Evidence from crop sequences with different land occupations: soybean sudden death syndrome and soil microbial community

Aims Crop rotations and cover crops influence the chemical and biological characteristics that define soil health, with the rhizosphere playing a crucial role in plant defense mechanisms. Soybean sudden death syndrome (SDS) caused by species of Fusarium, leading to substantial yield loss in major soybean-producing countries. The objective was to assess the long-term effects of crop sequences with different land occupations on SDS occurrence and soil microbial community composition. Methods Research was conducted over three agricultural seasons in a long-term field experiment on four crop sequences: full-season soybean monoculture (S-S); winter cover crop/full-season soybean (CC/S); full-season soybean - double-cropped wheat/soybean - maize (S-W/S-M), and winter cover crop/full-season soybean - double-cropped wheat/soybean - maize (CC/S-W/S-M). Incidence of soybean SDS (SDS-I) was measured as the percentage of plants exhibiting foliar symptoms. Soil microbial community composition was characterized through phospholipid fatty acid (PLFA) analysis. Additionally, soil organic carbon and nitrogen and, full-season soybean production were assessed. Results The highest percentage of SDS-I was significant for CC/S and CC/S-W/S-M. Total microbial biomass showed the highest value for sequences that included CC compared to S-S. Generalized Procrustes analysis was utilized to investigate the consensus among crop sequences, primarily distinguishing CC (CC/S and CC/S-W/S-M) from the others. Conclusions Even when crop rotations were observed to affect the microbial biomass nutrient contents, there was an increase in the incidence of SDS for sequences that included the cover crop. Therefore, the progression of this disease needs further analysis concerning the inclusion of cover crops and previous crops.