Nitrogen capture by grapevine roots and arbuscular mycorrhizal fungi from legume cover-crop residues under low rates of mineral fertilization |
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Authors: | Xiaomei Cheng Amy Euliss Kendra Baumgartner |
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Institution: | (1) Department of Biological Science, Mount St. Mary’s College, Los Angeles, CA 90049, USA;(2) Agricultural Research Service, USDA, One Shields Avenue, Davis, CA 95616, USA |
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Abstract: | The influence of mineral fertilization on root uptake and arbuscular mycorrhizal fungi-mediated 15N capture from labeled legume (Medicago polymorpha) residue was examined in winegrapes (Vitis vinifera) in the greenhouse, to evaluate compatibility of fertilization with incorporation of cover-crop residue in winegrape production.
Plants grown in marginal vineyard soil were either fertilized with 0.25× Hoagland’s solution or not. This low fertilization
rate represents the deficit management approach typical of winegrape production. Access to residue in a separate compartment
was controlled to allow mycorrhizal roots (roots + hyphae), hyphae (hyphae-intact), or neither (hyphae-rotated) to proliferate
in the residue by means of mesh core treatments. Leaves were weekly analyzed for 15N. On day 42, plants were analyzed for 15N and biomass; roots were examined for intraradical colonization; and soils were analyzed for 15N, inorganic N, Olsen-P, X-K, and extraradical colonization. As expected, extraradical colonization of soil outside the cores
was unaffected by mesh core treatment, while that inside the cores varied significantly. 15N atom% excess was highest in leaves of roots + hyphae. In comparison, leaf 15N atom% excess in hyphae-intact was consistently intermediate between roots + hyphae and hyphae-rotated, the latter of which
remained unchanged over time. Fertilization stimulated host and fungal growth, based on higher biomass and intraradical colonization
of fertilized plants. Fertilization did not affect hyphal or root proliferation in residue but did lower %N derived from residue
in leaves and stems by 50%. Our results suggest that even low fertilization rates decrease grapevine N uptake from legume
crop residue by both extraradical hyphae and roots. |
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Keywords: | Legume residue Medicago polymorpha 15N Soil fertility Vitis vinifera |
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