Abstract:

[Objective] This study aimed to assess the effects of nitrogen fertilizer application rates on the quality of forage oat, and to determine the optimal range of nitrogen fertilizer application rate for forage oat. [Method] Using oat grass as the experimental material, a total of 7 nitrogen fertilizer application gradients were set up, including 0 （N0）, 175 （N175）, 200 （N200）, 225 （N225）, 250 （N250）, 275 （N275）, and 300 （N300） kg/hm². At the seedling stage, tillering stage, jointing stage, and heading stage, 15%, 35%, 30%, and 20% nitrogen fertilizer topdressing were applied, respectively. A single factor randomized block design was adopted in the plots of the field trial, with 3 replicates in each block. At the jointing stage and heading stage, the alkali-hydrolyzed nitrogen content in the 0-10 cm, 10-20 cm, and 20-30 cm soil layers, as well as the contents of protein and cellulose of oat grass were measured, respectively. [Result] With the increase of nitrogen fertilizer application rates, the soil alkali-hydrolyzed nitrogen content elevated, and an accumulation phenomenon was observed. Compared with N0, the alkali-hydrolyzed nitrogen content in each soil layer of the different nitrogen fertilizer application rates at both jointing stage and heading stage increased in various degrees. The quality of forage oat did not continuously improve with the increase of available nutrient content of nitrogen, and had a peak. At the nitrogen fertilizer application rate of N225, the protein content of oat grass peaked at both jointing stage and heading stage, reaching 11.55% and 16.13% respectively, with an increase of 38.15% and 53.62%, respectively. The highest tillering number of forage oat was observed at the nitrogen fertilizer application rate of N175 （median=8）. The contents of protein and cellulose of oat grass exhibited a trend of first increasing and then decreasing with the elevation of nitrogen fertilizer application rates. At the nitrogen fertilizer application rates of N225 and N175, the contents of protein and cellulose reached the maximum values, respectively. [Conclusion] Within the range of nitrogen fertilizer application rate at N225-N275, the contents of protein and cellulose of forage oat reached the synergistic optimal value.

Key words: nitrogen fertilizer application rate, forage oat, protein, cellulose