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Fertiliser Considerations for This Year鈥檚 Silage Ground

Spring is here, and although听many of you will still be听feeding winter rations, now is the time to start thinking about this year鈥檚 silage crop as the days stretch and soils get warmer. Fertiliser prices have until recently been听stable, however as fertiliser volatility returns, it is important to听plan.听听

Before听applying any product to the grass there are a few听important factors听to consider,听to听ensure that the grass will get the听best utilisation of the product applied.听Knowing听the soil鈥檚听pH is essential for achieving听optimal听yield and quality听for any crop grown in the soil.听Optimum soil pH varies slightly depending on soil type and听cropping system听for听young grass destined for cutting听grown in a mineral soil听you听should aim for a pH of听around听6.2.听It is advisable to have a听soil sampling plan in place, sampling all fields听routinely every five years to听monitor听the soils pH,听phosphate听and potash levels. This听will help to develop a fertiliser plan听suitable听for听silage听crops.听听

Nitrogen is the first nutrient that comes to mind听for many听when thinking听about fertiliser听application,听applying it at the correct rate will ensure the best optimisation from the grass. For听a first听cut听silage听crop it is recommended to apply听120kg听N/ha听applied听eight听weeks before targeted cutting date. Higher rates and delayed application can result in the risk of nitrate N in the grass and poor silage fermentation.听Applications for听subsequent听cuts of silage should be made as soon as possible after the听previous听cut听at 90kg听N/ha and 70kg听N/ha for a third cut.听听

It is also important to consider sward type when applying nitrogen.听If applying to听swards with a high听clover听percentage of clover听care should be taken听with nitrogen quantity. Clovers are nitrogen fixing crops so naturally help to build nitrogen levels, they are also听sensitive to nitrogen and overapplication can lead to other grasses shading the clover reducing the percentage within the sward.听Red clover has听very low听requirements for supplementary nitrogen,听if听the grass appears nitrogen deficient a low rate of around 50kg N/ha could be considered but should be taken with caution.听If you have queries relating to nitrogen application and听clover,听speak to your consultant for advice.听All fertiliser advice should come from a FACTS accredited consultant or agronomist.听听

Phosphate (P) and Potash听(K)听levels within the soil听can also听be听monitored听through soil analysis. This helps听to听understand the P听and听K status and where applications听may or may not be听required.听Phosphate is听particularly听important听for grass establishment;听P aids the development of the听plant鈥檚听roots听and the early tillering听of the grass.听It听is particularly important in young grasses as their root systems are not fully developed.听An example听top-up rate of phosphate on听moderate soils would be between 15听and听20kg P/ha, this would听maintain听a moderate level, however tailored听fertiliser applications should be applied depending on soil analysis.听听

After听nitrogen,听potash听is the second most important nutrient听for grass听and听maintaining听M- status is a sign of good grassland management. Offtake levels of potash in grassland can be considerable (180 to 330kg K2O/ha from听two or three听cut systems) and light or sandy soils can quickly be depleted of potash reserves. Typically, first cut silage rates should be 60 -听90 kg K2O/ha and 50-60kg K2O/ha for second cuts. Exact rates will vary depending on soil status, nitrogen application听rate听and听anticipated听grass yield. Where required potash requirements are over 90kg/ha for听first听any surplus over the 90kg should be applied later in the season to avoid luxury uptake.听听听

N P听and听K are the听three听compounds听most often considered for silage听fertiliser applications, however in a silage cutting situations听it is important听to consider sulphur applications.听The grass cannot use the nitrogen applied to the best of its ability without adequate sulphur levels in the soil.听Just like when considering the rates and requirements of N, P听and听K听for the soil, it is important to understand the soil type and its condition听before听making a decision. Sandy听and听shallow soils听generally would听see the greatest deficiencies, along with this fields cut intensively for silage and receiving听large doses of nitrogen are at risk.听It听is important to look at the soil analysis of听the silage fields and consult with the farm鈥檚 FACTS advisor on selecting a product with听the correct sulphur content to best utilise the nitrogen being applied.听听

5 top tips for fertiliser applications to silage ground:听

1. To ensure听nutrients are fully utilised,听carry out soil analysis routinely听to manage soil pH and optimise inputs for maximum yields.听
2. Alongside a qualified,听advisor seek advice to develop a fertiliser plan for grazing and silage land.听听
3. Apply fertiliser at the听optimal听time to achieve the best results for silage.听
4. Good soil management听is required to听optimise nutrient use and maximise grassland productivity.听
5. Visit for more information.听听

Fiona Thomson, Senior Consultant and Area Manager, Fiona.Thomson@sac.co.uk

Posted by Unearthed News on 16/03/2026