Video: Understanding and mapping soil analysis results for your farm

The interpretation of soil analysis results – using these as a basis for developing a fertiliser plan for a farm – is the subject of the latest video from the Fertiliser Association of Ireland.

The fourth episode in the association’s Efficient Use of Fertilisers series, this builds on the information provided in the previous videos – which looked at soil sampling, fertiliser planning and the soil analysis process.

New soil test results will reveal current soil fertility levels and indicate changes in soil pH and nutrient supply since the last set of soil results were taken, the association says.

This information is very important as it will provide the basis for planning lime, organic manure and fertiliser applications for the next three to five years.

In the video, Dr. David Wall discusses lime recommendations and soil P and K results with dairy, beef and tillage farmer Michael Doran, from south Co. Wexford.

Michael’s recent soil analysis results show the status of soil pH (levels of soil acidity) and nutrients phosphorus (P) and potassium (K) on a field-by-field basis.

The soil test results provide lime requirement advice based on soil SMP pH test (buffer pH) with lime application recommendations in tonnes/ha.

Correcting soil pH is the first step to ensuring applied N, P and K and in organic manures or chemical fertilisers are used efficiently, the association says.

The soil analysis results are displayed for each field or paddock in colour coded maps which are easier to understand and helps to identify paddocks on the farm with low or high soil fertility.

Dr. Wall advised: “In grasslands aim for a soil pH of at and over 6.3 on mineral soils and while on peats soil pH 5.5 to 5.8 is adequate. Where clover establishment is planned maintain higher soil pH levels of 6.5 to 7.0 as clover likes higher soil pH.”

Correcting soil pH with regular lime applications and having an adequate supply of P will be important for maintaining sufficient clover in grass swards capable of supplying a proportion of nitrogen needs through fixation over the summer period.

Up-to-date soil analysis will also show the levels of P and K that are available for grass and crop uptake.

Where fields have had regular soil analysis (every three to five yrs), these results also reveal how soil fertility (P & K) levels have changed over time.

This is valuable information showing how responsive your soils are to the applications of Lime, and P and K as either organic manure or chemical fertilisers.

It also indicates how quickly your soil fertility levels will reach the target P and K index 3 level under the current management.

Mapping the soil P and K levels in each field will paint a picture of whole farm soil nutrient fertility status and very useful when deciding which fields or paddocks cattle slurry should be applied on the farm.

Dr. Wall highlights the importance of managing P and K on silage fields and the importance of balancing P and K inputs with offtakes where bale silage has removed, noting:

Where bale silage is cut it is important to account for K removed in bales.

The next step is to prepare a farm fertiliser plan with your advisor for each field for the year this will help target cattle slurry to the right parts of the farm.

It will also ensure that the correct fertiliser products are selected and that the fertiliser application rates and timings are optimised during the year to maximise the return on investment and ensure the sustainability of all nutrient applications, the association says.