Agronomy Library > Soil Conservation

Crop Rotation and Fertility Effects on Leaf Spot Diseases in Southwest Saskatchewan
Author: Fernandez, M.R., Zentner, R.P., McConkey, B.G., and Campbell
Date Created: February 13, 1998
Last Reviewed: February 28, 2007

Document Source: Canadian Journal of Plant Science. 78 (3): 489 - 496

Summary
The effects of crop sequence, summer fallow frequency, and fertilizer application, on the severity of leaf spotting diseases of spring wheat were investigated in Canada:

- In the field, Pyrenophora tritici-repentis (tan spot), was the most commonly isolated pathogen from leaf lesions followed by Phaeosphaeria nodorum (septoria).

- Leaf spot severity was higher after fallow than in continuous wheat monoculture or in wheat after a non-cereal crop. The percentage of leaf area with spots on crops grown after wheat was higher than in crops grown after flax or lentils in years with high disease pressure (1995 and 1996), but not in 1993 or 1994, when overall disease levels were low. 

- Under soil N-deficient conditions, leaf spot levels increased in years with dry summers (1994 and 1996).

- P-deficiency decreased leaf spot severity in years that had cool and wet springs (1995 and 1996).

It is concluded that the use of fallow, or 1-year rotation with a non-cereal crop, does not significantly reduce leaf-spotting disease of spring wheat in southwestern Saskatchewan. The best rotation aimed at reducing the levels of disease appeared to be 2 consecutive years of spring wheat, followed by a least 2 years of a non-cereal crop, or a non-cereal crop and summer fallow.