Pea cultivar and wheat residues affect carbon/nitrogen dynamics in pea-triticale intercropping: A microcosms approach

The underlying mechanisms by which legume cultivars contribute to nitrous oxide (N2O) generation are poorlyunderstood. The aim of the present study was to explore the effects of two pea cultivars (Zero4 and Nitouche)intercroppedwith triticale, with or withoutwheat (Triticumaestivum) residues incorporation, on soil C and N dynamics,on bacterial community structure and their linkswithN2O emissions.Monocrops and bare soil (no plant)treatments were used as an additional control in order to account for the level of mineralisation between treatments.Changes in total C and N contents and in some functionally-related soil pools (microbial biomass C and N,basal respiration, KCl-exchangeable ammonium and nitrate, potentially mineralisable N, DOC, ecophysiologicalindexes) were followed throughout a 97-day microcosm experiment carried out on a loamy arable soil. ARISAcommunity fingerprinting of soil extracted DNA and GHG emissions were carried out at two key stages (peaflowering and harvest). The addition of residues to the soil resulted in only small changes to the total C and Npools the Nitouche monocrop, which was found to have the highest potentially mineralisable N (13.4μg g−1 28 d−1) of the treatments with added residue. The different pea cultivar selectively affected N2O emissions,with highest emissions associated with the cultivar Nitouche in the absence of residues. The twointercropping treatments of triticale/pea were significantly different either with residues or without, especiallythe triticale/Zero4 which had the lowest values (356 g N2O-N ha−1). Similar patterns were also observed inbelowground data. ARISA analysis showed thatmonocropped legumes and the Triticale-based treatment clearlygrouped on separate clusters to the added residue treatment. We hypothesize that in pea-based intercrops variationsin carbon supply from different cultivars may contribute to differences in N2O emissions and thus influencethe choice of suitable cultivars, to optimize nutrient cycling and sustainable crop management.