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Submitted to: HortScience
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/11/2010 Publication Date: 5/3/2010 Citation: Schreiner, R.P. 2010. Foliar application of phosphorus has minimal impact on 'Pinot noir' growth, mycorrhizal colonization, or fruit quality. HortScience. 45:815-821. Interpretive Summary: A three-year field trial was undertaken in low P soils to determine whether Phosphorus (P) applied to the foliage of grapevines could boost vine P status, and if so, alter vine root colonization and benefit derived from beneficial, arbuscular mycorrhizal fungi (AMF). Foliar P applications increased vine P status as measured in leaves and petioles at one site where P was applied with a hand-sprayer, and this led to a reduction in root colonization by AMF. Vine P status and root colonization by AMF were not altered after foliar P applications at a commercial vineyard where P was applied using an air-blast sprayer. The uptake of other vine nutrients and vine water stress was not influenced by foliar P applications at either site. It can be concluded that the small negative effect observed on AMF colonization patterns after the application of P to grapevine canopies will likely have little impact on overall vine physiology or fruit quality. These findings also suggest that foliar application of P is not an efficient way to improve P uptake by grapevines, even in low P soils. Technical Abstract: Grapevines grown in low phosphorus (P) soils typical of western Oregon vineyards may benefit from additional P applied to the canopy using foliar sprays. Alternatively, vines may be negatively affected by foliar P sprays because lower root colonization by arbuscular mycorrhizal fungi (AMF) could reduce uptake of other nutrients or increase vine water stress. The impact of foliar P sprays on vine growth, nutrient status, AMF colonization, drought stress, and fruit yield and quality was studied in two 'Pinot noir' vineyards with a history of low vine P status over three years. Three foliar spray treatments (phosphite, phosphate, water[control]) were applied to vines three times each season using a standard air-blast sprayer at a commercial vineyard. Two foliar spray treatments (phosphite, water) were applied using a hand sprayer at a smaller research vineyard. Phosphite sprays increased leaf and petiole P concentrations and reduced arbuscular colonization of roots at the research vineyard, but neither phosphate nor phosphite significantly affected these variables at the commercial vineyard. Foliar P sprays had no effect on vine growth, vine water relations (leaf water potential and stomatal conductance), yield, or fruit quality attributes at either site. These results indicate that there is little benefit to spraying the canopy of grapevines with P, even in vineyards with low P status. |
