Sugarcane Productivity as a Function of Nitrogen Fertilization and Inoculation with Diazotrophic Plant Growth-Promoting Bacteria

Sugarcane ratoons respond to nitrogen fertilizer application, but the N efficiency is low. Diazotrophs applied as a growth promoter bacterium can influence crop yield by several mechanisms, including a greater root growth and higher N absorption. The objective of the present work was to evaluate the stalk and sugar yields, and the economic index of sugarcane as a function of nitrogen fertilization and inoculation with diazotrophic plant growth-promoting bacteria (DPGPB). Two experiments were implemented in areas of two sugarcane mills in the state of Sao Paulo, Brazil: one in the Diamante Mill and one in the Santa Helena Mill. The experimental design was a randomized complete block with four N-fertilizer doses (0, 50, 100 and 150 kg ha−1), with or without DPGPB inoculation using five replicates. The application of the inoculant promoted a productivity increase in the Diamante Mill for all treatments with N, even in the absence of N-fertilization, while at the Santa Helena Mill that occurred with the 50 kg ha−1 dosage. The inoculation with DPGPB, together with the application of the 50 kg N ha−1 dose, achieved the highest economic return at both mills. The application of the inoculant associated with a low dose of N-fertilizer was profitable and proven feasible for field application. The results evidenced the viability of the technology for sugarcane production, with gains in productivity and a possible reduction in nitrogen fertilization.