Effects of nitrogen application rates on the biomass accumulation and nitrogen uptake of oat

In this study, we examined the effects of nitrogen fertilization on the biomass accumulation and nitrogen uptake of oats (Avena sativa) ‘Baylor 2’ in the Horqin Sandy Land, based on the application of different amounts of nitrogen fertilizer, namely, 0 (N₀), 45.6 (N₁), 91 (N₂), and 137 (N₃) kg·ha⁻¹. The plant height, aboveground biomass, and nitrogen concentrations of oat grass was measured during the entire growth period, and the uptake of nitrogen was calculated. The results revealed that during the flowering stage of oats, compared with no nitrogen application, nitrogen fertilization significantly increased plant height by 10.83% to 10.92% (P < 0.05), and during the ripening stage, increased plant height by 5.37% to 8.53% (P < 0.05). From the heading to ripening stage, the response of biomass to nitrogen fertilizer was found to be dependent on the amount of nitrogen fertilizer applied. Compared with the N0 treatment, whereas we detected no significant increase in biomass in response to the application of 45.6 kg·ha⁻¹ (N₁) nitrogen fertilizer, the N₂ and N₃ treatments significantly increased the biomass by 26.60%～48.33% (with the exception of the heading stage), with no significant difference between the effect of these two treatments. Additionally, we found that from the booting to the ripening stage, the application of nitrogen significantly increased the nitrogen uptake of oats. During the course of the entire growth period, we observed a progressive increase in the biomass accumulation and nitrogen uptake of oats with incremental increases in the amounts of applied nitrogen, which peaked in response to the N₂ treatment, at which the accumulation and accumulation rate of oat nitrogen uptake were higher than those obtained with the N₃ treatment. In contrast, with an increase in the rate of nitrogen application, reductions in the nitrogen agronomic efficiency and nitrogen partial factor productivity of oats were observed at each growth stage. In summary, compared with application rates of 45.6 and 137 kg·ha⁻¹, application of nitrogen fertilizer at 91 kg·ha⁻¹ was established to be an appropriate amount of nitrogen for oat production in the Horqin Sandy Land. Our findings in this study will provide a valuable reference for enhancing oat productivity and promoting the efficient utilization of nitrogen nutrition.