Soil report shows we should all grow more of our own – New research confirms that soil in allotments and back gardens is richer – and more productive – than on farms
Soil is one of the great failures of modern intensive agriculture. Healthy soils, beneath natural grasslands and – especially – woodlands, contain lots of organic matter. This organic matter holds onto nutrients and gives the soil structural stability, allowing it to resist damage by, for example, heavy rain, thus preventing erosion. There’s also plenty of life in a healthy soil, lots of burrowing earthworms, and so lots of pore space too. A healthy soil is basically a giant sponge, which fills up with water after rain, gradually releasing that water to plants in dry weather.
When land is cleared for agriculture, and especially for arable crops, all that goes out of the window. The organic matter in arable soils is lost to the atmosphere as CO2, and the soil loses its structure and strength, leading to compaction and erosion. Arable soils also lose their ability to hold onto water, nutrients and pollutants, leaking nutrients into groundwater and lakes and rivers, causing eutrophication and, if the water is for human use, the need for expensive water treatment.
Although this is all depressingly well-known, the conventional view is that all this soil degradation is the price we have to pay for the high yields of arable crops on which we all depend. But, says new research just published in the Journal of Applied Ecology [Urban cultivation in allotments maintains soil qualities adversely affected by conventional agriculture], gardening proves the conventional view to be completely wrong. The researchers looked at the properties of soils on allotments in Leicester, along with those from other urban sites, and compared them with soils beneath arable fields and pasture in the countryside around Leicester.
The arable soils showed all the usual symptoms: compacted, lifeless and low in organic matter. Allotment soils, by contrast, were more open, more fertile, and higher in organic matter, in fact they weren’t all that different from soils beneath woodland. The reason isn’t hard to find: composting of allotment waste is virtually universal among allotment holders, most also import household green waste as well, and use of manure and other kinds of commercial compost is widespread. In short, soils on allotments are healthy because allotment holders go to a lot of trouble to keep them that way.
Nor are these healthy soils any barrier to high yields. During the Second World War ‘Dig for Victory’ campaign, allotments and gardens provided around 10% of food consumed in the UK, despite covering less than 1% of the area of arable cultivation. Recent research also shows that gardens and allotments produce yields of fruit and vegetables 4-11 times greater than conventional agricultural crops. In fact, soil organic matter is now so low beneath many agricultural soils that it makes it increasingly hard to maintain high crop yields.
These results are not unique to allotments; soils in private gardens were pretty good too. In fact garden soils beneath trees and shrubs were the best of all, presumably because they are undisturbed and also benefit from the organic matter added by fallen leaves. Nevertheless, allotments are unique in the way they manage to combine a productive ‘agricultural’ function (i.e. growing food) with healthy soils.
The policy lessons are clear, but I’ll spell them out anyway. Encouraging people to grow their own food simultaneously targets food security, improves the well-known (physical and psychological) health benefits of gardening, and helps to reduce climate change, flooding, pollution and erosion. You seriously want to save the planet? Give us the tools, and the land, and we – gardeners – will do it for you.
ARTICLE LINK: http://www.telegraph.co.uk/gardening/howtogrow/10792603/Soil-report-shows-we-should-all-grow-more-of-our-own.html
STUDY LINK: http://onlinelibrary.wiley.com/doi/10.1111/1365-2664.12254/abstract
Additional information comments from Dr Edmondson:
“We found remarkable differences in soil quality between allotments and arable fields. Our study shows how effectively own-growers manage soils, and it demonstrates how much modern agricultural practices damage soils.”… “An estimated 800 million city dwellers across the world participate in urban food production, which makes a vital contribution to food security. Our results suggest that in order to protect our soils, planning and policy making should promote urban own growing rather than further intensification of conventional agriculture as a more sustainable way of meeting increasing food demand.”