irrigation design and maintenance for uniform water and ... 2014.pdfdrip and micro irrigation design...
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Irrigation Management and Maintenance for Uniform Water
and Chemical Application
Dr. Ben Burgoa Resource Conservation District of
Monterey County
Application Efficiency
1) “meeting a target irrigation depth for that event”
2) It is influenced by irrigation management and the irrigation system
Irrigation Management: Depth of water applied
• How much irrigation water is required to grow quality wine grapes depends upon: – Site: soil, microclimate……… – Stage of vine growth – Row spacing – Size of vine’s canopy – Amount of rainfall occurring during the growing
season
Distribution Uniformity (DU) “Measure of the uniformity with which irrigation
water is distributed to different areas in the field"
applied water of depth averagedepthquarter -low averageDUlq =
Gross Irrigation to Applied
lqDUdepthtarget nApplicatio Gross =
DU (%) Gross Application (in) 60 1.67 70 1.43 80 1.25 90 1.11
Target = 1 inch
DU Components • Differences in Discharge Between Emitters:
– Pressure differences – Plugging and wear of emitters – Manufacturing variation – Different emitter types in the same field
• Volumes applied not proportional to plant area: – Variation in plant spacing – Unequal drainage
Pressure and Emitter Flow Rates
TORO Turbo Non PC
Pressure and Emitter Flow Rate
TORO NGE Self-flushing PC Emitter
Pressure Measurements
• Where: – At the pump – At the manifold/valve – At the end of the most
distant and uphill hose
Flow Meter • Provide a quick indication of the operational
performance of the irrigation system
Plugging of Emitters
• Suspended Solids: – Organic: algae – Inorganic: sand
• Chemical Precipitation: – Calcium, iron, fertilizers
• Bacterial Growth
Guidelines of Potential “Pluggability” of water
HAZARD LEVEL LOW MODERATE SEVERE
Suspended Solids 50 ppm 50-100 ppm > 100 ppm
pH 7 7-8 >8
Salt 500 ppm 500-2000 ppm > 2000 ppm
Bicarbonate 100 ppm
Manganese 0.1 ppm 0.1 -1.5 ppm > 1.5 ppm
Total Iron 0.2 ppm 0.2 – 1.5 ppm > 1.5 ppm
Bacterial Population 10,000/liter 10,000-50,000/liter > 50,000 liter
Filter Maintenance • Observe the system as it completes a
backflush cycle – Check pressure gauges
Hose Screen Washers
• Remove hose screen washers and replace with regular washers
Unequal Drainage
Unequal Drainage Problems
• Some emitters may continue to drain after shut off
• Important in sloping ground and very short duration irrigations
• Solution: Flushout manifold
Uneven Spacing
• Different number of emitters per unit area caused by different plant spacing
• Not a factor in most fields
System Startup
• Flush the well before operation through the filter
• Flush drip lines, laterals and mains before system operation
• Check for leaks in drip line laterals and plugged emitters
Cal Poly ITRC Field Evaluations: Average Causes of Non-uniformity
(Micro and Drip) in California
• Pressure Differences: 45% • Plugging, Wear, Manufacturing Variation: 52% • Unequal Drainage: 1% • Application rate: 3%
Fertigation
• Injecting fertilizers through the irrigation system
• Benefits: – Nutrients can be directly supplied to the plant
roots – Nutrients can be “spoon-fed” at a rate that follows
the pattern of uptake of the crop
Irrigation Uniformity and Fertigation Uniformity
• Uniformity of the fertilizer application will depend on the uniformity of the drip system
0
20
40
60
80
100
0 20 40 60 80 100
Fert
ilize
r DU
(%)
DU of Drip Tape System (%)
(Cahn, 2013)
Rules of thumb for injecting fertilizer (Cahn et al. 2007)
• After injecting, allow enough time to flush the system completely of fertilizer
• For nitrate, inject as slowly as possible to achieve similar distribution in the soil at the head and at the tail of the field
Reference
• Burt and Styles. 2007. Drip and Micro Irrigation Design and Management for Trees, Vines, and Field Crops. Cal Poly ITRC.