Consider the soil to be a community of inter related organisms, living creatures, minerals, gases and liquids. If you likened a healthy soil to a thriving densely populated city of humans with all these elements balanced, which work together to achieve benefits for each one of the elements and the soil as a whole, as the city works to feed, move and maintain it’s population. Ploughing, heavy cultivations, subsoiling etc could be compared to a massacre taking place in this city, blasting through the community on an annual basis, destroying the life and entire infra structure that the elements have tirelessly strived to create.
Cultivations, once they reach a certain depth, start to do damage to the soil in several different ways and the deeper they are, the more of an adverse effect they have on the soil and what nature is trying to do for you. The soil biology and the production of soil organic matter is destroyed mainly through the destruction of earth worms and their habitat as previously mentioned.
The most obvious advantage when considering direct drilling is the lower crop establishment costs, but in addition and more importantly, improved soil structure occurs naturally along with a vast increase in the number of earthworms and organic matter. It becomes apparent, after 2 or 3 years of non-inversion of the soil, when direct drilling, that all aspects of the soil begins to benefit significantly. The soil crumbles more easily, either when wet or dry. Non inversion produces a fine tilth in the top few inches of over wintered soil which is finer and more easily worked. When the same land is ploughed this fine naturally occurring tilth is buried and more compacted soil is brought to the surface which then requires further cultivation to create a suitable tilth to drill the seed in to. The more years that you do not plough means this tilth increases and the soil becomes more and more manageable usually requiring no more than a single pass with the seed drill to create and ideal seed bed. (see Claydon website http://www.claydondrill.com)
When ploughing and cultivating to create a seed bed the inverted soil usually requires pulverisation which is usually achieved by power harrowing. This process kills the soil bacteria and prevents the build up of soil organic matter, it also kills the earth worms and damages the labyrinth of holes they have created and dramatically reduces water infiltration. Worms are very good at removing compaction and in doing so they incorporate air into the soil and help to produce the soil organic matter.
There are a good number of publications (see publication ‘Soil Matters’) regarding the benefits of direct seed drilling, however few farmers are confident employing this method of crop establishment mainly due to the fear of being unable to control weeds, particularly grass weeds. Spring cropping and a more diverse crop rotation is required to keep on top of weed problems and along with utilising both new and old cultural methods of weed control. Using no-till methods of seed placement means that weed seeds are left on the surface and are subject to predation from beetles, insects and birds and damage to the seeds from UV light reduces their viability. In addition to no-till, shallow stale seed beds can be created easily and cheaply, allowing chitted weed seeds to be sprayed off with glyphosphate before drilling.
This field has not been ploughed or sub-soiled for 5 years and it clearly shows that there is no compaction and that roots can easily get down to the sub-soil level. This winter barley crop was drilled in mid September and this survey was carried out on in late December to establish plant root depth. (Mark Taylor- independent agronomist)
The correct soil structure occurs when the soil has not been inverted and it develops an incredible capacity to carry machinery without leaving as many visible wheelings as on ploughed land. Combine harvester and big baler wheelings are almost unnoticeable except in extremely wet weather.
When you do not plough or invert the soil the soil moisture stays in the right place and is not brought to the surface to dry out. The thin layer of fine dry soil which is already on the surface of a non cultivated field stays exactly where it should and is not turned downwards to be replaced by more solid soil brought up by the plough.
Whilst most growers would argue that you cannot grow crops without ploughing the more time you take to gain knowledge regarding the advantages of direct drilling the more you realise the damage the plough does to the soil. There are many publications readily available on the subject of direct drilling and the more information you glean the more fascinating the science of non inversion crop establishment becomes.