The majority of our clients are grass based dairy farmers in West Wales.  These systems focus on maximising grass dry matter production and utilisation.  As these farms are in a high rainfall area with moderate to high fertiliser use, soil acidification is expected.  As standard good practice these businesses sample the whole farm every four years.  However, the results taken on clients farms for 2017 (> 500 samples) show that soil acidity has increased significantly over the last four years.  The average pH across all 500 samples equated to 5.7, with only 23% of samples taken at a pH of 6 or over, i.e. the optimum level.  Results also show that the average soil acidification over the four year period being a drop in pH of approximately 0.4 across the whole farm.  During this period lime would have been spread on a proportion of the farms.

Based on the results farmers in high rainfall areas that have a moderate to high fertiliser use should consider the following:
• Increase frequency of soil testing.
• Apply lime to all fields below optimum pH, not just the worst, also ensure adequate lime is applied to reach and exceed optimum pH.
• Fertiliser type.  Reviewing the type of fertiliser used and its uptake will affect the soil pH.  As an example urea is less acidifying than ammonium based fertilisers.
• Amount and timing of fertiliser application.  The uptake of N by the plant also has an effect, if conditions or application rate mean that plant uptake is low and that Nitrogen is leached, this indirectly has an acidifying effect due to residual Hydrogen ions.

To discuss how you can improve your soil fertility cost efficiently, contact Cled at cledrichards@fcgagric.com or your local FCG office.