INTERACTIONS BETWEEN SEEDLINGS OF PERENNIAL RYEGRASS AND WHITE CLOVERCULTIVARS IN ESTABLISHING SWARDS

Interactions between perennial ryegrass (grass) and white clover (clov er) cultivars were investigated at the seedling stage in two experimen ts: (a) a field experiment in which two clovers, AberHerald and Grassl ands Huia, were grown in binary mixture with two grasses, Preference a nd Pa 10761; (b) a glasshouse experiment in which the same clover/gras s combinations were grown in low-N soil either with (+N) or without (- N) added N. In the field experiment both clovers produced larger and m ore complex seedlings with Preference, and this was particularly evide nt in Huia. In the glasshouse experiment grass dry-matter yield was gr eater in the +N treatment, and this effect increased with time. Clover seedling density and development were suppressed in the +N treatment, and the development of AberHerald was affected more than Huia. Morpho logical measurements of the clovers showed interactions between clover , grass and N level. In the -N treatment Huia plants were larger and m ore complex than those of AberHerald, but in +N conditions there was l ittle difference between them. Grass cultivar had an effect on clover via N-level interactions: in +N plants there was no grass effect, but -N plants were significantly larger with Preference. Comparison of the root and shoot morphology of the two grasses revealed no obvious diff erences that would account for these effects.