Chapter 8 - Soils / Food and Agriculture

O horizon

At the top. Mostly organic matter and organic waste in process of decomposition.

A horizon

“Topsoil”. A mixture of mineral grains and organic matter; where much of the biological and root activity in soil takes place

B horizon

accumulates the various nutrients, clays, and dissolved minerals carried downward by infiltrating water from the horizons above

E horizon

sometimes in between A and B

C horizon

composed of weathered rock, broken up by physical, chemical, and biological weathering processes, and altered chemically in preparation for perhaps, someday, becoming a B horizon

D horizon

unaltered rock of the earths crust

Mycorrhizal Fungi

In a commensal relationship with plants, fungi attach to plant roots, taking sugars for their own metabolism while providing the plant with water and nutrients.

Plow

A device used by farmers to tear up and turn over the upper part of the soil to loosen it for the planting of new crop seeds, while killing any weeds (indigenous ecosystem colonizers) that may be starting to grow

Haber-Bosch Process

The process combines nitrogen and hydrogen at high pressures and temperatures to produce ammonia, an energy-intensive method used to make agricultural fertilizer

Weathering

breaks down bedrock through physical cracking and chemical dissolution by water and acids, turning solid rock into smaller pieces.

Erosion

The removal of soil by water or wind. Once soil is being transported, it is considered sediment that will be deposited somewhere downstream or downwind, where currents or winds are reduced. The faster the water or wind moves, the larger the particles that can be moved.

Contour plowing

creates small dams that reduce water runoff and soil erosion compared to regular plowing, though still more than in a natural ecosystem.

Integrated pest management

The introduction of predator species to eat agricultural pests to keep the pest population low enough to be inconsequential to crop yield

Fishing down the food web

The practice of catching fish from lower tropic levels, because fisherman already caught so many higher trophic level fish as to deplete their populations below what is practical for commercial fishing

Aquaculture

Raising fish in confinement for human consumption in fresh water

Mariculture

Fish (or shellfish) farming in the ocean

Farming up the food web

Feeding lower trophic fish to higher trophic fish in aquaculture wastes energy and speeds up overfishing, as we could have eaten the lower trophic fish directly. This accelerates fishing down the food web.

Earthworms are not

native to the glaciated northern US

Invasive worms reduce

ecosystem function (and rapidly decompose leaf litter)

Dust storms

from drought, extensive plowing, and high winds

What are the consequences of soil loss on a large scale?

• Huge areas have lost their most productive soil

• One third of U.S. topsoil has been lost

• Globally, an area the size of China and India has been lost

• Soil forms very slowly, while eroded soil becomes excess sediment

• Excess sediment muddies rivers, fills reservoirs, and disrupts coastal zones

Global causes of soil degradation

Orgrazing - 35%

Agriculture - 28%

Deforestation - 30%

What are some methods of soil conservation?

• Contour plowing

• Spring tillage

• No-till agriculture

• Crop rotation

No Till Agriculture

Dont plow at all between crops, leave the residue from the last crop on top

Tillage Systems

• Conventional tillage

• Clean tillage

• Mulch tillage

• Conservation tillage

• Minimum tillage

Crop rotation

Plant different crops on each patch to maintain soil chemistry, then swap

Cows require

much more resources then other animals (10x as many)

Potatoes are

very productive per hectare (takes a lot less land to produce a lot of potatoes)

Wheat

This crop is well-suited to dry climates and can thrive in northern regions

Rice

needs warmer weather, wet conditions

Corn (maize)

highly adaptable crop that can grow in a variety of climates

Demand-Based Farming

Supply as much and as fast as you can sell in the market (can result in overproduction)

Resource-Based Farming

Conserve natural resources - soil, water, nutrients, and soil chemistry, etc (contour plowing)

Organic farming

Enhance biodiversity, biogeochemistry, soil microbial activity. Minimize energy, and material input from off-site. Minimize impact on ecosystem functions (crop rotation, composting, etc)

Traditional Farming Methods used

Fang, Milpa, Swidden agriculture (Partial clearing, mixed crops, then secondary succession)

Integrated Pest Management (IPM)

A pest control approach that reduces reliance on pesticides by using a mix of natural methods and careful monitoring.

Fish Farming Environmental Impacts

• Concentration of disease

• Local eutrophication from nutrient overload

• Escape of GMO populations into natural populations

We would be 10 times better off eating the fish

we catch to feed to our farmed fish, instead of eating the farmed fish.

Genetically Modified Crops Problems

concerns about uncontrolled spread, terminator genes increasing costs, genetic contamination

Climate, Agriculture, and society

Irregular seasonal rainfall threatens rain-fed agriculture, making rural communities vulnerable to droughts and floods, which increases food insecurity. Timely climate information is essential for farmers to make informed decisions and reduce the impact of climatic shocks.

Agriculture profoundly affects ecosystems

• Deforestation

• Soil erosion

• Soil contamination

• Increased sediment load in rivers

• Increased dust production

• Desertification

• Genetic contamination

• Fishing down the food web

• Farming up the marine food web

Impact of Climate Change on Phenology

altering of first leaf dates, causing mismatches between flowering plants and pollinators. This can reduce fertilization and negatively affect crop yields.