The Soil in my Salad
Soil, or more correctly sediment, is everywhere! It is the upper layer of earth in which plants grow, usually a black or dark or reddish brown material typically consisting of a mixture of organic remains, clay, and rock particles - an intricate matrix of compounds and elements. Soil is a major component of the Earth’s ecosystem. A micro investigation of soil can reveal pollutants, nutrients, permeability curves and its ability to retain moisture. Soil is a natural body that performs four important functions: it is a medium for plant growth; it is a means of water storage, supply and purification; it is a modifier of the atmosphere; and it is a habitat for organisms that take part in decomposition and creation of a habitat for other organisms. Soil, the ‘skin of the earth’ is the interface between the lithosphere, hydrosphere, atmosphere and biosphere but it was a simple salad that forced me to look at the broader view of soil analysis. It all happened over a lunch with my teenage daughters, enjoying a colourful and fresh salad: green lettuce, red tomatoes, black olives, yellow cucumber, orange carrot .… everything brought from an organic farmer near our home. My eldest daughter was explaining to me one of her school projects: to choose one of the biggest steps in human evolution and describe its importance. I was terrified when she explained her first choice: an app for instant messaging with the cell phone! Keep calm, I thought, while looking at the center of the table and feeling a little out of my depth! The remainder of the salad was there and suddenly I had a Eureka moment: “What do you think about agriculture”? I said. Take this salad – it is the result of a lot of intensive work, many people were involved in making these vegetables grow. Aaaahhhh no! My daughters explained to me that they had learnt at school that our ancestors moved from growing crops to creating cities and that was a sign of a developed society, an industrial revolution because growing vegetables was not so difficult compared to creating and manufacturing wealth. Try it, I answered and you will soon learn it is not so easy! You start with a pot, fill it with something and try to grow a tomato plant. Firstly you’ll have to learn about compaction (if the soil substrate is so dense roots will not grow; if too light, water will flow to the bottom and will not be available to the plants), fertilising, watering …. So you can quickly see - soil is important. Indeed, our ancestors learnt how to grow vegetables and how to optimize their crops, but it is only after years of studying soil that we have reached the point where we are now. We have moved from a point when research was needed to increase the yield for subsistence to the current point that forces us to dedicated soil treatments in order to not dry out the soil after continuous crop rotation.
Do you recognise the explanation given by that sommelier about the price of a wine when you asked (I wanted to hide below the table!) why does it costs so much? Yes! He talked about the care that was taken with the vineyards, about the type of fertilisation, the right amount of sun and the precise level of irrigation and, importantly, about the nature of the soil in that region. Soil again! In that moment of the discussion I felt I couldn’t stop, I was on a roll! Soil analysis is not just vital for agriculture, soil to grow my salad, soil research is important for so many other human activities. Think about the foundations of our houses and our roads, if we don’t do our research and look not just at the type of soil but also the topography of a site, our homes may collapse. Also let’s not forget about understanding soil in the face of natural disasters. Imagine a landscape or country that has experienced flood; no roads and
so no means of getting there except by air. Airplanes from everywhere arriving with first aid, supplies and food but where are they going to land? All too quickly a mechanical and scientific investigation to determine the penetration resistance of the ground where the terrain can support tons of weight, without collapsing, in order to safely site a runway. Can you imagine a plane landing in the sand on the beach, or the mud? So, knowledge of soil, and its properties is vital. When it comes to housing and site development it is not just a question of finding a nice place to build houses; where we’ll create some parks where children will play and drink fresh water from the wells that sit there. Great! But what was there before? It doesn’t matter, it is a nice place, close to rail links, schools and roads, say the developers. However, if we study the soil, we may discover that many years ago, a foundry was there. Tons of salt residues were left and with time these
residues went into the soil. Rain water helped these residues to vanish from the surface and conveyed them to the groundwater. We can build there, it is a nice place, but we will not be able to play in the park or drink water from the wells. We could maybe remediate the site and only then will it be safe to live there. Think of some areas of northern France where the legacy of the First World War is still felt today, 100 years later. Sustained and intense fighting has left a legacy of environmental contamination. Following the 1918 armistice, northern France, faced a huge clean-up and restoration effort which involved filling in trenches, removing barbed wire and the rebuilding and repair of 293,000 dwellings and farms that were fully or partially destroyed. The area of destruction covered 33,000 km2 including some of France’s most prized agricultural and industrial land. This area of devastation was divided up into different
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