Effects of polymer-coated nitrogen fertilizer combined with different potassium fertilizer dosages on physiological indicators and yield of ryegrass

To determine the best fertilization ratio for the growth of ryegrass (Lolium perenne), a potted experiment was performed to study the effect of polymer-coated nitrogen fertilizer combined with different potassium fertilizer dosages on the growth characteristics and yield of ryegrass. Compared with common urea, the polymer-coated nitrogen fertilizer significantly increased the SPAD (soil plant analysis development) value, plant height, leaf area, net photosynthetic rate, prolonged the green stage, and prevented the premature senescence of ryegrass (P < 0.05). Using the same amount of potassium fertilizer, the SPAD values of four grass cuttings increased by 11.2%, 6.9%, 33.6%, and 195.2%, respectively, and the plant height increased by 14.1%, 6%, 25.1% and 85.4%, respectively. Compared with urea treatment, polymer-coated nitrogen fertilizer increased the dry mass weight of ryegrass by 12.4%～25.0%. The leaf area index and net photosynthetic rate of ryegrass increased maximally following polymer-coated nitrogen fertilizer with moderate amounts of potassium fertilizer. Thus, it is recommended as an optimal fertilization ratio, providing a theoretical basis for the rational application of nitrogen and potassium fertilizer in ryegrass production.