Effects of Nitrogen and Phosphorus Fertilization on Photosynthetic Properties of Leaves and Agronomic Characters of Alfalfa over Three Consecutive Years

The present study aimed to investigate the nitrogen (N) and phosphorus (P) fertilization of continuous addition effects plant biomass, physiological properties leaves antioxi-dant enzyme activities alfalfa (Medicago sativa L) in northern Xinjiang region; including no (CK), (N, 120 kg·ha−1), (with low amount N) (P, 100 kg·ha−1 P 23.5 combined (NP, N P) on K well supplied soil. After three consecutive years supply fertilization, samples were taken at first flowering (four clippings total year) determine its pigment concentration, stomatal aperture, antioxidant activity hay yield. results showed that NP promoted growth with a higher number branches yield alfalfa, while or alone had positive effect alfalfa. However, significantly increased carotenoid (Car) content early stage (during four clippings) (p < 0.05), In addition, ferti-lization enhanced decreased oxidized substance leaves. balance rather than an absolute either fertili-zation affects traits differently. We propose increases nutri-tional characteristics characteristics, enhancing adaptive capacity making it better adapted external environmental changes.