ABSTRACT
The objective of this study was to analyze the variations of the decoupling factor and the aerodynamic and stomatal conductances for cowpea subjected to different levels of water availability during the reproductive phenological stages of the crop. The study was conducted in the municipality of Castanhal located in the northeast of the state of Pará, Brazil, in an area planted with cowpea, in 2013, 2014 and 2015 with four irrigation treatments: T100 - replacement of 100% of the crop evapotranspiration (ETc); T50 - replacement of 50% ETc; T25 - replacement of 25% ETc; and T0 - without any replacement (without irrigation). The interaction between the crop and the atmosphere in water vapor exchange was estimated through the decoupling factor (Ω), which was between 0.5 and 1, except for the treatment without irrigation, indicating a moderate to high decoupling between the crop and the atmosphere, so that the water vapor exchange process was controlled by the energy supply, instead of stomatal control.
Key words:
Vigna unguiculata (L.) Walp; decoupling factor; aerodynamic conductance; stomatal conductance
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T100 - Replacement of 100% of the crop evapotranspiration (ETc); T50 - Replacement of 50% ETc; T25 - Replacement of 25% ETc; and T0 - without replacement (without irrigation); FC - Field capacity; PWP - Permanent wilting point; The reproductive period began at 32, 33 and 31 days after sowing (DAS), respectively for the years 2013, 2014 and 2015
RH - Air relative humidity; Tair - Air temperature; Rg - Global solar radiation; Uz - Wind speed; VPD - Vapor pressure deficit; R5 - First floral bud); R7 - First exposed pod; R8 - Grain filling; R9 - Physiological maturity; θsT100, θsT50, θsT25, θsT0 - Soil moisture content, respectively, in the treatments T100 - Replacement of 100% of the crop evapotranspiration (ETc); T50 - Replacement of 50% ETc; T25 - Replacement of 25% ETc; and T0 - without replacement (without irrigation); DAS - Days after sowing
T100 - Replacement of 100% of the crop evapotranspiration (ETc); T50 - Replacement of 50% ETc; T25 - Replacement of 25% ETc; and T0 - without replacement (without irrigation); R5 - First floral bud; R7 - First exposed pod; R8 - Grain filling); R9 - Physiological maturity; DAS - Days after sowing
T100 - Replacement of 100% of the crop evapotranspiration (ETc); T50 - Replacement of 50% ETc; T25 - Replacement of 25% ETc; and T0 - without replacement (without irrigation); R5 - First floral bud; R7 - First exposed pod; R8 - Grain filling; R9 - Physiological maturity; DAS - Days after sowing