EFFECTS OF INCORPORATING STRAW, USING DIFFERENT CULTIVATION SYSTEMS, AND OF BURNING IT, ON DISEASES OF WINTER BARLEY

An experiment at Rothamsted in 1985-89 and another at Whaddon in 1986 studied the effects of incorporating straw on diseases of winter barle y. Net blotch (Pyrenophora teres) and leaf blotch (Rhynchosporium seca lis) were initially less severe where straw was burnt or incorporated by ploughing than where cultivations only partially buried it. However , by summer both diseases were usually more severe where straw had bee n burnt than where it had been incorporated. At Whaddon, eyespot (Pseu docercosporella helpotrichoides) tended to be less severe in tine-cult ivated plots where straw was incorporated than where it was burnt, but at Rothamsted, where the straw treatments were confounded with cultiv ations, there was no consistent effect. The disease was usually more s evere where straw was incorporated by ploughing than where it was inco rporated using other methods. In contrast, the severity of take-all wa s generally decreased by ploughing. Seedlings usually grew better wher e straw had been burnt rather than incorporated and grain yields were often larger. However, yields at Rothamsted in 1987 were unusually, an d inexplicably, smaller after burning the straw so that the 5-year mea n yields showed no significant differences between treatments.