From Conventional to Organic: Weed Management Principles for the Transition Years Fabián Menalled 719 Leon Johnson Hall Montana State University

A Disclaimer This is not going to be a “traditional” weed extension presentation Your best weed management tool is located between your ears

Today, we’ll talk more about principles than specific practices

Outline for Today ’ s Presentation  Transitioning to organic What to expect  Some basic concepts What is a weed? Why do we have weeds?  Integrated Weed Management (IWM) in organic systems

From Conventional to Organic What to Expect Yield Time Stop Synthetic Herbicide & Fertilizer Inputs Weeds

What ’ s the Impact of Transitioning from Conventional to Organic on Weed Communities?

Study Sites Big Sandy Moore

Methods Study Area: Moore & Big Sandy, MT Plots = 3 conventional (445.3 m 2 ) and 3 organic ( m 2 ) Measurements: Number of species Individuals/species Number of species/plot 0.1 m 2 10 m 2 1 m 2 Whole Plot

Shared Canada thistle Crazyweed Kochia Prickly lettuce Redroot pigweed Russian thistle Wild buckwheat Wild oat Conventional A. septentrionalis Perennial ryegrass Organic Alfalfa Barley Pea Winter vetch Common chicory Common lambsquarters Cowcockle Cheatgrass False flax Field pennycress Weed Species - Big Sandy, MT Canada goldenrod Green foxtail Cutleaf nightshade Tansy mustard Crossflower Milkweed Rush skeletonplant Common sunflower Tall tumblemustard Wild mustard Yellow starthistle

From Conventional to Organic What to Expect Abundance Diversity Species composition Spatial patterns in reduced input & organic systems Shift ??????

Why Assessing the Spatial Distribution of Weeds? Weeds in conventional systems are distributed as patches Dieleman et al., 1999; Faechner et al., 2002; Hughes, 1990; Mortensen et al., 1995; Rew and Cousens, 2001; Wiles et al., 1992 Precision agriculture Weed distribution in organic systems? Site specific agriculture

Spatial Patterns Percentage cover / spp. Weed species richness, diversity 1 m RANDOM Weed patch 100 m Big Sandy, MT 3 conventional fields 3 organic fields Stratified sampling

CON1 T2 ORG1 T2 Organic Patch Group of Patches Gap Patch Group of Patches No Gaps! Group of Groups of Patches Conventional

From Conventional to Organic What to Expect Abundance Diversity Species composition Spatial patterns in reduced input & organic systems Shift complexity

The sky is falling! X isn’t Weeds = Yields This relationship isn’t constant Yields = Profits

Weed Abundance & Yield Yield Weed abundance

When transitioning, don’t go “the whole enchilada” but take “baby steps”

Outline for Today ’ s Presentation Transitioning to organic What to expect  Some basic concepts What is a weed? Why do we have weeds?  Integrated Weed Management (IWM) in organic systems

Questions, so far?

Photos Source: WSSA web site. Ian Heap What is a Weed?

A plant that is growing where it is not wanted Roberts et al Weed Control Handbook

Any Problem With this Definition?

Source: C. Mohler Understand the source of your problems

LightWaterNutrientsSpace Why Do We Have Weeds?

BECAUSE WE CREATE THE ENVIROMENTS WHERE WEEDS THRIVE!

Weed Management is Achieved Through USDA Online Photography “large hammer”

Soil erosion Surface and ground water contamination Resistance Good in the short term, but don’t work on the long term We still have weeds! Doesn’t treat the source of the problem but its consequences Limitations of Large Hammers

SeedlingsAdults New SeedsSeedbank Weeds Are Plants! Seedling Recruitment Seedling Survival Seed Mortality Fecundity Seedbank Survivorship

Alternative Weed Management  Replace a “ few large hammers ” with “ many little hammers ” (herbicides, tillage, crop rotation, pathogens, insects, cover crops, etc)  Alone, each factor may have a small effect. Together, these factors may provide sufficient control Liebman and Gallandt 1997 Integrated Weed Management

Outline for Today ’ s Presentation Transitioning to organic What to expect Some basic concepts What is a weed? Why do we have weeds?  Integrated Weed Management (IWM) in organic systems

Questions, so far?

Weed Management Cultivation

Weed Management Cultivation Prevention

Standard weed management conducted at the field level 270% expansion over 6 years Standard weed management + weed shed prevention 24% expansion over 6 years After H. Beckie, Agri-Food Saskatoon Do Not Spread Weed Seeds!

Weed Management Cultivation Seeding density Row spacing Prevention

Row Spacing and Seeding Rate 20 site-years in Oklahoma lb/A lb/A Wheat yield (Bu/A) 9393 Row spacing (inches) Weed Free Cheat lb/A lb/A -- Epplin et al. 1996

Weed Management Cultivation Crop variety Seeding density Row spacing Prevention

Crop Variety After Jones & Murphy, 2006 Weed tolerance Weedy Weed Free Harrow tolerance Weed suppression

Crop Variety After Jones & Murphy, 2006 OrganicConventionalPercentage Madsen Eltan Rod Stephens Finch Mean Yield (bu/a) – Pullman WA

Crop Variety Cultivars vary in their competitive ability: Height Early season growth Tillering capacity Leaf area Some varieties are better adapted to weed competition than repeated harrowing and vice versa Mason and Spaner, 2006 & Jones and Murphy, 2006

Weed Management Cultivation Crop rotation Crop variety Seeding density Row spacing Prevention

fallowwheatfallowwheatfallowwheat Grassy Weeds

Crop Rotation and Cheatgrass Density Downy brome density (no. m -2 ) (After Blackshaw 1994)

Weed Management Cultivation Crop rotation Crop variety Time of emergence Seeding density Row spacing Resource management Time of control Weed Management

Relative Time of Emergence

Weed Management Cultivation Crop rotation Crop variety Time of emergence Seeding density Row spacing Resource management Time of control Integrated Weed Management

You Are Not Alone….

In Summary …

The sky is falling! X isn’t Principle # 1: Don’t hate weeds, manage them

Principle # 2: Take “Baby Steps”

Source: C. Mohler Principle # 3: Understand the source of your problems

Weed Management Herbicides Crop rotation Crop variety Time of emergence Seeding density Row spacing Resource management Time of control Principle # 4: Use All Your Tools!

Principle # 5: ASK!

Principle # 6: Your best weed management tool is located between your ears!

Be Smart!

Questions?