Description of the Business As Usual (BAU)
No till systems are opposite to conventional tillage systems with crop residues removed. Conventional soil ploughing that bales the straw and buries the stubble of the previous season. The sowing is performed with a standard sowing machine.
Description of the system change
No till practice avoids all soil disturbance and requires different soil and cropping system management. With this practice must leave at least 30% of area covered by plant residues right after crop establishment. Crops are sown using machinery capable of placing seeds directly through plant residues from previous crops into untilled soil, establishing a crop directly into a seedbed that has not been mechanically prepared. There should not be any periodic tillage that disturbs a greater area than 15 cm or 25% or cropped area.
No till, therefore, requires the use of appropriate equipment and machinery. Specific seed drills are needed, which must have several devices to ensure the correct placement of the seed in the soil. The aim is to place the seed in suitable conditions for germination and crop establishment in unploughed soil conditions and with plant residues on the surface. These direct seeders, direct seed drills or direct sowing machines are equiped with several tools:
- Tools that enable to remove or cut the crop residues before the furrows are performed on the sowing line. These can be cutting discs or residue sweeper on the sowing train
- Tools for furrow opening and seed placement, with coulter that can be classified in two types:
- Disc Coulters: the soil openers are discs (single or double) mounted in the forward direction. Single-disc machines usually do not have a front cutter, as the discs perform the cutting and opening functions of the sowing furrow. The outer edge of the disc can be smooth or grooved, which cuts the straw better.
- Tine (or knife) coulters: they act on the ground exerting the vertical cut upwards to open a narrow seed furrow. They need a minimum separation between the tine arms to avoid accumulating crop residues between the tines. However, this tine system adapts better to stony terrains and reduce the needed preassure to seed.
- Tools for closing the open sowing line. It is usually conducted by press wheels, sometimes rakes are also mounted behind to smoothen the soil surface.
The first step to perform No till is to spread the residue from the previous crop evenly. This can be carried out with a residue spreading system and deflectors in the harvester. This avoids sudden changes in the ground coverage for the next sowing, which is needed because the regulation of the seeder is not the same when there is a thick layer of residues and little amount of them.
To control weeds in minimally soils disturbance systems, herbicides are normally used under integrated weed management. Sinergies of no till systems are also considered; plant residues over the soil surface help control weeds by restricting light and nutrients supply to them. Furthermore, the straw mulch cover prevents the soil-seed contact, hindering and reducing weed germination.