Addressing soil health has never been more crucial. On a global scale, there is an alarming trend in soil fertility levels.

According to the United Nations, 40% of soils are now classified as moderately or severely degraded, with a staggering 24bn tonnes of topsoil lost globally each year to erosion—equivalent to more than three tonnes per person.

According to the European Commission, over 60% of soils in Europe are classified as unhealthy and the loss of essential services provided by healthy soils, including food production, water regulation, and carbon and nutrient cycling, among others, is costing the EU over €50bn each year.

In Ireland, while many soils remain relatively healthy, Teagasc has reported declines in national soil fertility levels in recent years, with issues around compaction and nutrient excesses in particular.

A national survey conducted by Teagasc in 2021 also reported that only approximately 16% of farms are reaching optimum levels for soil phosphorus (P), potassium (K) and pH.

Applying the right amount of fertiliser in the right place is one of the ways in which farmers can address these deficits in soil health and fertility, while also saving on costs and minimising environmental damage.

Soil sampling is key to this process, as it enables farmers to better understand how soil nutrient levels vary across the farm, allowing for targeted spreading.

Results for Footprint Farms

Soil sampling is complete on six out of eight of the Footprint Farms. The remaining two farms are waiting for conditions to improve and aim to soil test a little later in the year.

To date, 232 samples were taken across the mix of dairy, beef, tillage, sheep and equine enterprises.

All samples were tested for soil pH, phosphorus (K), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), zinc (Zn) and boron (B). In line with previous years, average index results were largely positive.

Of the 232 samples, 34% of soils were both at index 3 or 4 for P and K and had a pH of 6.3 or above. This is well above the national average for soils at optimum soil fertility.

In terms of P, index 3 had the highest proportion of soil samples (36%).

Soil index 3 is considered optimal and should be maintained, while samples classified as Index 4 (26%) are considered high and cannot receive any fertiliser P, while index 1 (11%) and index 2 (27%) are considered low and require additional applications to bring these indices up to optimal.

In terms of pH, the optimum pH for grassland is 6.3 while for arable land it is 6.5

In relation to K, 51% of samples were classified as either index 1 or index 2, which could impact crop yields.

These results are in line with previous results from soil testing on Footprint Farms in 2021 and 2023, which showed that maintaining index 3 for K was an ongoing challenge. High fertiliser prices in recent years have not helped to build soil index levels either.

In grass systems, silage ground can be particularly low in K: focusing on boosting K on silage ground can help raise average index values. On tillage land, straw incorporation can help to boost K, while also boosting soil health by returning organic matter to the soil.

In terms of pH, the optimum pH for grassland is 6.3 while for arable land it is 6.5.

On Footprint Farms, 27% of samples fell in the 6 to 6.4 range, while 38% of samples fell in the 6.5 to 6.9 range. Only 3% of samples had a pH of less than 6%.

This is a credit to the farmers, who took action on receiving their previous soil test results. One of the first things that they did was to apply lime to improve soil pH where necessary. This effort has paid off, and will continue to do so, as the optimum pH levels will enhance the availability of P and K in the soil.

Management decisions

Footprint Farmers had the opportunity to sit down with the Irish Farmers Journal technical team to discuss their individual soil results and how they should best act on them.

In the next instalment from the Footprint Farms, we’ll be discussing the issues raised at the meeting and the resultant management decisions that Footprint Farmers will be making this year.

Learn more: trace element results

The proportions of trace elements in soils tend to be dependent on geographical location and the parent material (bedrock) from which the soils were originally formed.

However, low minerals in soil analysis do not always translate to mineral deficiencies in crops.

Factors such as soil pH, soil drainage and soil organic matter can all affect the availability of trace elements to plants.

Leaf analysis can be a helpful next step to better understand how mineral levels in soils may be affecting the growth or nutritional quality of crops.