Field crop disease management with rotation, tillage, and fungicides
The impact of tillage, rotation, and fungicides on diseases and yield of wheat, barley, pea and canola were determined in an ongoing field study at Melfort in 1998 and 1999. A split-split plot design was used with conventional, minimum and zero tillage systems as main-plots, rotations (1 - canola, wheat, barley, barley; 2 - canola, barley, pea, wheat; and 3 - canola, pea, flax, barley) as sub-plots and fungicide treatments as sub-sub plots. The fungicides Tilt (propiconazole) for cereal foliar diseases, Quadris (azoxystrobin) for mycosphaerella blight of pea and blackleg of canola, and Ronilan (vinclozolin) for Sclerotinia stem rot of canola were applied at recommended rates and crop development stages. Tillage system had little impact on diseases of any of the crops examined except common root rot of barley, which was less severe under reduced tillage. Barley foliar disease levels were greater and yields lower in rotation 1 than either rotations 2 or 3. This indicates the benefit of a more balanced rotation of broadleaf crops and cereals over the cereal based rotation containing 2 barley crops in four years. Rotation had little impact on diseases of other crops, all of which were grown only once in each four year rotation. Fungicides reduced blackleg of canola in both years and Sclerotinia stem rot in 1998 but yield was only increased marginally in 1999. Canola diseases were not affected by tillage system or rotation. Fungicides had greater impact than tillage or rotation on diseases of wheat, barley and pea, reducing foliar disease severity and increasing yield in both 1998 and 1999. In summary, the results of this study demonstrate that fungicides had greater impact on crop diseases and yields than the tillage systems or rotations.
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