Abstract
Including pulse crops in cereal-based cropping systems has become a widely accepted and useful agronomic practice to increase crop diversification and biologically fixed nitrogen in agroecosystems. However, there is a lack of knowledge regarding how the intensification of pulses in crop rotations influence soil microbial communities. In this study, we used an amplicon sequencing approach to examine the bulk and rhizosphere soil bacterial and fungal communities from the wheat (Triticum aestivum L.) phase (final year of 4 years rotations) of a long-term pulse intensification field trial in the semi-arid region of the Canadian Prairies. Our results revealed pulse frequency had a minimal impact on microbial α-diversity, but caused a significant shift in the composition of the fungal (rhizosphere and bulk soil) and bacterial (bulk soil) communities. This effect was the most pronounced in the Ascomycete and Bacteroidete communities. Increasing pulse frequency also promoted a higher proportion of fungal pathotrophs in the bulk soil, particularly those putatively identified as plant pathogens. The network analysis revealed that rotations with higher pulse frequency promoted increased competition within the soil microbial networks in the rhizosphere and bulk soil. However, we also detected more negative interactions among the dominant pathotrophic taxa with increased pulse frequency, suggesting higher soil-borne disease potential. These findings highlight the potential drawbacks and reduced sustainability of increasing pulse frequency in crop rotations in semiarid environments.
Highlights
Among agronomic practices used in annual cropping systems, crop rotation is one of the most common management tools used to enhance soil nutrient and water availability, control weeds and pests, and improve the ecological and economic sustainability of cropping systems (Schönhart et al, 2011; Barbieri et al, 2017)
Despite the important role that crop rotations play in sustainable agriculture (Drinkwater et al, 1998; Foyer et al, 2016), there is still a lack of systematic analysis on how pulse crops influence soil microbial community dynamics (Hamel et al, 2018)
The results from our study provide insight into how pulse frequency in crop rotations impacts the soil microbial community, their diversity, interactions, potential eco-functions and relationship with environmental factors
Summary
Among agronomic practices used in annual cropping systems, crop rotation is one of the most common management tools used to enhance soil nutrient and water availability, control weeds and pests, and improve the ecological and economic sustainability of cropping systems (Schönhart et al, 2011; Barbieri et al, 2017). This trend has been evident in the Northern Great Plains for pulse crops such as field pea (Pisum sativum L.), lentil (Lens culinaris Medik.), and chickpea (Cicer arietinum L.), which are common grain legume crops that have been used to diversify cereal and oilseed cropping systems (Khakbazan et al, 2020). It is essential to select the right type of pulse crops for the rotation design and ecosystem, and incorporate them at an appropriate frequency to achieve the potential ecological and economic benefits linked to these crops. This type of information is still very limited, from long-term field studies
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