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

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

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: Accumulation of foliage biomass Accumulation of sub- surface biomass and tuber production Tubers’ sprouting Emergence

7. 1. Sprouting: Temperature Desiccation Depth

8. Heat Source The effect of temperature on sprouting 25 30 35 40 45 50 55 Temperature (°C) R 2 =0.86; P<0.0001 The relations between temperature and sprouting were addressed for developing a prediction means for purple nutsedege sprouting 80-120 GDD at sprouting

9. 1. Sprouting: Temperature Desiccation Depth

10. The effect of desiccation on sprouting 15°C20°C25°C30°C35°C Time (Days) Thermal time (GDD) accumulation

11. The effect of desiccation on sprouting R 2 =0.9; P<0.0001 R 2 =0.95; P<0.0001 Later than 200 GDD A tuber loses 55% of its biomass It has 30% chance to sprout

12. Illustration

13. After cultivation

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

15. 1. Sprouting: Temperature Desiccation Depth

16. The effect of tuber burial depth on sprouting Tested in 2 methods: Field experiment Homogeneous temperature regime 50 cm Heterogeneous temperature regime 234 Days from burial 10 20 30 Bud elongation (mm) Minirhizothron experiment

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

18. Key stages that were studied: Accumulation of foliage biomass Accumulation of sub- surface biomass and tuber production Tubers’ sprouting Emergence

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

20. The effect of radiation on tuber production Control35% 90%60% Natural sun light 35% shade 60% shade 90% shade

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

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 0100300400 Average time of sprouting Emergence of deep tubers Beginning of tuber production GDD Thermal time frame of control

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

25. 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 Temperature Water Content Radiation The predictive model might be of use as a tool in control management; e.g. – to imply on the optimal time frame of control 0100300400 Average time of sprouting Emergence of deep tubers Beginning of tuber production GDD Thermal time frame of control

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

27. Illustration

28. 0 GDD

29. 100 GDD

30. 250 GDD

31. 500 GDD 40% Shade

32. 800 GDD 65% Shade