Fire and iron: tools for disease management?
Large volumes of crop residue are often managed using tillage or burning. This study examined the effect of these practices on diseases of barley [leaf spots, Pyrenophora teres Drechsler and Cochliobolus sativus (Ito & Kuribayashi)] and canola [blackleg, Leptosphaeria maculans (Desmaz.) Ces. & De Not.; sclerotinia stem rot, Sclerotinia sclerotiorum (Lib.) de Bary]. The trials were conducted at Birch Hills and Star City, SK for 5 years with treatments of: zero (ZT) and conventional (CT) tillage, and burning (B) or no burning (NB) of previous crop residue. At each site an experiment for barley and for canola was established and a 2-year rotation followed between these crops. In barley, leaf spot severity was slightly lower under ZT than CT at 3 of the 6 site-years (SY) where leaf spot symptoms occurred, and higher under the B treatment than NB at 1 SY, but no significant treatment difference was detected at the other SYs. ZT resulted in a higher seed yield than CT at 6 of 9 SYs, but there was little relationship between leaf spot severity and barley yield. Yield was higher in the NB than the B treatment at only 1 SY. At 2 SYs, yield was higher for the ZT-B treatment than the other treatment combinations. In canola, moderate sclerotinia stem rot incidence occurred at only 1 SY, and blackleg incidence did not show a consistent pattern with treatment. Canola yield was higher under ZT than CT at 3 SYs, but B had no consistent impact. We conclude that use of fire to manage the diseases of barley and canola assessed in this study was not effective. ZT sometimes increased the severity of leaf spots on barley but had little impact on blackleg of canola. The impacts of tillage and residue burning on diseases were generally inconsistent and the magnitude of the reduction in disease usually small. Crop yield was more frequently impacted by tillage system than residue burning.
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