In traditional agriculture the soil is ploughed and then harrowed to make a fine, loose, fertile tilth in which annual vegetables can thrive. The soil is then worked again annually after the harvest to make a fine bed for the next crop.
The fact that farmers have been doing this for millennia suggests that the method must work at some level, but traditional tillage does have a number of drawbacks. Ploughing and other cultivations release the greenhouse gas carbon dioxide, kill beneficial soil life such as earthworms, increase the risk of soil erosion, expose weed seeds and can create panning and other drainage problems.
In recent years there has been a growing interest in ‘no dig’ or ‘zero tillage’ methods to get around these problems. At Vallis Veg, we’re sympathetic to these methods and try to keep our soil cultivations to a minimum. However, there are certain problems with zero till methods in ecological agriculture. The main one is that they tend to rely on fertility that’s imported from elsewhere, with a consequent environmental cost in terms of transport, soil depletion etc. We think that farms should (and increasingly in the future will have to) generate their own fertility on site.
The traditional way of doing this in organic agriculture is by sowing fertility-building grass and clover leys which must then be tilled in to grow vegetables, but this obviously fails to circumvent the tillage problem. An alternative is to grow a permanent fertility-building sward which is cut, composted and then applied as compost to the vegetables, thus avoiding any tillage.
The problem here is efficiency loss, since the system fails to exploit the fertility added to the soil in the permanent sward. At Vallis Veg we’re currently experimenting with both systems to determine the best option. We’re establishing a permanent green manure sward to provide compost for one of our crop rotations on a minimum till basis, while our other crop rotation uses the traditional organic ley/tillage method. We plan to monitor these systems over the next few years in order to judge which one works best for us. See the Fertility page for further information about fertility-building methods. |
