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.