Influence of crown height and clipping frequency on compensatory growth of Italian ryegrass

In this experiment, we examined the influence of crown height and clipping frequency on the compensatory growth of Italian ryegrass (Lolium multiflorum). Two light and dark experiments were conducted to test Italian ryegrass prior to the jointing stage. The light experiment included 5 treatments: clipping once to a 5 cm crown height (HS); clipping twice to a 5 cm crown height (HF); clipping once to a 2 cm crown height (LS); clipping twice to a 2 cm crown height (LF); no clipping (CK). The dark experiment included 3 treatments: 5 cm crown height without root clipping (B5); 2 cm crown height without root clipping (B2); 5 cm crown height with root clipping (BD5). Results of the light test showed that the content of soluble carbohydrates of single clipping of high crown Italian ryegrass in roots was higher than in crowns, which increased the photosynthetic rate and organic matter accumulation. Reduced biomass due to clipping was compensated for and the compensatory growth occurred in single clipping of high crown Italian ryegrass. However, this was not observed in the frequent clipping and low crown treatment. Results of the dark experiment showed that the regeneration ability of high crown Italian ryegrass increased after clipping. Additionally, the energy needed for regeneration was mainly derived from crown rather than root. Thus, stubble height and clipping frequency had an important influence on the regeneration of Italian ryegrass, and results showed that single clipping of high crown Italian ryegrass had the highest regeneration ability.