This refers to the tillage of harvested fields as soon as the combine harvester has left the field and the weather conditions allow for it. The main objective is toencourage volunteer crops and seed weeds to germinate and break capillarity. To ensure that stubble cultivation actually achieves these objectives, it is worthtaking a closer look at the timing, technology and procedure.
Stubble cultivation should be carried out as soon as possible after the harvest. However, whether early tillage also helps to conserve soil moisture heavily depends on existing soil moisture levels, weather conditions and the soil cover. If the topsoil has already dried out to a large extent, evaporation losses are generally significantly lower. However, if moisture is still present in the topsoil after rainfall, a good straw and stubble cover can provide additional protection against evaporation. A shallow tillage pass should therefore always be assessed in the context of current conditions and the specific cultivation objective.
The art of stubble cultivation in summer is to retain as much soil moisture as possible without losing the effect of weed control. Stubble cultivation resp. the first pass should therefore be shallow. A depth of 5 to 6 cm is sufficient, or even 2 to 3 cm on problem sites with black grass. This allows weed seeds and volunteer crops to germinate without burying them too deeply.
Choosing the right machine is crucial to the success of stubble cultivation. An initial shallow cultivation can be managed with a knife roller, but also with a cultivator or disc harrow. The former primarily complies with the aim of bending the stubbles, minimally moving the soil and bringing volunteer seeds onto the soil in the fine mulch layer. A second, slightly deeper stubble cultivation (8-10 cm) is usually carried out to mechanically control weeds and volunteer crops.
Depending on the site and conditions, you have to differentiate as to which machine is used and whether a third stubble cultivation with a tine tool or a primary soil cultivation should follow. The focus is always on distributing the harvest residues evenly across the field. We summarised in a blog which machines achieve which results.
If, for example, straw is left in swaths on the field, the share of organic matter is higher in these areas and zones with different nutrient ratios are created. This leadsto problems as soon as the following crop emerges: the more straw is incorporated, the more nitrogen is required for decomposition – a fact that can delay plant development.
In addition, unevenly incorporated straw can also cause disturbance layers. As part of a bachelor's thesis, we carried out a test to examine how different tillagetools distribute the straw horizontally.
