Deficit Irrigation of Sunflower under Mediterranean environmental conditions

1. Deficit Irrigation of Sunflowerunder Mediterranean environmental conditions STREP EC 6th FP INCO-CT-2004-509087 Mladen Todorovic & Rossella Albrizio (CIHEAM-IAMB, Italy) Ljubomir Zivotic (Institute for Water Management “Jaroslav Cerni”, Belgrade, Serbia)

2. Objectives DIMAS overall objective: • to reduce the consumptive use of water by crops in the Mediterranean agriculture and thereby to release water resources for other uses Objectives of the experiment: • to analyse sunflower growth under five water regimes • to determine critical stages of crop growth to water deficit • to quantify the impact of water stress duration and intensity

3. Sunflower characteristics • Helianthus annuus L. hybrid Sanbro_MR • Origin Spain • Early flowering • Early maturity • Very good and good mid-late and late early vigour • Drought and heat tolerant • High yield potential • Medium oil content • Objective density 60000 per hectare

4. (Valenzano - BA, Southern Italy; 4103’N, 1652’E, 72 m a.s.l.) Clay loam soil, of 70 cm depth and two layers, avg. SWC 150 mm/m

5. Agronomic parameters • Sowing on April 10th • Plant density 5.56 plants / m2 • Harvesting on August 8th • Water regimes: • Full irrigation • Rainfed conditions • Full irrigation until the flowering and then 70% of CWR • 70% of CWR during the whole season • 70% of CRW until the flowering and then rainfed conditions

6. Measured parameters • Plant measurements (11 times during season, each 7-15 days): • Leaf number, plant height, leaf area index, dry biomass of each plant organ (roots, stems, leaves, heads, seeds) • FINT values obtained 6 times during a growing season (LI-COR, Light bar) • Soil characteristics: • -Depth, texture, nutrients • Climatic data: • -maximum and minimum air temperature, maximum and minimum relative humidity, solar radiation, wind speed, precipitation • Management data: • Irrigation water volumes

7. Estimated parameters • Climatic data: • -reference evapotranspiration FAO P_M equation • Soil parameters: • -Water holding capacity (saturation, field capacity, wilting point), infiltration rate • Plant characteristics: • -each phenological stage (emergence, head visible, flowering, maturity) was considered to occur when it was observed in 80% of plants • crop coefficient Kc • Management: • soil water balance and irrigation water requirements were calculated on the basis of FAO 56 Irrigation and Drainage paper

8. Weather data ETo module Optional ETo method FAO P_M Hargreaves FAO P_M_Rs_mod ETo Soil data Crop data Soil water balance module ETc; Rz_SWB; IRR_net; Y/Ymax variable number of growth stages Management data Irrigation module IRR_gross variable application efficiency Source: Todorovic, 2006

9. Root zone soil water depletion for full irrigation treatment F M Days after sowing 8th April 8th August Depletion (mm)

10. Root zone water depletion for treatment with full irrigation until flowering and then 70% of full irrigation requirements (slight water stress) F Days after sowing M Depletion (mm)

11. Root zone water depletion for 70% of full irrigation requirements during the whole season(moderate water stress) Days after sowing F M Depletion (mm)

12. Root zone water depletion for 70% of full irrigation requirements until the flowering and then rainfed(strong water stress) Days after sowing F Depletion (mm) M

13. Root zone water depletion for rainfed treatment Days after sowing Depletion (mm) F M

14. Irrigation Water management Total Precipitation during growing season – 110.0 mm (at the beginning of full development, after head apperance/10 days before flowering, between flowering and maturity and one week after maturity)

15. Cumulative crop ET M 473.2 A B 456.3 F C 424.1 293.3 D 180.4 E

16. Seasonal variation of LAI Flowering 3.69 2.72 1.82

17. FINT Few days before flowering 86% 74%

18. FINT vs. LAI R2=0.926

19. Biomass seasonal variation [t/ha] M F 14.9 13.0 9.9 6.6 6.5

20. YIELD [t/ha] 6.14 5.42 A A 4.22 B 2.10 2.07 C C 70_0 Rainfed 70 100 100_70

21. Harvest index 70_0 Rainfed 70 100 100_70

22. Biomass vs. Cumulative IPAR (two stages) 1 – pre-anthesis 2 – post-anthesis A2 B2 C2 A1,B1 D2 E2 E1 C1,D1

23. Linear regression for pre- and post-anthesis RUE Full irrigation 70% irrigation Rainfed

24. Biomass vs. ETc (three stages) 1 – initial phase 2 – intensive growth 3 – post-anthesis A3 B3 C3 A2,B2 E3 D3 E2 C2,D2 A1-E1

25. Linear regression for three stages WUE 1 – initial phase 2 – intensive growth 3 – post-anthesis

26. Conclusions • Deficit irrigation (up to 70% of CWR) is an acceptable strategy for sunflower. • Importance of irrigation between head appearance through flowering up to maturity has been demonstrated. • Possible rainfed production under Southern Italy climatic conditions has been observed (early sowing, depends on rainfall distribution, initial soil water content…) • Strong correlation of irrigated water and obtained biomass and yield was observed. Translocation of assimilates is favored under mild and moderate water stress, while harvest index is strongly reduced under severe water stress. • Both RUE and WUE have shown not conservative behaviour for different water regimes • RUE should be presented as a two stages value (pre- and post-anthesis) • WUE should be presented as a three stage value (initial, pre- and post-anthesis)

27. Acknowledgements: • EC 6TH Framework Programme (INCO-MED) • DIMAS Partners • IAMB Technical staff: Mr. C. Ranieri, Mr. R. Laricchia, Mr. A. Divella, … Thank you