This work posed an isolation of cyanobacteria present in rice crops, with the purpose of determining the growth promoting activity of these, under greenhouse conditions in Bean, Maize and Rice crops. The cyanobacteria were obtained from the sampling done in the rice fields of the municipalities of Fonseca, Distraccion and Dibulla of the department of Guajira. Initially an identification of the species present in the soils of the rice fields was made. Strains were grown on BG-11 medium. The species found were Gloeocapsa sp, Oscillatoria sp and Anabaena sp being one of the ones that provides the greatest amount of nitrogen to the plant, which fixes nitrogen from 10 to 50 kg N / ha / year; however, it makes potent neurotoxic substances. To determine the growth promoting activity of cyanobacteria in the pepper, tomato, bean, maize and rice plants, four experimental plots with certified seeds were made. The lots used were 1 m2 at the Agroenterprise and Aquaculture center Riohacha, which were inoculated two species of cyanobacteria of the genus Gloeocapsa sp and Oscillatoria sp and were compared against a White. Cyanobacteria increase soil fertility because they are nitrogen fixing organisms capable of generating their own photosynthesis which makes them especially attractive for use as a biofertilizer.