By Jonathan Long
GRASSLAND MANAGEMENT is top of many producers” spring to-do lists and those planning to increase sward productivity, while reducing fertiliser use, by increasing clover content should be sowing now.
Warm, moist conditions are ideal for germination, so now is the time to harrow swards and oversow with clover, says Barenbrug Seeds” David Long.
“Ground temperatures are warming up and grass growth has yet to take off in many areas, so clover will have a chance of establishing before being outcompeted.”
Ensuring seed has contact with soil and limiting competition are essential for good germination, he adds. “One of the best ways of managing these factors is to harrow swards to remove thatch and dead plants and open up space for clover to grow in. Clover will also find its own gaps, so a complete spread is not always essential.
“Best results will be achieved by using a spring-tined harrow to break open swards, but pastures must be grazed tightly before seeding. With a dense matted sward it may be worthwhile harrowing the field twice, the second time harrowing across the direction of the first pass.”
For most situations, where the intention is to increase clover over 12 to 18 months, seed should be spread at about 2.5kg/ha (1kg/acre). But where a rapid increase in clover content is required, such as when converting to organic production, it may be necessary to double this, suggests Mr Long.
But producers should not be overly concerned with apparently low germination rates. “Often when clover is sown only about half will germinate the first time, some more will probably germinate in autumn, with the remainder germinating the following spring,” he believes.
Another essential point is to avoid applying nitrogen fertiliser, reckons SAC consultant Peter Lindsay.
“Low nitrogen levels encourage clover, as it fixes its own nitrogen. Nitrogen will also push grass on and increase competition in the sward.”
Oversown clover should be grazed fairly hard in the first year, he adds. “Where oversown fields are left for silage, grass often grows too fast, blocking out light to clover seedlings.”
And while some may recommend treating swards with limited applications of paraquat to cut competition, Mr Long is wary of this. “Paraquat can sometimes remain active in swards, killing emerging seedlings,” he warns.
Other options include feeding clover seed to livestock so it is distributed in dung, but little is known of the effectiveness of this, he adds.