Sir, – Studying the Environmental Land Management (ELM) consultation, the environment, soils and soil nutrients feature centre stage when, by comparison, evidence from the latest 2018 British Survey of Fertiliser Practice reports agricultural lime applications on only 7.2% of fields surveyed.

With only 8.5% of cropped land and 5.6% of grassland treated, this indicated attention to soil pH and liming only one in every 14 years!

The tried and tested PAAG soil database highlighted pH was below pH 6.0 in 19% of arable and below 5.5 in 19% of grassland samples. Aggregated annual PAAG reports report mean soil pH has decreased steadily in arable samples from around 7.0 to 6.6, highlighting a need to address liming on significant proportions of arable and grassland areas.

The pH scale is logarithmic working to the power of 10, meaning pH 6.0 is 10 times more acidic than 7.0. There are many penalties with sub-optimal pH including a reduction in the activity of beneficial soil micro-organisms which are essential for creating a healthy vibrant soil environment, this in turn leads to a reduction in the solubility and availability of essential soil nutrients and beneficial cations like calcium, potassium and magnesium.

Sub-optimal pH can result in a marked effect on yield and quality due to the nutrient imbalance and aluminium toxicity. Attention to and maintaining an optimal mean soil pH throughout the liming-cycle is the most remunerative crop input investment.

Ag-lime is controlled and regulated by the 1991 Fertiliser Regulations, as well as being a dual action ag-lime provides the essential plant nutrient calcium, but it is the chemical base, carbonate, that neutralises the excess +hydrogen ions producing water and carbon dioxide.

Quality ag-lime determines its efficacy and benefit, while the combination of neutralising value and fineness determines both the reactivity or efficacy value – coarse or out of specification materials will help neutralise your bank balance, but not your soil acidity!

The Agricultural Lime Association initiated the UK's first ag-lime quality standard (AQS), with samples analysed for chemical and fineness for regulatory compliance, purchasing lime from producers who promote their compliance with the approved AQS logo is a guarantee of product quality and efficacy that is sure to repay the investment.

Stephen Hill


Agricultural Lime Association,