Feeding the soil to feed ourselves
The soil is vital to everything that lives on Earth; if we want healthy bodies & a healthy planet then we need healthy soil. So we must make choices that encourage this & support farming systems that feed the soil rather than deplete it. Soil is a miraculous substance, a place where air, water, minerals & micro-organisms can work together to nourish plant growth, but they must be present in the right proportions. A healthy soil has good structure & consists of approximately 25% air, 25% water, around 40% minerals & up to 10% organic matter. Natural systems build such soils & modern farming practices degrade them. The normal rate at which nature builds soil is around 0.2 tonnes per hectare per year, yet the rate at which it was recently being lost on US farmland was measured at around 40 tonnes per hectare per year! The reasons for this dramatic loss lies in the increased wind & water erosion facilitated by the removal of surface matter (mulch & cover vegetation), natural windbreaks & the effect of ploughing (& digging) in particular.
Whilst ploughing is done to accomplish certain tasks, there are so many more reasons why we shouldn’t do it. The structure of the soil is vital for healthy plant growth, but ploughing damages that structure in several ways. When the level of organic matter in the soil falls below 3.5%, the soil structure cannot be maintained. Ploughing permits excessive amounts of air into the soil, which oxidises this organic matter, causing it to break down & as a result this structure is lost. Most arable land has only 1-2% organic matter & a close look at any such field will reveal a compacted unhealthy looking soil. No wonder farmers are throwing so many chemicals at it to get anything to grow!
Ploughing & digging also has a direct impact on vital soil life. Earthworms, who aerate the soil with their tunneling, are killed in great numbers by the mechanical action of the plough or spade. Similarly, micro-organisms (which interact with plant roots to enable them to take up nutrients) mostly live in the aerobic conditions near the surface of the soil, but are killed by being buried deeper by the plough or spade. The final insult to the soil by intensive farming is the use of tractors. On steeper land, a tractor can only plough up & down the slope – which maximises water erosion down the channels they create. The evidence for the insanity of this practice can be seen in streams & rivers during & after heavy rain & on the white tops of fields of chalk farmland from where all the soil has been lost.
So it’s time we started putting the life back in the soil & there are various permaculture practices that can encourage this. Most importantly, the soil prefers to be covered, either by living plants or by leaf litter (which earthworms will drag down under the surface & convert into great compost). This simple act will halt erosion & start to build the soil again. It will reduce the extremes of day & night temperature & provide a habitat for beneficial soil organisms to thrive.
If we mulch with well-rotted compost we also feed the soil in a ‘slow-release’ fashion, which avoids the dramatic changes in pH associated with ‘digging it in’ & the ‘burning’ effect that it can also have on plants. If necessary we can provide additional aeration for the soil with a fork (or on a commercial scale with a sub-soiler), which allows air in without disturbing the different layers. To maintain good structure, we’d be well advised not to walk on our garden beds as compacting the soil, expels the air & affects essential drainage. This is why appropriately sized raised beds with clearly defined paths are such a good idea.
Only a well balanced soil is going to grow us truly nourishing food. If the nutrients aren’t available to the plant, then they won’t be available to us either. So it’s never been more true that we get back what we give out.