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Optimum Pumpkin Production: Plastic Mulch versus Bare Soil at Variable Irrigation Rates
Brian Leib & Wesley Wright – BESS Walt Hitch & Brent Smith – Plateau REC Rob Ellis – REC at Greeneville
WTREC Pumpkin Field Day – September 27, 2012
100% Irrigation
50% Irrigation
No Irrigation
Bare Soil Plastic Mulch & Raised Beds
Treatments: Pumpkin Production and Effective Rainfall
Pumpkin Growth In Mid July
-2004 planted June 23 -2006 planted June 14&15 -2007 planted Mid June
Magic Lantern in 2004 & Sorcerer in 2006 & 2007 at a 4’x6’ Admire seed treatment Pre-plant fertilizer Pre-emerge Weed Control
Pumpkin Growth in Mid August
Sometimes Additional Weed burn Required Weekly fertigation Fungicide and insecticide
Pumpkin Harvest
Crossville – Oct 1, 2004 Crossville – Sept 13, 2006 Greeneville – Oct 10, 2006 Crossville – Sept 10, 2007 Greeneville – Oct 5, 2007 Greeneville – Oct 1, 2008
Pumpkin Yield
Rainfall, Water Use & Irrigation
Crossville Greeneville Average Year
Rain Rain Water Balance
2004 2006 2007 2006 2007 2008 Rain Use Irrig
Inch Inch Inch Inch Inch Inch Inch Inch Inch
JUNE 4.6 4.5 3.2 4.0 2 2.4 4.5 1.4 0.7
JULY 6.1 4.4 2.6 5.4 5.6 4.0 4.9 3.6 4.5
AUG 2.4 3.3 2.2 7.1 0.6 3.9 3.9 4.8 4.3
SEPT 8.4 5.9 2.9 7.9 2.8 2.1 3.6 3.6 1.1
TOTAL 21.6 18.1 10.8 24.4 11.0 12.4 16.9 13.5 10.5
Conclusions Plastic Mulch and Drip Irrigation look like a good investment for
Pumpkin Production based on the data from wet & dry years.
Soil was drier under Plastic Mulch but a good portion of the Rainfall was Effectively used by the Pumpkins. The drier the soil under the mulch, the higher the rainfall effectiveness. The larger the rainfall event, the greater the soil water increase under the bed.
Soil Moisture Sensors can be used to Manage Irrigation under Plastic Mulch but the Water Balance Approach will require more effort. A simple rule like 50% effective does not always apply.
Pumpkin yield always responded to the Higher Irrigation Levels (irrigate like rain does not count). Is there enough savings in water and fertilizer to Economically Justify a high level of Irrigation Management to prevent over watering? Be a Good Neighbor.
Basic of Drip Irrigation for Fruit and Vegetables
Slide Set and Narrative Provided by Dr. Brian G. Leib Biosystems Engineering & Soil Science
The University of Tennessee Extension
2012 Profit & Production on Small Acreage
Availability of Water Supply?
Depth Applied
On-Time Well or Pump Flow Rate
Storage Volume
Humid Region 1.5 inches per week
24 – 7 zones
4.5 gpm per acre
0.14 ac-ft per acre per week
Safe Deficit w/ Good Soil
1.0 inch per week
24 – 7 zones
3.0 gpm per acre
0.09 ac-ft per acre per week
Drip Irrigation (possible rate)
24hrs at 1”/wk No zones
21 gpm per acre
Frost Protect Sprinklers
12hrs-7 nights No zones
70 gpm per acre
1.08 ac-ft per acre per week
Drip Type & Placement for Fruit & Vegetables Sub
Surface Ground Surface Trellis
Drip Emitters
Perennial Perennial
In-line Drip Tube
Perennial
Weed Barrier
Perennial Perennial
Drip Tape
Annual Perennial
Plastic Mulch
Annual
Hydraulics of Drip Irrigation
Flow is 20 gpm 1.5” pipe 1” pipe
0.71 psi/100’ 4.59 psi/100’
2.31 feet 1 psi
23.1’ 10 psi
Change In Pressure From Elevation
Loss In Pressure From Pipe Friction
Increased Pressure & Orifice Size Increases Flow
In-line Slope (%) Emitters -5.0 -2.5 0.0 2.5 5.0
18mm, 24”, 0.55 gph 850’ 920’ 920’ 920’ 920’
Works from 7 to 60 psi for Pressure Compensating
Length of Run for Drip Irrigation
Drip Slope (%) Tape -5.0 -2.5 0.0 2.5 5.0
508-12-450 225’ 600’ 800’ 225’
Usually 8 to 15 psi depends on wall thickness
Determine Number of Irrigation Zones (flow of product divided by flow available)
5 gpm available to operate 2000’ of 450 drip tape 0.45 gpm/100’ x 2000’ = 9 gpm 9 gpm / 5 gpm = 1.8 or 2 zones needed Use Valves and Pipes to create Zones
Simplified PVC Pipe Chart (5 ft/sec Rule) for Delivery and Header Lines
Size in Inches Flow (gpm) 1 1 – 15 1 ¼ 16 – 28 1 ½ 29 – 37 2 38 – 59
Pressure Regulators for Drip
Designated Pressure over A Specified Flow Range
Can be Adjustable
Protects Drip Equipment
Maintains Proper Operating Pressure even when the Source Pressure Varies
Prevent Emitter Clogging Filters and Flushing
1. sediment 2. biological
Chlorine Injection 1. biological growth 2. root intrusion
Filtration Equipment Water must be cleaned with
120 mesh filters for most drip emitters and with 160 mesh filters for drip tape.
Screen filters are recommended for well and utility water.
Disc filters are better for surface water irrigating a small area.
Sand media filters or automated disk filters are best suited for surface water and large drip projects.
Ar = 96.3 Q = Application rate in inches per hour A Q = Flow or discharge in gallons per minute A = Area into which flow is applied in feet2
Example: Pumpkins irrigated with .450 gpm/100’ drip tape at 8 psi on a 6 foot spacing.
Ar = (96.3 x .45) / (100 x 6) = 0.072 inches per hour
OTP = Water Use / AR = Operation Time Peak 1.0” per week / 0.072 in/hr = 14 hrs or 7 hrs twice per week
Application Rate – Flow into an Area used to calculate Peak Operation Time