Soil pH and Fertiliser Efficiency

With the ongoing impact of the war in the Middle East on fertiliser pricing and the drive to more carbon-efficient farming, the need for farmers to monitor and manage their nutrient use efficiency (NUE) and nutrient availability to maintain the profitability of farming operations is more important than ever.

As part of this quest towards efficiency, testing of soil plays a vital role. Not just the basic soil tests that farming has utilised over the last 60 years, but a more enhanced analysis which includes the major cations (Calcium, Magnesium, Sodium and Potassium), micronutrients, the soil’s cation exchange capacity (CEC) and soil pH.

Soil pH is a critical driver of NUE. Fertiliser efficiency falls with a reduction in pH. Phosphorus is most at risk, easily becoming ‘locked up’ by the presence of Iron and Aluminium in more acidic soils. Even at a pH of 6.0 its availability is reduced by 48%, with Nitrogen experiencing losses of at least 11%.

Lower Phosphorus availability contributes to poor rooting and shooting, resulting in a detrimental impact on crop growth. When coupled with the lower Nitrogen efficiency, it could equate to at least a tonne of dry matter lost, therefore reducing the profitability of all crops.

The resulting financial consequences of sub optimal pH (below 6.3) are clear. At a price of £550 for compound fertiliser, a pH of 6 could see wastage of 15% - the equivalent of £82.50 per tonne! At a pH of 5.5 this increases to 25%, giving an equivalent loss of £137.50 per tonne of fertiliser.

Using soil analysis, and particularly one that measures Calcium levels, allows you to ensure optimum soil structure and enhanced biological function, which in turn aids the exchange and availability of nutrients within the soil, increasing both the yield and the profitability as a direct consequence of improving NUE.

And as one of the best sources of Calcium, a high quality and targeted application of granulated lime will allow you to correct and optimise pH, simultaneously supplying the soil with essential Calcium for all your structural soil and plant benefits.

The lime landscape has changed, and for the better. Spreading every five to seven years, deploying a low-quality bulk lime, is no longer the wisest investment for your soil. Rather, a little and often approach, perhaps with as little as 80kg per acre (depending on your soil and starting pH), is the absolute best way to ensure your soil remains consistently at its optimal level and makes every nutrient available to the plant from day one.

In an increasingly challenging financial climate, no farmer can allow either their pH or their calcium to fall below necessary levels, leading to significant fertiliser wastage and radically reduced yields. Simply by applying lime first, before fertiliser, you can ensure your pH is maintained and optimised for growth, making nutrients more available, utilised more efficiently, driving more yields and finally farming for profit.

If you’ve received soil results from the SNHS programme and aren’t sure what to do next K Lime can help. K Lime offers a free soil health hub, a dedicated portal for soil testing. Simply input your results for nutrient guidance, lime recommendations and access to a unique soil health dashboard specific to your farm for result tracking. If you haven’t had your soil tested order your soil packs through the portal and we will support you through the process and provide advice and guidance on what you need to do specific to your farm.