Irrigation and Drainage

Question 1

Furrow

Answer 1

• irrigation
• water flows down path between crop rows
  
  • made by tillage equipment
• inexpensive
• not most efficient irrigation system

Question 2

Sprinkler

Answer 2

• efficient reducing surface runoff erosion
• expensive
  
  • but automated, reducing labor costs
• if evapotranspiration exceeds maximum application rate, crop damage can occur

Question 3

Drip / trickle

Answer 3

• water applied at low volume in specific areas
• efficient
• can be automated

Question 4

Subsurface Irrigation

Answer 4

• water applied through buried tubes that contain openings
• installed in rootzone below tillage depth
• can be automated, but is expensive
• Water use very efficient, application rates reduced
• Dist of water uniform where plant roots are active

Question 5

Subsurface Drain / tile

Answer 5

• line of tiles, is placed in soil to lower the depth of qter table to the depth of the tiles
• SPacing of tiles is dependent on the permeability of the soil
  
  • more permeable the sol, the wider the spacing

Question 6

Water Balance Equation to Schedule Irrigation

Initial soil moisture deficit 1 inch, and present soil moisture deficit is 6 inches, Irrigation would be needed in how many days if 2 inchs of rain fell and average ET is .6 inches per day.

Answer 6

• (irrigation deficit - current deficit) + (rainfall) / ET
• (6 - 1 + 2) / .6 = 11.7 days

Question 7

Water Use Efficiency Calculation

Answer 7

• Water productivity (WP) - the ratio of crop production or yield to the amount of water trasnpired by the crop
  
  • if 10,000 lbs / acre of hay is produced, and 12 inches of water / acre are transpired,
    
    • WP = 10,000 / 12 = 883 lb / inch
• • WUE = the amount of water transpired by the crop to water applied to the crop
    
    • expressed as a percentage
    • 15 inches/acre applied and 12 inches/ acre transpired
      
      • 12/15 = 80% WUE

Question 8

Soil Texture and Tile Drains

Answer 8

• Tile drains function in saturated soils and are designed to lower water tables near soil surface
  
  • must be cost effective
• Tile line spacing increases as the rate of saturated water movement in the soil increases
  
  • tile line spacing is larger for sandy soil than clay soil
• Depth of Tile drain is a function of depth of water table, depth lowered to
  
  • The depth to which a water table can be lowered increases as the rate of saturated movement in the soil increases
    
    • (soils are sandier)

Question 9

Eutrophication, hypoxia, anoxia

Answer 9

• refers to the enrichment of a surface water with particular emphasis on increased concentrations of
  
  • Phophorus, Nitrogen, organic C
  • Eutropic bodies of water tend to have low levels of dissolved oxygen, algal blooms, and excessive aquatic plant growth
• hypoxia refers to bodies of water that have low Oxygen levels detrimental to aerobic life
• Anoxia is the complete lack of oxygen

Question 10

ppm vs mg/L

Answer 10

• ppm = mg/L

Question 11

Nitrate analysis as nitrate (NO₃^-)

vs

Nitrate analysis

Answer 11

• Nitrate Analysis = mg of NO₃^- in a liter of water
  
  • molecular weight of Nitrate 62
• Nitrate N = mg of nitrogen in the nitrate form in a liter of water
  
  • molecular weight of Nitrogen 14

Question 12

Health Risks of Nitrate Nitrogen or coliform bacteria

Answer 12

Nitrates in drinking water

• methemoglobinemia (blue baby syndrome)
  
  • very poor oxygen transport in blood

Coliforms

• microorganisms found in the intestines of man and other warm blooded animals

Question 13

Bioreactors

Answer 13

• subsurface trenches that are filled with wood chips
  
  • water held within the drainage control structure is passed through the bioreactor where nitrate is denitrified and released to the atmosphere as nitrogen gas
    
    • wood chips serve as energy source for the anaerobic process
  • removes nitrate from water leaving the field

Question 14

Salinity water quality

Answer 14

• salinity in drinking / irrigation waters increases potential to damage humans, plants, animals
  
  • salinity tolerance greater in animals than humans
  • plants vary in salinity tolerance
• sodicity
  
  • high levels of sodium has same health problems as ingesting too much sodium with food