Pea cultivar and wheat residues affect carbon/nitrogen dynamics in pea-triticale intercropping: A microcosms approach.
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The underlying mechanisms by which legume cultivars contribute to nitrous oxide (N2O) generation are poorly understood. The aim of the present study was to explore the effects of two pea cultivars (Zero4 and Nitouche) intercropped with triticale, with or without wheat (Triticum aestivum) residues incorporation, on soil C and N dynamics, on bacterial community structure and their links with N2O 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, ecophysiological indexes) were followed throughout a 97-day microcosm experiment carried out on a loamy arable soil. ARISA community fingerprinting of soil extracted DNA and GHG emissions were carried out at two key stages (pea flowering and harvest). The addition of residues to the soil resulted in only small changes to the total C and N pools the Nitouche monocrop, which was found to have the highest potentially mineralisable N (13.4gg-128d-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 two intercropping treatments of triticale/pea were significantly different either with residues or without, especially the triticale/Zero4 which had the lowest values (356gN2O-Nha-1). Similar patterns were also observed in below ground data. ARISA analysis showed that monocropped legumes and the Triticale-based treatment clearly grouped on separate clusters to the added residue treatment. We hypothesize that in pea-based intercrops variations in carbon supply from different cultivars may contribute to differences in N2O emissions and thus influence the choice of suitable cultivars, to optimize nutrient cycling and sustainable crop management.
