A three-step approach to tackling the most common soil fertility issues
New research from Teagasc shows that while there is finally some improvement in in terms of pH, Phosphorus (P) and Potassium (K) levels, our soils are still far from optimum fertility and the requirement for significant investment in fertilisers continues.
While they don't come cheap, fertiliser programmes to address soil fertility issues are not complicated.
There are three layers to a fertiliser programme: the soil pH level; the Phosphorus (P) and Potassium (K) status, and the appropriate nitrogen (N) rate to be applied.
Unless the soil pH level is at a workable level, growth response to any nutrient applied, whether that is N, P or K will always be disappointing. If the soil P levels or soil K levels are deficient, response to applied N will also be muted.
There is no point applying more nitrogen on a soil that is deficient in lime. The crop, be it grass, cereal, potato or vegetable, just won't respond.
A soil sample costing €30 will determine the soil pH level. One tonne of lime costs slightly more than one 50kg bag of compound fertiliser. If the soil is lime deficient, that bag of compound won't work the way it should. If a soil is seriously lime deficient, it is better to spend money on rectifying the soil pH first and spend little or nothing on any other fertiliser.
The application of lime often has an added benefit of releasing previously applied nutrients that were unavailable as they couldn't be 'activated' because of the soil pH issues. So in the absence of applying other nutrients, lime application can result in the soil supplying other nutrients to the crop from reserves, so there is a 'double whammy' benefit from applying lime.
Once the soil pH has been addressed, the next step is to build up the P and K levels.