Effects of pre-sowing herbicide and subsequent sward mass on survival, development, and production of autumn oversown Wana cocksfoot and Tahora white clover seedlings

Abstract

Although oversowing new grass and legume cultivars offers potential for development of hill country, the success of this technique is variable. The objective of this experiment was to assess the effect of pre-sowing herbicide and subsequent grazing management on autumn oversowing into dense, hill country pastures. Three herbicide treatments (paraquat, glyphosate, and unsprayed) and four spring grazing treatments (average cover of 500,1000,2000, and 3000 kg DM/ ha) were compared. In general, ‘Grasslands Wana’ cocksfoot (Dactylis glomerata L.) and ‘Grasslands Tahora’ white clover (Trifolium repens L.) seedlings were more numerous (490 Wana /m² and 90 Tahora /m² versus 35 Wana/m² and 40 Tahora /m²), larger (6–12 tillers or stolons/plant versus 1 tiller or stolon/plant), and more productive in herbicidetreated than unsprayed swards. Lax grazing ( about 3000 kg DM/ha) did not influence the survival of seedlings during spring, but resulted in smaller cocksfoot and clover seedlings. Rapid growth of these seedlings occurred after uniform grazing (release from competition) and resulted in few subsequent differences in plant size and contribution of Wana to pasture production. Once established, Wana and Tahora seedlings were tolerant of a range of grazing conditions, but with the high fertiliser input in this trial, did not appear to benefit annual production.

Keywords:

• paraquat
• glyphosate
• Dactylis glomerata L.
• Trifolium repens L.
• seedling dynamics
• plant morphology
• ‘Grasslands Wana’
• cocksfoot
• ‘Grasslands Tahora’
• white clover
• pasture establishment
• oversowing