Why is it important to protect our soil?
By Anne Marie Butler
Soil is essential for life. Soil is an ecosystem in which millions of living creatures live and interact. A mere tablespoon of good-quality soil can hold more creatures (bacteria, protozoa, fungi, nematodes, micro-arthropods) than there are people on planet earth.
With the importance of soil for plant and animal growth, water quality, climate, human health and ecosystem sustainability, one wonders why our soils are so often forgotten?
With over 65% of Ireland’s land area devoted to agriculture and 90% of this agricultural land under grassland, nourishing and protecting our valuable soils is essential.
Good Soil pH Improves And Enhances Soil Fertility
Recent years have reported a worrying and continued deterioration in Irish soil pH levels. Lime is one of the most important nutrients any farmer can spread to rectify soil pH. Maintaining good soil pH directly improves and enhances soil fertility.
Of the major nutrients, phosphorous (P) is the one most affected by a low soil pH as at a pH below 5.5, P becomes unavailable for use by grass.
Some simple guidelines for improved soil fertility:
- Every farmer should soil test their land every three to five years to gain a full and true understanding of actual soil fertility levels. Soil testing a proportion of the farm each year will spread the cost. Standard testing includes soil pH, lime requirement, phosphorous (P) and potassium (K).
- With these results to hand, an accurate and responsive plan should be implemented to address any identified issues.
- Know the soil pH of your lands and rectify those fields or paddocks identified as suboptimal. This should take priority over the application of chemical fertilisers which will not work effectively in acidic soils. Aim to have the whole farm at pH 6.5.
- Manage slurry and soiled water to maximise the fertiliser value.
- Apply nutrients in the proper balance and avoid oversupply of individual nutrients.
- Nutrient advice is based on a simple soil index system. Fields or paddocks can be categorised on a soil index scale of 1-4 for each nutrient (Level 1 low nutrient with Level 4 high nutrient). Nutrient advice is based on a target of maintaining soils in Index 3. At Index 3, soils have a bank of available nutrients to deliver nutrients to the grass.
- It is important to recognise that it may take some soils several years to improve fertility.
As we examine the financial returns from systems and the total costs incurred across the year, it is imperative that farmers recognise the intrinsic role played by soil.
A healthy nutritious soil will bring quantifiable financial benefits to the farm in addition to the wider ecosystem returns. Teagasc¹ research has detailed a minimum increase in profitability of €173/ha for each additional tonne of grass utilised in a grazing system.
As grassland systems will continue to predominate, we must recognise that each 10% increase in the proportion of grass in the diet will reduce the cost of milk production by 2.5c/L.
As we seek to manage climate change while building environmentally and economically sustainable agricultural systems, perhaps we need to renew our focus and return to the soil.
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¹ Hanrahan et Al., 2018