill erosion moves the most topsoil, followed by sheet and splash erosion
- Predicting losses by erosion: Universal Soil Loss Equation (USLE) and Wind Erosion Prediction Equation
Soil Erosion and Its Consequences
- Humans are the primary cause of erosion.
- 19 billion hectares of croplands worldwide suffer from erosion.
- Kazakhstan lost tens of millions of hectares to wind erosion.
- Soil degradation over the next 40 years in Africa could reduce crop yields by half.
- The on-farm cost of agricultural land degradation in Canada is $670 million per year.
Desertification
- Desertification: a loss of more than 10% productivity from erosion, soil compaction, forest removal, overgrazing, salinization, climate change, and depletion of water sources.
- A type of land degradation that affects 1/3 of the planet’s land area.
- Most prone areas are arid and semiarid lands.
- Climate change could result in the displacement of 50 million people in 10 years.
The Dust Bowl
- Native prairie grasses originally held erosion-prone soils in place.
- Widespread cultivation of wheat and grazing of many thousands of cattle from 1879-1929.
- The Great Depression brought a cycle of poverty and overly intensive agricultural practices.
- Dust storms (black blizzards) travelled up to 2000 km, causing lung irritation, dust pneumonia, and grasshopper infestations.
Soil Conservation
- The Soil Conservation Council emerged from the experience of drought.
- 1935: Prairie Farm Rehabilitation Administration (PFRA).
- Soil at Risk: Canada’s Eroding Future (1984).
- Soil Conservation Council of Canada:
- National plan
- Better public awareness
- Better communication among stakeholders
- Develop policies and production methods.
Soil Resources
- Soil can take anywhere from 500 to 100 years to produce 1 cm of natural topsoil, depending on local conditions.
- Soils are the foundation of food production and food security, supplying plants with nutrients, water, and support for their roots.
- Soils function as Earth’s largest water filter and storage tank, filtering and cleaning tens of thousands of cubic kilometers of water that pass through them each year.
Soil as a System
- Soil consists of mineral matter, organic matter, air, and water.
- Dead and living microorganisms, and decaying material.
- Bacteria, algae, earthworms, insects, mammals, amphibians, and reptiles.
Soil Formation
- Soil formation begins when parent material is exposed to the effects of the atmosphere, hydrosphere, and biosphere.
- Parent material can be lava, volcanic ash, rock, dunes, or bedrock.
- Weathering: the physical, chemical, or biological processes that break down rocks to form soil.
- Climate, topography, source material composition, and time are factors.
Soil Profile
- Soil profile: the cross-section of soil as a whole.
- Horizon: each layer of soil.
- Topsoil: inorganic and organic material, most nutritive for plants.
- Leaching: dissolved particles move down through horizons.
- Litter: surface deposits of leaves, branches, mosses, animal waste.
Soil Properties
- Soils vary in color, texture, structure, and pH.
- Soils are classified into 10 orders based largely on the processes thought to form them.
- Soil color indicates its composition and fertility.
- Soil texture: the size of particles (clay, silt, sand).
- Soil structure: a measure of soil’s “clumpiness”.
- Soil pH influences a soil’s ability to support plant growth.
Soil Degradation and Contamination
- Soil degradation: the decline in soil quality caused by its improper use, usually for agricultural, pastural, industrial, or urban purposes.
- Fertilizer: substances that contain essential nutrients but over-application can damage soils.
- Inorganic fertilizers: mined or synthetically manufactured mineral supplements.
- Organic fertilizers: the remains or wastes of organisms, such as manure, crop residues, and fresh vegetation.
- Compost: produced when decomposers break down organic matter.
- Nitrogen and phosphorous runoff from farms and other sources can lead to algal blooms.
- Nitrates can leach through soil and contaminate groundwater.
- Pesticides are another source of soil contamination.
- Industrial activity contaminates soil through inappropriate disposal of wastes and improper storage.
Sustainable Soil Management
- Minimize further degradation of soils and restore the productivity of soils that are already degraded in regions where people are most vulnerable.
- Stabilize global stores of soil organic matter, including both soil organic carbon and soil organisms.
- Stabilize or reduce global use of nitrogen and phosphorus fertilizer, while increasing fertilizer use in regions of nutrient deficiency.
- Improve our knowledge about the state and trend of soil conditions.
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Description
Learn about soil formation, renewal time, and its impact on food production and security. Understand the importance of soil management and its role in supplying plants with nutrients, water, and support.
