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