Establishment of new pastures free of ryegrass contamination

Abstract

Various pre-sowing management systems were applied from spring to early autumn, before drilling a new 'lolitrem-free' perennial ryegrass. These treatments aimed to evaluate the level of contamination over a range of ryegrass natural reseeding levels. Strips in the plots were left unsown or sown in prairie grass in order to assess the levels of natural reseeding. A late hay crop resulted in the largest contamination (27%) of the establishing pasture. Lax grazing and spring barley (pasture direct drilled in autumn) resulted in approximately 3.5% contamination. Silage and early hay crops harvested before mid-December controlled most ryegrass seedheads, but further seedheads developed during summer. Control of seedheads in these treatments and the hard grazing treatment was difficult to achieve by grazing. A summer fallow, using a double spray with glyphosate (spray/fallow), successfully killed all existing vegetative plants and prevented natural reseeding, but seed present in the soil germinated to produce seedlings in autumn. Contamination levels in hay, silage, hard grazing, and spray/fallow treatments were 0.9%. Although the reseeding levels in this trial were generally very low, when comparisons are made with other data, every effort should be made to minimise seedhead development and ripening of seed during spring/summer. Keywords Acremonium lolii, grazing,Lolium perenne, natural reseeding, pasture establishment