Soil Inversion Research
Peter Matthesen
(Danish Forest and Landscape Institute) - Deep Ploughing 1993
Advantages
In trials as well as in practice deep ploughing there was less plant fatality than with other treatments, when all the other factors were the same. In the dry season of 1992 deep ploughing stood out as being the most successful treatment for sandy arable land. Larch, Alder and other pioneer trees show a rapid early growth after deep ploughing.
If the perennial weeds are treated before deep ploughing and the seed rich topsoil completely buried, it is unnecessary to continue treatment after the trees have been planted. This is the case if there is a covering of over 10cm of subsoil.
Disadvantages
Deep ploughing can destroy archaeological evidence that is typically found at a depth of 60 - 70cm. It is therefore very important to inform archaeologists before this type of ploughing is carried out. The physical properties of the subsoil and the fact that it is weed free for such a long period makes it susceptible to erosion. The long-term effects on fertility are still to be investigated.
Affects on common annual weeds
Deep ploughing has a major effect on the percentage cover of common annual weeds when compared to normal ploughing.
Summary of Danish and Lithuanian Academic Research
Sapling survival rates
The research on the effects of deep ploughing in forestry started in 1960. When the Heath Community of Denmark started organising the establishment of multi-row wind shelter belts.
The Forest and
Landscape Institute of Denmark (1989) launched four tests on using deep ploughing
for afforestation.
The tests showed that seedlings planted in a deeply ploughed soil
- Survived
much better.
- Were growing
faster.
- Were drought resistant.
The latter fact became evident during the drought in summer of 1992.
The explanation is that the deeply ploughed humus layer accumulates and maintains moisture.
Saplings planted in sandy soils showed nearly 100 per cent survivorship and no replanting was needed.
Other Benefits of deep ploughing
This method is also more economical in the sense that:-
- High forest
weeding costs are reduced
- Tree species
are growing especially fast on deep ploughed land
- The established forest stand is also more stable.
Potential management problems
1. Deep rooted weeds
Danish specialists recommend the removal of weeds before ploughing by using Roundup, as deep rooted weeds may survive soil inversion. However, chemical use has to be very limited on sandy only a very small amount of them should be applied on such soils as the risk of polluting the ground water sources is quite high.
2. Soil Erosion
It is also necessary to plan erosion protection measures. Agricultural crops grow rather fast and do not provide favourable climate for the planted trees.
After deep ploughing the soil is loose, therefore it should be ploughed one month before the afforestation or the soil should be treated with a roll. The weed-free subsoil layer raised to the top by ploughing may be harrowed or otherwise levelled (if necessary) before the afforestation.
Deep ploughing makes soil rather permeable, dry and weed-free for a long time.
Additional Considerations
1. Applicability to different soil types
Deep ploughing was mainly used in light sandy soils in Denmark. Even though this method is currently applied on fertile and heavier soils, the effectiveness is not known.
No tests have clarified, if deep ploughing can enhance the growth of seedlings of other tree species in the first year.
All these effects manifestly reduce afforestation and further tending costs, which are very important to a contemporary land owner willing to establish a new forest.
2. Archaeology
Due to the depth of the plough - areas that are archaeologically sensitive should be avoided.
3. Technical Note
Contact with Karl Alleso, secretary of the World Ploughing Organisation, based in Odense Denmark, identified the best plough for the job to be the Bovlund 64d plough . This Danish plough had been successfully trialed by the Danish Forest and Landscape Institute in Denmark and as part of a major agro-forestry project in Lithuania.
