20 March 1998

SLOT SEEDING FILLS THE GAP

By John Burns

VERY high output from grassland is only possible in leys less than five years old, and if a full reseed is not possible then slot seeding is the next best thing.

That is according to Sinclair McGills Ian Misselbrook, who believes slot seeding is particularly relevant where a heavy stocking rate makes it difficult to spare a field long enough for a full reseed.

The technique is also useful where shallow or rocky soils make ploughing difficult, or on wetter land where it is felt unwise to invert the existing turf, he says.

Speaking at a demonstration of the updated Aitchison slot seeder from New Zealand on Graham Bigwoods Binham Farm, Old Cleeve, Somerset, Mr Misselbrook said slot seeding would give 50% to 75% of the output of a full reseed without the field being out of production for long.

If the sward contained less than 50% ryegrasses a full reseed was called for; if it comprised between 50% and 70% ryegrass, then slot seeding would be suitable.

Tetraploid varieties are ideal for slot seeding because they have big seeds with good energy stores to help them grow quickly, even in less than ideal conditions. Mr Misselbrooks companys mixtures for slot seeding are based on tetraploids with the best seedling vigour.

The mix chosen for the demonstration, on a field covered in white clover, which had survived the herbicide used to kill off the old sward, was Elgon – top conservation yield in late tetraploid group, Condesa -persistent grazing tetraploid, Aubisque – productive mid-season tetraploid, and Molisto, a hybrid tetraploid combining the yield of Italian with three to four-year persistency and good early season growth.

Molisto is normally only used in short-term mixtures but was included here because of the late drilling date. Clover was left out of this mix because there was plenty in the sward already.

Mr Misselbrook advises a seed rate of 25-37kg/ha (10-15kg/acre). And protection against pests like slugs, frit fly and leatherjackets is also recommended. Slug pellets could be applied mixed with the seed through the Aitchison drill. Typical costs would be £85 to £100/ha (£35 to £40/acre) for seed and about £37/ha (£15/acre) for drilling by contractor.

Normally slot seeding would be done after a second silage cut and without any herbicide unless there is a high proportion of weed grasses or perennial weeds. No nitrogen fertiliser should be used until the new seeds are established, or they would be swamped by strong growth of the existing sward. &#42

Need to boost pasture productivity? Slot seeding could prove to be a cheaper option than a full reseed.

SLOT SEEDING

&#8226 Consider if sward still contains between 50-70% ryegrass.

&#8226 Tetraploid varieties ideal because have big, seeds.

&#8226 Seed after second silage cut – no N until established.

Big improvement

Aitchison drill importer James Horford from Sussex said the drill had been significantly improved and vibrated more to give a better tilth in the slots. He said this drill gave better results than disc drills because it was less likely to smear the slot and produced a tilth to cover the seeds. Good results depended on drilling when soil conditions were right, and ensuring the old sward was as short as possible, the field surface not too bumpy, and soil P and K levels correct.