The role of arbuscular mycorrhiza in legume symbiotic performance

Product Description
This digital document is a journal article from Soil Biology and Biochemistry, published by Elsevier in 2006. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
Legumes may respond to non-rhizobial inoculants such as arbuscular mycorrhizal (AM) fungi either through an effect on plant growth or, in addition, through an effect on the function of the legume-Rhizobium symbiosis. We have examined the literature where the application of ^1^5N isotope dilution methodology permits the effect of indigenous AM and AM inoculants to be quantitatively separated into plant-growth-mediated and biological N”2 fixation (BNF)-mediated components. These studies clearly demonstrate the beneficial effects that both indigenous and inoculated AM have on legume growth, N uptake and the proportional dependence of the legume on atmospheric N”2. While the published data allow an assessment of various biological, edaphic and environmental factors that affect the response of various legumes to AM inoculation, they also highlight the paucity of quantitative field data and the lack of understanding of the interaction of legume genotype with AM species with respect to legume symbiotic performance.

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In situ carbon and nitrogen dynamics in ryegrass-clover mixtures: Transfers, deposition and leaching

Product Description
This digital document is a journal article from Soil Biology and Biochemistry, published by Elsevier in 2007. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
Carbon (C) and nitrogen (N) dynamics in a third production year ryegrass-clover mixture were investigated in the field. Cylinders (diameter 29.7cm) were installed to depths of 20, 40 and 60cm and equipped with suction cups to collect percolating pore water. Ryegrass and clover leaves were cross-labelled with ^1^4C- and ^1^5N-enriched urea and the fate of the two tracers was studied for 3 months during summer. Transfer of ^1^4C occurred mainly from ryegrass to clover, whereas the largest transfer of ^1^5N was in the opposite direction. The average transfer of N from clover was 40% (SE+/-3.1, n=9) of N in ryegrass, whereas the fraction of N in clover donated by ryegrass was 5% (+/-1.2, n=9). The amount of ^1^4C transferred from ryegrass to clover was 1.7% (+/-0.1, n=9) of the ^1^4C-activity in the total above-ground plant biomass found in the unlabelled clover and with a transfer from clover to ryegrass being 0.4% (+/-0.1, n=9). ^1^5N-enriched compounds were not detected in percolating pore water, which may be caused by either dilution from irrigation or low availability of leachable N compounds. ^1^4C was found solely as ^1^4CO”2 in the pore water indicating that dissolved organic carbon (DOC) did not originate from fresh root deposits. Transfer of ^1^4C between the two species in the mixed crop alongside with high transfer of ^1^5N despite a large percolation of pore water indicates that part of the N transfer occurred in non-leachable N-forms. The amount of N transferred between the two species was found to depend on the ratio between dry matter accumulated in the donating and receiving species, the ^1^4C-allocation within the receiving species and the root turnover rate in the soil.

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