Nitrogen management at sowing and topdressing with the time of supply in the main biotype of oats grown in southern Brazil

Adjusting the nitrogen dose at sowing and topdressing with the time of application can improve nutrient management and increase oat productivity. The objective of the study is the most efficient and sustainable management of nitrogen use in the adjusted combination of nutrient dose at sowing and for topdressing with the moment of application on the productivity of biomass and oat grains, considering the main systems of cereal succession in southern Brazil.. The experiment was conducted in the years 2015, 2016 and 2017, in Augusto Pestana, RS, Brazil. The design was a randomized block with four replications, in a 4 x 4 factorial model, consisted of four doses of nitrogen at sowing time (0, 10, 30 and 60 kg ha-1), and topdressing dose by the total supplied of 70 and 100 kg ha-1 in succession system soybeans / oats and corn / oats, respectively, in the expectation of grain yield of 4000 kg ha-1, with the supply for topdressing considering four application times (0, 10, 30 and 60 days after emergence). The most efficient and sustainable management of nitrogen use for biomass and oat grains productivity occurs with the total supply of the covered nutrient around 30 days after emergence, regardless of the condition of the agricultural year and succession system.