Thursday 19 July 2018

Conditions make this a good time to reseed pastures

Munster farmer

Kevin O'Sullivan, Teagasc Adviser

There is huge variation in grass production on Irish farms. There are many reasons for this variation such as soil type, rainfall, and drainage problems, but the most common cause is poor sward quality and lack of perennial rye-grass in grassland. It's difficult to get good animal performance from old pasture, with some old pasture only producing 50 per cent of the grass dry matter of recent well-managed reseeds.

Before reseeding, any drainage problems should be identified, and any drainage required should be addressed if possible. Perennial rye-grass does not survive well in very wet soils.  Soil fertility should also be assessed by soil testing, and any lime, phosphate and potash applied. This can be done during the reseeding process. Reseeding can be done from now on until September, but now that the weather has improved, and silage has been conserved, it is a good time to consider it.  Reseeding can be done with conventional ploughing and harrowing, or with a variety of surface cultivation methods. The benefit of surface seeding is that there is minimal burying of surface fertile soil, and little or no stones will need to be picked.

Surface seeding can also be carried out relatively quickly.  A popular system of surface cultivation is one pass of a disc harrow combined with one pass of a power harrow. The top two inches are harrowed, and this ensures quick germination of grass seeds.  The grass seed can be sown in conjunction with the power harrow. It is important to roll the seedbed after sowing. Some thought should be given to choice of grass varieties that can be used.  Production and persistence qualities are the two most important traits in grass varieties.

Heavy soil mixtures should be made up of predominately late diploids while, on better soils, some intermediates diploids can be used.  Tetraploids should not exceed 30 to 40 per cent of the grass seed mixture; three to four different grass varieties are sufficient in any grass seed mixture. A clover inclusion rate of 0.5kg should be incorporated in most mixes. Recommended seeding rates are 14 kilogrammes per acre. Lime at two to three tonnes per acre is generally applied at sowing. Bag lime is a worthwhile alternative to ground limestone at reseeding.

Standard fertilizer recommendations are two to three bags of 18-6-12 or 10-10-20 per acre at sowing, but account should be taken of soil tests and nitrates restrictions. When reseeding, always spray with glyphosate a minimum of six to seven days before cultivating. It's also advised to apply a post-emergent herbicide 30 to 35 days after sowing, to control broad-leaved weeds.  Grass reseeds can usually be grazed 60 to 70 days after sowing. Small cattle or sheep are ideal for the first grazing.  It's very important to graze new reseeds at least once before the winter, as this encourages tillering and ensures a dense sward the following year.