Magnitude and mechanisms of persistent crop sequence effects on wheat

摘要: Abstract The impacts of broadleaf crop, pasture or fallow breaks within cereal-based cropping systems are widely acknowledged, but most studies have focussed on the first cereal crop after break. We report a series four field experiments in semi-arid zone Southern Australia which range Year 1 sequence options (crops, and fallow) 3 4 wheat crops were investigated. In three experiments, two phases same experiment commenced successive years, providing seven phases. (at sites), treatments influenced yield by 0.6, 0.9 0.9 t ha−1, although different responses between at sites provided clear evidence significant seasonal interactions. Interactions with tillage, species/varieties and/or added P-fertiliser intervening years also occurred some sites. largest persistent related to preservation differences residual nitrogen (N), cases water following through subsequent dry seasons, frequent experimental Higher N levels legumes canola could persist for 2–3 induce penalties due “haying-off” when experienced spring conditions. Such effects offset increased depth. Increases root diseases take-all (Gaeumannomyces tritici) rhizoctonia (Rhizoctonia solani AG8) persisted seasons reduced experiments. found no role arbuscular mycorrhizal fungi crops. demonstrate that large (>0.5 t ha−1), both positive negative, can 3–4 environments as result water, disease inoculum legacies choices. Prolonged periods help preserve these legacies, so unpredictable will be feature areas variable climates.