* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Using the Biology of Weeds to Leverage Weed Management
Banksia brownii wikipedia , lookup
Ecology of Banksia wikipedia , lookup
Gartons Agricultural Plant Breeders wikipedia , lookup
Renewable resource wikipedia , lookup
Crop rotation wikipedia , lookup
Sustainable agriculture wikipedia , lookup
No-till farming wikipedia , lookup
Genetically modified organism containment and escape wikipedia , lookup
Farmer-managed natural regeneration wikipedia , lookup
Using the biology of weeds to leverage weed management • Chuck Mohler • Cornell University Weeds are plants that thrive in disturbed environments • For example, in a farm field • Our crops are mostly annual plants - they live for one season • We kill off natural vegetation & disturb the soil to make conditions suitable for crops • But this also creates habitats for weeds Many ways to be a weed • Annuals – Summer annuals – Winter annuals • Perennials – Stationary perennials • Taproots • Fibrous roots – Wandering perennials • Bulbs & tubers • Rhizomes or storage roots Outline • Two general examples • Managing perennials through exhaustion of roots and rhizomes • Choosing an appropriate tillage regimen for depleting a weed seed bank • A specific example – your choice Wandering perennials • Spread by thickened storage roots or by rhizomes (underground stems) Apical dominance in perennials Tillage Shoot above ground Shoot below ground New rhizomes Old rhizome fragment Management of perennials • • • • • Key is exhaustion of reserves. Time shoot removal relative to growth stage Shallow roots & rhizomes – chop & bury, Deep roots & rhizomes – hit them often Competitive crops, frequently cultivated crops, short season crops Choosing a tillage regimen for managing a weed seed bank Seeds of most weeds are tiny – why? • Disturbed environments are risky • Tiny seeds spread the risk over many offspring • Seedlings can be small because in a recently disturbed environment they have little competition. • Seedlings have limited resources Small seeded species only emerge if near the soil surface Seed longevity Loss per year (%) Species Cultivated Uncultivated Lambsquarters 31 8 Annual bluegrass 26 22 Common chickweed 54 32 Common groundsel High 45 1.0 Seed survival (%) 0.8 Seeds survive better deep in the soil Velvetleaf 0.6 0.4 Pigweed 0.2 0.0 0 2 4 6 Depth in soil (inches) 8 10 Death near the soil surface • Seed predation • Wetting and drying • Freeze-thaw Plowing vs. minimum tillage? • Small seeded species with short lived seeds plow them under – Most will die before they find their way to surface again – Example: hairy galinsoga – Needs to be in the top ¼” to emerge – So if mixed into 8” of soil, the average return time will be 32 years – But few live longer than 2 or 3 years. • Large seeded species with long lived seeds keep them near the surface – Their mortality will be greater at the surface – And most that are tilled under will come back to bother you later – Example: velvetleaf – Emerges well from the top 2” of soil – So if mixed into 8” of soil, the average return time to the emergence zone is 4 years – 80-90% survival below 4” – 0.85x0.85x0.85x0.85=0.52 so 50+% will make it back into the safe-to-emerge zone before they die – <20% survival near the surface Species with small, long lived seeds? • Lambsquarters • Wild mustard Many other examples • Germination cues – Cultivated fallows – Mulches – Stale seedbed • Relative size of crop and weed seeds – Management of crop competition • Plant size distributions – Reduction of weed seed production “Manage Weeds on Your Farm: a Guide to Ecological Strategies” Mohler and DiTommaso, SAN • • • • • Ecology of weeds Cultural control methods Physical control methods Farm case studies Identification, ecology and management of the 75 worst agricultural weeds in the United States A specific example • Most farms have many weeds, but only one or two really problem weeds • Often need to focus on those • http://www.css.cornell.edu/weedeco • http://www.organic.cornell.edu/ocs/index.html