A healthy soil is critical for all terrestrial life. It is the source of all our food, regulates flooding and water storage: soil organisms regulate nutrients as well as recycle waste, and it's a major storage organ of carbon dioxide. But for all that we know very little about it.
The pressures on the world's soils to deliver more and more food is making them increasingly vulnerable to degradation. Soil is linked to our survival. Kelvin Bood, the regular scientist on Shared Planet, said, "There are about 50,000 different types of soil across the world. It's the organic material in the soil that holds it together. We know little about soil but we do know that a healthy soil contains around a third of all living organisms. It seems that the activities of humans that lead to the degradation of the soil led to the collapse of the Mayan civilisation, among others. Soil forms very slowly. Estimates vary, but a layer of soil 2 cm thick can take a thousand years to accumulate, but the rate of soil loss globally is 10 times the rate of accumulation. We might be able to replace the soil physically but we can't replicate it biologically - we can't replace the life in the soil that makes it what it is. Some people estimate that we will run out of soil in decades."
There are 25 species of earthworm in Britain, and 3,000 species world wide. By and large they all perform the same function and they are critical to the health of the planet's soils.
Professor Karl Ritz and Dr Tom Sizmur of Rothamsted are researching into soil. "In a handful of soil there are a hundred billion bacteria, hundreds of kilometres of fungal threads such as what grows on your bread, tens of thousands of other tiny organisms. The soil biota is the engine of the earth, driving the key processes such as carbon recycling and making nutrients available. An engine needs fuel and the fuel is organic matter derived from plants.
The largest animal in the soil is the earthworm. There are three groups of these.
1. Those that are predominantly surface-dwelling - they eat the litter and straw on the surface and they are very weak burrowers.
2. There are those that live in vertical persistent burrows down to several metres in depth. These produce worm casts. They are borers and pull the nutrients down.
3. The third group lives within the soil matrix and these mix up the organic material and move it around.
The vertical burrowing earthworms can move about 30 times their own body weight a day. If you scale that up that is several hundred tons of soil being moved per hectare per annum.
Tom Sizmur, studying soil at Reading University, counts worms as a general index of the health of the soil. "The hypothesis is the more carbon you add the more worms you get and the more work is down by the whole biology of the system. "
The scientists explore the soil to a depth of 20 centimetres. When you harvest a crop you are removing material from the field, that material came from the soil. Heavy cropping without paying back into the soil with organic material is a kind of mining.
Scientists look to see how natural systems keep soils functioning healthily. "They tend to be founded on great diversity, which is well-adapted to the local circumstance. If we used that information we could generate much greater sustainability in our systems."
The data globally is that soils are being impoverished. Because it takes so long to produce new soil scientists suggest we regard them as non-renewable resources. We are heading for a peak soil scenario. Then the amount of soil runs down.
Conserving our planet's soil is one of the most important of our conservation needs. In the UK we have leading soil scientists. Prof Wilfred Otten of Abertay University said, "We are working on developing techniques to enable us to look at soil structure. In the past we broke the soil up into pieces before studying it, which is like looking at the rubble after blowing up a building. We need to look at it intact. We use X-ray tomography which allows us to look inside soil. The soil has a lot of air space in it, and water. That area of soil with the air and water flowing through is what is making life possible."
"The size of the pores defines the structure of the soil. These create a network. (a road map or computer network). Soil must have good structure as well as good components. There are phenomenal numbers of organisms in soil but they are a very small percentage. Only one per cent of the solids of soil are occupied by life. What limits growth? is it the amount of organic material in the soil or the access organisms have to soil? Access to the soil is partly regulated by the structure. The structure of soils can be very different but still have functioning ecosystems which shows how well soil adapts to the way we use it.
"In part the adaptation is self-regulating. On a microscopic level, bacteria can play an important role - they emit compounds which act as a glue and cement the soil together."
"World wide we are losing soils for productivity rapidly through erosion - one short heavy rainfall can take away soil that will take twenty years to replace. How can we slow down this decline? A good way of doing that is to replace the organic matter in soil. Not using fertilisers to produce food but organic matter to produce soil."
Is anything being done to conserve soil? Yes: an intergovernmental technical panel of 27 experts has been set up to provide knowledge and technical advice on soils to governments at United Nations level. This panel will raise awareness of the global problem and help governments decide where to prioritise action on soil. There is very little legislation on soil or legal protection of soil.
http://www.fao.org/globalsoilpartnership/intergovernmental-technical-panel-on-soils/en/
Water companies spend billions of pounds a year cleaning up our water supplies. Sediment, nitrogen and phosphorus are all coming into our water from the soil and need to be taken out before water can be used to drinking or industry. We also need the soil to regulate the amount of carbon in soils relative to in the atmosphere. There is roughly 10 times as much carbon in the world's soils as in the world's forests, but we lose carbon into the atmosphere every time we till the soil.
In general soils are resilient when it comes to growing plants, but we have ignored their multifunctional aspect, for example, how they operate as a drain for water in a water catchment area, or sustain bio-diversity. The benefits of managing the soil is probably not going to be apparent to those who manage it.
Governments have so many other priorities. But we are beginning to have better information about the cost of not managing soils.
Soil-less agriculture is possible - the use of coir, liquid growing media - hydroponics. It seems only possible for high value luxury crops - not wheat for example. If we have to use fossil fuels to generate electricity to power lights to grow crops in artificial conditions the overall environmental costs will be too high.
There is more recent research in a subsequent programme. Work in progress.
No comments:
Post a Comment