Oklahoma Market Gardening School Season Extension: Plastic Mulch, Row Covers & Organic Mulch Jim Shrefler Area Extension Horticulturist Oklahoma Cooperative

Oklahoma Market Gardening School

Season Extension: Plastic Mulch, Row Covers & Organic Mulch

Jim Shrefler

Area Extension Horticulturist

Oklahoma Cooperative Extension


Season Extension: Use of techniques and practices that enable planting or harvesting horticultural food crops at times other than those when outdoor field planting can be used.

It may include reducing risks during any season having widely variable weather conditions.


Why use season extension?

● Gardening fanatic

● Want a produce source for own use

● Need a produce source for business

● Opportunities for premium price or market presence


Season Extension Practices

● Hoophouses – Recent work at Noble Foundation: A tremendous local resource!

● Create temporary conditionsStart plants in greenhouse

Grow in containers in the shade

● Open field practices


Developing your system

● Think about plant growth needs and hazards to them Temperature of soil

and air daily weekly

Light Intensity Duration


Developing your system (cont.)

● Think about plant growth needs and hazards to them

Moisture soil air

Wind


Before getting started ….Why use season extension?

● You may have specific goals example – want tomatoes and lettuce for Thanksgiving

● Maybe you just want to get a jump on things in the spring

● Other reasons?

Careful consideration of your needs will help you determine which techniques are best for you!


General Reasons for SE

● Get crops started early in the spring

● Deal with adversity of summer conditions

● Growing and harvesting in the fall and winter


Early planting in the spring

● Situation during February thru AprilWide temperature variation 20 – 80oF; April

freeze is possible

Soil is cool; soil warming lags air temperature increase

Days are short but getting longer


Early planting in the spring – Cold hardy crops

● Onions, lettuce, cabbage, carrots, English pea● Can be planted in the open garden●May benefit from floating row covers during

freezes● Black plastic mulch may speed plant growth● Use transplants for onions, lettuce, & cole

crops



Early planting in the spring – Moderately cool tolerant crops

● Sweet corn, Irish potato

● Germination will depend on soil temperature

● Chill injury with low 30’s to 40 oF

● Use clear plastic for early soil warming

● Use row covers to protect from frosts / late freezes



Early planting in the spring – Non cool tolerant crops

● Tomato, cucurbits, snap beansStart as transplants

Temperatures in 30’s to 40’s oF will arrest growth

Use clear plastic for early soil warming

Use row covers, hot caps, “water walls” to protect from frosts / late freezes

Hoop house better than open field system



Deal with adversity of summer conditions

●Situation during April thru AugustWide temperature variation possible:

30’s (April) – 100+ oFSoil warming is adequate for most crops

by MayDays increase then decrease but are at the

longest during this periodPrecipitation extremely variable


Early planting for summer – Warm season crops that stop fruiting with extreme heat● Tomato, pepper, cucumber, snap bean● Objective: get crop producing before heat

sets in ● Contrast with early production in hoop

houses● Start as transplants● Use row covers, hot caps, “water walls” to

protect from frosts / late freezes



Controlling growth conditions for variable summer weather

● Optimize conditions that favor crop growth Temperature, soil moisture, root zone

● Minimize possible hazards Excess soil water, excess soil heat, disease favoring

conditions● Possible practices to use:Raised planting bedsKilled cover crop mulchesOrganic mulch: straw, paperBlack, white, colored mulches & fabrics


Controlling growth conditions: Optimize conditions that favor crop growth

● Temperature: allow soils to warm to 70 – 80oF range

● Soil moisture: maintain soil moisture to favor an extensive root system

● Root zone: adequate tillage depth and raised beds favor a deep rooting zone



Controlling growth conditions: Minimize possible hazards

● Excess soil water: brief waterlogged conditions cause prolonged harm: tomato is especially susceptible but most vegetables affected

● Excess soil heat: crusted and bare dry soil is most susceptible to heat accumulation

● Disease favoring conditions: bare soil harbors organisms that may lead to plant diseases when plants contact soil or soil is splashed onto plants



Controlling growth conditions: Useful practices

● Raised planting beds

● Killed cover crop mulches

● Organic mulch: straw, paper

● Black, white, colored mulches

● Landscape fabrics




Fall and Winter Growing and Harvesting

● Adapt to adverse conditionsHigh soil temperatures Short days

● Minimize possible hazards Early frosts and freezesHigh residual pest populations

● Possible practices to use: Shade producing structures Irrigation Transplants


Fall and Winter Growing and Harvesting: Adapt to adverse conditions

● High soil temperaturesKeep soil moist after seeding crops Shade soil surface until seedling emergence occursUse transplants when feasible

● Short daysCrop growth slows with shorter days and sunlight light

intensity Smaller fruited crops may mature quicker (cherry

tomato) Shade tolerant crop advantages (lettuce)


Fall and Winter Growing and Harvesting: Minimize possible hazards

● Early frosts and freezes in fall Pepper, cucurbits, beans could be covered with row

cover material

May be less practical for staked crops

sprinkler irrigation an option for light frosts

● High residual pest populations in fall Scout late season crops frequently

Squash bugs a major cucurbit threat – row covers may also help here



Materials used in Season Extension: Plastic Mulch

● Blackgets hot in sun!

provides moderate soil heating

● Cleargreatest soil heating of the plastic mulches

condensation helps with heat retention


Materials used in Season Extension: Plastic Mulch

● Whitemay provide slight soil cooling

sometimes combined with black or silver backing

● Colored red, blue, green, yellow

specific uses for some

● Infrared-transmitting heating and weed control



Materials used in Season Extension: Non plastic

● Paper Mulchcan provide benefits similar to black plasticbiodegradeablespecial papers availableshredded paper an option if available

● Organic mulchesconserve moisture and suppress weedsinsulate


Materials used in Season Extension: Row Covers

● TypesClear polyethylene Spunbound polyester or polypropylene

● Properties vary in thickness, weight & size

● When selecting, consider crop temperature sensitivity growth habit pollination


Materials used in Season Extension: Clear Row Covers

● A mini greenhouse

●Will get very hot in sunshine

● Some are vented

● favor crop and weed growthplan for controlling weeds

use with black plastic mulch


Materials used in Season Extension: Spunbound Covers

● Functionstrap heat: 2-4oF frost protectionexclude insectsblock windallow water passage

● Use 0.5 – 1.25 oz. per yardheavier gives too much shadethinner gives little protection


Questions?

Documents

Oklahoma Market Gardening School Season Extension: Plastic Mulch, Row Covers & Organic Mulch Jim Shrefler Area Extension Horticulturist Oklahoma Cooperative