|Smith, Richard - UNIVERSITY OF CALIFORNIA|
|Bettiga, Larry - UNIVERSITY OF CALIFORNIA|
Submitted to: International Symposium on Soil and Plant Analysis
Publication Type: Abstract Only
Publication Acceptance Date: 5/5/2009
Publication Date: 7/12/2009
Citation: Baumgartner, K., Fujiyoshi, P.T., Smith, R.F., Bettiga, L. 2009. VINEYARD FLOOR MANAGEMENT HAS MINIMAL EFFECTS ON MYCORRHIZAE. International Symposium on Soil and Plant Analysis.
Technical Abstract: Arbuscular mycorrhizal fungi (AMF) are one of few groups of soil microbes that have been shown to benefit grapevine nutrition. Grapevines respond positively to AMF, as evidenced by increased growth with inoculation. Furthermore, their low root density and coarse root texture reflect their relatively high mycorrhizal dependency. In a series of greenhouse studies with the stable isotope of Nitrogen, 15N, we demonstrated the role of AMF in grapevine nutrition. We found that AMF increase N-uptake from no-till cover crops, specifically when the fungal filaments (hyphae) connect cover crop roots to grapevine roots. AMF also increase uptake of N from decomposing cover crops after they are tilled into the soil. The fungal hyphae support other soil microbes that decompose cover crops and cycle nutrients, and at levels of microbial biomass as high as that of roots. In addition, AMF are responsible for a greater proportion of N-uptake from decomposing cover crops when grapevines are grown in low fertility soil than when they are grown in N- and P-sufficient soil. The findings of our greenhouse studies suggest that while roots are clearly most important for uptake of nutrients from till and no-till cover crops, AMF significantly increase nutrient uptake, especially in low fertility soils, and they have an equally important role in supporting microbial biomass. In the field, we find that vineyards support indigenous populations of AMF. However, increasing AMF populations and species diversity through manipulation of the vineyard floor cover has not been successful. Therefore, the prospects for enhancing AMF-mediated uptake of soil-derived nutrients in low fertility soils may be a challenge.