Letter to the Editor: Maintaining soil fertility is a necessity for survival

Agricultural activities are blamed as the major contributors to the damage being caused to our ecosystems. 

I have been trying, repeatedly and totally unsuccessfully, to draw attention to the effects that monoculture and long-term cultivation practises are having on the global degradation of soil organic matter (SOM) reserves that is leading to soil degradation, the loss of soil fertility, and to soil erosion.

There are three to four times more SOM below the earth surface than all the organic material, including plant, animal and human life above it, and it is important to maintain that level in order to sustain long term soil fertility. 

STRIVE 58 of EPA Report Series 2007-2013 shows the extent to which annual cultivation for wheat cropping has, even in our temperate climate, led in 30 years to more than 50% SOM degradation, and importantly it has shown that the degradation is experienced at all depths to which organic matter exists in the soil profile.

Most of the highly fertile soils of the world are under long-term cultivation and it is estimated that 50 to 100 crops from now the SOM in these soils will be so exhausted that soil degradation will be inevitable. In my student days nearly three generations ago it was emphasised that there are more microorganisms in a thimbleful of fertile soil than there are people in China.

 The same will apply today.

Soil organisms gain their energy from transformations of biomass, and in the transformation processes the sources are converted to what are called humic substances (HSs). 

These include the reactive organic molecules that form and stabilise the soil aggregate structures and have a degree of resistance to degradation. In the absence of a supply of biomass the organisms will slowly degrade the HSs.

The great organic chemist Maurice Stacey wrote two generations ago that in order to maintain soil fertility all that comes from the soil that is not used for food and fibre should be returned to the soil. 

That of course should include crop residues and all sludges. We have the technologies to ensure that manures and sludges are free from pathogens and heavy metals, and can be prevented from entering into waterways and causing pollution and eutrophication.

There is an emerging technology that causes the HSs to form giant molecular structures with a high degree of resistance to degradation and with an ability to give rise to enhanced carbon sequestration in soil.

Thus we already have, or there soon will emerge, the technologies to enable us to maintain SOM levels and soil fertility, and microbial diversity below the soil surface. 

Such will be essential if we are to provide food for the 9bn to 10bn anticipated world population in the next 30 years. Maintenance of biodiversity in the vegetation and life above the soil surface is another challenge.

Brazilian scientists are aware of this, and point out that the felling of Amazonian woodlands, and the mining of their soils for the production of soya beans by factory farming methods are attributable to foreign investors.

They realise that the Amazonian rainforests are vital to world environmental interests, but the rest of the world is not contributing to the maintenance of these vital resources.

I leave it to others better qualified than I am to indicate how plant and biota diversity can be maintained in soils with optimum levels of SOM and soil health.

We can say that there should not be cause for gloom, but we must recognise that all must be aware of the challenges we face, and of the fact in order to achieve the food and environment standards we require we must be willing to pay more for what is essential. 

The farming community cannot bear all the burden.

Michael HB Hayes

CS Department
University of Limerick

This reader's opinion was originally published in the letters page of the Irish Examiner print edition on 9 May 2019.

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