Lime is a significantly under utilised resource on farm. A recent report by the Professional Agriculture Analysis Group, showed over half of Northern Ireland soils analysed in 2014/2015 below a pH of 6.0. That is an alarming statistic. Especially considering as pH drops, availability of Nitrogen, Phosphorus and Potassium is impacted. As pH levels drop, up to half of every tonne of fertiliser can be wasted, locked into the soil and unavailable to plant roots for uptake. That is huge money tied up in soil reserves at a time when farmers can ill afford to waste a penny.
After an extended period cutting costs and maximizing on-farm efficiency, it seems pertinent to remember many of thesuccesses and failures of farming start and end with the soil. Each farm has its own challenges when it comes to soil, whether drainage, compaction, fertility or pH. Lime is one of the easiest and most inexpensive methods of improving the soil, yet often falls by the wayside, despite the fact soil pH is likely the most fundamental factor in determining the success or failure of any given crop.
While adding lime to the soil seems simple enough, many farmers do not pay a great deal of attention to the differences that exist in the various sources of lime that are available, generally using price per tonne as the deciding factor in where to source lime. However, there is more to consider than just cost per tonne. The rate of lime applied should change with the quality of lime selected. Even when choosing a lime source with a high neutralising value (NV) of greater than 50%, farmers should still consider the grading of their lime. You can get away with less lime per acre if the lime has fewer coarse particles, and conversely you should increase the rate of lime applied if the lime consists of more coarse particles.
There seems to be a prevailing thought in the countryside that coarse lime lasts longer in the soil. But it doesn’t make sense for lime to sit in the soil. Lime raises the pH in a chemical reaction whereby Calcium Carbonate reacts with the Hydrogen ions that make the soil acidic. If you add Calcium Carbonate to the soil and it does not react, it means there aren’t enough Hydrogen ions in the soil to cause a reaction, meaning the lime sitting in the soil is doing absolutely nothing. Over a period of years the soil acidifies again and particles remaining in the soil may react, but not until field pH drops back to the level when lime was first applied and the field again needs lime as it is no longer productive.
In order to maximise their spend, farmers should look for lime with a Neutralising Value (NV) greater than 50% CaO (89.4%CaCO3) and ask for a certificate declaring the particle makeup of the lime they buy. In general terms, a coarse lime will have 97% of material passing through a 3.15mm screen, a fine lime will have 97% passing through a 2mm screen. Granulated lime goes a lot further and can have up to 99.7% passing through a .125mm screen an is the ideal solution to maximizing the value of lime.
Lime does not get enough attention as a critical component of crop production and soil fertility. Yet without lime, soil pH and fertiliser efficiency drop off and yield and quality suffer as a result.
Sourcing the finest lime with a high NV such as granulated lime is the best option for a fast pH correction and making the most of your soil’s productivity.