Nitrogen fertilizer application for improving the biomass, quality, and nitrogen fixation of alfalfa (<i>Medicago sativa</i> L.) at different growth stages in a saline‒alkali soil

Overall, this study revealed the essential role of N fertilizer application at low rates in alfalfa production, as this practice not only increases alfalfa yield but also improves N fixation in saline‒alkali soil. However, it did not result in further improvement in alfalfa quality at the early flowering stage. The findings provides valuable guidance for N fertilizer application in alfalfa production on saline‒alkali soils.