Microrganismos promotores de crescimento e tolerância do sorgo biomassa à restrição hídrica e de nitrogênio em ambiente semiárido

Abstract

Sorghum is a great crop that has been used for thousands of years, it is more rustic than corn and can be used in the Brazilian semi-arid region. Some sorghum hybrids are suitable for biomass production, being an alternative energy matrix that can be used in thermoelectric plants or industrial furnaces. However, to achieve high yields, water and nutrients must be provided like any temporary crop, especially water, a limited resource in semi-arid regions. In this aspect, the inoculation of growth-promoting microorganisms can alleviate the effects of water and nutrient restriction, especially nitrogen in the biological fixation process. Thus, the objective of this work was to identify the potential of using microorganisms to increase the tolerance of sorghum biomass to water and nitrogen restriction in the Brazilian semiarid soil. This work evaluated sorghum BRS 716 at the Bebedouro Experimental Farm of Embrapa Semiarid, in an experiment in a 2x16x2 factorial scheme, arranged in sub-subdivided plots, with the plots being composed of two irrigation depths (45 and 100% of the crop's evapotranspiration - ETc); the subplots by 15 inoculants and a treatment without inoculation (the inoculants were composed of the bacterial strains M163, Ab-V5, BR 11005, ESA 13, ESA 402, ESA 600, ESA 674, ESA 29, ESA 424, ESA 15, ESA 001, BR11417, ESA 601, and two fungi, strains ESA 37, ESA 41), the subsubplots by two doses of nitrogen fertilizer (20 and 140 kg ha-1). The lowest dose was applied in foundation, while the highest dose was split, 20 kg ha-1 in foundation and the remainder in top dressing, and two applications of 60 kg ha-1 at 15 and 30 days after planting. Biometric characteristics, aerial part dry mass production (PMS), chlorophyll content, fertilization efficiency (EFA) and fertilization and inoculation efficiency (EFAI) were evaluated, in addition to nutrient extraction by the aerial part of the plant. The data, evaluated using classical statistics and principal component analysis (PCA), show that the strains ESA 13, ESA 29 and ESA 37 provided higher PMS in conditions without deficits (100% of ETc and with complete nitrogen fertilization) and with deficits (45% of ETc and with nitrogen fertilization only at the foundation). The highest PMS is correlated with greater plant height, leaf area, number of clusters, total chlorophyll content and nitrogen extraction, with the order of nutrient extraction by the aerial part being K > N > Ca > Mg > S > P > Fe > Mn > Zn > Cu > B. The strains that provided the highest PMS showed EFAI above 50% at 100% ETc, with complete nitrogen fertilization.