BRAE 340 Final with verified answers
(latest update)
What should you do with a saline (high ECe and non-alkaline) soil? What's the rule of thumb for
it - correct answer ✔✔Reclamation leaching. Rule of thumb is reclamation leaching can lower
salinity by 90% if an equivalent root zone depth of water is applied.
What should you do for a soil with high ECe and an ESP higher than 15? This is a saline-alkaline
soil - correct answer ✔✔If the soil has free lime, then either add sulfur or sulfuric acid before
reclamation leaching. If no free lime, add calcium then irrigate heavily to leach
What happens to ECe throughout an irrigation cycle? - correct answer ✔✔It stays steady
WHat happens to ECsw throughout an irrigation cycle - correct answer ✔✔Increases
True or Falfe: ECe is always less than ECsw - correct answer ✔✔True
What are the 4 types of EC - correct answer ✔✔ECiw or ECw: EC of irrigation water
ECsw: EC of the soil water
ECe: EC of the saturation extract from the soil.
ECe*: the critical value of ECe for a specific crop, beyond which yield declines occur.
As the soil drys out and SMD gets larger, what happens to ECe - correct answer ✔✔It doesn't
change
What is a crop stage that's very sensitive to Salinity - correct answer ✔✔Germination.
,Give me 3 general principles of why salt accumulation occurs on top of the soil - correct answer
✔✔Salt moves with water, Water moves from wetter to dry portion of the soil (i.e. the surface
where evaporation occurs), And salt stays behind after evaporation.
Where should you plant on the seed bed to avoid salt damage - correct answer ✔✔To avoid salt
damage, do not plant seeds under the highest point of the seed bed.
What can make the drainage coefficient increase and decrease drain spacing? - correct answer
✔✔Deep percolation: Leaching requirement, Distribution Uniformity, and Poor timing
What can make the saturated hydraulic conductivity (K) go up and increase drain spacing? -
correct answer ✔✔The K will go up and increase drain spacing with coarse textured sandy soils.
What can make the height of the water table (m) above drains go up? - correct answer
✔✔Deeper drains, shallower root zones.
When is the impermeable barrier below the drains (a) larger? - correct answer ✔✔Shallower
drains, When the barrier itself is deeper
Name some concepts that can increase drain spacing and decrease costs - correct answer ✔✔-
Higher AE's (reduce deep percolation and drainage coefficient)
o Higher DU's (reduce deep percolation due to DU)
o Lower LR's Crops that are relatively salt tolerant Irrigation water that isn't very salty (low ECiw)
o Perfect timing (provides adequate leaching while minimizing deep percolation)
o Coarser textured soils (increased hydraulic conductivity)
o Deep impermeable barriers (allow large m, d and/or a values)
, Name some things that would decrease drain spacing and increase costs - correct answer ✔✔o
Lower AE's (increased deep percolation and drainage coefficient)
o Lower DU's (increased deep percolation due to DU)
o Higher LR's Crops that are relatively salt sensitive Irrigation water that is more salty (high
ECiw)
o Over irrigation (increased deep percolation due to poor timing)
o Under irrigation (provides insufficient leaching, and increased salt accumulation in the field
o Finer textured soils (decreased hydraulic conductivity)
o Shallow impermeable barriers (need smaller m, d and/or a values)
What is the drainage coeffecient and the equation for it - correct answer ✔✔Its the amount of
water that needs to be drained away, usually measured in inches/day. Equation is gross-ETc. and
gross is just ETc/(AE x (1-LR))
What's the equation for SMDmax - correct answer ✔✔AWHC (in) x MAD (%)
What Dmin equal with perfect timing/good management - correct answer ✔✔SMD + LR
WHat is Dave equal to - correct answer ✔✔the infiltrated amount or Dmin/ D.U.
What are the two basic questions in irrigation scheduling? - correct answer ✔✔How much
water should I apply? and When do I irrigate?
How do you figure out the time between irrigations? - correct answer ✔✔SMDmax (in)/ETc
(in/day)
What is ETc and what's the equation for it - correct answer ✔✔ETc=Kc x ETo.
ETc is the crop evapotranspiration, usually in inches per day
(latest update)
What should you do with a saline (high ECe and non-alkaline) soil? What's the rule of thumb for
it - correct answer ✔✔Reclamation leaching. Rule of thumb is reclamation leaching can lower
salinity by 90% if an equivalent root zone depth of water is applied.
What should you do for a soil with high ECe and an ESP higher than 15? This is a saline-alkaline
soil - correct answer ✔✔If the soil has free lime, then either add sulfur or sulfuric acid before
reclamation leaching. If no free lime, add calcium then irrigate heavily to leach
What happens to ECe throughout an irrigation cycle? - correct answer ✔✔It stays steady
WHat happens to ECsw throughout an irrigation cycle - correct answer ✔✔Increases
True or Falfe: ECe is always less than ECsw - correct answer ✔✔True
What are the 4 types of EC - correct answer ✔✔ECiw or ECw: EC of irrigation water
ECsw: EC of the soil water
ECe: EC of the saturation extract from the soil.
ECe*: the critical value of ECe for a specific crop, beyond which yield declines occur.
As the soil drys out and SMD gets larger, what happens to ECe - correct answer ✔✔It doesn't
change
What is a crop stage that's very sensitive to Salinity - correct answer ✔✔Germination.
,Give me 3 general principles of why salt accumulation occurs on top of the soil - correct answer
✔✔Salt moves with water, Water moves from wetter to dry portion of the soil (i.e. the surface
where evaporation occurs), And salt stays behind after evaporation.
Where should you plant on the seed bed to avoid salt damage - correct answer ✔✔To avoid salt
damage, do not plant seeds under the highest point of the seed bed.
What can make the drainage coefficient increase and decrease drain spacing? - correct answer
✔✔Deep percolation: Leaching requirement, Distribution Uniformity, and Poor timing
What can make the saturated hydraulic conductivity (K) go up and increase drain spacing? -
correct answer ✔✔The K will go up and increase drain spacing with coarse textured sandy soils.
What can make the height of the water table (m) above drains go up? - correct answer
✔✔Deeper drains, shallower root zones.
When is the impermeable barrier below the drains (a) larger? - correct answer ✔✔Shallower
drains, When the barrier itself is deeper
Name some concepts that can increase drain spacing and decrease costs - correct answer ✔✔-
Higher AE's (reduce deep percolation and drainage coefficient)
o Higher DU's (reduce deep percolation due to DU)
o Lower LR's Crops that are relatively salt tolerant Irrigation water that isn't very salty (low ECiw)
o Perfect timing (provides adequate leaching while minimizing deep percolation)
o Coarser textured soils (increased hydraulic conductivity)
o Deep impermeable barriers (allow large m, d and/or a values)
, Name some things that would decrease drain spacing and increase costs - correct answer ✔✔o
Lower AE's (increased deep percolation and drainage coefficient)
o Lower DU's (increased deep percolation due to DU)
o Higher LR's Crops that are relatively salt sensitive Irrigation water that is more salty (high
ECiw)
o Over irrigation (increased deep percolation due to poor timing)
o Under irrigation (provides insufficient leaching, and increased salt accumulation in the field
o Finer textured soils (decreased hydraulic conductivity)
o Shallow impermeable barriers (need smaller m, d and/or a values)
What is the drainage coeffecient and the equation for it - correct answer ✔✔Its the amount of
water that needs to be drained away, usually measured in inches/day. Equation is gross-ETc. and
gross is just ETc/(AE x (1-LR))
What's the equation for SMDmax - correct answer ✔✔AWHC (in) x MAD (%)
What Dmin equal with perfect timing/good management - correct answer ✔✔SMD + LR
WHat is Dave equal to - correct answer ✔✔the infiltrated amount or Dmin/ D.U.
What are the two basic questions in irrigation scheduling? - correct answer ✔✔How much
water should I apply? and When do I irrigate?
How do you figure out the time between irrigations? - correct answer ✔✔SMDmax (in)/ETc
(in/day)
What is ETc and what's the equation for it - correct answer ✔✔ETc=Kc x ETo.
ETc is the crop evapotranspiration, usually in inches per day
