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Weed Control in Organic Production
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Weed Control in Organic Production

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Weed Control in Organic Production …

Weed Control in Organic Production

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  • 1. Weed Control in Organic Production Jason Lewis Ph.D. Cal Poly- San Luis Obispo PolyHorticulture and Crop Science Department “It’s not easy being green” 1
  • 2. General Weed Management Factors • • • • • Exclusion Elimination Prevent Establishment Removal Management Exclusion • Field Selection – A good choice – Knowledge needed of sites – Usefulness depends on available certified land • Prevent weed additions – Critical for organics – “Bring-ins” may contain weed seed “Bring• Organic mulches • Raw manures 2
  • 3. Elimination • Prevent weed build-up build– Timely cultivation tillage cultivation, – Purposeful plantings- don’t let weeds take plantingsover • Weed population reduction – Perennial management through grazing – Fallow/tillage cycles – Solarization Prevent Establishment • Preemergence “herbicides” – Corn gluten meal, mustard meal • Timely cultivation • Cover crop management – Species important – Crop sequence • Mulches – Organic and synthetic 3
  • 4. Weed Removal • Mechanical – cultivation – Keep it shallow – Minimize injury to the crop – Improve the rootzone • Manual –R Removes remaining weeds i i d – Supervision, monitoring, and incentives for optimum results Weed Removal • Physical: energy consumers! – Flame • Special equipment, directed flame • Best for small, annual weeds – Steam • Herbicides 4
  • 5. USDA National Organic Product Standards • Crop pests, weeds, and disease will be controlled primarily through p y g management practices including physical, mechanical, and biological controls – When these practices are not sufficient, a biological, botanical biological botanical, or synthetic substance approved for use on the National list may be used. Corn Gluten Meal • Herbicide – Dipeptides inhibit root formation by inhibiting cell division – Established plants are not affected 5
  • 6. Organic Herbicides • Most active ingredients: – Vinegar (acetic acid), clove oil (eugenol) or (eugenol) soap (fatty acids) • Contact herbicides – Will cause crop injury – Control small annual weeds Management • Crop Selection – Use crops that tolerate weeds • Rapid growth, dense canopy – Crops that allow for weed control • Sweet corn – easy cultivated • Give crops an edge – Getting “THERE” first 6
  • 7. Weed Competition • Our goal as weed managers: minimize acquisition of resources by weeds, maximize acquisition by crop • This is a TIME and SPACE problem: getting “there” first Crop vs. Weed Response Weeds tend to do better in poor conditions: they don’t prefer them to resources (light, water, nutrients) weed crop Maintain optimal resource level for crop, uniformly across field high low Resource level (e.g. water, light, nutrients) * 7
  • 8. Planting into moisture: establishing a “dry mulch layer” After removing plastic, rotivating, or herbicide/flaming on last irrigation: Allow surface layers to dry without disturbing Dead seed Bed tops are split and crop seeds B dt lit d d planted into underlying moisture Viable weed seed crop seed Dry “dirt mulch” on surface 1-2”. Weeds seeds will usually not germinate from below 1-2” and will not germinate in dry soil Giving the crop a head start by taking advantage of its initial size Instead of splitting the bed top, large-seeded crops ( g (e.g. corn, bean, squash) or transplants could be , , q ) p planted deep into the bed. Large-seeded crop transplant 8
  • 9. Planting into moisture Hold off on irrigation until crop plants need it. Crop roots follow moisture downward. Furrow irrigation will soak across g bed from below---leaving weed seeds in dry “mulch” Nutrient Management • It might seem logical to add supplemental fertilizer to make up for weed presence • Usually the added nutrients will go to the weeds • Weeds tend to be better luxury consumers of nutrients 9
  • 10. Fertilizing weeds Added N goes to weeds Carlson and Hill 1986 Nutrient Management • Put the fertilizer when and where crops will use it first • Weeds are better competitors for nutrients plasticity e o e eeds o ot et e • Remove weeds Do not add fertilizer to make up for weed competition 10
  • 11. Conclusions • You have to be smarter and harder working • Work to get crops “there” first • Don’t fertilizer weeds, remove them • Organic herbicides are generally nonnonselective Thank You Questions? Jason Lewis, Ph.D. Assistant Professor of Turfgrass Science jlewis07@calpoly.edu 11
  • 12. USDA National Organic Program Standards • Consistent national standards • Anyone that wants to sell an agricultural product as organically produced must adhere to the NOP standards • Requirements apply to the way the product is created, not to measureable properties of the product itself 12
  • 13. Management effects on seed banks Crop rotation effects seedbank species composition and abundance different cropping systems favor different weed species rotational effect >tillage effect 13