Effects of nitrogen rates and pulsed versus continuous subsurface drip irrigation on gas exchange in sugarcane

The pulse irrigation presents itself as a strategy capable of contributing to the efficient management of water and nitrogen, resulting in the optimization of agricultural cultivation. The objective of this study was to evaluate the influence of the application of nitrogen doses, applied via pulse and continuous fertigation, on gas exchange in sugarcane crops. For this, a field experiment was set up at the Carpina Sugarcane Experimental Station (EECAC) in the State of Pernambuco, Brazil. The experimental design was randomized blocks, in a 5 × 2 factorial scheme, with five nitrogen doses (80, 120, 160, 240 and 320 kg ha − 1 ) and two types of irrigation application (pulse and continuous), with four replicates. At 240 and 300 DAH, gas exchange evaluations were performed. Pulse irrigation combined with an estimated N dose of 189.4 kg ha − 1 , determined through regression analysis, promoted higher net photosynthesis in sugarcane. Applying nitrogen doses higher than 168.4 kg ha − 1 reduced carboxylation efficiency and water use, indicating a physiological limit for the nutrient. Pulse irrigation improved net photosynthesis, transpiration, stomatal conductance, internal CO 2 concentration, instantaneous water use efficiency, intrinsic water use efficiency and instantaneous carboxylation efficiency, highlighting the potential of integrated management of irrigation and nitrogen fertilization in the physiological performance of the crop.