Many of us are guilty of making the same application of 20:10:10 fertiliser every spring at the same rate because that’s what we’ve always done regardless of whether the field needs it or not. 

With the industry and press quoting ever increasing fertiliser prices this season growers are holding off ordering for next year.  However, maybe a simple soil test could help farmers decide if, when, and what, would be the most economical use of their money when it comes to fertiliser purchasing.  For grassland management it enables planning a fertiliser programme that is accurate, timely, cost effective and environmentally responsible.

Soil testing can give you a snapshot of your soil health allowing you to build a nutrient management plan for Nitrogen (N), Phosphorus (P) & Potassium (K) & Magnesium (Mg).  It will also measure the soil pH is and if lime is necessary.  More detailed soil tests can also check for any trace element or nutrient deficiencies.

Soil maintained at a pH of 6.3 or above shows increased grass yields, increased resilience of beneficial species such as clover or perennial ryegrass and allows more efficient uptake of fertilisers and manures.  Limed soils allow more Nitrogen to be unlocked from the soil.  Ideally grassland should be limed every 5 years but regular soil sampling will allow the farmer to ensure the correct amount is applied and whether it is necessary. 

Farming Connect can support you in soil testing your farm through Technical Advice, which is 80% funded on an individual basis, or 100% funded if you are undertaking the work as part of a group. To arrange this service contact your local Farming Connect Development Officer.

Alternatively, you can either get a local representative to take a soil sample for you or do it yourself and send it off to a soil lab for analysis.

 

How to take a soil sample in grassland:

 

  1. Make sure it is representative of the area sampled. 
  2. Do not take samples where muck heaps or feeders have been or other unusual features.
  3. Walk a ‘W’ pattern across the sampling area, taking regular samples using a gouge corer or screw auger.
  4. Sample to 7.5 cm depth in long-term grassland fields, sample to 15 cm depth in short-term (<5 year) leys or grassland about to be ploughed and re-seeded.
  5. The samples should be mixed together and a representative sample sent for analysis. 

 

Surface acidity often occurs in the top 50 mm in grassland soil with high rainfall (common in Wales) and heavy usage of nitrogenous fertilisers; this reduces the availability of Phosphorus which plants need to create good root structure.  Conversely, for farms using high levels of slurry or digestate on their ground high levels of phosphate can be an issue.

For this reason it is better to have frequent small applications of lime than one large application to reduce soil acidity. Keeping the pH above 6.0 in grassland improves N recycling and reduces total N requirements.  When P & K soil indexes drop below 2 less beneficial grass species such as Creeping Bent and Yorkshire Fog can dominate over more nutritious species such as ryegrass.

Soil testing can be a farmers best friend in saving money on fertiliser application.  From as little as £10 per field per test they can plan the correct fertiliser purchase.  If there are the on-farm resources of slurry, digestate or manure these could save money and also manage a potential waste problem.

If the farmer is using a company that provides the soil-testing services they will also be able to provide farmers with recommendations for fertiliser & nutrient application based on those results.  Farmers should always use a FACTS-qualified adviser or consult the RB209.


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