R. Paul Schreiner,* Tian Tian, Santosh Kalauni, Devin Rippner, and Elizabeth Gillispie
*USDA-ARS, 3420 NW Orchard Avenue, Corvallis, OR, 97330
(paul.schreiner@usda.gov)

Grapevine roots are heavily colonized by symbiotic arbuscular mycorrhizal fungi (AMF) that enhance nutrient uptake, especially of phosphorus (P). However, their role in the uptake of other nutrients, including nitrogen (N) and potassium (K), is unclear. Further, knowing how fertilizers added to vineyards alter AMF and their ability to supply nutrients is important to develop sustainable nutrient management practices. Data from numerous vineyard trials and controlled greenhouse studies are summarized here to provide a clearer picture of how best to manage AMF and vine nutrition. In vineyard trials, N additions to soil, but not to foliage, reduced AMF colonization in roots and, in some cases, this reduced vine P status. Foliar P additions in vineyards reduced AMF colonization, and foliar P additions in greenhouse trials rapidly reduced arbuscules in roots. However, adding P fertilizer to soil in a recent vineyard study had no negative impact on AMF in roots. A recent trial indicated that K fertilizer additions to soil had no impact on AMF in roots. These results contrast with findings under controlled conditions, where we have shown that AMF vastly improve vine P uptake, often improve K uptake, but do not improve N uptake by grapevines. AMF have also improved uptake of zinc and copper in controlled studies. Soil N inputs appear to have an outsized impact on AMF in grapevines compared to soil P or K, even though AMF do not appear to enhance vine N uptake. Therefore, soil N additions to vineyards should be managed carefully to maintain AMF and ensure that N use does not interfere with uptake of other nutrients. These findings will be discussed in light of sustainable nutrient management in vineyards and the regulation of AMF by grapevines.

Funding Support: USDA-ARS