Long-term straw management effects on yields of sequential wheat (Triticum aestivum L.) crops in clay and silty clay loam soils in England

The incorporation of chopped wheat (Triticum aestivum L.) straw into soil by tine cultivation (non-soil inversion) or ploughing was compared with burning straw followed by tine cultivation at six sites in England over a period of 11 years. Three sites had clay soils and three silty clay loam soils. Effects of straw management on weed incidence, take-all (Gaeumannomyces graminis var. tritici) infection and grain yield of following wheat crops and occasional break crops were studied. Soil mineral nitrogen and organic matter contents were measured at the end of the study. Incorporating straw by tines rather than burning reduced mean yield at all but one site. The yield reduction from tine incorporation ranged from 5 to 8% on clay soils and 3-18% on silty clay loam soils. Ploughing straw into soil only had an occasional adverse effect on yield of following crops. Much of the yield penalty associated with tine incorporation of straw was attributed to weed competition by Bromus spp. Difficulties in preparing a good seedbed, resulting in variable plant emergence, was the other main cause of lower yields with tine incorporation and in situations where plough incorporation reduced yields compared to burning straw. Method of straw disposal had no consistent effect on take-all infection. The effects of straw incorporation on soil mineral nitrogen and organic matter contents were small and inconsistent. There was no consistent effect of straw management practice on yield response to additional autumn application of nitrogen fertiliser. These results demonstrate that on those soils where ploughing is preferred, it is a suitable option for disposing of straw. Where non-ploughing methods have traditionally been used after straw burning they can still be employed with success, but occasional ploughing or planting of suitable break crops may be required to control grass weeds.