Conventional tillage - the way forward?
Conventional or conservation tillage – does getting off to a clean start pay off?
To plough or not to plough, this is the question that many are asking as that time of year heads again towards bare stubbles. With your soil being your most valuable asset on the farm we look at some of the pros and cons of the differing tillage systems.
Initially let’s just to remind ourselves of the primary soil tillage classifications:
Conventional – plough-based system involving complete soil inversion
Conservation – a homogeneous mix of crop residues and soil left in the upper soil profile
Direct – no prior soil tillage before sowing
StripTill – targeted mix of conservation tillage in and around the seeding area with strips in between left un-tilled
The decision as to which technique is adopted must to be based on both ecology and economy with the aim being to sustain long-term soil fertility and yet achieve both the highest yields and a decent quality in the most cost-effective manner. Soil organic matter levels have fallen dramatically over the past few years reducing the ability of the soil to maintain soil moisture, friability and nutrients as well as an increased risk in erosion. Soil type will play a prime part in the system used, as will the possible crop rotation options. Soils on the heavier side are generally more self-structuring due to pore size and these also benefit from being worked without inversion, keeping the friable tilth on the surface alongside the organic matter resulting, after time, in more workable soils and reduced cultivation costs. Lighter land, with its inherent smaller particle size, can tend to pack tighter leading to bad drainage and a lack of oxygen in the soil plus the increased risk of water erosion due to a poor infiltration capacity. Water run-off can lead to a decimation of crop coverage through soil erosion as well as chemical and nutrient loss into water courses. Wind erosion can also be accredited to the lack of organic matter in the upper profile.
But problems due to disease pressure, weed seeds and volunteers may be more susceptible when mulch sowing than when utilising the plough and these can then only be compensated for by the relevant crop protection measures and by taking a greater care in the choice of variety. Even if, because of this, costs rise then normally these extra measures pay off due to the lack of additional expenditure in time and fuel arising from when operating with the plough.
On the positive side, conventional soil tillage is relatively simple to manage and has the benefit of giving the following crop a clean start. The drilling system can be cheaper and less complicated plus the risks of disease and pest carry-over are mitigated; reducing the need for crop protection agents and the proceeding crop can germinate free from competition. Soils are warmed faster in the spring with the increased proportion of air in the upper soil layer speeding up the germination of spring-sown crops. These advantages generally mean that crop rotations can potentially be tighter. Ploughing leads to a looser soil surface down the worked profile and this helps when trying to establish root crops which require a deep-worked seedbed.
However, when we look at the cons of conventional tillage we see the reasons why farmers have tended to adopt a conservation tillage system. This looser soil surface, which is of such an advantage when preparing for a crop of potatoes, becomes a disadvantage when cultivating ahead of cereals. A better carrying-capacity of the soil is paramount, not only for when following the primary soil tillage operation with a secondary seedbed preparation pass and the drill, but also when it comes to working in the tramlines afterwards with the sprayer and spreader.
The high work rates made possible by the lack of soil movement leads to better timeliness as well as a huge reduction in fuel consumption. With larger areas for farmers to cover now and drilling windows shortened by extremes of weather it is important that a system is adopted that can cope with the work necessary. To only cultivate as deep as necessary is paramount to maximising work rates and improving soil life levels. 1cm per tonne/ha of straw is sufficient to incorporate last year’s residues. Increasing the cultivator depth from 15cm to 22cm has been shown to add 50% more to the fuel consumption.
Direct drilling offers the optimum in terms of energy input and emissions release. The lack of soil movement prevents soil moisture loss and demineralisation of the soil. Soil organic levels are more easily maintained, if not increased, by this reduction in cultivation and the soil life activity is accelerated even in comparison to a min-till system. However, from a management point of view direct drilling needs more thought with regard to crop rotation, vehicle traffic and weed and disease control. The use of cover crops in the rotation can assist in controlling the pressure from weeds and, at the same time, improve soil structure.
StripTill is becoming increasingly discussed especially when looking at the establishment of oil seed rape. StripTill forms a bridge between no-till and min-till so that the strips of soil left untouched help to increase soil life and soil organic matter levels without promoting a flush of weed germination post cultivation. Soil traffic-carrying capabilities are also increased and the energy input can be possibly reduced by moving less soil. A Europeanisation of the system, by adding a preliminary stubble chitting cultivation into the technique ahead of the StripTill pass, can help in the control of weed and pest carry-over which is under more pressure due to our climatic conditions than in the Sates where the technique is most used. The stubble chitting operation can consist of a straw harrow type of approach or a pass with a Catros compact disc harrow at 5-6cm of depth.
As oppose to a few years ago, the adoption of differing soil tillage systems today is significantly higher and more flexible on many farms. So, farms which formerly only ploughed now rely on conservation soil tillage within individual crop rotation links to save costs. However, other farms which for decades cultivated only using conservation cultivation techniques, have reached their limits of practicability in narrow crop rotations or in extremely dry or extremely wet years.
This has resulted, so to say, that the trend in modern arable farming is that more and more farms are utilising two or even three soil tillage systems in parallel.