The objective of this experiment was to study the effect of nitrogen levels (0, 40, 80, 160, 320 kg ha-1 N) and forage cutting intensities (none, one and two cuts) on nutrient uptake and nutritional efficiency of oats (Avena byzantina / Avena sativa). The potential mineral uptake by forage and grains and their cycling through their straw, were also evaluated. This experiment was conducted on a Hapludox soil, in a split-plot design with complete randomized blocks and four replications, using the São Carlos and UPF 3 oat cultivars. Increasing levels of N affected both, the extraction of S and N in the first forage cut of São Carlos, influenced the K assimilation of both cultivars in the second cut, and S uptake, in both cultivars and cuts. In addition P uptake by straw of both cultivars, and Zn, Cu and Mn by São Carlos, were altered. The K concentration and extraction decreased from the first to the second cut. Potassium uptake was higher when oats were used as forage, at a level of 145 kg ha-1. Straw assimiliation of K was about 60 kg ha-1, which returned to the soil, while grain uptake was about 6 kg ha-1. Potassium, N, Fe and Mn were the nutrients of highest demand by both cultivars, which had similar nutritional efficiency and produced the same amount of forage dry matter. For grain production and use of nutrients, UPF 3 was more efficient than São Carlos.
Avena sativa; Avena byzantina; cutting intensity; nutrient uptake; forage; grain; straw; nitrogen levels
