SURVIVAL OF OVERDRILLED RYEGRASS IN DAIRY PASTURES CONTAINING PASPALUM

Abstract

The growth end st~rv~val of ryegrass plants Introduced 111 autumn/winter into dairy pasture contammg paspalum, were momtared in a series of field experiments from 1978 until 1982. In each expermwnt plant losses were highest (30-40X of total) in the summer iollowmg their mtroductlon resultmg in only small short term improvements (<500 kg DM/ha) in seasonal productIon About 208 of total losses were directly related to damage caused by cow grazing (severe yrazing,"pulllng", dung and wine deposition, trampling). The mechamsms accountmy ior the other 80% were less easy to quantify but apparently Involved factors llke competition for light, water and nutrients, climatic stresses and subtle ammal damage to plant growth pomts, leaves and roots. Large plants (20-30) tillers had a higher probablllty of survwny summer than did small plants :< 10 tillers) A number of modifymg factors were used in an attempt to Improve the size and therefore survwal of introduced ryegrass plants. These mcluded additions of mtrogen fertiliser m late winter/spring, Irrigation during summer/autumn and contmuous severe clipping of resident herbage surroundmg introduced ryegrass plants. Only the clipping treatment sigmficantly improduced ryegrass survival. A short (14 d) grazing interval over summer was also detrimental to ryegrass survival, compared to a long interval (28 d). The presence of summer growing paspalum as the main resident competitor reduced ryegrass survival compared to other resident species, and the effect was most noticeable if the plants were further stressed by grazing at a short interval over summer. Practical methods 01 reducmg competitlon between established species and establishing ryegrass seedlings are discussed. Keywords: pasture renovation, ryegrass persistence, ryegrass survival, Paspolum dilatotum, Lolium pewnne, seasonal pasture production, grazing damage, competition control, nitrogen, irrigation, grazing interval.