COMPARISON OF IMPROVED LOW-FERTILITY GRASS SPECIES AND RYEGRASS WITH WILD POPULATIONS FOR PERFORMANCE UNDER VARYING LEVELS OF NITROGEN AND MOISTURE IN A SIMULATED HILL SOIL-PROFILE

This study compared improved ''low-fertility'' grass species and ryegr ass with wild populations for performance under varying levels of nitr ogen (N) and moisture. The species studied were: Lolium perenne L.; Ag rostis capillaris L.; Cynosurus cristatus L.; Festuca rubra L.; Dactyl is glomerata L.; Anthoxanthum odoratum L.; Bromus mollis L.; and Holcu s lanatus L. Wild-type seed was collected randomly from moderate hill country; bred genotypes were either selection lines, cultivars, or ran dom collections. The plants were grown in simulated hill soil profiles . Each species was represented by 24 seedlings planted in a 6 x 4 bloc k. N was applied in solution at three concentrations (0, 7, and 21 kg N/ha per fortnight). Three harvests were taken. A rain shelter was pla ced over the plants from December until February 1991 and recovery yie ld noted. Throughout the N experiment, yields of wild and bred genotyp es of the same species were generally similar. The response to N diffe red. During Harvest 2, ryegrass showed an increasing yield response to N whereas the other species gave no or little response to the high N rate. At zero N, ryegrass outyielded plants normally found in low-fert ility areas but equalled sweet vernal, cocksfoot, and browntop. The im plication of these results is discussed. The recovery from moisture st ress indicated the supremacy of the bred genotypes over the wild popul ations. Wana cocksfoot, wild red fescue, and browntop had greater yiel ds than ryegrass after moisture stress. The results are from single sp ecies plantings and the realisation of their potential under field con ditions will be dependent on competitive ability.