Soil fertility is essential for optimum agriculture yields

Soil fertility is a key component of sustainable agricultural production and is critical for low-cost, grass-based livestock systems.

On many drystock farms there is considerable potential to increase grass production.

Maintaining or improving soil fertility is the first step in increasing annual grass production.

However, the national soil fertility trends paint a worrying picture.

Over the last 10 years Teagasc has analysed about 38,500 soil samples annually. These samples provide an insight to national soil fertility trends (soil pH, phosphorus (P) and potassium (K)) for each farming sector.

Figures for for 2015 didn’t show any signs of things getting better, with sub-optimal fertility status in about 90% of samples tested (soil pH under 6.3, P & K index 1 or 2), a situation that has persisted for the last number of years.

Mark Plunkett, Teagasc soil and plant nutrition specialist said: “This is a serious limitation to the production potential of our soils and limits our ability to maximise our most competitive advantage in the market place, which is our ability to grow high yields of quality grass.”

Currently 64% of grassland soils and 45% of tillage soils have below the optimum soil pH (i.e. pH 6.3 for efficient grassland production and pH 6.5 for tillage crops).

According to David Wall, leader of the Teagasc Soil Fertility Research Programme at Johnstown Castle: “Nationally, we are applying less than half the quantity of lime that was applied in the 1970s and early 1980s.

“Applying lime to correct soil pH is the cornerstone for maintaining the productivity of our soils, something that has been largely overlooked in recent decades. Identifying fields that require lime for pH adjustment should be the first step towards correcting soil fertility.”

A major concern emerging is the continuous decline in soil P levels over the last decade with the majority of both grassland (61%) and tillage (59%) farms having sub-optimal P fertility (i.e. P index 1 or 2).

About 50% of grassland and tillage soils have low K fertility levels (54% and 47%).

However, soil K trends show a stabilisation or gradual improvement over the last five years.