No more hoeing in organic oilseed rape (DiverIMPACTS Practice abstract)

Benefits - Suppression of seed weeds - Reduction of soil erosion - Reduction of nutrient leaching - Nitrogen is fixed and utilised by the oilseed rape. - Weed control is usually not required, which helps to reduce variable costs. - Carbon is stored and released less from soil Disadvantages - Significant competition with the oilseed rape crop is possible (depending on the undersown crop and the date of dieback). - No mechanical weed control possible in autumn - Additional costs for undersown crop seed Practical recommendations - Sowing should occur between 25 August and 10 September (in central Europe), if possible before a longer period of precipitation; otherwise, weeds may develop first. - Fertilization: 20-30 t composted manure in autumn, 30 50 m3 of slurry in early spring (as soon as vege-tation restarts and the soil is dry enough), if organic commercial fertilizer is used, apply in February - Either mix legume and oilseed rape seeds and sow them at the same time, or sow the legumes at the last tillage and a few days later sow the oilseed rape with precision seeding. Recommended species and mixtures - Only mixtures of frost-sensitive species are suitable for undersowing. Based on previous experience, a mixture of fenugreek (Trigonella foenum-graecum), peavines (Lathyrus sativus) and lentils (8 kg/ha each) or vetch, clover (Trifolium alexandrina), phacelia and guizotia are recommended (choose varieties that are as frost-sensitive as possible). - In dry conditions, the addition of some flax can be interesting. Flax also has an inhibiting effect on germination of weeds. - In case of increased weed pressure, the addition of 20 to 50 kg per hectare of a frost-sensitive faba bean can improve weed suppression. In autumn, faba beans can also have a positive effect against flea beetles (Psylliodes) and other pests. If the legumes and oilseed crop are sown the same day, sow the faba bean first at a sowing depth of 5-8 cm and then the rape in only 1-2 cm. Advice - The weed pressure in the seedbed should not be too high; if necessary perform a weed treatment before sowing (better after barley than wheat). - After cereals, it is essential to germinate volunteer grains in advance with a stubble cultivation. - Undersowing is not recommended if root weeds such as docks (Rumex obtusifolius) and couch grass (Agropyron repens) are present, as these weeds cannot be hoed due to the undersown crop. Practical testing If this method seems to be suitable for your farm, we recommend that you test it under your own farm conditions as follows: 1. When sowing the oilseed rape, delimit a part of the field for testing. 2. Apply the new method on one of the two plots. The other plot can be cultivated as usual.