Characterisation of phosphorus uptake by perennial ryegrass (Lolium perenne L.) during regrowth

Abstract

The leaf regrowth stage of perennial ryegrass (Lolium perenne L.) is an effective and generic measure to determine the optimum time for defoliation and reflects important physiological processes. Previous research suggests that uptake of phosphorus (P) fertiliser by perennial ryegrass during regrowth may vary with leaf development stage, however little research has been undertaken in this area. The current study aimed to characterise P uptake with sequential leaf development, in order to provide knowledge which could be used to improve the efficiency of P fertiliser uptake. A glasshouse study was used to investigate the uptake of P by ryegrass grown in soil with optimum P fertility. Results showed a positive linear relationship between the 10‐leaf stage increments (ranging from 0 to 4 leaves) and both the change in P content in leaves and P uptake by the whole plant (leaves, tiller bases and roots) (P < 0.001 forbothrelationships and R 2 = 0.58 and 0.48 respectively). The linear relationship showed that an increasing amount of P was removed from the soil as the regrowth cycle progressed and, although P uptake was greatest at the 4‐leaf stage of regrowth, the optimum time of defoliation for perennial ryegrass is between the 2‐leaf and 3‐leaf stages of regrowth. This suggests that the greatest uptake of P by the plant can be enabled by providing adequate soil P availability prior to the optimum 2‐leaf to 3‐leaf defoliation interval.