Sunday Feature: Soil and Water: The Origins of Life


This is heavy land and not so easy to manage, but when the drains are working and the grass is set, it's rich and productive.

Sunday Feature: Soil and Water: The Origins of Life

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  • 3 years ago

This is heavy land and not so easy to manage, but when the drains are working and the grass is set, it's rich and productive.

When we drive through the countryside we usually look over the ditches and comment to our passengers about the quality of the land. Ah that's good land there, you see, the tillage fields, the height of those ash and oaks. Sometimes old estate walls are an indicator, for the lords of the vale liked to situate themselves in the richest spots. Then we cross over into hill-country and the dark masses of Sitka spruce plantations indicate a change. Climbing up a valley wall to the summit, we see the brown bogs and bare treeless heath-lands stretch out before us. In these dusky lonesome highlands, occasional grass fields shine out like emeralds, hard-won from the rushes and the rocks. This is heavy land and not so easy to manage, but when the drains are working and the grass is set, rich and productive.

Near the western seaboard is another type of land, bare rock interspersed with light fields, where delicate-looking plants flower with every imaginable shape and colour, defying the strong winds that constantly buffet the marvellous cattle-sheltering stone walls. Here the fields are known to have been manufactured through years of toil. Countless generations engaged in that endless gathering of dung and seaweed, spreading it out on bare rock, year after year, the same routine, and for what? To make something very precious, which those who already have it often take for granted: soil. Perhaps it is only those farmers in the western enclaves who truly understand how precious a healthy soil is.

The most fundamental element of every farm is its soil. Without it we cannot grow grass or crops. Awareness of its importance to agriculture is growing in Ireland. Farmers are constantly adopting more scientific approaches, which inculcate a necessary recognition of the fundamental need for good soil structure. Progressive farmers measure their soil's structure and nutrient content, trying to keep the balance right. However, when it comes to erosion and extraction of DMD through constant harvesting, especially on tillage land, there is still some way to go.

In the 1930s US farmers had a harsh lesson in the need to take care of their soil. During the so-called dust bowl, around 100 million acres of farmland across five states was lost forever because of over-intensive farming methods on delicate prairie land. Deep ploughing loosened the grasses that bound the soil together. Drought brought hot winds that burned the land into a dust which rose up in massive clouds, leaving behind only rock and the scorched, barren earth. It is little wonder that zero-till is a US invention. Farmers there understand the fundamental importance of maintaining healthy soil structure.

In Ireland we do not have many problems with drought but erosion from heavy rains on bare fields is a significant concern. That is why recent regulations have tried to discourage winter ploughing. The old method of leaving ploughed fields exposed over winter was believed to benefit soil, because frosts would soften the sod, making the work of preparing a seed bed in Spring much easier. Soil erosion was not a well-understood phenomenon in those days. Before one-pass sowing systems, farmers would traverse the fields many times with grubbers and harrows, trying to achieve a soft, even seed bed. This was later found to be very damaging both in terms of soil compaction and nutrient loss, through those dust clouds that followed the machines from one headland to the other. It is a rare sight nowadays as we have learned our own lessons from the past.

Indeed soil researchers now have a very nuanced understanding of the subtleties of soil types, their structures, traits and limitations. Teagasc, with the EPA and Cranfield University have produced a terrific online tool for helping farmers to educate themselves on their own soil. Launched in 2014, the Irish Soil Information System includes a detailed countrywide map in which each area is divided according to its soil type. Soil types are categorised into their respective hierarchical groupings and taxonomy. For example, river alluvium soils have silty textures with alluvium subtrate, but can be fine loamy over non-calcareous gravels, as they are in Finisk, or sandy as they are in Aherlow. Having a detailed understanding of their own soil allows farmers to make better decisions, knowing what mineral content it is likely to have in abundance and which it might lack. This resource contains, in addition, very informative historical documents from a mid-twentieth century countrywide survey, available for download on a county-by-county basis.

Hill farmers with mountain grazing rights have a particular responsibility not to over-stock their holdings. Over-grazing can lead to erosion of upland areas, which might never regenerate. This problem has also been identified with popular upland paths where hikers wear down the peat, which in turn is washed away by rains. For example, the MacGillycuddy Reeks receive between 80,000 and 100,000 visitors every year and erosion there has frustrated local action groups like Friends of the Reeks, who receive little public money and need to fundraise to make repairs to the paths. Patricia Deane, South Kerry Development Partnership rural recreation officer said of the Reeks, “This area is a significant resource in terms of outdoor activity in Kerry and one that needs to be carefully managed to ensure its long-term sustainability as working farm land, as well as a magnificent walking route and a sensitive environmental area.”

While most farmers are doing their best to minimise soil disturbance, a certain amount of erosion is inevitable. Certain crops contribute more than others to problems caused by compaction and erosion. One of these is maize, which is particularly associated with a phenomenon known as 'muddy flooding', caused by runoff carrying soil from bare or relatively bare fields. Muddy flooding can happen in Summer and is not necessarily associated with heavy rains. It is worst with crops such as maize, because the presence of ephemeral gullies or rills with associated access roads offers surface water a chance to run off fields. This water carries fine soil particles which, when they enter water courses, become a major problem to fish and river life by silting up breeding grounds and increasing the nutrient content of the water. It also carries fertilizer and pesticide traces which can do enormous damage to insect life in streams and rivers, with knock-on effects for those who rely on them for food. As yet, very little has been done in Ireland to recognise the effect of muddy flooding, much less alleviate it.

Soil erosion does not just threaten our ability to farm. Most eroded soil ends up in rivers and lakes where it can cause havoc through eutrophication of lakes and rivers. This can cause algal blooms which block the light reaching the bed of the waterway, preventing other plants from growing and disturbing the natural balance of life. Silting affects species such as lamprey, salmon, trout and pearl mussel. Salmon and pearl mussels are particularly vulnerable to the presence of silt as they need clean stony gravel beds in which to spawn and the silt tends to cover these over, which kills the young offspring.

Although tillage land tends to lose a lot of soil to erosion, despite improvements in practises, in Ireland farming is not the biggest culprit with regard to soil erosion. Both Coillte and Bord na Mona (as well as myriad unlicensed peat extractors) have been accused of systemic failures over the way in which they deal with soil erosion. For example, Coillte are supposed to use a series of safety measures to prevent runoff from clearfells entering watercourses, but in reality they often cannot prevent pollution from occurring.

A study from 2013 tested the effect of clearfelling activities on lake water near Glannamong forest north of Clew Bay in Co Mayo. The study found alarming levels of nutrients and chemicals, including “phosphorus (P), nitrogen (N), total dissolved organic carbon (TDOC), aluminium (Al) and iron (Fe), with the highest concentrations of each parameter recorded from lakes with catchment clearfelling.” The study also found decreased oxygen levels in these areas and drew the following conclusions: “Inorganic fertilisers applied at the start of the forest cycle, the decay of the underlying peat soil and accumulated surface tree litter, and leachate from felled trees are the likely sources of the elevated concentrations of plant nutrients, [total dissolved organic carbon (TDOC)], heavy metals and major ions, with excessive peat soil disturbance during clearfelling likely exacerbating the runoff into lakes.” This has much to do with the vagaries of Irish weather and suggests that clearfelling is an unsuitable method for timber extraction here, because of the vast amount of runoff generated by the inevitable rainfall that follows.

In Ireland we are very lucky to have such a rich diversity of soil types and in such abundance. With good management and responsible husbandry it will continue to feed us for generations to come. But we cannot take it for granted. In the last hundred years we have industrialised our boglands, our forests and our farms. With bigger machines we can do a lot more damage and very quickly. It is important for us all to be aware of the destructive potential of what we do with regard to our soil and our waters. These are the fundamentals of all life. We must treat them with care.

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