5.15: Sustainable Agriculture

Learning Objective: Describe sustainable agricultural and food production practices

Essential Knowledge:

• The goal of soil conversation is to prevent soil erosion. Different methods of soil conservation include:

  • Contour plowing

  • Windbreaks

  • perennial crops

  • terracing

  • no-till agriculture

  • and strip cropping

• Strategies to improve soil fertility include crop rotation and the addition of green manure and limestone

• Rotational grazing is the regular rotation of livestock between different pastures to avoid overgrazing in a particular area

Soil Conservation

• Agricultural techniques that minimize erosion (US is losing topsoil to erosion 10x faster than it forms)

• Prevents loss of

  • Nutrients in topsoil

  • Soil moisture

  • decomposers in topsoil

  • organic matter that traps soil moisture

Types of Soil Conservation

Contour Plowing:

• Plowing parallel to natural slopes of the land instead of down slopes prevents water runoff & soil erosion

• Forms mini terraces that catch water running off, conserving soil & water

Terracing:

• Cutting flat “platforms” of soil into a steep slope

• Fatness of terraces catches water & prevents ti from becoming runoff and eroding soil

Perennial Crops:

• Crops that live year-round and are harvested numerous times

• Loner, more established roots & prevention of bare soil between harvest

Windbreaks:

• Using tees or other plants to block the force of the wind from eroding topsoil

• It can be used as a source of firewood, fruit (income)

• Can provide a habitat for pollinators & other species

No till:

• Leaving leftover crop remains in the soil instead of tilling under

• Adds organic matter to soil (nutrients, soil cover, moisture)

• Prevents erosion from loosened soil

Strip Cropping:

• Another name for intercropping

• Alternating rows of less dense crops (corn, soy, cotton) to prevent runoff from eroding soil from less dense rows of crops

Improving Soil Fertility:

• Methods of restoring nutrient levels in the soil (N, P, Ca, Mg)

Crop Rotation:

• Replanting the same crops continuously depletes soil of the same nutrients

• Crop rotation can allow soil to recover from nitrogen-demanding crops like corn

• Peas/beans (legumes) have nitrogen-fixing bacteria in their root nodules that can return nitrogen to the soil

Green Manure:

• Green manure is leftover plant matter from a cover crop - a crop planted in the offseason, between harvest & replanting of the main crop

  • Cover crop roots stabilize soil limiting topsoil erosion

  • Remains of cover crops (green manure) left in field breakdown to release nutrients into the soil

Limestone:

• Limestone releases calcium carbonate (base) which neutralizes acidic soil

  • Acidic soil has a high H+ ion concentration, which displaces + charges nutrients from the soil (leeching them out)

  • Acidic soil also makes toxic metal (aluminum) more soluble in soil

  • Calcium is a needed plant nutrient as well

Rotational Grazing:

• Regular rotation of livestock to different pastures to prevent overgrazing

• Overgrazing can kill plants, compact soil, and lead to erosion to topsoil

• Rotational grazing can actually promote pasture growth at than normal rate

• Clips grass back to length where growth is fastest & encourages deeper root growth