Principle Soil Science

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class: k46b

principle soil science

• Inputs and losses affecting water budgets?

Irrigation, rain

Transpiration, evaporation

• How do water budgets influence cropping systems?

  The amount of water stored in the soil at the beginning of a crop growing season is measured. Then the total amount of water supplied to the plant by rainfall and irrigation during the growing season is recorded. Finally, the amount of water stored in the soil at the end of the crop growing season is measured. The difference between the beginning soil water and end soil water, plus rainfall and irrigation, is approximately equal to crop water use.

 • What are the benefits and problems with irrigation?

benefits

Increase of food production.

Increase income & national cash flow.

Increase labor employment.

Increase standard of living.

Increase value of land.

problems

Salinity and alkalinity of land.

Pollution of underground water.

• Types of irrigation? Pros and cons of each?

Flood and Furrow

Conts:

– Use lots of water

– Variable water distribution

- Waterlogging if soil not permeable

• Benefits:

– Don’t need $$ for specialized equipment

– easy to maintain

– labor costs lower

• What soil properties affect infiltration?

It is dependent on:

– Soil Texture: infiltration is higher in sandy soils than clayey soils

– Soil Water Content: infiltration will be higher in dry soils than in wet soils

– Soil Structure: Infiltration can decrease if soil structure is disrupted

• Purpose and principals of soil drainage?

Lowers water tables

 Carries away salts

 Increases aeration, mineralization, nutrient availability

What is ion exchange?

ion exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex.

• What determines the adsorption strength of a cation?

Adsorption strength depends on:

– Valence (Higher charge, stronger attraction)

– Hydrated radius (Larger hydrated radius, weaker attraction)

– Cation solution concentration (Higher concentration, stronger adsorption)

• What is CEC?

  Cation exchange capacity

  Total amount of exchangeable cations that can be held by a given mas of soil

• What determines CEC?

    pH level

    How much clay is present

    Type of clay that is present

    How much OM is prsent