Late nitrogen topdressing increases nutritional and industrial quality of white oat (Avena sativa) grain

Nitrogen is a nutrient that most limits the development, biomass yield and protein composition of Poaceae. The N losses can be reduced by synchronizing fertilizer additions with plant uptake requirements. The objective of this study was to investigate the effect of N topdressing at different rates and times on grain yield and industrial quality of two white oat cultivars. The experiment was carried out under field conditions, from July to November of 2014, in a factorial design 2 x 3 x 4, with four replications. Two oat cultivars (URS Guria and URS Brava) combined with nitrogen topdressing were applied under three management systems: (i) semi-late, (ii) late and (iii) semi-late plus late, described as a growth stages (GS) GS31 (first node visible) and GS45 (booting) or split N on GS31 plus GS45 and N rates (0, 30, 60 and 90 kg ha-1) with urea as a source. White oat cultivars responded differently to nitrogen fertilization. The URS Brava cultivar showed higher hectoliter weight (HW) and crude protein in the grains (CP) and URS Guria higher number of spikelets per panicle (NSP) and plant lodging (LOD). Application of at least part of the N at the first detectable node played important role on grain yield and yield components. Splitting N fertilization in two applications, 50% at the beginning of stem elongation and 50% at booting, favored higher yield and protein content of the grains. The increase in N rates up to 90 kg ha-1 did not promote grain yield, but it provided increases in grain thickness and protein content in white oats cultivars, increasing the nutritional (more protein), industrial quality (more flakes per ton of the grains) and grain yield leading to more profit to farmer.