Selecting a cultivation system was never easy. Even when plough-based systems were the only option, there was a range of tools and techniques to be chosen from, which, depending on soil type and condition, could significantly affect crop establishment and yield. Today the challenge is greater, with a range of non-plough systems on offer, each with their own attributes.

While creating a seedbed for good establishment is still critical, other criteria such as cost and sustainability in continuous cropping systems must be considered, making selection even more difficult. The demonstrations at Crops & Cultivation will provide an excellent opportunity to see what each of the systems does and for discussion and consideration of cultivation systems.

Why cultivate the soil?

We cultivate to provide good conditions for seed placement, crop establishment and subsequent growth. The objective is to modify aggregate size, pore space and density while retaining soil moisture.

However, the choice of cultivation system affects:

  • Energy requirement, which affects power demand, labour requirement, fuel use and consequently total machinery costs.
  • Crop growth, crop establishment, root development and water availability.
  • Weed competition, which will be affected by soil inversion, intensity of cultivation and stale seedbed systems.
  • Soil quality and structure. Compaction and soil structure are influenced by cultivation, as are soil carbon, earthworms and potentially many aspects of the chemistry and biology of the soil.
  • Greenhouse gases: both CO2 and Nitrous oxide (NOX) emissions can be increased or decreased.
  • Pests and diseases: a range of pests and diseases can be reduced in severity as part of an IPM approach.

    • Cultivation systems

    One of the big challenges with cultivation systems is their description and definition. The systems are normally defined by their primary tillage operation, eg ploughing, minimum tillage, direct drill etc. There are two primary challenges however:

  • Terminology: For non-plough systems, a range of different terms are used, such as min-till, non-inversion tillage, eco-tillage and conservation tillage, which may have slightly different interpretations depending on the user and the country where it’s applied.
  • Intensity and depth: There are potentially huge variations in depth and intensity within systems which hugely affect their characteristics, but are frequently ignored. For example, the term “min-till” could be used to describe a pass of a simple stubble cultivator at 50mm depth or the use of a multi-element (deeper tines, discs etc) system to cultivate at 200mm. In terms of intensity and soil disturbance, the latter is much closer to a plough-based system than a shallow min-till system.

    • When describing a system, it is therefore important to state the depth and intensity of cultivation that is involved.

    Systems used in Ireland

    Commonly used systems in Ireland include:

  • Plough and one-pass (rotary power harrow and drill): This is still the most commonly used system and is characterised by its flexibility and suitability for both winter and spring establishment. Intensity can vary depending on needs and preference by varying the depth of plough and one-pass and the forward speed of the one-pass.
  • Plough press and drill: Typically, the ploughed ground is pressed with a furrow press (or lightly cultivated) and sown with a cultivator-drill allowing faster sowing. Intensity depends on the pressing/cultivation or cultivation elements on the drill.
  • Min- till: Typical min-till operations involve a stubble cultivation soon after harvesting with a tine or disc cultivator to create a stale seedbed followed by total herbicide use prior to sowing with a cultivator drill. There is a huge range of depth and intensity possible depending on the equipment used, the number of passes and the depth selected.

  • Strip-till: In this system cultivation is carried out in strips where tines at typically 330mm spacing (in cereals) disturb approximately 33% of the surface area to about plough depth. Seeding is carried out on the same machine in a band or double row over the disturbed slot. While this can be carried out without previous cultivation, it is common to have a stale seedbed type stubble cultivation (or straw ‘combing’) in advance for winter cereals and a preliminary cultivation for spring cereals.

  • Direct drill: In this system, the seed is simply placed directly in undisturbed stubble with a disc or tine seed coulters. In practice there is quite a bit of difference in the design of the various models affecting soil conditions where the seed is placed.

    • Cultivation systems research

    Research on cultivation systems is not simple. The cultivation system used can have many different effects (other than on yields) which may affect sustainability and the ability to achieve viable yields in the longer term. Consequently, longer-term trials are required. Also climate, soil types and yield potential can affect the relative performance of cultivation systems. Many of the reduced cultivation systems (min-till, direct-drill, etc) were developed in regions where water conservation is vital and cereal yield potential is lower than in Ireland. Consequently, the lower operating costs and ability to conserve water can make these systems relatively more attractive in those regions. A summary of Irish (Oak Park) and international research for cultivation systems in climates like Ireland follows.

    Impact on yields

    With winter cereals, in the absence of grass weed problems, well-managed min-till systems will give similar yields to plough-based systems in most years. However, wet autumns can present a challenge, particularly if shallow cultivation hinders near-surface drainage, this negatively affects yields, both in trials (Fig 1), and commercially. Many growers now cultivate deeper to avoid this problem, but this reduces some of the cost and sustainability advantages of the system. Earlier sowing can help avoid these problems, but can compound grass weed and autumn disease problems.

    With spring cereals, Oak Park research has shown that it is vital to get the crop established quickly to allow it take up nutrients early and develop good tiller counts. On many soils, ploughing is the most reliable way of achieving that (Figure 2) when compared with relatively shallow min-till systems. Non-ploughing systems could indeed be adapted to improve their reliability compared with ploughing, but on many soils, the level of cultivation intensity may then get close to ploughing.

    Grass weeds

    By far the biggest challenge with non-plough systems is grass weed proliferation, with both winter and spring crops. Sterile brome presents a particular challenge and, if not controlled, can incur costs which would negate any cost savings made from adopting a min-till system. The strip-till system needs to be very carefully managed in this regard, as, if operated without a stale seedbed, grass weeds would rapidly multiply. Also, the wider row structure of the strip-till system can allow more space and light for grass weeds to proliferate, the choice of strip-till system and whether or not the soil between the rows is disturbed will affect weed establishment. Grass weed management is probably the most important aspect of operating non-plough systems. Optimum use of stale seedbeds, crop rotation, herbicide use (and possibly ploughing) is essential to avoid problems.

    Power, fuel and labour

    Reducing tillage depth and intensity will save fuel and reduce the power input required to establish crops. This can result in substantial cost savings (Fig 3), but if deeper cultivations are required to improve the performance of the system, then the savings will be reduced. The equipment used for min-till or strip-till is easy to scale-up, facilitating high-output systems capable of establishing larger areas of crops in a short time.

    Earthworms, slugs and aphids

    Reduced cultivation systems can lead to beneficial increases in earthworm populations.

    However, this effect is “tillage intensity” related and changes in earthworm numbers are slow. Slug numbers can also increase. Aphids are less attracted to soil partially covered in straw, slightly reducing the threat of autumn barley yellow dwarf virus.

    Soil carbon and soil structure

    Shallow low-intensity tillage will tend to burn off less soil carbon, resulting in slightly higher soil carbon levels compared with deep and intensively cultivated soil. This effect is small and related to depth and intensity of cultivation, but may be beneficial over time. The aim of direct drill and shallow low-disturbance systems is to allow a more permanent vertical pore structure to develop in soils, thereby improving soil structure. However, in wetter climates with our current practices, this may be difficult to achieve as there may often be a reason to work deeper either continuously or occasionally.

    Greenhouse gas emissions

    While CO2 production is lower with shallow min-till systems, in our wetter climate, NOX production is often greater as the slightly wetter intact soil structure promotes de-nitrification and some gaseous N loss. In contrast to dryer continental climates where min-till is promoted to reduce GHG emissions, on balance the effect on GHG emissions in our conditions is small.

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    Focus supplement: Crops and cultivation