Reseeding is not a cheap exercise. If you add up the costs of spraying off the old ley , ploughing, cultivations, seed and drilling and it is easy to reach a figure of around £400/ha (£160/acre).
Additionally if you factor in the time that ground is out of production and the potential costs of subsequent weed control and it is easy to understand why reseeding has taken a backseat on many farms. There are many reasons why reseeding is a very sound business investment.
From the first day a new ley is established there is a continual decline in the percentage of sown species as weed grasses and broad leaved weeds move into the sward, even under good management it is likely that after six years a medium term ley based around intermediate perennials could contain less than 60% ryegrass.
The impact of declining ryegrass content is a drop in both yield and quality. A young perennial ryegrass ley should yield well in excess of 10tDM/ha/yr in the first few years of its life if the correct P & K requirements are met – and if managed correctly should maintain quality above 11.5 ME and 20% crude protein. Much of this yield and quality is driven by a high response to applied nutrients; for every kilogram of nitrogen applied (from bag/slurry or clover) expect to get back 25-30kgDM of grass
Old leys may struggle to produce 6tDM/ha/yr and quite often because of poor response rates they may need greater nutrient inputs to achieve even that. The impact of this means more fertiliser is needed to produce the same amount of grass costing more per Ha
Whilst leys deteriorate at different times late perennials will survive longer than intermediate varieties and far longer than hybrids, which will struggle to make five years in most leys.
The decision on when to reseed generally needs to be governed by when ryegrass falls to below 50% of the sward. Ideally this observation would be backed up by production data; either some measure of stock performance on the ley (level of milk production or number of grazing days) or ideally, records of grass yield and quality from plate measurements and analysis.
Below shows how a typical silage ley based on a hybrid and perennial ryegrass mix can decline in productivity and quality as the hybrid ryegrass component drops and the content of weed species increase. The economic threshold is year five when the differential between the performance of the existing ley and a reseed (£637/ha) is significantly higher than the costs of a reseed at £400/ha. If you try and stretch the life of the ley an extra year then costs start to increase rapidly.
Ploughing and reseeding is the most expensive option it does provide an opportunity for weed control and the correction of any soil structural issues
I will now demonstrate the difference between a 2 and 5 year old ley in Milk, Meat and cake equivalent, the last one slightly controversial although I get asked all the time “how much feed can I save” My stock answer to this would be why would you want to save feed you had already planned to feed why not take the extra litres from forage or live weight gain you could achieve
Example 100 acre cutting
Year 2 ley should yield 15 tonnes per acre so a total of 1500 tonnes of silage @ 11.8 ME total energy = 5,310,000 MJ energy which is equivalent to
1,264,285 litres of milk @ 4.2 MJ per litre or
151,714 KG LWG @ 35MJ per KG/LWG or
408.84 Tonnes of Cake
Year 5 ley will potentially yield 11.5 tonnes per acre so a total of 1175 tonnes of silage a considerable drop of 325 tonnes but contractor costs will stay the same!!! @ 11.4 ME the total energy of silage on this farm is 4,018,500 MJ energy applying the same maths to farm A these are the results
956,785 litres of milk or
114,814 KG LWG or
309.11 tonnes of cake
As you can see the difference in ME is only .4 but add to that the yield difference the financial benefit between the two farms would be
307,500 litres of milk @ 29p = £89,175
36,900 KG LWG @ £3.40 per KG = £121,770
99 Tonnes of cake @ £260 = £25,740
Small difference make BIG differences on farm.