Inoculation of cotton improves plant growth under reduced nitrogen fertilization

The environmental impacts caused by the use of mineral fertilizers contribute significantly to the loss of quality of soil, water resources and the atmosphere. At a global level, there are increasing investments in the search for alternatives that reduce the use of chemical inputs in agriculture and contribute to sustainable production. In this sense, the use of growth-promoting microorganisms is one of the most promising techniques. In soybean cultivation, for example, inoculation makes it possible to eliminate the use of nitrogen fertilizers. The objective of the present work was to evaluate the effects of inoculating cotton plants with Azospirillum brasilense and Pseudomonas fluorescens. The experiment was conducted under greenhouse conditions in a completely randomized design, with five treatments and five replications, as follows: T1: 100% N; T2: 75% N; T3: 75% N + Azospirillum brasilense; T4: 75% N + Pseudomonas fluorescens; T5: 75% N + Azospirillum brasilense + Pseudomonas fluorescens. Inoculation was performed at the time of transplanting. After five months, the growth and mass production of roots and shoots were evaluated. The data were submitted to analysis of variance and the means were separated by the Scott–Knott test at 5% probability of error. The use of Pseudomonas fluorescens with 75% nitrogen fertilization increased the mass of fresh roots by 150% and the volume of roots by 167% in relation to 100% fertilization. Inoculation with P. fluorescens appears to be a promising tool for better rooting of cotton seedlings and reducing fertilization costs, and should be better explored to understand its benefits in field conditions, as well its effects on the productivity of this crop.