Soil fertility a growing concern

Analysis of 2012 data for soil samples submitted to Teagasc continues to show worrying declines in soil P levels while soil K levels seem to be stabilising.

Analysis of 2012 data for soil samples submitted to Teagasc continues to show worrying declines in soil P levels while soil K levels seem to be stabilising.

These results are not based on a random national sample but the decline in soil P and K sample results since 2008 highlights a potentially serious emerging problem. These declines in soil nutrient levels are likely to lead to reductions in crop and grass yields. Research has shown that the grass yields on fields low in phosphate (P) can be 1.5 t/ha lower than optimum P levels.

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Highlights

• The percentage of soils with Index 1 for P (Index 1 = very low nutrient status) has increased from 14% in 2007 to 30% in 2012 and continues to increase.

• The percentage of soils with Index 1 and 2 (very low and low) has increased from 40% in 2007 to 59% in 2012

• It is very positive news that the percentage of soils with Index 4 for P has dropped from 32% to 18%. Index 4 = excess nutrient status posing a potential risk for loss to the environment.

• Soil K levels, which were dropping in line with P seem to have stabilised in 2012. However, about 53% of soils still remain at K index 1 and 2 (very low and low).

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Teagasc will be highlighting the actions needed to improve soil fertility on farms during the first week in February with a series of local seminars around the country, and a series of press articles detailing the information needed for preparing a nutrient management plan in 2013.

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The planning process will focus on five steps:

• Take a soil sample (or use samples already taken).

• Apply lime to achieve desired pH.

• Target index 3 for P and K.

• Apply slurry to fields with a P & K requirement and apply in spring to maximise N uptake.

• Balance with chemical fertilizer using most appropriate compounds

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Having an up-to-date nutrient management plan for your farm is the best way to identify potential soil fertility problems, make the best use of the available nutrient resources on your farm, to calculate you fertilizer requirements for the year, to increase farm productivity and to save time and money in the long run. To maximise these benefits, it is important that a plan is prepared early and on a field-by-field basis and followed throughout the year.