Strategies to increase the efficiency of nitrogen fertilizers and benefit plant development and metabolism may reduce production cost and contribute to a more sustainable agriculture. To this end, the development of applied studies is necessary, especially for crops that occupy large areas, like grasslands. Our objective is to quantify the contribution of Herbaspirillum seropedicae inoculation in the recovery of N applied via fertilizer and originated from BNF in marandu grass, by means of isotopic techniques (15N). In addition, we seek to fill gaps about the possible mechanisms of plant-bacteria interaction in the development of this forage. The experiment will be conducted in a greenhouse, with a randomized block design in a 4x2 factorial scheme, with 6 repetitions. The treatments consisted of four levels of N-fertilization (using 15N-urea, with 1% 15N atoms, in coverage) in marandu grass submitted or not to foliar inoculation with H. seropedicae. At the end of the experiment (60 days after planting), the growth (shoot and root dry matter), physiological parameters (gas exchange and photochemical phase of photosynthesis), biochemical (lipid peroxidation, H2O2 and soluble protein) and nutritional (accumulation of P, K, Ca, Mg, S and 15N isotopic analysis) will be evaluated. It is expected that the inoculation of H. seropedicae contributes to the increase of N use efficiency by increasing the recovery of N-fertilizer and acquisition of N via BNF, and that in a complementary way, it acts in reducing oxidative damage (especially in low N-fertilization treatments), promoting increased photosynthetic activity and an greater efficiency in the use of water by marandu grass plants.
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