White clover is critical to New Zealand’s pastoral farming systems. However, clover content in perennial pastures is typically 10-20%, much less than the optimum of 30-40%.
A new Agriseeds trial confirms the method by which pastures are sown can significantly influence white clover population. Results showed a 20% increase in clover content when ryegrass and clover were sown separately.
White clover seed is small and needs to be sown shallow for best germination, otherwise clover seedlings struggle to compete against faster establishing ryegrass plants. However, modern high production farming systems demand new pastures are back into full production as soon as possible and in many cases little thought is given to white clover establishment.
Five different treatments were autumn sown in Canterbury, with sowing rates of 20 kg ryegrass and 4 kg bare clover seed/ha. Clover content was measured in January.
Nine months after sowing, broadcasting ryegrass and clover (similar to roller drilling) or drilling the ryegrass and broadcasting the clover, resulted in over 20% more clover in the sward than sowing ryegrass and clover in the same drill row.
To maximise clover establishment where cultivating, use a roller drill followed by harrows, on a fine, firm well consolidated seedbed. This results in seed being spread evenly across the surface, giving cover more space and light than when sown into tight rows. It also helps suppress weeds, because the sown species better cover the soil surface.
Where drilling in rows (especially wide 15 cm row spacing), the space in between the row allows weeds to establish. If you or your contractor use a coulter drill, check if it has two seed boxes. If so drill the ryegrass seed through the main seed box, and allow the clover (and possibly up to 5 kg/ha of ryegrass) to be broadcast on the surface through the small seed box at the front of the drill. Follow this with harrows and a Cambridge roller. This will give the clover space between the ryegrass rows to establish. The use of a drill with a smaller row spacing (ideally 7.5 cm) also helps weed control.
Note: In the establishment trial, oversowing clover separately in the following spring did work, although it was not as successful as the best autumn methods. Nonetheless this option can be useful where a winter herbicide programme is needed to control specific problem weeds.
Take home message
Sow white clover seed according to its needs, and it will pay you back with good establishment and plant population.