Be Wise: Lime First

With the recent focus on the Soil Nutrient Health Scheme in Northern Ireland, many of us are becoming much more aware of the balance of nutrients already in our soil. The habits of a lifetime, however, are hard to break, and as an industry we remain heavily focused on the price and availability of nitrogen - often leading to a deeper analysis of our soil results being ignored in favour of rushing out to purchase and apply nitrogen before anything else.

As can be seen in the widely available chart below, an optimised pH of 6.5 vastly improves the availability of almost all key nutrients and reduces the presence of more damaging elements such as aluminium and iron. And with soil acidifying from the surface downwards, with cations such as calcium, magnesium and sodium moving through the soil profile, more attention should be placed on achieving and maintaining a higher pH to maximise the nutrient use efficiency of the soil.

This ongoing acidification is the inevitable result of frequent rainfall, slurry usage and the over-application of nitrogenous fertilisers.

Prioritising lime, therefore, is the only logical and essential first step in ensuring that your soils are sufficiently optimised for growth before any fertiliser is spread. Frequent application of lime helps to position and maintain soil pH in the “rhizosphere” - the zone around the vicinity of plant roots in which the chemistry and microbiology of the soil directly influences the growth, respiration, and nutrient exchange of the crop.

The initial development of roots within the soil is of primary importance as a plant must first grow down before it grows up. The three elements of calcium, boron and phosphorus are primarily responsibility for root growth and development, and of these three it is calcium which is often the most deficient in our soils. It is therefore critical that a high-quality calcium carbonate lime is applied, giving your crop the very best chance to succeed. The benefits of calcium also extend to an improved development of cell walls to protect against nature and disease, and longer and healthier roots, which ensure greater resilience through an unpredictable growing season.

Of the other nutrients, it is the macronutrient phosphorus that is most effected by sub-optimal pH, and again provides a strong argument for applying lime before you do anything else. For example, if your soil analysis was showing pH less than 6.2 and a low available phosphorus, it would, in most cases, be cheaper and smarter to improve availability of phosphorus by applying lime to address pH, rather than applying fertiliser to address P.

As you can see, the traditional approach of liming every five to seven years, with a cursory nod towards pH, is no longer the wisest attitude to soil health or to improving your nutrient use efficiency. Rather, a little and often approach, perhaps with as little as 80kg per acre (depending on your soil), is the best way to ensure the pH remains at optimal levels and that every nutrient is available to the plant from day one. Liming comes first, and must become an essential component and regular fixture in all of our discussions around annual nutrient planning.

Particularly in these difficult days, no farmer or grower can afford to let either their soil pH or their calcium fall below optimised levels, leading to fertiliser wastage and radically reduced yields. But by applying lime first, before any fertiliser, you can ensure that soil pH is maintained and optimised for growth, making nutrients more available, utilising them more efficiently, increasing crop yields and farming, once again, for profit.

If you have received your soil results from the SNHS programme, please don’t hesitate to contact us and we’ll be able to let you know if lime is required, and how much you need over the next 5 years to save on fertiliser. You can also benefit from the excellent training provided by CAFRE.

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 via our website or call Jonny McKinney on 07841 341305.