Seedbed Preparation

Pre-sowing tillage is, as the name suggests, the final agrotechnical operation before sowing—although treating it as a completely separate stage on the path from sowing to yield best fits traditional plough-based tillage. In ploughless and reduced systems (and sometimes also in plough-based ones), seedbed preparation is often combined directly with sowing (for example, using seedbed cultivator combinations such as the U659 from Rolmako).

In general, the goal is to create ideal conditions for seed growth: a level field surface, a loose and finely crumbled top layer, and a slightly firmed base in the seed zone. This “ideal” seedbed looks somewhat different in conventional tillage than in no till systems, but overall the field surface before sowing should be:
- Level—free of clods, ruts and crusting,
- Fine-textured and loosened to a depth of 1–2 cm,
- Slightly firmed in the load-bearing layer,
- Moist—neither dry nor wet,
- Free of crop residues in the seed zone (with ploughing – across the entire field surface; with ploughless and reduced tillage – in the seed rows),
-With a good crumb structure,
- With a temperature suited to the planned crop.

Plough-based tillage

Traditionally, after ploughing, one or more passes are carried out with tillage tools (harrow, cultivator, roller) to break clods, stabilise the soil and prepare an even, loosened seedbed. In this system, harrowing or using a cultivator with a roller is almost essential, and sowing should not be delayed—leaving ploughed soil uncovered for too long results in significant moisture losses. On light soils that dry out quickly, many farmers plough and sow on the same day to make use of residual moisture from deeper layers, or use seedbed cultivator combinations to complete the operation in a single pass.

Reduced / no till farming

In reduced tillage systems (without ploughing), pre-sowing cultivation can often be limited to a minimum, as the soil has usually already been pre-conditioned earlier (shallow stubble cultivation and, if needed, deep loosening without inversion) and is fairly level. Often a single pass with a light cultivator (e.g. harrow + roller) is sufficient, or sowing can be carried out directly using a seedbed cultivator.

In extremely simplified systems such as direct drilling into mulch, pre-sowing tillage across the entire field is omitted altogether, while in strip-till systems it is omitted in non-seeded strips (inter-rows). With mulch seeding, the field remains undisturbed after earlier operations (for example, only after stubble cultivation or even directly after harvest), and seeds are placed using a specialised no till drill that inserts seed into a narrow slot using slim coulters or seeding discs. While strip-till is gradually gaining popularity in Poland, direct drilling (no-till) is still much less common.

Important! The choice of pre-sowing method depends on the adopted tillage system. The less the soil has been disturbed earlier, the less (or not at all) it should be disturbed before sowing.

Golden rule of reduced tillage: cultivate only as many times and as deep as necessary—the less and the shallower, the better.

The importance of soil moisture and structure before sowing and pre-sowing tillage

Proper soil moisture and structure (which are closely linked) determine sowing success. Poorly timed or unnecessary pre-sowing tillage can do more harm than good.

Dry soil

Under drought conditions, every drop of moisture is precious. Unfortunately, every machinery pass on dry soil causes further water loss—the soil crumbles, exposes moister particles and moisture escapes into the atmosphere. Therefore, it is advisable to avoid unnecessary pre-sowing operations that only loosen dry soil and create a layer of dry dust.

Sometimes the soil is extremely dry down to a depth of 30–40 cm—then performing traditional pre-sowing tillage borders on impossible (it is difficult to maintain a constant working depth, the equipment bounces on clods, and the soil turns into loose ash). In a dry season, it is best to sow directly into existing conditions, or minimally disturb the soil only where seeds will be placed (e.g. narrow cultivation to sowing depth). This gives seeds a chance to reach residual moisture below the surface and germinate.

Important! Practitioners warn: there is no point in cultivating dry soil and waiting for rain. On the one hand, rain may not arrive before sowing. On the other hand, when rain eventually does fall, even a single event can cause a compacted crust to form on overly pulverised soil, preventing seedlings from breaking through.

Wet soil

A heavy tractor and cultivator on wet soil cause compaction and smearing—dense clods and sealed muddy surfaces form. Shiny, smeared furrow walls (the smearing effect) harden after drying like bricks, making it difficult for roots to penetrate and seedlings to emerge. Unfortunately, this mistake affects the entire season—compacted soil lacking structure cannot be repaired before sowing.

Important! When soil is too wet and plastic, it is better to delay tillage, as it will cause more damage than benefit. To assess this, mirror, rolling or ball tests can be used, as described below.

Practice: assessing field conditions before pre-sowing tillage and sowing

PBefore deciding whether to carry out pre-sowing tillage or not, it is worth checking several factors.

Soil moisture

Mirror test. Dig a soil sample with a spade and examine the cross-section. Is the furrow surface smooth, shiny and wet? The soil is too wet. Does it break into friable aggregates and look matte? You can enter the field with tillage.

Rolling test. Try forming a soil roll. If it moulds like plasticine, it is still too wet.

Ball test. Form a ball from a handful of soil and drop it from about 1 m. Does it crumble easily? The soil is dry enough for tillage. Does it remain compact? Better to wait.

Weed and volunteer crop emergence

If weed pressure is high, consider controlling weeds before sowing (with a harrow or herbicide). If it is minimal, avoid “provoking” the entire soil surface—sow without tillage, or disturb only the seed row if necessary.

Residue decomposition and stubble condition

Well-executed stubble cultivation should leave residues chopped and mixed with the soil. In that case, you may consider skipping further tillage. If large patches of straw and undecomposed residues are visible, it is worth carrying out very shallow cultivation (e.g. a disc harrow set to 3–5 cm) or using a heavy harrow to spread and break up residue accumulations.

Ideally, when entering the field you should feel stable ground—not sinking ankle-deep into dust or walking over large clods. Check whether the field needs leveling with a pre-sowing cultivator (e.g. Rolmako U382, U659, U445 or U684), breaking a surface crust, or rolling and firming.

“The drill test”

Finally, it is always worth performing a “drill test”—sow a few metres and check how the machine performs. If coulters maintain depth well, do not clog with residues and seeds are placed in neatly covered furrows, field conditions are suitable. If the drill clogs with straw or runs too shallow or too deep in places (due to unevenness or clods), it is better to stop and correct the field condition (cultivate or roll) than risk uneven emergence.

The decision on pre-sowing tillage should be based on careful observation. Sometimes the best pre-sowing tillage is… none at all—especially when the soil has good structure and lacks moisture. At other times, a single additional pass can save the sowing operation (for example, by breaking a crust after rain). A good farmer can “read the soil” and flexibly adapt to conditions to give seeds the best possible start.