Winter cereals in autumn: dealing with black-grass and manganese deficiency

Crop advisers at the agricultural office in Ravensburg, southern Germany, Maria Längle, Stefanie Löbner and Markus Kreh, have set out what farmers should do with winter cereal crops in November. The key issues are controlling black-grass (a troublesome grass weed) and manganese deficiency in winter barley, according to the German farming portal agrarheute.

Black-grass: when a follow-up treatment is needed

In many regions the sowing of winter cereals is largely complete. On fields drilled within the past ten days, some pre-emergence or early post-emergence herbicide work may still be due. For crops sown by early October that have reached BBCH 12 (the growth stage with two leaves unfolded), farmers should check how well the earlier herbicide treatment worked, paying particular attention to known problem spots and black-grass patches.

The approval for herbicides containing flufenacet has expired. They may be used only until early December 2026, and unused remnants must be disposed of through hazardous-waste collection.

If black-grass is still vital and well rooted more than 14 days after treatment with flufenacet, diflufenican and/or prosulfocarb, a follow-up with chlortoluron may make sense. It acts through soil and leaves, and works best before the weeds develop a second leaf. Not all winter wheat varieties tolerate chlortoluron. If about 120 g of diflufenican was already applied the first time, it should be omitted from the follow-up, which rules out products such as Carmina and Trinity. The advisers name Lentipur 700 and CTU 700, without diflufenican, as alternatives. From November, chlortoluron products may no longer be applied to drained fields, a rule enforced through sampling.

For more advanced weeds, Axial 50 works better in winter barley and Traxos is an option in winter wheat. The advisers recommend saving both for spring to protect against resistance.

Manganese deficiency in winter barley

Yellowish, stunted barley can point to manganese deficiency. A typical sign is barley staying clearly greener in compacted wheel tracks than in the rest of the field. The problem is more likely on light soils with insufficient consolidation. Loose, dry conditions and possibly a high pH promote manganese oxidation, making it less available to plants.

Affected plants develop weaker roots, often lag behind in spring and yield less on the affected areas. Manganese fertilisation can begin at tillering or from the three- to four-leaf stage, using foliar micronutrient fertiliser, preferably with manganese in nitrate or sulphate form. Chelate products exist but are usually pricier. Epsom salt supplies magnesium and sulphur, but not manganese.