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Factors affecting soil sub-surface phase of purple nutsedge ( Cyperus rotundus ) development

The 2 nd International Conference on: Novel and Sustainable Weed Management in Arid and Semi-Arid Agro-Ecosystems. Factors affecting soil sub-surface phase of purple nutsedge ( Cyperus rotundus ) development. Tal Naamat 1,2 , Hanan Eizenberg 1 and Baruch Rubin 2

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Factors affecting soil sub-surface phase of purple nutsedge ( Cyperus rotundus ) development

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  1. The 2nd International Conference on: Novel and Sustainable Weed Management in Arid and Semi-Arid Agro-Ecosystems Factors affecting soil sub-surface phase of purple nutsedge (Cyperus rotundus) development • Tal Naamat1,2, Hanan Eizenberg1 and Baruch Rubin2 1 NeweYa’ar Research Center, ARO; 2The faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot

  2. The problem: Purple nutsedge A troublesome weed causes heavy damages in irrigated summer crops Photographed by Baruch Rubin A sweet potato field in Israel infested with purple nutsedge

  3. The biology: Mostly vegetative reproduction by tubers and bulbs The tuber contain many buds It can survive in moist soil long time Although the sub-surface development affects the above ground growth the knowledge of the factors affecting the soil sub-surface development of purple nutsedge is limited

  4. Temperature: • Temperature is considered as a main regulator in purple nutsedge development • Based on preliminary experiments, temperature data can be converted to physiological age (thermal time) units, expressed in Growing Degree Days (GDD)

  5. Objectives: • To study the effect of various environmental conditions on key stages in the sub-surface development of purple nutsedge • Specifically, to study the effect of: • Temperature • Radiation • Tuber burial depth • Desiccation • To appoint the development on a time course of GDD

  6. Key stages that were studied:

  7. 1. Sprouting: Temperature Desiccation Depth

  8. The relations between temperature and sprouting were addressed for developing a prediction means for purple nutsedege sprouting The effect of temperature on sprouting Heat Source 80-120 GDD at sprouting R2=0.86; P<0.0001 30 35 40 45 50 55 Temperature (°C)

  9. 1. Sprouting: Temperature Desiccation Depth

  10. The effect of desiccation on sprouting Thermal time (GDD) accumulation Time (Days) 15°C 20°C 25°C 30°C 35°C

  11. The effect of desiccation on sprouting R2=0.95; P<0.0001 R2=0.9; P<0.0001 Later than 200 GDD A tuber loses 55% of its biomass It has 30% chance to sprout

  12. Illustration Illustration

  13. After cultivation

  14. Irrigation at 200 GDD Control 90-100% sprouting 30% sprouting

  15. 1. Sprouting: Temperature Desiccation Depth

  16. The effect of tuber burial depth on sprouting Tested in 2 methods: Minirhizothron experiment Field experiment 30 20 Bud elongation(mm) Heterogeneous temperature regime Homogeneous temperature regime 10 50 cm 2 3 4 Days from burial

  17. The effect of tuber burial depth on sprouting Field expt. Minirhizothron expt. N.S LSD 4 DAP 4 DAP N.S LSD Sprouting (%) 7 DAP 7 DAP N.S N.S 11 DAP 11 DAP Tuber’s depth (cm)

  18. Key stages that were studied:

  19. 2. Underground biomass accumulation 3. Tuber production Temperature Radiation

  20. The effect of radiation on tuber production • Natural sun light • 35% shade • 60% shade • 90% shade Control 35% 60% 90%

  21. The effect of radiation on tuber production Temperature and radiation are key factors affecting the sub-surface biomass accumulation Therefore, both factors and their interactions must be taken into consideration when developing a mathematical predictive model for the sub-surface growth of purple nutsedge

  22. Conclusions: • The sub-surface development of purple nutsedge is environmental related • The effect of sub-surface biomass accumulation on shoots biomass • accumulation can be quantified • The combined effects can be theoretically integrated for the entire model on a GDD time course • This empirical model must be validated in field conditions

  23. The predictive model might be of use as a tool in control management; e.g. – to imply on the optimal time frame of control Emergence of deep tubers Beginning of tuber production Average time of sprouting Thermal time frame of control 0 100 300 400 GDD

  24. Thanks… • My advisors – HananEizenberg and Baruch Rubin • EWRS - for funding my trip • NeweYa’ar, the Department of Weed Research: • Joseph Hershenhorn, Radi Ali, Daniel Joel, • Evgeny Smirnov, Tal Lande, Guy Achdari, • EvgenyaDor, Dina Plakhin • The Faculty of Agriculture, • Weed Lab • My fellow students

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