Crop establishment systems
In Ireland crops are established using many different methods depending on the crop being established, the time of year and the weather and soil conditions at the time of sowing.
Below is a brief synopsis of the commonly used establishment systems here in Ireland.
The most common establishment system practiced by famers in Ireland is still based around the plough. This is a conventional soil inversion method that usually takes place at a depth of 150 -300mm (6-12 inches). The plough inverts the top layer of the soil; burying all crop residues and providing loosened and cultivated soil in which to establish crops. Having undergone the ‘test of time’ in the Irish climate, it allows farmers to establish crops in less favourable conditions and is seen as a very reliable way of establishing crops. In autumn, it often allows dryer soil from depth to be presented for sowing even when weather conditions have deteriorated, while in spring, the loosened soil usually dries and warm quicker than less disturbed soil. .
The first ploughs were developed thousands of years ago and although much has changed in the their design in that time, the principles remain the same; turning up fresh soil for sowing seeds into, burying residue from the previous crop and helping with weed control by burying weeds. However, the draw backs of these systems include: high cost and slow work rates; increased risk of soil erosion; accelerated carbon (organic matter) loss and soil damage due to their ability to work in wetter conditions. These can combine to result in a degradation of the soil structure.
Non-inversion tillage systems
The term non-inversion tillage is used to describe all systems that do not invert the soil, including min-till (reduced tillage), strip-till and direct-drill (no-till, zero-till); that is, systems other than ploughing. However within this category, systems can vary massively in terms of the depth and intensity of their cultivation; the level of disturbance they achieve and the distribution of any crop residue. Occasionally these terms are interpreted and used differently so it is important for any user to define the system that is being described in terms of depth and intensity. Their benefits compared to ploughing in terms of soil structure protection and reduced carbon loss are largely dependent on the depth and intensity of the tillage associated with them.
The term Min-till or minimum tillage is most commonly used to describe soil cultivation that does not involve soil inversion. It implies a reduction in the level of cultivation (depth and intensity) compared to a plough establishment system and encompasses many systems which use a tine or disc cultivator to perform the cultivation. In its original form, only one cultivation between crop harvest and sowing was practiced and to a shallow depth of 50 to 100mm (2 to 4 inches). However in Ireland, the depth and intensity has generally increased with two cultivation runs frequently used and depths typically 150mm and occasionally more. Stale seedbeds in combination with herbicides are used for weed control. A tine or disc drill designed to cope with levels of surface residue is used to sow following cultivation. The type of cultivation equipment used and the depth and number of cultivations will depend on a number of factors, with user preference, soil type, previous cropping, current crop being sown and the time of year being major considerations.
Internationally Min-till is described as a method of establishing crops with the least amount of cultivations necessary while also retaining a minimum of 30% of the previous crops residues on the soil surface. It can be debated as to whether a lot of the Min-till systems practiced in this country could claim to achieve these requirements. Min-till systems should reduce energy consumption, reduce labour, establishment time and machinery costs, help to conserve moisture and retain plant cover to minimise soil erosion, compared to conventional plough based systems, but these advantages are entirely related to the depth and intensity of cultivation.
Strip till is a method of crop establishment that sows and carries out limited cultivation in strips, in one machinery pass. A lead tine working at 100mm to 200mm depth cultivates strips of soil at a row spacing of 300 to 330mm in advance of a sowing coulter. Strip tillage typically cultivates about one third of the field area, seeds are sown in these strips of disturbed soil and the area between the strips is left untouched. For weed and volunteer control, some growers will carry out a very light surface cultivation followed by herbicide use to create a stale seedbed. Claydon and Mzurri are examples of strip-till drills used in Ireland.
No till/Direct drill/Zero till
Direct drilling is a method of crop establishment that involves planting crops without disturbing the soil beyond that necessary to place the seed at the required depth. No-till farming systems require permanent soil cover to remain on the soil surface in order to prevent soil erosion and conserve moisture. The lack of soil disturbance can help to reduce carbon loss and to increase biological activity such as earthworm numbers. An aim with these systems is to allow a more resilient soil structure to develop with more vertical porosity that should help drainage and soil function. There are two types of machine that can be used in this system either a disc drill which makes a narrow slit in the soil with a disc, then places the seed into the slit before covering it with soil or a tine coulter machine which opens a narrow band just deep enough to place the seed and then covers it with soil. Examples of direct drills used in Ireland include Weaving, John Deere, Cross-slot and Duncan machines.