Perennial weeds: anaerobic soil disinfection & mechanical methods

1. Perennial weeds: anaerobic soil disinfection & mechanical methods Hilfred Huiting, Piet Bleeker & Marleen Riemens EWRS workshop Physical & Cultural Weed Control – Samsun, March 2011

2. Perennial weeds: setting the scene • Difficult to control: • Species intrinsically are very resilient → exhaust strategy • Perennial weed problems take a long breath to control • In organic farming: • No chemical options • Increasing labour cost • In conventional farming: • Increasing farming scale • Weed problems may stay unnoticed longer • Tendency towards ”easy” solutions may increase problems • Herbicide availability

3. Research on perennial weeds • Two field experiments, in Wageningen and Lelystad, integrating reasearch on: • Weed phenology • Chemical weed control strategies • Non-chemical weed control strategies

4. Materials & methods: weeds Root pieces planted spring 2009 • Cirsium arvense – creeping thistle • Rorippa sylvestris – creeping yellowcress • Sonchus arvensis – field sowthistle • Calystegia sepium – bindweed • Equisetum arvense – field horsetail • Tussilago farfara – coltsfoot • Elymus repens – couch grass • Rumex obtusifolius – bitter dock • Polygonum amphibium – water smartweed

5. Materials & methods: treatments • Mechanical weed control • Broadcast blade • Application at 5 cm depth; ”superficial” • Application at 15 cm depth; ”deep” • Rod weeder • Mounted behind rigid tine cultivator • Application at c. 6 cm depth • Anaerobic soil disinfection, 11 week period • Incorporation of weed biomass and covering • Incorporation of weed biomass and additional 40 ton/ha fresh grass and covering

6. Materials & methods: treatments • Mechanical weed control • Broadcast blade • Application at 5 cm depth; ”superficial” • Application at 15 cm depth; ”deep” • Rod weeder • Mounted behind rigid tine cultivator • Application at c. 6 cm depth • Anaerobic soil disinfection, 11 week period • Incorporation of weed biomass and covering • Incorporation of weed biomass and additional 40 ton/ha fresh grass and covering

7. Materials & methods: treatment schedule

8. Mechanical weed control – blade Sandy soil Marine loam soil

9. Mechanical weed control – rod weeder Marine loam soil Sandy soil

10. Results Sonchus avernsis

11. Results Polygonum amphibium

12. Results Tussilago farfara

13. Results Calystegia sepium

14. Results Cirsium arvense

15. Results Equisetum arvense

16. Results Elymus repens

17. Results Rorippa sylvestris

18. Results Rumex obtusifolius

19. Overview efficacy mechanical weed control Efficacy: • -: insufficient • X: >85% • XX: >90% • XXX: >95% • XXXX: > 99%

20. Anaerobic soil disinfection Without grass With grass

21. Anaerobic soil disinfection: % soil covering

22. Discussion & conclusions • Rod weeder very effective after frequent passes • Broadcast blade effective as well, if used superficially and frequently • Anaerobic soil disinfection may be promissing • Results only after one season !!