C10 Farming

Lecture Overview

  • Title: Farming: Conventional and Sustainable Practices

  • Source: © McGraw Hill LLC.

  • Goal: End hunger, achieve food security and improved nutrition, and promote sustainable agriculture.

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Agenda

  • Understanding Soil

  • Soil Use, Erosion, and Conservation

  • Pests and Pesticides

  • Solutions to Current Challenges

10.1: Soils are Complex Resources

  • Definition of Soil: A mixture of five components:

    • Mineral grains: sand, silt, and clay.

    • Soil organic matter.

    • Living organisms.

    • Water.

    • Air.

  • Characteristics of Soils:

    • Complex and diverse.

    • Fragile and easily damaged.

    • Fertile soils are renewable but can be damaged to the point of non-repair.

  • Soil Development:

    • Takes 500-1000 years to grow 1 inch of fertile topsoil.

    • In the U.S., soil disappears 10 times faster than its natural replenishment rate.

    • Annually loses 1.7 billion tons of farmland, resulting in economic losses of approximately $37 billion from soil loss alone.

Variation in Soil Composition

  • Variation in composition leads to an almost infinite variety of soil types.

  • Soil texture (the amount of sand, silt, and clay) is crucial for soil characteristics:

    • Loam soils, ideal for crop cultivation, consist of:

    • 45% minerals (mix of sand, silt, and clay).

    • 5% organic matter.

    • 25% water.

    • 25% air.

Soil Components

  • Grain Sizes:

    • Sand: 0.05 - 2 mm.

    • Silt: 0.02 - 0.05 mm.

    • Clay: less than 0.02 mm.

Soil Fauna and Fertility

  • Role of Soil Organisms:

    • Soil bacteria, algae, and fungi decompose leaf litter, making recycled nutrients available to plants.

    • Nematodes help process organic material and create air spaces in the soil.

    • Larger macroinvertebrates (insects, spiders, mites) aerate the soil.

    • Mycorrhizal symbiotic relationships between plants and fungi:

    • Plants feed fungi, and fungi provide water and nutrients to the plants, enhancing growth.

Soil Ecosystems

  • Various organisms and their roles:

    • Centipedes, wood roaches, pseudo-scorpions, snails, mites, soil fungi, nematodes, cicada nymphs, and more contribute to the soil ecosystem.

Soil Stratification

  • Soils are stratified into horizontal layers called soil horizons:

    • O-Horizon: Loose and partly decayed organic matter.

    • A-Horizon: Mineral matter mixed with humus.

    • E-Horizon: Light colored mineral particles, zone of eluviation and leaching.

    • B-Horizon: Accumulation of clay transported from above.

    • C-Horizon: Partially altered parent material, weathered rock fragments.

10.2: How Do We Use Soil?

  • Arable Land:

    • Total ice-free land surface: 35.7 billion acres; only 11% (3.7 billion acres) is arable.

    • The rest is unsuitable due to various factors like climate, topography, or soil quality.

  • Arable land characterized by:

    • Best farming conditions in moderate climates with thick fertile soils.

    • Increased production has stemmed from enhanced fertilization, pesticides, and irrigation, not merely more cultivated land.

Importance of A Horizon

  • Identification of soils is primarily based on the thickness and composition of the upper layers:

    • Mollisols: Dominant in farming areas; thick, organic-rich A-Horizon from deep roots of prairie grasslands.

    • Alfisols: Crucial for farming; developed from deciduous forests with thinner A-Horizon and less organic matter.

Impacts of Conventional Agriculture on the Environment

  • Soil Degradation:

    • The deterioration of soil quality and capacity, leading to:

    • Soil erosion.

    • Soil compaction.

    • Nutrient loss.

    • Reduced biotic activity.

    • Salt accumulation.

  • Soil Erosion:

    • Removal of topsoil accelerated by wind and water; poor agricultural practices increase susceptibility.

    • Historical loss in the U.S.: 1/3 of topsoil lost between 1776 and 1976.

  • Modern Soil Loss:

    • USDA estimates a loss of 5 tons of soil per acre annually without productivity loss; Iowa's erosion rates are approximately 12 times higher.

    • Current loss in topsoil to the Mississippi River amounts to 64 tons per acre annually.

  • Worldwide Soil Loss:

    • Annual crop loss globally amounts to approximately 3 million hectares due to erosion.

    • From 1961 to 2021, arable land per person shrunk from 0.36 hectares to 0.18 hectares.

Soil Erosion Mechanics

  • Water Erosion Processes:

    • Sheet Erosion: Thin layer of surface removed.

    • Rill Erosion: Formation of small channels by gathering water.

    • Gully Erosion: Enlargement of rills into larger channels.

    • Streambank Erosion: Washing away from the banks of streams and rivers.

  • Wind Erosion:

    • Wind can match or exceed water as an erosive force, particularly in dry climates and on flat terrain.

  • Desertification:

    • Productive land converting to desert, often due to intensive farming practices, leading to increased soil loss and declining fertility.

Environmental Impact of Conventional Agriculture

  • Desertification:

    • Caused by salinization from overuse of water resources. Evaporation leaves behind toxic salt residue detrimental to soil health.

  • Biodiversity Loss:

    • Lower genetic diversity in crops increases vulnerability to diseases (e.g., U.S. corn blight of 1970 caused $2 billion in losses).

  • Groundwater Depletion:

    • Agriculture's significant freshwater use results in over-pumped aquifers, leading to saltwater intrusion.

  • Poor Irrigation Practices:

    • Result in large water waste and salinity issues.

  • Pesticide and Herbicide Dependency:

    • Over-reliance leads to pest resistance and impacts non-target species and human health.

Energy Intensity of Farming

  • Fossil fuel usage began with tractors in the 1920s; increased after WWII due to synthetic fertilizers.

  • The average distance food travels from farm to consumer is about 2400 km, emphasizing the benefits of local food consumption.

Agricultural Resource Management

  • Water Use in Agriculture:

    • Accounts for the largest global water use.

    • Issues include waterlogging and salinization.

  • Fertilizer Usage:

    • Essential for plant growth; however, excessive use leads to pollution. Nutrient replenishment through alternatives like manure and nitrogen-fixing bacteria is encouraged.

    • Average fertilizer use increased from 20 kg/ha in 1950 to ~100 kg/ha in 2022, with potential for higher production in Africa.

Soil Conservation Practices

  • Management Techniques:

    • Contour Plowing: Plowing along the slope to slow water flow.

    • Strip Farming: Planting alternating crops along contours.

    • Terracing: Creating level shelves to retain water and soil.

    • Using perennial species.

Best Management Practices (BMPs)

  • Erosion Prevention:

    • Minimum tillage or no-tillage.

    • Cover crops and strip cropping.

    • Windbreaks and terracing crops.

  • Enhanced Soil Fertility:

    • Trickle and drip irrigation.

    • Crop rotation and polyculture farming.

    • Use of green manure and mulch.

  • Reduced Pesticide Use:

    • Integrated Pest Management (IPM) techniques.

Cover Crop Benefits

  • Environmental Benefits:

    • Erosion reduction by maintaining soil structure.

    • Improved soil and water quality by retaining nutrients.

    • Nitrogen conservation through legume cover crops (e.g., up to 100 pounds of plant-available nitrogen).

  • Agronomic Benefits:

    • Enhanced weed suppression and soil health.

  • Economic Benefits:

    • Increased crop yields related to improved soil health.

    • Cover crops replenish soil nutrients reducing fertilizer costs.

Ground Cover Importance

  • Cover Methods:

    • Planting cover crops after harvest (e.g., clover).

    • Interplanting two crops in one field.

    • Mulching techniques.

10.3: Pests and Pesticides

  • Biological Pests:

    • Organisms such as insects or fungi that consume agricultural crops.

  • Pesticides:

    • Chemicals classified as:

    • Biocides: Kill a wide range of organisms.

    • Herbicides: Specifically kill plants.

    • Insecticides: Target insects.

    • Fungicides: Target fungi.

  • Synthetically produced pesticides are predominant in controlling pests.

Historical Context of Pesticide Use

  • Ancient civilizations utilized various substances to control pests:

    • Sumerians: sulfur; Chinese: mercury and arsenic; Greeks and Romans: oil, sulfur, ash.

  • Longstanding methods like crop rotation and burning were also used historically.

Modern Pesticide Considerations

  • Synthetic Organics:

    • Began with DDT in 1939; known for effectiveness but later determined harmful to ecosystems (e.g., eagle populations).

  • Current Usage:

    • Total U.S. pesticide use: about 5.7 billion pounds annually, predominantly in agriculture.

Types of Pesticides

  • 1. Organophosphates:

    • Common with significant toxicity; Roundup is widely used.

  • 2. Chlorinated Hydrocarbons:

    • Highly toxic and persistent; examples include Atrazine and DDT.

  • 3. Neonicotinoids and Fumigants:

    • Targeted for specific pest control but hazardous to health.

  • 4. Inorganic Pesticides:

    • Derived from toxic elements (mercury, arsenic); act as nerve toxins.

  • 5. Natural Organic Pesticides:

    • Extracted from plants with various efficacy.

Environmental Impact of Pesticides

  • Risks include harm to non-target species (e.g., honey bees), pest resurgence, and reliance on new chemicals as pests evolve resistance.

  • Persistent Organic Pollutants (POPs):

    • Substances like DDT that accumulate in fatty tissues and concentrate in food chains, posing risks to wildlife and humans.

Human Health Considerations

  • WHO reports significant pesticide poisoning cases worldwide, primarily affecting laborers in developing countries.

  • Long-term health effects remain challenging to assess with potential links to cancer, neurological issues, and other health problems.

Agricultural Treadmills

  • Concept introduced by Willard Cochrane in 1958:

    • Describes economic pressures to adopt new technologies continuously to improve yields, creating a cycle difficult to escape (e.g., pesticide, fertilizer, seed treadmills).

Food Security Challenges

  • Addressing climate change and agricultural dependency is essential for food security, especially for vulnerable populations.

  • Emphasis on utilizing current food production capacity to combat hunger, focusing on harvest efficiency and distribution.

Solutions for Sustainable Agriculture

  • Definition of Organic Farming:

    • Aims to emulate natural systems, excluding synthetic fertilizers and pesticides.

    • Regulations vary, focusing on ecological balance and biodiversity conservation.

  • Benefits of Sustainable Agriculture:

    • Studies indicate that organic practices improve soil health and environmental outcomes compared to conventional agriculture.

    • Adoption rates are low but growing, encouraging greater market presence.

Consumer Influence on Agriculture

  • Shifting towards vegetarian and organic diets can reduce environmental impacts.

  • Locally sourced food initiatives and community-supported agriculture (CSA) programs encourage sustainable practices.

Urban Agriculture

  • Increasing urban farming initiatives as more people reside in urban areas. Encouragement of local farms and community gardens.

Ending World Hunger

  • Goals focus on eradicating poverty and environmental sustainability initiatives to address root causes of hunger.

  • The United Nations’ Sustainable Development Goals aim for global equity, influencing health, education, and environmental health positively.

Conclusion

  • Soil conservation is critical for future food security and sustainable agricultural practices.

  • Implementing adjustments in farming methods, like cover cropping, can significantly reduce erosion and enhance yield potential. Despite production increases, food insecurity remains a pressing global issue.