Scotland’s wet winter and late spring put silaging at least 2-3 weeks behind in many parts of the country with difficult decisions now needed to ensure adequate forage quantity and quality for the coming winter.
Second cut silage is going to be more important than first for many Scottish livestock producers this year as grass in many parts of the country has been exceptionally slow to get going following challenging conditions for growth, says independent grassland specialist Dr. George Fisher.
"Importantly those farmers who have made the decision to delay taking the usual early cut need to think carefully about what this will do to grass growth for the rest of the season."
Those leaving swards beyond the usual first cut window could be storing up major problems later, he warns.
"Grass maturity depends mostly on day length so leaving it in the field longer simply results in crops going into seed head production and the corresponding drop in feeding quality far outweighs any gain in yield."
Far better is to take as close to normal as practically possible and then pay careful attention to the state of the soil and the nutrition needed to help second and, potentially, third cuts make up for the slow start, Dr. Fisher advises.
"As well as ensuring adequate supplies of nutrition in the weeks ahead, particular attention also needs to be paid compacted and oxygen-starved soils resulting from the poor conditions."
Checking for compaction
"Wheelings can cover up to 85% of a field used for silage production so the chances are compaction will exist. Use a spade to dig three sides of a square then lift the turf up and take a good look for obvious pans."
"Compaction created by sheep typically exists in the first 2” of the soil profile whilst that from cattle could be at 4” of depth. Damage from machinery wheelings, meanwhile, will usually be from 4” deep and beyond."
Such compaction reduces soil microbe populations which in turn limits those making nutrients from soil organic matter, manures and purchased fertilisers available to plants, he explains.
Top tips for addressing compaction
"Sward lifting can be a very effective way of addressing these problems, but it has been shown to reduce grass yields by up to 10% in the four weeks after it is carried out and that is not something you want to risk in the next few vital weeks."
"If compaction is only in the top 5-6” then spiking soil will get air into it and whilst this can quickly improve soil microbes and structure, it is essential you get below the compaction layer to allow water to drain and get air in."
Another current issue that impacts on grass yields is the use of urea as a Nitrogen fertiliser. Farmers need to be careful in this regard, he warns.“
Trials have consistently shown urea is a false economy for grassland when you look at the bigger picture. It can be tempting to use because of the lower purchase price, but it almost always limits potential production.
"Grassland trials at Reaseheath College in Cheshire, have shown savings of £1900 from using urea over Nitram Ammonium Nitrate on a 80ha system, but this also resulted in a 17% loss in grass yield, worth at least £8500."
"Even with inhibited urea designed to make Nitrogen loss to air less of a problem, a 15% reduction in grass yield compared to the Ammonium Nitrate was seen."
The main problem is weather and its effect on urea stability and utilisation, he adds.
"With urea you need significant rainfall within 3 days of application to wash the fertiliser into the soil where the microbial urease can convert it into nitrate. Without that, losses to air through volatilisation make it wholly uneconomic."
"In most year’s there’s generally only a 30% chance of getting an economic benefit from using urea over Ammonium Nitrate which is much more reliable and can be used precisely to produce maximum Nitrogen response and utilisation."
CF Fertilisers’ regional manager for Scotland, Mark Garrett, says as well as applying Nitrogen carefully, soil pH, P and K need to be taken into account this year to avoid potentially low grass yields and quality, too.
"Soils with low pH are generally pretty inactive biologically and unlikely to promote uptake of the key nutrients efficiently at times when they are needed most."
"In most years, grassland usually has adequate amounts of P and K because of the slurry and FYM applied but this may not be the case this year after the high winter rainfall."
"Even if you put as much slurry and FYM on as possible earlier in the year, available Nitrogen from this will largely have been used or lost by this stage of the season."Importance of Sulphur
Sulphur behaves like Nitrogen in the soil, so if N has been lost you will have lost Sulphur, too, he warns.
"Trials suggest a 20 - 40% increase in dry matter yield are possible from using Sulphur and it has been shown to lift protein and soluble sugar levels as well. 2016 is proving to be the year Sulphur really comes into its own on grassland."
NKS products are particularly beneficial where P index is high and soil Potash levels need to be maintained, he says.
Regular testing and analysis of soil is the only way of knowing where you are with basic fertility, Mark Garrett says.
"Work from your soil analysis and take into account all the nutrients from manures, but for second cut you need to be typically apply the following:
Product Rate (kg / ha) Nitrogen 80-100 Potash 60-90 Sulphate 25 – 40 KayNitro Sulphur is ideal for this
Grassland producers have a lot to gain from taking a more agronomic approach to their crops, he adds.
"At the very least, regular soil sampling for P, K, Mg and pH is essential to identify nutrient needs accurately."
"With the difference between profit and loss so small these days, the cost of such testing is minimal compared to the potential downside."