Scatter method gives clover best odds

Farmers can get up to 20 per cent more white clover established in their new paddocks simply by sowing it differently, a Canterbury trial has found.

Agriseeds compared five different techniques for establishing new pasture in autumn, plus a control treatment, to find out more about what effect sowing method has on clover population in the sward.

Broadcasting clover and ryegrass seed on the surface, then harrowing and rolling it to simulate the effect of a roller drill, gave the best result when the swards were analysed nine months after sowing.

The second best result came from sowing ryegrass seed in 10mm to 15mm rows, broadcasting clover seed on the surface, then harrowing and rolling.

Broadcast treatments averaged 50 per cent clover content in the sward nine months later and 20 per cent more than the plots where ryegrass and clover seed were sown together in 10mm to 15mm rows.

The poorest result in terms of clover population was caused by sowing ryegrass and clover together in rows 10mm to 15mm rows deep.

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White clover seed broadcast separately later in spring did establish, but was at lower levels when assessed in January because of the later sowing.

Although it was not as successful as the best autumn methods, it can be a useful option where a winter herbicide programme is needed to control specific problem weeds.

Sowing rates of 20kg per ha ryegrass and 4kg per ha clover were used for all treatments.

Agriseeds agronomist Matt Smith ran the trial and will take more samples this autumn to find out what, if any, changes take place in the swards 12 to 15 months after his initial measurements, and how well the spring oversowing option catches up.

Although it remains key to New Zealand pastoral farm systems, white clover content in perennial pastures is typically much lower than the recommended optimum of 30 to 40 per cent, he says.

The prevailing emphasis on fast turnaround for new pastures doesn't always help.

"Modern high production farming systems now demand new pastures are back into full production within three months, and at the same time more cost- effective drilling techniques -- such as grass to grass renewal through direct drilling -- have become popular.

"In many cases little thought has been given to white clover, reducing the chance for successful establishment. This is made even more difficult if conditions for initial emergence are not maximised."

With its small seed, white clover requires shallow sowing and it also needs light and space after seedlings emerge. While ryegrass can successfully emerge from a sowing depth of 20mm, optimum sowing depth for clover is much closer to the surface at 2mm to 3mm.

Results from the trial showed just what a difference sowing technique can make to clover establishment, Smith says, and reinforced Agriseeds' advice to use a roller drill followed by harrows when planting new pasture.

"This spreads the seed evenly across the surface of the paddock and gives the clover more space and light than when it is compacted into tight rows with ryegrass seed. Roller drills are also excellent for suppressing weeds because there is less space for weed seedlings to emerge in the first place."

Farmers can also help their clover get a good start by following general principles for establishing pasture, including ensuring correct soil fertility; creating a firm, fine seedbed and preventing ryegrass from becoming too long and shading out clover plants in early establishment.