Cropping diversity is a main driver of soil health under intensive organic cropping systems

Abstract

The ability of organic cropping systems to sustain soil health may vary with management intensity. Little research has examined the impact of varying management practices on soil health within intensive organic field crop production systems. A field survey was conducted in the fall of 2019, 2020, and 2021 on 10 certified organic farms in Québec, Canada. Their cropping systems comprised an intensive three-year maize (Zea mays L.)-soybean (Glycine max [L.] Merr.) – small grain (i.e., winter or spring cereals) rotation. On each farm, soil health was measured on the three rotated crop fields in the fall of 2019, 2020, and 2021 (n = 90). The relationships between soil health indicators and indices of management practices were assessed. The 3-year Crop Diversity Index (CDI) ranged from 2 to 16 across the sampled fields, with the highest values observed where cover crops were used annually, and winter cereals were included in the rotation. Soil physical health indicators were positively influenced by higher CDI values. In contrast, higher Soil Tillage Intensity Ratings for tillage (STIR_tillage) had a negative effect on soil organic carbon (SOC) concentrations. Soil health indicators did not vary among crop phases, except for water-stable aggregates (WSA) which was greater in small grain fields (43.5 %) than in soybean fields (33.9 %). The results from this study demonstrated that soil health was positively influenced by increased crop diversity and reduced tillage intensity. These findings will help organic growers choose and refine best management practices to maintain soil health when cropping intensively.