The Overseer Technical Manual Chapters do not provide a specific definition of what each of the available cultivation types might include, rather assuming that farmers and expert users will have a reasonable understanding of the differences between the available options:
The cultivation method represents the relative degree of soil disturbance associated with crop establishment. It is not intended to identify specific machinery. The selected method influences the rate of organic matter mineralisation and crop residue decomposition following cultivation.
- Direct Drill – Minimal soil disturbance with residues largely remaining on the soil surface.
- Minimum Tillage – Partial soil disturbance with some residue incorporation and moderate stimulation of mineralisation.
- Conventional Cultivation – Extensive soil disturbance with substantial residue incorporation and the greatest stimulation of mineralisation.
From the model implementation, and commentary provided in the Technical Manual Chapters we have created the table below to support users:
| Overseer cultivation method | Inferred definition | Typical field operation | Relative soil disturbance | Residue incorporation | Expected effect in Overseer |
|---|---|---|---|---|---|
| Direct Drill / No Till | Crop established with minimal soil disturbance. Seed is placed into untilled soil with only a narrow slot opened by the drill. | Direct drilling, no-till seeding | Very Low | Very Low | Lowest cultivation-induced mineralisation. Residues remain largely on the surface. |
| Minimum Tillage | Soil is cultivated sufficiently to prepare a seedbed while avoiding full inversion. Residues remain partly on the surface and partly incorporated. | Discing, power harrow, shallow cultivator, grubber | Moderate | Moderate | Moderate increase in mineralisation and residue decomposition. |
| Conventional Cultivation | Full seedbed preparation involving multiple passes and substantial mixing or inversion of soil. Most residues incorporated into the cultivated layer. | Plough followed by discs, harrows, rollers | High | High | Highest cultivation-induced mineralisation and rapid residue breakdown. |
To further assist users, we have provided a comparison of some real-world cultivation practises, and their possible definition within Overseer. It should be considered however, that we would recommend selecting cultivation based on the overall amount of soil disturbance, not the name of the machinery.
| Real-world practice | Recommended Overseer selection |
|---|---|
| Cross-slot drilling into pasture | Direct Drill |
| Aitchison direct drilling | Direct Drill |
| Seed drilled after spraying with no cultivation | Direct Drill |
| One shallow disc pass before drilling | Minimum Tillage |
| Power harrow seedbed | Minimum Tillage |
| Rotary hoe seedbed | Minimum Tillage |
| Plough → discs → harrows | Conventional Cultivation |
| Multiple cultivation passes before crop establishment | Conventional Cultivation |