Soil pH and Fertiliser Efficiency

The ongoing impact of the global trade market on fertiliser pricing and the drive to more carbon-efficient farming makes it essential for farmers to monitor and manage their nutrient use efficiency (NUE) and nutrient availability to maintain the profitability of farming operations.

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. The table below illustrates how 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 £500 for compound fertiliser, a pH of 6 could see wastage of 15% - the equivalent of £75 per tonne! At a pH of 5.5 this increases to 25%, giving an equivalent loss of £125 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, you can contact us to share your soil test results with our agronomy experts and we’ll be able to let you know if any lime is required, and how much you would need over the next 5 years to save on fertiliser. You can also benefit from the excellent nutrient health training provided by CAFRE, which can be found HERE.

For more information, or to discuss how you can apply a high-quality Granulated Lime every year for less than the historical “2 tonnes per acre of conventional limestone every 5 years” (providing your pH is above 5.6), contact us HERE or call Jonny McKinney on 07841 341305.