Cover crops

reinventing the wheel

The use of cover crops has a very long history. Yet these systems virtually disappeared due to the use of synthetic chemicals and the green revolution . In more recent times cover crop trials have been taking place since the 1980’s and it is an approach that I have been using and teaching to others for 30 years now. Done well it’s an approach which works fine, used as a part of an integrated agricultural approach it works even better.

Recent trials in Texas and Mexico demonstrated the benefits of cover crops under cow pea and sunn hemp but also revealed that in low rainfall conditions the cover crops can provoke water stress in the crop plants. This brings me straight back to the lack of holistic approaches and a fixation on one technique as opposed to a group of techniques integrated together.

The advantages of cover crops are numerous. They protect the soil from sun, water and wind erosion, they encourage a wider insect and polliniser diversity, some cover crop plants fix nitrogen, they add nutrition to what is browsed by stock animals post harvest. Trials, over recent decades, have shown the advantages of a cover crop ley when used in conjunction with numerous types of crop culture. Wheat in a clover ley is the best known and the most tested. In 1991 I visited a trial plot where oats were grown in a clover ley. When harvested the combine harvester left one metre width strips across the field between each pass. These remaining oat plants dropped their seeds into the recovering clover and the next year they germinated and the subsequent harvest was as good as the previous year, without the need for reseeding.

The Texas/Mexico trials seemed to show, as I have noted, that, in some circumstances the cover plants can cause water stress in the maincrop. This isn’t a problem with the cover crops but a wider problem that comes from the continuing insistence on growing crops in huge open fields without tree cover and without a rational approach to landscape water management.

Permaculture designers think holistically, which is one of the big differences between Permaculture and the type of Agroecology that is being promoted today. Permaculture designers will combine regenerative cultural techniques with regenerative water management systems (including methods to reduce irrigation need and increase the capacity of soils to retain humidity). A Permaculture designed agricultural landscape looks very different to the large scale agricultural expanses we see too often today.

For a start there are trees, organised to give dappled shade to crop plants, tree varieties selected to give other harvests ranging from nuts, to leaves or for timber/firewood. The presence of trees also encourages the development of an extensive mycelial network, amongst other things these networks can liberate mineralised soil phosphate and make it available to crop plants. Water harvesting from roads and buildings are often a feature of these designed systems.

This designed landscape features a variety of water management systems ranging from keyline approaches to swales and channels. These systems will also integrate regenerative soil management approaches, these can involve the use of tall cover crops grown before the maincrop/cover crop. The former are rolled using a Faca roller or a variant, the flattened plants then acts as a mulch layer into which the cash crop and it’s cover ley can be sown. Biochar can also be used to further increase the soil moisture retention capacity.

Animals can be introduced post harvest to eat the crop residues, they will fertilise the soil with their dejections. An even more sophisticated approach is to use either a series of different animals or one or more types of animal at the same time, cows and sheep for example.

Windbreaks and hedge row corridors surround the cropped areas further increasing biodiversity and reducing crop loss from wind damage. Both designed and planted with varieties of bushes and trees that will provide other harvests, fruits, leaves for animal browsing, plants useful for reducing the parasite load of domesticated animals.

On the business side many farms are reorientated from the global food markets towards more local ones. This reduces transport costs and product damage, reduces grade out losses, gives local people access to higher quality products and encourages closer farmer/consumer links.

Basically we have in hand all the different approaches that we need to restructure our existing agricultural production areas and transform them into sophisticated, ecological and sustainable units. The question arises as to why we are not leaping forwards and witnessing a massive restructuring of farms.

In many ways the agricultural world is deeply conservative, if something works why change it? This hinders the adoption of more sophisticated approaches.

Each generation starts by reinventing the wheel. Many if not most of the trials being done today have already been done and replicated elsewhere. This is encouraged by the different industries that supply seeds, synthetic chemicals and machines to farmers. We are losing precious time, over my 30 plus years as a Permaculture designer I have seen this happening far too often, tried and tested practices are reinvented using another name, these are then tested again and more time is lost. The recent promotion of ‘regenerative water’ is a case in point, virtually all of the ideas being promoted by the proponents of regen water have been used over many years by Permaculture designers. More time and effort is wasted promoting the ‘new’ approach and again the necessary integration of multiple systems is forgotten as the rising stars of the ‘regen’ water movement promote it as ‘the solution’.

For too long now Permaculture has been associated with a sort of happy gardening, many books, podcasts, youtube films about Permacuture promote this idea. The negative consequences of this are numerous and mean that Permaculture designers such as myself are immediately categorised as gardeners rather than designers who create sustainable systems of all types and all linked together. This is particularly true in OECD countries, in other countries where I work this is much less the case and the holistic integrated Permaculture approach is much more appreciated. It is pretty frustrating.

We have the solutions we need to restructure our agricultural systems, what we urgently need is a sort of paradigm shift away from piecemeal non-integrated approaches and we need more Permaculture designers capable of helping farmers transform their lands.