To get the most out of grassland and maximise forage production for the coming winter, aftercut nitrogen applications should not be delayed.
Grassland hit hard by last year’s cold spring and following drought will need special care and attention in the next few weeks if it is to yield well through this season and help rebuild forage stocks.
Independent grassland specialist Dr George Fisher says while reseeding is a valuable option for many growers, there is a lot that can be done to boost the production of existing grassland, with good fertiliser management being critical this year.
“Reseeding will undoubtedly be top of the agenda for many producers in 2019, as it was last autumn. But this has to be managed alongside restoring existing grassland as much as possible.
“Many leys have come out of last year looking patchy and a bit battered with variable weather conditions at the start of the year contributing to a ‘hit and miss’ picture of fertiliser and manure applications to silage ground up and down the country.”
Indications are that grass growth has been good running up to first cut for most, he says.
“Mid-April AHDB data showed a grass growth rate of 40kg/day dry matter [DM] per hectare compared to almost 80kg/day DM/ha at the same time last year and 55kg/day in 2017.
“Growth rates stepped forward in late April and early May for most, but not for all, depending on rainfall and temperature.
“Multi-cutters in some parts of the country made a start in April with the bulk of two- and three-cut systems going by mid-May. Whatever the system, managing aftercut nitrogen [N] applications effectively is now going to be essential.”
Dr Fisher explains the timeliness of applications is the first priority.
“The more you delay applying N after your first cut, the more yield you will lose. Get it on more or less straightaway and you will be okay, but delay it by one week and you will see a yield drop approaching 10 per cent and if this extends to 14 days it will be nearer 25 per cent.
“Delaying the application of second cut fertiliser will cost you 370kg/ha of fresh grass per day so these are significant losses.”
“To put this into perspective it is worth remembering that one tonne of grass DM for silage at a typical 11.5 MJ ME contains enough energy to produce nearly 1,500 litres of milk worth £400 at 27ppl or 170kg liveweight gain worth £340 at £2/kg of liveweight gain.
“It will cost you about 6.1p to produce a litre of milk from good first cut silage and while this will increase to 6.9p for second cut, it is still a lot less than the 10.1p for a litre of milk from parlour concentrate.”
Nitrogen should, therefore, be applied quickly after the first cut with a slightly higher rate being considered to make up for the slow start to the year, he advises.
“Use a high quality ammonium nitrate [AN] based fertiliser to maximise quick N uptake and consider a rate of 2.5kg N/ha/day if you are disappointed with first cut yields.
“Fertiliser use will need to be balanced against manure application and good quality NPKS, NKS or NS true granular compounds should be used according to soil analyses.
“Even if you are able to apply 30cu.m/ha of 4 per cent DM slurry, you will be well short of the fertiliser manual recommendations for N, P K and S.
“In terms of nitrogen alone, such an application will only provide 17 of the 90kg/ha recommended for a high yielding system.”
As well as focusing on nitrogen, the importance of potash should not be overlooked in situations where plants can be stressed, adds CF Fertiliser’s James Holloway.
“Potash is essential in ensuring N is taken up by the roots effectively and has an important role in the plant’s ability to withstand drought.
“Its role is important in less than perfect years and can often be overlooked if you are just focusing on the relationship between N levels and yields.
“In trials over three years where 320kg potash/ha have been added to soils with K index 1, the average ME increased from 10.9 to 11.5 MJ ME/kg DM which is considerable in terms of utilising home-grown forage energy to support profitability.”
Sulphur is also important in helping swards recover, because it optimises N use and can also help with boosting crude protein levels, he points out.
“Sulphur is critical in the production of two vital amino acids – methionine and cystine – and without it protein cannot be synthesised efficiently. There is less of it available from the atmosphere now, so supplying it additionally is widely regarded as essential.
“In one trial where sulphur levels were restored to optimum, proteins increased by 7 per cent and yields lifted by nearly 2.0t/ha and at another site a 1t DM/ha lift over the farm’s standard practice urea regime was recorded while proteins increased by 5 per cent.”
The safest way to ensure grassland receives all the nutrients it requires this year is to focus on AN based true granular compounds containing the required N, P, K and S levels, Mr Holloway advises.
“Nutrition has a lot of work to do this year to help grass recover and get it back to high levels of production, so if ever there was a year to invest in good quality products, this is it.”