The Effect of Management and Competition on the Uptake of 32 Phosphorus by Ryegrass, Meadow Fescue and Their Natural Hybrid

Abstract

O'Brien, Whittington & Slack (1967) showed that in small plots in which the three forms grew together, the proportionate contribution to dry matter yield of the triploid hybrid between ryegrass and meadow fescue increased over 3 years while the contribution of the parent species declined. This occurred under both 'hay' and 'grazing' managements. Since competition for light is less likely to have been important in the latter treatment because the sward was kept shorter, it seemed likely that effective competition for soil factors had contributed to the success of the hybrid. It was decided, therefore, to investigate the rooting habit of the three species in both pure and mixed plots. The depths to which roots penetrate have often been studied by separating them from the soil by washing. This is a laborious and unattractive method because it entails destructive sampling, loss of roots and, as Newbould & Taylor (1964) have pointed out, provides little information about the rates at which the roots can absorb ions or water. Consequently, radio-isotopes have increasingly been used to study the absorption of ions from different depths, in different soil types and under varying cultural conditions (e.g. Nye & Foster 1961; Milbourn & Taylor 1962). In the study to be reported, 32P was used to follow the effects of management and competition on the root growth of ryegrass, meadow fescue and their natural hybrid in pure and mixed plots.