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

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

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

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)

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

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

1. Sprouting: Temperature Desiccation Depth

Heat Source The effect of temperature on sprouting Temperature (°C) R 2 =0.86; P< The relations between temperature and sprouting were addressed for developing a prediction means for purple nutsedege sprouting GDD at sprouting

1. Sprouting: Temperature Desiccation Depth

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

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

Illustration

After cultivation

Control Irrigation at 200 GDD 30% sprouting % sprouting

1. Sprouting: Temperature Desiccation Depth

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 Bud elongation (mm) Minirhizothron experiment

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

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

2. Underground biomass accumulation 3. Tuber production Temperature Radiation

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

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

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

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

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

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

Control Irrigation at 200 GDD 30% sprouting % sprouting

Illustration

0 GDD

100 GDD

250 GDD

500 GDD 40% Shade

800 GDD 65% Shade