Relação entre a bactéria Nitrospirillum viridazoti e a adubação nitrogenada na cultura da cana-de-açúcar

Abstract

The use of diazotrophs in sugarcane crops, such as Nitrospirillum viridazoti, is a practice with the potential to increase yields and reduce nitrogen fertilization in plant cycle. The objective of this study was to evaluate the effect of the application of the inoculant containing Nitrospirillum Viridazoti in the sugarcane planting furrow and different doses of N in the operation of the loin breaker on the development, yield and raw material quality of sugarcane, as well as on leaf N contents and biological indicators of soil health. Three experiments were conducted in sugarcane crop areas located in Itapagipe - MG, Itumbiara - GO and Serrana - SP. All experiments were conducted in randomized blocks, with four replications. In Itapagipe - MG, four N doses in topdressing were evaluated (0, 30, 45 and 60 kg ha-1 of N) associated with the presence of the bacteria at planting and a control treatment with 60 kg ha-1 of N in tropdressing and no bacteria. In Itumbiara - GO and Serrana - SP, the experiments were conducted in a 2 x 4 factorial design, with the presence and absence of the bacteria at planting and four N doses in topdressing (0, 20, 40 and 60 kg ha-1 of N). In all areas, the number of tillers and stalks per linear meter, leaf N contents, soil health bioindicators, stem yield, sugar yield and total recoverable sugarcane were evaluated. The presence of Nitrospirillum viridazoti resulted in improvements in sugarcane tillering, leaf N content and biological indicators of soil health, especially to acid phosphatase enzyme activity. Gains in stalk and sugar yields and total recoverable sugar values were observed in the presence of the bacteria, with better results in the absence or lower doses of N, as well as in areas with low response to nitrogen fertilization, making it possible to reduce or eliminate mineral nitrogen fertilization when Nitrospirillum viridazoti is inoculated under these conditions.