Yara: Managing fertiliser effectively for first cut silage

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With increased fertiliser prices and cost of inputs, many livestock farmers are considering how best to manage their grassland and maximise their return on investment when it comes to first cut silage crops. Yara recently held a webinar informing farmers of the latest advice and guidance on how best to manage fertiliser applications and ensure a strong first cut.


Philip Cosgrave, Country Grassland Agronomist at Yara, shared the findings from Yara/Farming Connect silage trials at three Welsh farms. “Those fields using our granular compound NPKS fertiliser saw yields increase by up to 11%,” says Philip. “Sulphur deposition in soils is at pre-industrial revolution levels, which effects yields and nutritional quality of grass. With the typical cost of adding sulphur to each silage cut at around £7/ha, the extra grass grown in this trial – 300kg DM/ha – is worth nearly £50 in terms of energy and protein. That gives a healthy 7:1 return on investment.”

Many believe that sulphur response is only seen on very light soils with low organic matter. However, other trials have demonstrated a response between 10% and 37%, even on heavier type soils.

“We’re not getting the same amount of sulphur from the atmosphere, so we need to top up in some way,” says Philip. “We know organic manure is not enough so using the right product with sulphur is important.”

Philip is quick to point out that organic manure does have its place, especially when fertiliser costs are so high. “Slurry is variable in nutrient content,” says Philip. “However, it should be used primarily as a resource for P & K rather than N, as 64% of the value in slurry comes from P & K. It’s worthwhile sending a sample to a lab for analysis or using a slurry hydrometer. For spring applications, we aim to optimise N content and use low emission spreading equipment.”

Is it worth lowering your N rate?

Next, Philip examined two scenarios. One with the recommended optimal N rate of 120kg/ha N, the other scenario using an N rate of 100kg/ha, with slurry making up 31kg/ha of N in both scenarios. We can estimate from first cut N response trials that reducing the N rate by 20kg/ha will lower grass yields by 2 t/ha.

“The cash cost of growing and harvesting the 120kg scenario works out at £20.07 per tonne, while the 100kg N rates comes to £20.08,” says Philip. “Costs are lowered per hectare when applying less N, but the cost per tonne didn’t change, because most of the cash costs are charged on a per ha basis and not by yield.”

“In this scenario, for grass produced, they’re no better off and have two tonnes of silage less, which is equivalent to 70kg of protein. It’s a balance and reducing N rates needs to be carefully considered.”

Another option for those considering lowering N rates is to delay harvest for a week or more, this will increase the rate of dry matter you produce. However, as Philip explains, this will also cause a decline in quality. “In just one week, quality falls by 3.3%,” says Philip. “It’s not a straightforward decision. Consider all your options and whether allowing a longer period is right for you, as it obviously has an impact.”

Optimising your nutrients

The webinar closes with Philip providing a range of extra tips for getting the most from your first cut this spring. Chief among these is focusing on establishing a strong nutrient management programme to ensure the best results possible.

“Creating a fertiliser plan is key,” says Philip. “Calculate the NPKS requirement of the crop and determine how much you can provide with slurry and how much mineral fertiliser you need. Ensure sulphur is going in and don’t put apply any more than 90kg/ha of potash.”

“Optimising nutrient applications for your first cut is important. This is where we see the best nutrient response, and ultimately helps produce the best quality silage.”


For more information, please visit www.yara.co.uk

Image: Philip Cosgrave

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Deborah Laird

Deborah Laird

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