No differences in soil structure under winter wheat grown in different crop rotational positions

Yield decline in wheat grown after wheat is frequently attributed to fungal disease occurrence, but it is also found without visible disease infection. Thus it is hypothesized, that other factors such as N supply or soil structural degradation may lead to wheat yield decline when grown after wheat. The aims of this study were to analyze if (i) the crop rotational position of winter wheat causes differences in soil structure at the beginning of the growing season and (ii) the soil structure is related to differences in wheat biomass formation by this date. Different soil structural properties under winter wheat as well as total aboveground biomass of wheat grown in different crop rotational positions (monoculture, first, second and third wheat after oilseed rape) were investigated in two long-term field experiments with contrasting soil texture. At both field sites no significant effect of the crop rotational position in any of the analyzed soil structural parameters was found. Wheat biomass in spring was on average 54% higher for wheat grown after oilseed rape compared to second and third wheat after oilseed rape or monoculture. In conclusion, growth reduction of wheat cultivated after wheat was not linked to soil structure as measured in spring.