Effect of Continuous Deficit Irrigation of Soybean [Glycine max (L.) Merril] in a semi-arid environment of Argentina Salvador Prieto Angueira 1,2 , Daniel R. Prieto Garra1 y Gabriel A. Angella 1,2 1 INTA EEA Santiago del Estero. 2 National University of Santiago del Estero, Faculty of Agronomy and Agribusiness
Background and justification What is happening in the world? Water scarcity and more population www.ceres.org www.ceres.org Less available water and more food demand
What is happening in the world? Water scarcity and World Climate Change more population I- Increase of www.ceres.org temperature Allen et al. 2006 y 2007 Could increase the vapor water demand of the atmosphere Less available water and II- Increase in extreme events, for more food example: DROUGHT demand We must generate or evaluate strategies to increase "water productivity”
Irrigation strategies like continuous deficit irrigation (CDI) would achieves this challenge Irrigation scheme in which the plants are exposed to a certain level of water stress throughout the growing season without causing significant decreases in performance. In SOYBEAN , the major economical crop in Argentina, results are contradictories and we don´t have antecedents in Argentina Objective Evaluate the effect of different strategies of CDI during the cycle of soybean
Material and Methods Experimental site Experimental Station “Francisco Cantos” - Latitud: 28° 01' 27" S - Longitud: 64° 13' 55" W - Altitud: 169 msnm
Site characteristics Climate: Semi-arid monsoon type Reference evapotranspiration (mm) 200 200 Precipitation (mm) 150 150 100 100 50 50 0 0 J A S O N D J F M A M J J A S O N D J F M A M J Month Month 300 40 Tmax Tmin Water balance (mm) 200 Temperature (°C) 30 100 0 20 -100 10 -200 -300 0 J A S O N D J F M A M J J A S O N D J F M A M J Month Month
Soil: Aridic haplustoll with no drainage problem. Texture is silty loam throughout the profile. Total available water is 180 mm.m -1 in the first 3 meters profile. Water regimenes (WR) Irrigation depth (mm) = ETc – Pef. = (ETo×kc)-Pef Rainfed 25% ETc Irrigation intervals: 10 to 15 days. 50% ETc 75% ETc 100% ETc
Crop Management Variety: DM 8002 (MG VIII – GH determinate) Late sowing date (SD2) Optimal sowing date (SD1) 25/01/2012 12/22/2011 Reference evapotranspiration (mm) 200 300 Water balance (mm) 200 150 100 100 0 -100 50 SD2 -200 SD1 0 -300 J A S O N D J F M A M J J A S O N D J F M A M J Month Month SD2 SD1
Field Measurements - Crop phenology - Yields and its components (number and grain weight) - Actual evapotranspiration (ETa) using soil water balance method ETa (mm) = ∆ S+Peff where: ∆S is the change of soil water storage considering a depth of 2 meters (gravimetric procedure), and Peff is the effective precipitation (Dardanelli et al., 1992) - Water productivity as the ratio Y and ETa (WP ETa )
Results and discussion Crop development and weather conditions R1-R5 Weather condition S-R1 R5-R7 during SD2 R1-R5 R7-R8 SD1 PVD 8% less 12/22/2011 Radiation 10% less ETo 8% less 6 VPD (kPa) / Eto (mm.día -1 ) 5 SD2 01/25/2012 4 3 0 20 40 60 80 100 120 140 2 Days after sowing SD2 cycle duration 1 decrees 20% 0 SD1 SD2 VPD ETo
Actual evapotranspiration and yield Sowing date 600 F SD1 Source p-value Yield (kg.ha -1 ) GN.m -2 F SD2 a SD GW (mg) SD <0.0001 500 SD1 3093 (91) a 1959 (56) a 158 (1) WR <0.0001 SD2 2473 (130) b 1569 (81) b 157 (1) SD*WR ns 400 b SD <0.0001 <0.0001 ns WR 0,002 (mm) 0,0027 ns 300 SD*WR ns ns ns 200 The yield decreased with the retarding on the sowing date 100 as a consequence of a reduction in the grain number 0 Precipitation Irrigation ETa
Actual evapotranspiration and yield Water regimenes Source p-value SD <0.0001 WR <0.0001 SD*WR ns SD1 SD2 (Eff. precipitation 228 mm) (Eff. precipitation 149mm) 700 700 a 700 700 Irrigation depth Irrigation depth b ETa ETa 600 600 600 600 c c c 500 500 500 500 a b 400 400 400 400 100% c c mm mm mm mm c 300 300 73% 300 300 100% 47% 200 200 200 200 73% 45% 28% 100 100 100 100 24% 9% 0% 0 0 0 0 T100% T75% T100% T75% T50% T50% T25% T25% T0% T0% T100% T75% T100% T75% T50% T50% T25% T25% T0% T0% The treatments T100 and T75% were the most ETr, being higher in T100%
Soil water use Source p-value Water regimenes SD ns WR <0.0001 SD*WR ns a 200 200 Soil water consumed b a 150 150 b c (mm) c c 100 100 c c c 50 50 0 0 T100% T75% T50% T25% T0% T100% T75% T50% T25% T0% Although water consumption in T75% and T50% was higher compared to T100%, the differences were only statistically significant in T25% and T0%
Yield an components Water regimenes Yield (kg.ha -1 ) Yield (kg.ha -1 ) GN.m -2 SD SD GW (mg) SD SD <0.0001 <0.0001 <0.0001 ns WR WR 0,002 0,002 0,0027 ns SD*WR SD*WR ns ns ns ns SD1 SD2 4000 4000 abc a ab a ab bc c abc Yield (kg.ha -1 ) 3000 3000 bc c 2000 2000 1000 1000 0 0 T100% T75% T50% T25% T0% T100% T75% T50% T25% T0% Yield did not decrease in the treatments CDI 75% and T50% in relation with T100%
8 Water productivity b a Sowing date WP ETa (kg.mm -1 ) 6 WPETa (kg.mm -1 ) SD 4 SD 0,0014 WR 0,0912 SD*WR ns 2 8 0 WP ETa (kg.mm -1 ) 6 SD1 SD2 4 2 0 T100% T75% T50% T25% T0% Only difference was found in water productivity between planting dates, being higher in the FS2. This could be associated with lower average vapor pressure deficit (VPD) during the second sowing date
Yield production function 4000 y = -0,01x 2 + 16,1x - 1407 Yield (kg.ha -1 ) R² = 0,88; p<0,05 3500 3000 2500 2000 1500 T100% T75% 1000 T50% 500 T25% T0% 0 0 200 400 600 800 Actual evapotranspiration (mm) 4000 y = -0,05x 2 + 32,6x - 2375 4000 y = -0,29x 2 + 81,3x - 2356 Yield (kg.ha -1 ) Yield (kg.ha -1 ) R² = 0,89; p<0,05 R² = 0,89 ; p<0,05 3500 3500 3000 3000 2500 2500 2000 2000 1500 1500 T100% T100% T75% T75% 1000 1000 T50% T50% 500 T25% 500 T25% T0% ) T0% 0 0 ) 0 100 200 300 400 0 50 100 150 200 mm Normalized ETa (mm.kPa -1 ) Normalized ETa (ETa/ETo) m l (m ) ) ) ) mm mm m m) l (m l (m
Conclusions In soybean and in Santiago del Estero, irrigation water depth could be reduced by 25% without any yield losses. Although we could not show changes in WPETa with the use of CDI, we show that is it possible to increase the WPETA with change in SD.
Acknowledgements Water National Program Project: Evaluation of changes in water productivity against different climate scenarios in various regions of the Southern Cone ¡Many thanks!
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