Stomatal Conductance of Cowpea Submitted to Different Hydric Regimes in Castanhal, Pará, Brazil

Cowpea is a culture of great socioeconomic relevance for northern Brazil, but the knowledge about technology that increases productivity, such as irrigation, is still incipient. The objective of this work was to evaluate the stomatal conductance (g s ) of cowpea, in different hydric availabilities, Castanhal-PA. For this, it was planted the cv. BR3 Tracuauteua was planted in 0.5 ha in the year 2013, in the center of this area was instrummented a micrometeorological tower for measurements of atmospheric variables. The experimental design was in randomized blocks with 4 treatments, which were: 0%, 25%, 50% and 100% of the water slide as a function of crop evapotranspiration. The treatments started in the reproductive phase. The gs readings were performed at different phenological stages through a porometer, the data were subjected to analysis of variance (Tukey, p < 0.05). In the reproductive phase, the lowest gs values were found in the 0% 0% of ETc, which were 141.08 and 186.80 mmol m -2 s -1 , respectively, in the R7 and R8 stages. In contrast, the highest values were observed in T100%, 777.76 mmol m -2 s -1 (R7) and 754.50 mmol m -2 s -1 . The ideal water depth for cowpea stage R7 was 25% of ETc, whereas from R8, the ideal water depth was 50% of crop evapotranspiration.