Abstract
Cover crops (CC) provide important ecosystem services that are demanded to achieve more sustainable agrosystems. However, the legacy effects of CC on the microbial community structure and its interactions with the subsequent cash crops (CaC) are still poorly understood, especially when CC mixtures are involved. In this work, five CC (3 monocultures and 2 mixtures) were selected in an experiment under semi-controlled conditions to investigate if CC monocultures and mixtures differed in their effects on soil and crop variables and if the identity of the subsequent crop modulates these effects. The two most consumed crops worldwide, wheat and maize, were sown separately after CC. The legacy effects of CC on the studied microbial variables largely depended on the interaction with the CaC. The vetch and the barley-vetch mixture stood out by providing the microbial conditions that enhanced the absorption of macro- and micronutrients, to finally seek the highest wheat biomass (>80% more than the control). In maize, the effects of CC on soil microbiota were more limited. The soil microbial responses for CC mixtures were complex and contrasting. In wheat, the barley-vetch mixture behaved like barley monoculture, whereas in maize, this mixture behaved like vetch monoculture. In both CaC, the barley-melilotus mixture differed completely from its monocultures, mainly through changes in archaea, Glomeromycota, and F:B ratio. Therefore, it is necessary to deepen the knowledge on the CC-CaC-microbial interactions to select the CC that most enhance the sustainability and yield of each agrosystem.
Highlights
The study of cover crops (CC) is booming due to their potential to improve the sustainability of agricultural systems and to contribute to mitigation and adaptation to climate change
The benefits for arbuscular mycorrhizal fungi (AMF) differ according to the host Cover crops (CC), for example, legume CC can increase the abundance of AMF [18,19], but the ability to inoculate them in the subsequent crop seems to be lower than that of grasses in a Mediterranean climate [20]
Regarding the abundance of genes related to the large groups of the microbial communities, we found that the abundance of bacteria showed its lowest values in both CC mixtures, whereas CON and CC monocultures showed similar values
Summary
The study of cover crops (CC) is booming due to their potential to improve the sustainability of agricultural systems and to contribute to mitigation and adaptation to climate change. Most CC serve as hosts for AMF and, can help to maintain or increase the inoculum potential of these important microorganisms in subsequent crops [14]. In this way, the ecosystem services provided through AMFs are enhanced, such as nutrient absorption [14,15], stress resistance, soil aggregation [16], or pathogen control [17]. The benefits for AMFs differ according to the host CC, for example, legume CC can increase the abundance of AMF [18,19], but the ability to inoculate them in the subsequent crop seems to be lower than that of grasses in a Mediterranean climate [20]. The mixture of different species influences the composition of the soil microbiota [24,25,26], and has positive effects such as the increase in the microbial biodiversity [22]
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