Micro Irrigation Is it the right choice and design considerations

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)

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)

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?…...

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

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

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

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…..”

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

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

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

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