Produção e efeitos de biofertilizante bioprotetor com quitosana na alface

Abstract

Nitrogen is one of the macronutrient that affects plant growth, and is usually not found on the rocks. Thus the study involving N-fixing bacteria with free living or symbiotic associations are of extreme importance for the development of agriculture. The objective of this study was to evaluate the enrichment in N of the organic matter (earthworm compound) by inoculation with free living diazotrophic bacteria and the addition of fungi chitosan adding Cunninghamella elegans that contain chitosan in their cell wall, a biopolymer that have the properties to act in the control of plant diseases. Diazotrophic bacteria were isolated from Brazilian soils and selected at the Nucleus of Biologic Nitrogen Fixation in the Tropics (NBNFT/UFRPE). The diazotrophic bacteria, were isolated in silica gel plaques and grown in liquid culture (LG medium), maintained under shaking during 15 days (± 28ºC). The biofertilizer (NPKB) and the Protector (NPKP) production were processed in laboratorial assay using plastic trays, and in field conditions in furrows at the University Federal Rural of Pernambuco Horticultural Station. In field the diazotrophic bacteria was inoculated adding 30 L of the culture medium (108 viable cells mL-1) for each 3000 kg of organic matter (earthworm compound). The fungus C. elegans was grown in potato-dextrose medium (PD) and the inoculation was processed in the same manner described for the diazotrophic bacteria. In all assays samples were collected weekly (T0, T7, T14, T21, T28, T35 e T42, after inoculation) for chemical analyzes. By the results it was observed that the time for maximum efficiency for increment of the biological N fixation by the free living diazotrophic bacteria was achieved at 35 days after inoculation and N increase up to 100% compared with the initial N (T0). The research work showed the possibility to obtain a mixed fertilizer (NPKB) with higher N rate due to the free living diazotrophic bacteria inoculation. The bioprotector (NPKP) increments the N, P and K content of the product and have potential to provide nutrients for plants.