Uso de bactérias diazotróficas na produção de mudas de cana-de-açúcar em diferentes substratos

Abstract

Sugarcane is a very important culture in Brazil, the country is the world's first in the production of cane and sugar, second of ethanol and increasingly conquers the foreign market with the use of biofuel as an alternative energy. One of the problems of this crop is conventional planting, because in it occurs the excessive spending of stalks that could be destined to the industry, besides increasing the risk of diffusion of plagues and diseases. Moreover, sugarcane is extremely dependent on nitrogen fertilization, because among the nutrients responsible for its nutrition, nitrogen is the element absorbed in greater quantity. In this sense, the objective of this work was to evaluate the effects of the inoculation of diazotrophic bacteria in the promotion of growth, rooting and biological nitrogen fixation of pre-sprouted and micropropagated sugarcane seedlings produced in alternative substrates. Were used the sugarcane varieties RB867515, RB92579, RB966928 and RB975932, and substrates produced from the mixture of carbonized rice rusk and organic compound, in addition to a trademark. And several experiments were developed, where they were evaluated: the survival of the diazotrophic bacteria species in the substrates; parameters related to sprouting, aerial part and root development, and nitrogen accumulation of seedlings; the response of these seedlings to inoculation for tillering, chlorophyll content, leaf area, biomass accumulation, dry mass increase, nitrogen content and biological fixation; And in the in vitro cultivation the multiplication of the shoots and the growth of seedlings in glass jars containing semi-solid medium and in temporary immersion bioreactor, the response of these plants to the inoculation in rooting and the acclimatization in the different substrates. The results indicate the interaction between the varieties, inoculation and substrates for all evaluated parameters that involved these factors. The substrates containing carbonized rice rusk and organic compost present better results in the survival of diazotrophic bacteria and can be used from acclimatization to the development of seedlings. All varieties show excellent development of seedlings from micropropagation and also minitoletes, and somehow respond to the inoculation of diazotrophic bacteria, but nevertheless, only in RB92579 and in RB975932 the biological fixation of nitrogen.