Agronomic evaluation of varieties of sugar cane inoculated with diazotrophic bacteria and fertilized with nitrogen

The objective of this work was to evaluate the efficiency of inoculation with diazotrophic bacteria and nitrogen fertilization, in two varieties of sugarcane grown under the same edaphic and climatic conditions. The experiment was carried out during the agricultural years 2006/2007 and 2008/2009, in a randomized block design with four replicates, installed in March 2006 in an area of commercial cultivation in Campos dos Goytacazes city, in Rio de Janeiro state, Brazil. The treatments were: inoculation with diazotrophic bacteria, fertilization with 120 kg ha(-1) N, and a control without inoculation and without nitrogen fertilization. The sugarcane varieties evaluated were RB72454 and RB867515. The inoculant was composed of five strains of diazotrophic bacteria. Evaluations were done for fresh stalk yield, total dry matter accumulation, total N of shoots, and N-15 natural abundance from available N in the soil and in sugarcane. The varieties performed differently to treatments, in which RB867515 was responsive and RB72454 unresponsive to inoculation and nitrogen fertilization. In the variety RB867515, growth and accumulation of total N in the shoots, promoted by inoculation, were similar to the ones in the treatment with N fertilization.