Quite rightly there is a lot of talk about finite natural resources, the raw materials that we get from the earth. They are finite because they occur naturally and thus cannot be replicated by man. Instead we have become very proficient in using and modifying natural resources in ways from which we can derive some benefit. When we talk of natural resources we are usually talking about air, coal, minerals, oil, natural gas, sunlight, water, plants. A word that you will rarely hear mentioned in a list or discussion of non renewable natural resources is soil, specifically topsoil.
The first subject any Horticulture student tackles is soil; its properties, formation, scientific make up, texture, density. It is telling that an in-depth study of soil is the starting point for anyone setting out on the Horticultural path. Even before plant science, plant identification or plant use. The role of soil and the importance of it being understood is prioritised in the formal learning sphere. And for good reason.
Topsoil is the upper, outermost layer of soil, usually the top 50 – 200mm. It has the highest concentration of organic matter and micro organisms and is where most of the Earth’s biological soil activity occurs. Plants generally concentrate their roots in and obtain most of their vital nutrients from this layer. The actual depth of the topsoil layer can be measured as the depth from the surface to the first densely packed soil layer known as subsoil. Topsoil is formed from parent rock over thousands of years. The dimension and chemical make up of the parent material establishes the characteristics of the soil ; for example pH level and whether it is silt, clay or sandy.It is a slow precious process and one which cannot be replicated. Much like oil; when it’s gone , it’s gone.
Its importance is self evident so why are we so complacent about it? In February 1937 Franklin D. Roosevelt wrote in a Letter to all State Governors on a Uniform Soil Conservation Law “The nation that destroys its soil destroys itself”
Conventional agriculture encourages the depletion of topsoil by ploughing and replanting each year. One inch of topsoil can take between 500 and 1000 years to form and when you consider that it is estimated that the U.S. alone loses almost 3 tons of topsoil per acre per year we get a sense of the potential ecological catastrophe we are facing. According to research carried out by the Food and Agriculture Organisation (F.A.O.) and published in Scientific American in 2014, on current trends the world has about 60 years of topsoil left.
Intensive agriculture is the biggest culprit but everywhere we look we see examples of profligacy and complacency. Construction sites are proven offenders; to be fair the attempt is usually made but sufficient care is rarely taken to ensure that the topsoil is “warehoused” and reinstated satisfactorily.
So what can be done? In any discussion of soil conservation we inevitably come up against the conundrum of how to feed a planet of seven billion people using non intensive techniques.
No-till is a way of growing crops or pasture from year to year without disturbing the soil through tillage. The multiple benefits of no-till farming are well known; increase in the amount of water that infiltrates the soil, increase in organic matter retention and recycling of nutrients in the soil, reduction or elimination of soil erosion,increase in the amount and variety of disease suppression organisms in and on the soil, improvement in soil biological fertility making soils more resilient, more efficient farm operations. From the farmer’s viewpoint studies have found that no-till farming can be more profitable if performed correctly; less tillage reduces labour, fuel, and machinery costs. No-till can increase yield because of higher water infiltration and storage capacity and less erosion. Sounds like a no brainer but we need to shake off our cultural attachment to tillage and give it a chance.
Soil is an endangered species, no-till’s time is now.