Mladen Todorovic & Rossella Albrizio (CIHEAM-IAMB, Italy) Ljubomir Zivotic (Institute for Water Management “Jaroslav Cerni”, Belgrade, Serbia) Deficit Irrigation of Sunflower under Mediterranean environmental conditions STREP EC 6 th FPINCO-CT

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

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 per hectare

(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

Agronomic parameters  Sowing on April 10 th  Plant density 5.56 plants / m 2  Harvesting on August 8 th  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

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

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

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

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

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

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

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

Days after sowing Depletion (mm) Root zone water depletion for rainfed treatment FM

Irrigation dateDASNet irrigation supply (mm) Treatment ATreatment BTreatment CTreatment D 15-Apr Apr May May May May Jun Jun Jun Jul Jul Jul TOTAL (mm) Irrigation Water management Total Precipitation during growing season – mm (at the beginning of full development, after head apperance/10 days before flowering, between flowering and maturity and one week after maturity)

Cumulative crop ET A B C D E F M

Seasonal variation of LAI Flowering

FINT Few days before flowering 86% 74%

FINT vs. LAI R 2 =0.926

Biomass seasonal variation [t/ha] F M

YIELD [t/ha] A A B CC _ _0 Rainfed

Harvest index _ _0 Rainfed

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

Linear regression for pre- and post-anthesis RUE TreatmentSlope (gMJ -1 )R2R2 A B C D E A B C D E Full irrigation 70% irrigation Rainfed

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

Linear regression for three stages WUE TreatmentSlope (kgm -3 )R2R2 A1, B C1, D E A2, B C2, D E A B30.44 C D E – initial phase 2 – intensive growth 3 – post-anthesis

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)

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