Firm soil mulch husbandry, especially direct seeding, may provide an opportunity for Organic Agriculture to increase soil fertility by efficient erosion control and save labour and energy. In this context, occasional direct seeding (oDS) of faba bean into a straw mulch of residues from precrop oats should be scrutinized. A one-factorial field trial with four replicates was carried out 2010 at the organic research farm Wiesengut of the University of Bonn in Hennef/Sieg. Direct seeding was performed into mulch layers of 0, 4 and 6 t ha-1 of straw residues, respectively. Mouldboard ploughing combined with conventional seedbed preparation was used as control. Compared with the oDS treatment without straw residues, oDS treatments with straw residues (4 and 6 t ha-1) reduced weed density by about 40 and 63% after five assessments (not significant). Compared with the control weed shoot dry matter in oDS treatments were lower. No difference was determined between oDS treatments. Shoot dry matter and grain yield of oDS faba bean treatments with straw residues did not differ from the control. Results suggest that oDS of fababean into straw residues from precrop oats can sufficiently control annual weeds without relevant crop yield reduction compared with mouldboard ploughing
