Previous legume identity influences wheat protein content through organic matter depolymerization

In crop rotation systems, plant-soil feedback (PSF) effects can modulate nutrient cycling in soil, like organic nitrogen cycling. Organic nitrogen (N) is present in plant and microbial necromass, and it must be depolymerized by microbes to become available for crops. Since plant identity can modulate the microbial communities diversity and composition, we thought that previous crop identity would also change the microbial depolymerization capacity, and thereby impact soil N availability, and the quality and yield of the following crop. To test this, two legumes (Vicia faba L., i.e. faba bean, and Pisum sativum L., i.e., yellow pea) were grown in two fields in Abitibi-Temiscamingue, Quebec, Canada. During the following growing season, spring wheat (Triticum aestivum L.) was sown and received, or not poultry manure as an organic fertilizer. We determined the diversity and composition of the microbial communities and their enzymatic depolymerization capacity in the soil and the rhizosphere each growing season. During wheat growth, previous legumes shaped bacterial (p-value = 0.006) and fungal (p-value = 0.001) communities and modulated the enzymatic activity of wheat-associated rhizosphere microbes. Faba bean increased {beta}-glucosidase activities by up to 13% (1.13-fold) in the wheat rhizosphere compared to peas. Faba bean as a previous crop also increased wheat grain protein content at harvest by up to 0.17% as compared to peas. Altogether, our results show that faba beans, through lasting shifts in the microbial communities, can enhance microbial depolymerization activities in the wheat rhizosphere, impacting its N nutrition. Understanding plant-soil feedback in crop rotation systems is crucial to improve our practices and sustainably meet crops nutritional needs. Highlights- Previous crop identity distinctively shaped wheat rhizosphere microbial communities - Previous legume altered the wheat rhizosphere microbial depolymerization capacity - Wheat grain protein content was higher following faba bean than peas Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=123 SRC="FIGDIR/small/694934v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@189ddcorg.highwire.dtl.DTLVardef@23f971org.highwire.dtl.DTLVardef@1cd805aorg.highwire.dtl.DTLVardef@a5cd07_HPS_FORMAT_FIGEXP M_FIG C_FIG