It is not always necessary to plough ground to introduce new grass seed. Trails carried out in Northern Ireland have shown that it is possible to reseed or renovate grass swards using direct seeding or over-seeding techniques. However, establishing new grass varieties using such techniques is dependent on reducing the competition from the existing sward until the new grass seed has germinated and established.
Normally this is achieved by tightly grazing or cutting a field for silage prior to reseeding. Alternatively the existing sward can be sprayed with a suitable herbicide at a reduced rate. The grass seed is normally then sown at two thirds of the normal rate using a machine such as the Einboch reseeder.
Apply fertiliser only when the new seed has germinated and started to establish within the sward. Such operations cost significantly less than ploughing ground and have the added benefit of bringing the fields back into production a lot sooner than conventional reseeding.
It is important to choose a grass seed mixture that is suitable for the intended purpose of the sward and which is suitable for the soil type. On wetter ground it is important to choose varieties which have good sward density and persistency characteristics. Select grass varieties which are either mid or late heading for grazing swards as this will greatly ease the management of these swards throughout the grazing year.
Where heavy ground is being reseeded include Timothy in the seed mixture as it will help to create a dense and palatable sward that is capable of withstanding difficult grazing conditions. Tetraploid and hybrid grass varieties are best suited for silage swards where they will produce a good yield, however they tend to create more open and less persistent swards than diploid varieties.
Recent developments in plant breeding have produced clover varieties that are better able to withstand nitrogen applications but yet will be productive within a grass sward.
Broadcasting or drilling grass seed are equally effective ways of sowing grass seed if carried out under good weather and soil conditions. A seed rate of 30kgs per hectare is adequate, however this should be increased for sowing after mid-September. If broadcast, grass seed should then be lightly harrowed and rolled to consolidate the seedbed thereby preserving moisture which is critical for germination.