Hughie Jones1, 2, T. Andrew Black2, Rachhpal S. Jassal2, Zoran Nesic2, Mark Stephen Johnson2, 3, Sean Smukler4, 5

1 Alexis Nakota Sioux Nation1 Biometeorology and Soil Physics Group, Faculty of Land and Food Systems, University of British Columbia, Vancouver, Canada

2 Institute for Resources, Environment and Sustainability, University of British Columbia, Vancouver, Canada3 Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada

4 Sustainable Agricultural Landscapes Lab, Faculty of Land and Food Systems, University of British Columbia, Vancouver, Canada5 Centre for Sustainable Food Systems, University of British Columbia

The microclimate of plastic mulches and low tunnels

Certified Organic Associations of BC Conference 2019February 22 - 24, 2019

Biometeorology and Soil Physics Group

Biometeorology studies how climate impacts the well-being of plants and animals.

Biometeorologists seek to understand the impact of climate on the balance of inputs and outputs in agricultural, forest and aquatic ecosystems.

• Radiation Balance• Carbon balance • Water balance

1. How do plastic film mulches impact radiation balance and soil heating or cooling?

2. How do low tunnels impact radiation balance, crop microclimate and productivity?

Plastic mulches andlow tunnels

3000

2300

1600 (mm)

900

200

AnnualPrecipitation

Cropthorne Farm

Mackin Creek Farm

UBC Farm

3 organic farms

Study sites

Sites: Experimentaltimeline

3 certified organic farms

Mackin Creek Farm (Near Soda Creek, BC) Owner: Robert Borsato and Catherine Allen 2016 - Lettuce and Spinach mix2017 - Broccoli

UBC Farm (Vancouver, BC)2015 - Experiment #1 (Plastic film mulches)2016 - Experiment #2 (Vegetated-free low tunnels)2017 - Experiment #3 (Vegetated low tunnels)

Cropthorne Farm (Westham Island near Ladner, BC)Owner: Lydia Ryall2015 - Melons2016 - Zucchinni

UBC Farm Plastic film mulches

Mulches are protective covers placed on the soil surface.

Like mineral and organic mulches, plastic mulch has the potential to alter:

• Soil erosion• Weed growth• Soil temperature (Ts)• Soil moisture (changes in soil evaporation, protection from rainfall)• Greenhouse gas emissions• Crop productivity

But, unlike “thick” mineral or organic mulches, plastic film mulches arethin allowing them to have unique radiative properties!

Plastic films in agriculture

Three radiation bands can be manipulated

using plastic films

Longwave (Far IR, L)

PAR/visible

Shortwave (i.e., Solar, S)

We can determine the film radiative characteristics:

• Reflectivity

• Transmissivity

• Absorptivity

Wavelength (nm)500 3000 10000

Sd Ld

Su Lu

Radiation balance

Net radiation (Rn) is the sum of incoming and outgoing radiation at the surface.

Rn = (Sd + Ld) - (Su + Lu)

Net radiometer

Incoming shortwave

Outgoing shortwave

Incoming longwave

Outgoing longwave

Net = (inputs) - (outputs)

Plastic film mulches

BE2 RD C BEP

S4 WB TMX IRT100

GN BW

Plastic film mulches

Plastic mulch

abbreviation

Shortwave

Reflectivity Transmissivity Absorptivity

BW 0.05 0.00 0.94

TMX 0.05 0.82 0.14

WB 0.45 0.00 0.55

C (bare soil) 0.17 0 0.93

Black

Clear

White

Plastic film mulches radiative properties

Plastic film mulches

July 23, 2015 July 24, 2015

UBC Farm: Low tunnels

Plastic cover

name

Plastic cover

abbreviation

Shortwave

(Sunlight)

transmissivity

Longwave

(Thermal)

transmissivity

Perforated

polyethylenePOLYperf High High

Polyethylene POLY High Medium

Thermax TMX HighLow

(glass-like)

Control No cover - -

Low tunnels

POLYperf

POLY

UBC Farm

TMXNLT

UBC Farm

Unvegetated low tunnels

Mulch temperature (Tm)

Cover temperature (Tc)

Radiation balance of low tunnels: Daytime

~75% of heating “Wind effect”

Sd Ld

Ldin Ldw

Lu

Sdin

Su “Thermal effect” (i.e., Ldw)~25% of heating

Will improve daytime heating efficiency

Radiation balance of low tunnels: Nighttime

“Wind effect” = ~75% of heating

Ld

Ld in Ldw

Lu “Thermal effect” (i.e., Ldw)~25% of heating

Will improve nighttime heating efficiency

August 1, 2017

UBC Farm: Low tunnel air temperature

August 2, 2017

OnlineTool !

Crop productivity

Cropthorne Farm, Ladner

Photo credit: Melissa Quantz

Cropthorne Farm, May 12 2016

Nikki Lax

n = 18

POLYp

NLT

Zucchini productivity

~20% increase in yield

Mackin Creek Farm

Early broccoli productivity

Month (2016 and 2017)

NLT

POLY

Pepper measurements

1. #of peppers2. Pepper fruit mass3. Pepper height4. LAI

UBC Farm: Padrón pepper productivity

NLTpp

Padrón pepper microclimate and productivity

Increased late growing seasonproductivity

CO2 depletion

June 27, 2017

June 27, 2017

July 31, 2017

July 31, 2017

• When an air gap exists between soil and mulch Tsblack < Tsclear

• When an air gap does not exists between soil and mulch Tsblack > Tsclear

• Highly reflective plastic mulches (i.e., white) can cool soils during the midday.

• A low tunnel cover with a low thermal transmissivity can increase air temperature during the daytime and nighttime.

• Low tunnels can increase crop productivity, but the mechanisms that increases air temperature may have negative trade-offs (e.g. low CO2 and high H2O concentrations).

Conclusions

Acknowledgements

BC Farm Adaptation and Innovator Program

Brian Wang, Summer Research Assistant

Nikki Lax, Summer Research Assistant

Nick Grant, Biometeorology and Soil Physics Group

Thea Rodgers, Summer Research Assistant

Ernest Wu, Summer Research Assistant

Robert Borsato & Catherine Allen, Mackin Creek Organic Farm

Lydia Ryall, Cropthorne Organic Farm

Rickey Yada, Dean, Land and Food Systems, UBC

David Kitts, Assoc. Dean, Land and Food Systems, UBC

Amy Frye, Former Director, CSFS, UBC Farm

Tim Carter, UBC Organic Farm

Michael Millar, UBC Organic Farm

Melina Biron, UBC Greenhouse Manager

Nicholas Coops, Faculty of Forestry, UBC

Chris Osborne, Osborne Seed Company

Jacob Slosberg, Osborne Seed Company

Eric Menard, Dubois Agrinnovation

AT Films

William Dam Seeds Ltd.

Allen Dobb, Climate Action Initiative

Samantha Charlton, Climate Action Initiative

Emily MacNair, Climate Action Initiative

Alexis Nakota Sioux Nation

Thea Rodger

Questions?

hughie.jones@alumni.ubc.caErnest Wu

Nikki Lax

Brian Wang

CO2

Photosynthesis: Flux of carbon dioxide (CO2) to make sugars.

H20Evapotranspiration: Flux of water (H2O) from forest to atmosphere.

Atmosphere

Forest

Use of plastic films in agriculture

Annual production (Mt yr-1)

Global 6.5

China 1.25 (20 Mha to 50 Mha)

Europe 0.7 (0.75 Mha)

N. America 0.2 (0.22 Mha)

Other major users are: Japan, Korea, Spain

The “Plastic Sea”

Southern Spain

Espi et al (2006)

https://asterweb.jpl.nasa.gov/gallery/images/almeira.jpg

Since the 1950’s global annual production of plastic has increased from1.3 to 322 Mt yr-1 in 2016, of which ~ 6.5 Mt yr-1 is consumed inagriculture.

Area covered by mulches Plastic mulches in China Okanagan Regional District

10,000,000 ha 290,000 ha

Need alternatives that are equally good!

June 27, 2017

July 31, 2017

We install sensors to continuously measure:

Climate

• Photosynthetically active radiation

• Air temperature

• Humidity

• Pressure

• Wind speed

• Precipitation (rainfall and snow)

• Soil temperature

• Soil water content

Ecosystem-scale gas exchange/flux

• H2O flux (E, evapotranspiration)

Hybrid poplar water balance study (AB and MB)

Water Balance

(Jobbagy et al. 2004)

P ≈ E

P - Precipitation (mm)E - Evapotranspiration (mm)

E > P

E < P

Low tunnel air temperature model

Plastic mulch andlow tunnel project

How do plastic film mulches and low tunnel impact crop microclimate and productivity?

We install sensors to continuously measure:

Climate

• Photosynthetically active radiation

• Air temperature

• Humidity

• Pressure

• Wind speed

• Precipitation (rainfall and snow)

• Soil temperature

• Soil water content

Ecosystem-scale gas exchange

• Evapotranspiration

Fast-growing hybrid poplar water balance study (AB and MB)

St. Albert AB 2010 (2nd yr of growth)

2013 (5th yr)

St. Albert AB, 5th year of growth (2013)

522 mm

335 mmE

P

Low tunnels are temporary hoop-like enclosures that can be covered withvarious cover types. Very versatile and allow for quick managementdecisions.

Plastic covered enclosures have the potential to alter:

• Canopy transpiration and stomatal conductance (stomatal openness)• Vapor density• Turbulence• Air temperature in the crop canopy• Crop productivity

Low tunnels in agriculture