Influence of cropping system on sharp eyespot in winter wheat

Abstract

Wheat was assessed for sharp eyespot in three field trials using factorial designs which investigated preceding crops and soil tillage effects (inversion vs non-inversion), soil structure (compacted vs non-compacted) and wheat management techniques (sowing date and density, nitrogen fertiliser rate and form, removal or burial of cereal straw). A previous host vs non-host crop increased sharp eyespot. The effect of soil tillage depended on crop succession: if the previous crop was a host, soil inversion vs non-inversion decreased disease by burying infectious host crop residues; if the previous crop was a non-host itself preceded by a host, soil inversion vs non-inversion increased disease by carrying infectious material back to the soil surface. Uncompacted vs compacted soil increased sharp eyespot, but only at early stages. Early sowing always increased disease. High plant density (giving rise to low tillering) increased early and decreased late disease levels. A high vs low nitrogen rate and a low vs high ammonium content of the fertiliser slightly increased sharp eyespot. Removal or burial of straw did not affect disease. A hierarchy of the factors was established: crop succession and soil tillage were dominant factors; among the wheat management practices, only sowing date and plant density had important effects.