06. Agriculture, Soil, and Food Systems Free Online FlashCards

What is commercial agriculture?

Commercial agriculture produces crops or livestock mainly for sale in regional, national, or global markets.

What is polyculture?

Polyculture grows multiple species together or in rotation. Diversity can interrupt pest cycles, improve nutrient use, and reduce the risk of one disturbance destroying the entire harvest.

What does agricultural yield measure?

Yield is production per unit of land, such as kilograms of wheat per hectare.

Which soil horizon is topsoil?

The A horizon is topsoil: a mixture of mineral particles and organic matter that is usually the most biologically active and agriculturally valuable soil layer.

Which soil texture is often favorable for agriculture?

Loam is a balanced mixture of sand, silt, and clay that is often favorable for agriculture.

What does cation-exchange capacity measure?

Cation-exchange capacity is soil’s ability to hold positively charged nutrients such as potassium, calcium, magnesium, and ammonium.

Which erosion stage forms large, persistent channels?

Gully erosion occurs when concentrated runoff forms large channels that are difficult to eliminate with ordinary tillage.

What is agricultural soil salinization?

Salinization occurs when irrigation water evaporates and leaves dissolved salts in soil. High salt concentrations make it difficult for plants to absorb water.

Which irrigation method delivers water near plant roots?

Drip irrigation delivers small amounts of water near plant roots through tubes or emitters, reducing runoff, evaporation, and deep percolation.

What happens when groundwater pumping exceeds recharge?

Aquifer depletion occurs when groundwater is pumped faster than natural recharge. It can lower water tables, reduce streamflow, increase pumping costs, and cause land subsidence.

How can excess fertilizer cause fish kills?

Eutrophication is nutrient enrichment that promotes algal growth; decomposition of excess algae can deplete dissolved oxygen and cause fish kills.

What are the four principles of the 4R nutrient approach?

The 4R nutrient approach uses the right source, rate, time, and place to reduce nitrogen and phosphorus losses to surface water and groundwater.