Eficiência fisiológica em cana-de-açúcar submetida a adubações foliares

Abstract

The culture of sugarcane is now considered a great alternative for the biofuels sector inBrazil and the world. Its main product is ethanol, but there are by-products that are obtained by the national sugar and alcohol industry. The objective of this work was to evaluate how gas exchanges related to the splitting of foliar fertilization in sugarcane. The work was conducted between May 2019 and July 2020 at the Experimental Farm Chã de Jardim, of the Departmentof Phytotechnics and Environmental Sciences (DFCS),at the Center for Agricultural Sciences (CCA), of the Federal University of Paraíba (UFPB), in the municipality of Areia-PB. The treatments were: T1) 1 application at 100DAP, T2) 1 application at 180 DAP, T3) 1 application at 240 DAP, T4) 2 applications (100 and 180 DAP), T5) 2 applications (100 and 240 DAP), T6) 2 applications (180 and240 DAP) and T7) Control, in random blocks with 4 repetitions. For the analysis of the physiological responses of the plants as a function of the adopted treatments, liquid photosynthesis (A) (µmol m-2 s -1), stomatal conductance (gs) (mol m-2 s -1), internal concentration of CO2 (Ci) (µmol mol-1), transpiration (E) (mmol m-2 s-1), through the portable infrared gas analyzer, IRGA (LI-COR®, Nebraska, USA), model LI-6400XT. Subsequently, they were calculated as A / E ratios (instant water use efficiency), A / gs (intrinsic water use efficiency) and A / Ci (instant carboxylation efficiency). The data were prepared for analysis of variance and as means compared by the Scott-Knott test (p<0.05). The results indicate that the positive efficiency response due to sugarcane has a high photosynthetic rate and CO2 recovery. For liquid photosynthesis, the treatment with split fertilization between 100 and 180 days was superior in relation to the control, the stomatal conductance did not differ statically between the treatments where the split occurred, since the internal concentration of carbon in the leaves was the same for the control treatment and treatment with installments between 100 and 240 days.