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Developing a Temperature-Light Based Model for Predicting Purple Nutsedge Spatial Growth

This study presents a spatial growth predictive model for purple nutsedge (Cyperus rotundus), one of the world's most problematic weeds, using temperature and radiation as primary growth factors. The model aims to quantify the effects of environmental conditions on growth and improve predictive capabilities. Field studies conducted in 2008 under varying temperatures and shading levels have shown that while temperature is the major determinant of growth, photosynthetically active radiation (PAR) significantly influences growth only in optimal temperature ranges. The integration of these factors enhances the model’s accuracy in predicting purple nutsedge growth dynamics in diverse environments.

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Developing a Temperature-Light Based Model for Predicting Purple Nutsedge Spatial Growth

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  1. Developing a temperature-light based spatial growth model for purple nutsedge • Ran lati1,2,Hanan Eizenberg2, and Sagi Filin1 • 1Mapping and Geo-Information, Technion - Israel Institute of Technology, 2Newe Ya’ar Research Center, ARO The 2nd International Conference on: Novel and Sustainable Weed Management in Arid and Semi-Arid Agro-Ecosystems

  2. Purple nutsedge (Cyperusrotundus) • Among world's most troublesome weeds • High photo-synthetically efficiency (C4 plant) • Rapid growth during the summer in irrigated crops

  3. Biology- vegetative growth 45 DAP 14 DAP Rapid spatial growth

  4. Purple nutsedge “patches”

  5. High infestation level

  6. Vegetative spatial-growth model (Webster, Weed Science, 2005)

  7. Purple nutsedge spatial-growth gaps of knowledge • Modeling and prediction purple nutsedge spatial growth • Quantification the impact of growth factors • Interaction between growth factors

  8. Objectives Developing a spatial-growth predictive model for purple nutsedge Temperature-radiation based model Understanding the relative contribution of temperature and radiation on its growth

  9. Field studies 2008 • Weeds grown under diverse environmental condition • Wide range of temperature and radiation • Temperature- weeds were planted at 4 planting dates: Jun. 08, Jul. 08, Aug. 08, Oct. 08 • Radiation- weeds grown under 4 shading levels: • 0%, 20%, 45% and 60%

  10. Field study 2008 Individual plants were grown for 60 days One tuber was buried Actual environmental measurements Temperature and radiation were continuously logged Leaf cover area was measured 5 times Using image data methods Weed-growth models Based on temperature and radiation

  11. Environmental measurements Temperatures Data logger [C°] Tbase- minimal growth temperature (10°C) Tmean- mean daily temperature Photosynthetic active radiation PAR Pyranometer [µmol m-2 s-1] CPAR-daily cumulative PAR

  12. Leaf cover area measurements- using image data

  13. Weed-growth models- assumptions • Annual model is composed of seasonal sub-models • Plant's growth is exponentially related to time under optimal and constant conditions • Under varying conditions- plant growth is better described by physiological-time 19:00 7:00 12:00

  14. Thermal model (degree-days) L -leaf cover area L0 -initial leaf cover area a -growth rate

  15. Photo-thermal model (Effective-degree-day) L -leaf cover area L0 -initial lead cover area a -growth rate EDD- effective-degree-days

  16. Effective-degree-day (EDD) The conductance concept: f- PAR coefficient (Aikman and Scaife, Annals of Botany 1993)

  17. Environmental growth factors

  18. Optimal temperatures for purple nutsedge growth are 25-35°C Naamat et al., current conference

  19. Final leaf cover area (SED=0.0874) 28-33°C 18-21°C Final leaf cover area (m2) Planting date

  20. Summary • Under optimal temperature, purple nutsedge growth is linearly related to PAR • Below optimal temperature range, PAR level does not affect purple nutsedge growth

  21. Predictive growth models

  22. Seasonal growth-models Thermal Photo-thermal (Growth season: August-September)

  23. Annual growth-model Photo-thermal Growth season: June-December

  24. Final conclusions • Temperature • Major growth factor required for purple nutsedge • Insufficient for purple nutsedge spatial growth prediction • PAR • Determines purple nutsedge growth under optimal temperatures conditions • Does not affect purple nutsedge growth below optimal temperature range

  25. Final conclusions • The photo-thermal model • Successfully integrates temperature and PAR measurements • Integration of temperature and PAR improves the prediction ability of the model • Enables annual prediction of purple nutsedge spatial growth • Accurate under varying temperature and PAR conditions

  26. Thanks • EWRS - for the generous scholarship • Advisors- Hanan and Sagi • Tal L., Gay and Evgeny • Members in the Dept. of Weed Research in NeweYaar • Fellow students- Tal N., Daliya, Shalev , Rim, Fadi and Amit

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