Introduction to Sustainable Agriculture (College Board AP® Environmental Science) : Study Guide

Soil conservation methods

What is soil conservation?

• Soil conservation involves practices aimed at:

  • Preventing soil erosion

  • Preserving soil fertility

• Protecting soil prevents loss of productivity and maintains ecosystem health

Methods of soil conservation

Contour plowing

• Plowing along (i.e. parallel to) the contours of slopes rather than vertically up and down

  • Minimises soil erosion by reducing length and speed of water flow downhill

  • Prevents gully formation

  • Increases water infiltration, conserving moisture

Windbreaks

• Rows of trees or shrubs planted to reduce wind speed across fields

  • Provides physical barrier to wind

  • Reduces wind erosion by decreasing wind velocity

  • Protects topsoil

  • Helps protect crops from wind damage and damage caused by wind-blown soil

Perennial crops

• Crops that live and produce yields for multiple years without needing replanting annually

  • Deep roots help anchor the soil, preventing erosion

Terracing

• Creating level areas on steep slopes by building steps or terraces

  • Significantly reduces water runoff, protecting against erosion

  • Increases infiltration

  • Commonly used on hillsides for farming, especially in mountainous regions

No-till agriculture

• Farming without disturbing the soil through plowing or tilling

  • Protects soil structure, reduces erosion, and maintains soil biodiversity

  • Retains organic matter and moisture

Strip cropping

• Alternating rows of different crops planted side by side

  • Protects the soil by covering it throughout the growing season

  • Reduces erosion by preventing continuous soil exposure to wind and water

Strategies to improve soil fertility

Importance of soil fertility

• Soil fertility is crucial for growing healthy crops and ensuring high agricultural productivity

• Improving fertility involves

  • replenishing nutrients

  • maintaining soil structure

  • promoting beneficial organisms

Methods to enhance soil fertility

Crop rotation

• Alternating different crops in the same area over different seasons or years

  • Prevents nutrient depletion as different crops use and replenish different nutrients

  • Disrupts pest and disease cycles, reducing the need for chemical treatments

• Example: Alternating legumes (beans, peas) that fix nitrogen in the soil with nutrient-intensive crops like corn

Green manure

• Growing plants specifically to be incorporated into the soil as organic matter

  • This is achieved by cutting, mowing, or plowing them under the soil surface before they fully mature

  • This process allows the decomposing plants to

    • improve soil structure

    • release nutrients, increasing soil nutrient content

    • add organic nitrogen and carbon to soil

    • boost microbial activity

    • increase soil moisture retention

  • Common green manure plants include clover, alfalfa, and vetch

Limestone application (liming)

• Adding crushed limestone to acidic (low pH) soils to increase pH and improve fertility

  • Neutralizes soil acidity, improving nutrient availability (particularly calcium and magnesium)

  • Encourages beneficial microbial activity and plant growth

• Example: Widely used in acidic agricultural soils to maintain ideal pH levels for crops

What is rotational grazing?

Definition of rotational grazing

• Rotational grazing is the practice of regularly moving livestock between different pastures

Benefits of rotational grazing

Prevents overgrazing

• Overgrazing depletes plant cover

  • This can lead to soil erosion and decreased land productivity

• Rotational grazing limits grazing pressure in any single area, giving plants time to regrow

  • This allows vegetation time to recover, improving pasture health

Improves soil health

• Healthier vegetation protects soil from erosion and enhances soil structure

• Increased plant diversity improves nutrient cycling and organic matter in the soil

Increases livestock productivity

• Livestock have consistent access to fresh, nutritious forage

  • This leads to healthier livestock and better livestock growth rates

• Reduces the spread of parasites and diseases by preventing animals from grazing in contaminated areas

Enhances water retention

• Well-managed pastures have strong root systems, reducing water runoff and improving infiltration

• Helps maintain moisture in the soil, supporting plant growth even in dry conditions

Challenges of rotational grazing

• Requires careful planning to determine grazing schedules and pasture recovery times

• Fencing and infrastructure costs may be higher than continuous grazing systems

• Monitoring is essential to prevent overuse of specific areas and ensure optimal forage regrowth

Awaiting image: Rotational grazing
Image caption: Rotational grazing is the practice of regularly moving livestock between different pastures