The fourth video in the Fertilizer Association of Ireland’s video series on the Efficient Use of Fertilisers focuses on understanding and mapping soil test results for your farm.
New soil test results will reveal current soil fertility levels and indicate changes in soil pH and nutrient supply since the last set of results. This information will provide the basis for planning lime, organic manure, and fertiliser applications for the next 3 to 5 years.
Dr David Wall discusses lime recommendations and soil P and K results with dairy, beef, and tillage farmer Michael Doran, 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 & K in organic manures or chemical fertilisers are used efficiently.
The soil analysis results are displayed for each field or paddock in colour-coded maps. This makes it easier to understand and help to identify paddocks on the farm with low or high soil fertility.
Michael Doran said: At a glance, soil fertility maps make it very easy to see where I need to target my lime and which paddocks are at optimum soil pH.”
David Wall said: “In grasslands, aim for a soil pH of ≥6.3 on mineral soils and while on peats soil pH 5.5 to 5.8 is adequate. Where clover establishment is planned to 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.
Furthermore, up-to-date soil analysis will also show P & K levels that are available for grass and crop uptake. Where fields have had regular soil analysis (every 3-5 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 & K as either organic manure or chemical fertilisers. It also indicates how quickly your soil fertility levels will reach the target P & 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.
David and Michael discuss soil P and K results and the colour coded maps of the farm prepared by Michael’s advisor.
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. David said: “where bale silage is cut it is important to account for K removed in bales.”
Farm fertiliser plan
Lastly, 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 you select the correct fertiliser products and optimise application rates and timings to maximise the return on investment and ensure the sustainability of all nutrient applications.