Reseeded swards have higher yields
Research at Moorepark has shown old pasture to yield on average, 3 tonne of Dry Matter (DM) /ha less than perennial ryegrass swards.
In Moorepark, pastures with 100% perennial ryegrass had February growth rates of more than twice those with 40% perennial ryegrass. The annual improvement in profitability is worth over €200 per hectare for the 100% perennial ryegrass sward.
Information on recommended grass and clover varieties is available from the Dept. of Agriculture (www.agriculture.gov.ie) and Agri-Food Biosciences Institute (AFBI) (www.afbini.gov.uk/reclists).
Role of clover in grassland
James Humphreys, Moorepark Research, says that €7,000 can be saved on the nitrogen bill on a moderately stocked 50 hectare (2.2 cows/ha) dairy farm. Only 72 units/acre of bag N is required with clover. White clover does not persist indefinitely in permanent grassland. Therefore, over-sowing 20% of the farm each year for a five-year rotation is necessary.
Before any cultivation take place, it is important to burn off the existing pasture and weeds with Roundup or a similar product. Products such as Roundup will not eliminate nettles, so you may have to add another chemical to the mix. Allow adequate time (usually seven days) for the spray to work before grazing/cutting and removing the burnt-off vegetation.
Seedbed preparation
Ploughing will bury parasites, trash and provides a good seedbed but avoid going too deep in order to avoid burying the top layer of fertile soil. Sowing with the one pass system avoids bringing up unwanted stones.
Minimum cultivation involves the use of a power-harrow, rotavator or similar type of machine.
For good results it is important to have low levels of trash and a compact seedbed through rolling.
Direct seeding involves the use of a drilling machine which may use a tine or disc to cut a slit in the soil. To help this process the existing sward should be cut as bare as possible to give the new seeds a chance to germinate and establish.
Slurry seeding: For this system you also need a bare sward. Generally grass seeds should be covered with 2,000-3,000 gallons of slurry per acre.
When using a minimum cultivation technique, it is a good policy to apply one tonne of lime/ac to counteract the acidity that develops when the old sods rot. Teagasc advice is to produce a fine firm seed bed and roll it before and after sowing.
Nitrogen should be withheld until the crop is established to avoid encouraging weed growth. Once the seedlings emerge, keep a close eye for damage caused by Frit Fly, slugs, etc Around five to eight weeks post-germination, spray fields to eliminate broadleaved weeds that have germinated and before they develop root reserves. If there is clover in the seed mix, the choice of sprays is limited so check with your adviser.
