Azospirillum brasiliense como atenuante do efeito da salinidade em milho irrigado.

Abstract

Salinity, in general, affects the growth and development of plants, causing problems in the yield. However, studies related to the attenuation of this abiotic factor must be essential, especially in regions that are prone to water scarcity. Thus, this research aimed to evaluate the attenuating effect of doses of the peat inoculant of Azospirillum brasilense in a hybrid maize cultivar submitted to different salinity concentrations of irrigation water. The experiment was carried out in a greenhouse located at campus I of the Federal University of Campina Grande - UFCG. Seeds of the variety NS PRO of maize were used, being inoculated and sown at this day. The experimental design was a randomized block (DBC), with a 3x5 factorial arrangement, in 4 blocks, totaling 60 experimental units, with three doses of Azospirillum brasilense (0.0; 0.32 and 0.48 mL) associated with five levels of electrical conductivity of the water ( 0.3; 0.6; 1.1; 1.7 and 2.3 dS m-1). The emergency evaluation took place from the first to the tenth day after emergence (DAE), analyzing the percentage of emergence (PE) and emergence speed index (ESI). Growth evaluations, on the other hand, took place at three different times, every 15 days, between the vegetative stages V8, V10 and Vt (weighing). In these periods, the plant height (PH), stem diameter (SD), number of leaves (NL), leaf area (LA), dry leaf masses (DLM), stem (DLS), tassel (DLT) and roots (DLR) were verified. The analyzes of photosynthetic pigments, gas exchanges, relative water content in the leaves and electrolyte leakage were carried out at the Vt stage, while the production was analyzed at the end of the entire culture cycle. The association treatments between salinity and Azospirillum brasilense had no effect under the emergency. Salinity affected significantly the growth variables, but the number of leaves presented increase of 12.8% (V8) and 18.8% (V10) comparing the difference between minor and major salinity studied. The plant height registered increase of 3.7% until the limiar salinity of the crop (1.1 dS m-1). The dry mass of the roots increased with the application of bacterial doses in each salt level studied. The photosynthetic apparatus was affected from saline concentrations of 1.1 dS m-1. Gas exchange and chlorophyll content were positively influenced by bacterial doses. The yield was negatively affected by the high levels of electrical conductivity of the irrigation water, even with the application of doses of Azospirillum brasilense.