1. Micro Irrigation Is it the right choice and design considerations

2. First of all, micro irrigation is….
…the broad classification of frequent, low volume, low pressure application of water on or beneath the soil surface by drippers, drip emitters, spaghetti tube, subsurface or surface drip tube, basin bubblers, and spray or mini sprinkler systems. It is also referred to as drip or trickle irrigation. (NEH Part 652, Irrigation Guide, ‘97)
…an irrigation system for distribution of water directly to the plant root zone by means of surface or subsurface applicators. (Draft PS 441, ‘00)

3. Why would I use micro?
high uniformity with good design (90+ % achievable)
MAY result in excellent efficiency   inputs of water, power, and chemicals
 growth/production
less wetted surface area   evaporation &  weed problems
good in windy conditions (Uniformity &  evaporation)
good in undulating or steep areas (Uniformity)
excellent system control with automation
system flexibility
odd “field” shapes
supply nutrients to a specific point so spacing/variety of plant is not limiting
soils with low water holding capacity (frequent, low volume applications)

4. Why would I use micro? (cont.)
low operating cost
high efficiency with low pressures & flow rates  energy savings
less labor
odor control for waste water applications (esp. subsurface)
climate control
 or  temperature
 or  humidity
“disease” control
eliminate wetting of tree trunks
eliminate wetting of leaf/fruit
easily adapted to automation
……any others?…...

5. Why wouldn’t I use micro?
Issues associated with “dirty” water
potential clogging of emitters
cost of filtration
High Level of O&M Required
High Pest Damage Potential
High Initial Cost
Most, if not all, of these issues can be overcome but at some point it becomes a matter of economics

6. So, if micro is right for the situation….. Micro Design Considerations

7. Information Needed for Micro Design
Soil Characteristics (Water Holding Capacity, pH, etc.)
Tree/Shrub/Crop Characteristics
Layout (spacing, numbers, etc.)
Tree/Shrub/Crop Water Requirements over time
Root Zone over time
Sensitivity to Available Moisture (MAD)
Sensitivity to Water/Soil Quality
Good topographic survey - at least 2 foot intervals.
Water & Power Source
Location
Quantity
Quality
Owner/Operator Characteristics & Desires

8. Micro Design Considerations
NRCS Standards, Specifications & References
PS and GS 380 Windbreak/Shelterbelt Establishment
“…supplemental or permanent watering of the planting will be evaluated in areas with less than 20 inches average annual precipitation……”
“… Use Idaho Forestry TN 14 (12/93) for water requirements.”
“soak soil to 3 to 5 ft depth”
MAD of 50 to 60%
if poly fabric mulch used, supplemental water use may be reduced by up to 50%
PS 441 Irrigation System, Trickle (‘82)
design application efficiency not to exceed 90%
for individual laterals, individual emitter q ± 15% of average q
main and submains must meet PS 430
“A filtration system shall be provided…..”

9. Micro Design Considerations
NRCS Standards, Specifications & References
Draft PS 441 Irrigation System, Microirrigation (‘00)
max time of operation for design is 22 hr/day
design application efficiency not to exceed 90%
# & spacing of emitters (Pw) based on NEH 623, Ch. 7
manufacturer’s coefficient of variation
for individual subunits (blocks), individual emitter q ± 10% of average q (total variation of 20% allowed)
main and submains must meet PS 430
“A filtration system shall be provided…..” with constraints
other: pressure regulators, chemical treatment, flushing, subsurface installation, chemigation, germination, water quality, salinity issues
NEH Part 623, Irrigation, Chapter 7, Trickle Irrigation

10. Micro Design Considerations
NRCS Standards, Specifications & References
NEH Part 652, Irrigation Guide, Chapter 6, Irrigation System Design (9/97) - Windbreaks
if designing to irrigate throughout lifespan, use NEH 623, Ch. 7
if designing just for establishment
design to last at least first 5 years
after initial establishment of trees/shrubs water applications should be greater in volume and less frequent to encourage root zone development
suggests augering and backfilling a deep, small diameter hole near each tree/shrub to allow deeper penetration of water and, hence, deeper rooting
for arid & semiarid climates, apply water early in spring after soil thaws to fill soil profile
discontinue watering in the fall before freezing to encourage “hardening” (perhaps should irrigate after “hardening,” however)
do not provide full irrigation

11. Micro Design Considerations
System reliability/management is important
 soil volume wetted   WHC  “dry” quicker
Flushing ability
individual laterals
connect ends with flushing main (also gives system resiliency)
required velocity at end of lateral > than operating velocity
Runoff - Infiltration Rate vs. Application Rate
frequent applications  typically “wetter” soils   infiltration capacity during storm events
effects of weed barrier fabric
point sources
Saline/Sodic conditions
frequent applications  continuous dilution of salty water
but, “salt profile” can be moved back into root zone with precip
System Drainage
frequent cycling  overapplication in drainage areas

12. Micro Design Procedure (Irrigation Guide)
NOT a linear procedure since these steps are interrelated
Step 1: Determine net amount of water required
Step 2: Emitter design
Step 3: Subunit/block design
Step 4: Size laterals, submains, & mains
Step 5: Pump selection
Step 6: Filtration design
Steps 7 & 8: Fertilizer & chemical injection design
Step 9: Pressure gauge, valves, drains, measuring devices
Step 10: Irrigation scheduling plan
Step 11: O&M plan