Minimum cultivation for reseeding
Ploughing has the disadvantage of bringing up stones and burying the top fertile soil. However, ploughing is sometimes necessary to level ground.
Teagasc recommends sowing 14kg of seed per acre into a fine, firm seed bed, which should be well rolled.
There must be good seed to soil contact.
It is essential that soil samples are taken from the soil on which the seeds will be sown (not before ploughing).
With minimum tilling systems, lime is always required, to neutralise rotting stubble.
Germinating seeds require extra phosphorous, generally 2.5 to 3 bags of a P-rich compound per acre, plus nitrogen.
Potential 33% increase in yields of grass and silage (depending on how bad the old pasture is, and how well the reseeding is carried out).
Better response to fertilisers (25% better response to fertiliser)
20% higher digestibility
Better seasonal growth
Better quality silage, easier to preserve, a gain of 10 DMD digestibility units
Big savings in concentrate requirements, worth 60 cent per animal per day
Better animal performance — higher milk yields (adding one gallon per cow per day), higher milk protein (adding 0.16%) and live weight gain.
Excluding the costs of fertiliser and lime (which should be the same for old and new pastures), the extra costs associated with reseeding vary from €150 to €220 per acre, including grass seed mixes which are about €80 per acre.
The extra grass output should be about 1.25 tonnes of dry matter (6.5t of grass) per acre, per year, which is worth about €200 per tonne.
In addition, the reseeded pasture is much higher quality and grows earlier in the year.
Assuming that you maintain the reseeded pasture in a highly productive state for seven to eight years, reseeding is the best investment a farmer can make, because the cost can be recouped in less than two years.
If, on the other hand, you allow reseeds to revert back to poor, weedy pastures in a few years, reseeding is not worthwhile. Therefore the job should be done right, with proper follow-up, or not done at all.
In order to justify the cost of reseeding, many different factors should be considered. The botanical composition of the existing swards, and the management of the grassland after reseeding should be the main influencing factors.
The demand for extra feed on your farm is another factor to be considered.
Generally, only varieties from the Irish or Northern Ireland Departments of Agriculture recommended list should be used.
These recommended lists are available from Teagasc.
In addition to cutting trials by the Department of Agriculture, Moorepark researcher Michael O’Donovan and colleagues are now testing the digestibility and other aspects of varieties, and are finding some significant differences which may not be showing up in the official list.
This work should result in some useful information after a few years. Eventually an economic index (similar to EBI for bulls) will be developed for different varieties.
Every year, a few varieties are added to the official list, and few drop out.
The main choice farmers have to make is between late, medium and early varieties (based on seed heading dates). These varieties are further divided into diploids and tetraploids.
Within each classification, there is very little difference between the recommended varieties.
Availability and price often influence decisions to include them in seed mixes.
Most reputable grass seed merchants and co-ops have good quality seed mixes that have been formulated by seed experts and Teagasc to suit different farm situations. Farmers can confidently depend on these mixes.
If you use recommended varieties and seed mixes, the final result from reseeding will depend more on the standard of reseeding and subsequent treatment than on any particular varieties.
Tetraploids are very high yielding and palatable.
However, due to their open growth habit, it is generally recommended not to include more than about 30% in the seed mix.
Farmers are using mostly late varieties for grazing, and most of these have early growth.
Silage mixes could contain up to 30% medium varieties, for early silage cuts.
Autumn is not suitable for sowing clover-rich pasture, because clover seedlings are vulnerable to early frosts. However, clover seed should be included in all August-sown reseeds.
Most reseeds will need to be sprayed for weeds four or five weeks after sowing.
This is particularly important where dock seedlings are appearing. (I will cover this topic in September).
Apart from bad seed preparation and late sowing, frit fly poses one of the biggest threats to reseeds.
Direct drilled crops that are emerging slowly and sown near old grass areas are particularly vulnerable.
The frit fly larvae burrow into the shoots of seedling grasses.
Infected shoots, although still green, will pull away easily, showing a brown feeding area at the point of breaking off.
There are two main approaches to control:
* Spray routinely with an insecticide when the crop is emerging.
* Check crops daily by gently pulling the centre shoots, and if close to 10% of shoots are infected, spray immediately with an insecticide such as Dursban, Clinch, Grubber, etc.
Slugs
There are many situations where slug pellets are required, especially in wet weather and late sown crops.
