Pulses and intervals of subsurface drip irrigation on sugarcane gas exchange and yield

Pulsed irrigation is an alternative for irrigation management capable of reducing the harmful effects of stress. The objective of this work was to evaluate the effect of the number and intervals of irrigation pulses applied by pulsed subsurface drip on gas exchange in sugarcane. The experiment was conducted in the field at the Carpina Sugarcane Experimental Station (EECAC), from October 2022 to October 2023. The experimental design used was completely randomized, in a 4 x 2 + 1 factorial arrangement, the first factor consisting of 4 different numbers of pulses (2, 3, 4 and 5 pulses), the second factor consisting of 2 application intervals between pulses (20 and 40 minutes) and the third factor consisting of a control treatment (irrigation applied in a continuous), with 4 repetitions. The sugarcane cultivar evaluated was RB 041443. The following variables were analyzed with an Infrared Gas Analyzer (IRGA LI-6400): Internal CO2 concentration (Ci), Stomatal conductance (gs) mol, transpiration (E), net photosynthesis (A), instantaneous water use efficiency (A/E), intrinsic water use efficiency (A/gs) and instantaneous carboxylation efficiency (A/Ci). The best responses for net photosynthesis, stomatal conductance and intrinsic water use efficiency were obtained with the application of 4 irrigation pulses. The highest values of transpiration and instantaneous carboxylation efficiency were obtained with an interval of 40 minutes, the number and intervals of irrigation did not influence the internal carbon concentration and instantaneous efficiency of water use.