Phytotoxicity of horticultural oil, applied shortly before antifungal sulfur, was evaluated for 23 grape cultivars. Oil application significantly reduced accumulation of soluble solids in berries of 9 of 23 cultivars, but there was no relationship with visible foliar injury. Treatment of leaves of Vitis labrusca `Catawba' with 1.5% JMS Stylet-Oil reduced leaf net photosynthesis (Pn) by 50% to 60% and of Vitis vinifera `Chardonnay' by 20% to 30% 1 day after application. Pn was reduced only when the lower (abaxial) leaf surface was treated; treatment of only the adaxial leaf surface had little effect. The Pn depression in `Catawba' persisted 3 to 4 weeks, whereas reductions in `Chardonnay' persisted less than 2 weeks. The Pn-depressing effect of oil was not significantly ameliorated by real or simulated rainfall, and washing the lower leaf surfaces with water and detergent also had only limited effect. There was no significant difference in Pn depression from oil applications made in the middle of the day (stomata open) compared to application in the evening (stomata closed), or from oil applied at higher versus lower application pressure. The greater sensitivity of `Catawba' than `Chardonnay' to Pn depression by oil may be related to the amount of oil retained by the leaves; the pubescent lower leaf surfaces of `Catawba' retained more than twice as much spray emulsion as did the more glabrous leaves of `Chardonnay'. Visible injury was mild in both cultivars, with small water-soaked lesions developing more commonly on `Chardonnay' than on `Catawba' leaves. Spray oil retention data for additional cultivars suggested that differences in retention can explain a portion of the differences in horticultural oil phytotoxicity.

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Information about the use of alternative management practices (AOFMP) in perennial systems to manage soil biota and influence the uptake of nutrients is limited. The objectives of this study are to evaluate AOFMP on soil quality, focussing on soil biology, and on nitrogen uptake efficiency. Research plots are located in Lewis-Brown Farm (LB), Corvallis, OR (`Fuji' apple trees) and Mid-Columbia Ag. Research & Extension Cent. (HR), Hood River, OR (`Red Delicious' apple trees). Main plot treatments were weed control methods: herbicide or cultivation. Sub plot treatments were soil amendments: no amendment, bark mulch (BM), compost, and green vetch/barley mulch (VB). A split-plot completely randomized design with 3 replications was used. Depleted NH3 SO4 was applied to single-tree replicates at bud break in 2001, 2002, and 2003. Compost amended plots contained more fungivorous nematodes than other treatments, although this difference was not significant at LB. At both sites there was a significant interaction between main and sub plot treatments in the number of bacterivores. At LB, the interaction between main and sub plot treatments affected the number of enrichment opportunists and the F-ratio was affected by amendment. At HR, the structural index was also affected by amendment. Compost resulted in the most diverse populations. Soil respiration rates in compost and BM plots were consistently higher than in unamended and VB treated plots. Soil P, pH, and organic matter content were increased by compost amendment and bulk density was decreased. At HR mid-season leaves, fruit, and first year growth from compost treated plots contained the least nitrogen derived from fertilizer, followed by bark mulch. The highest nitrogen derived from fertilizer was in unamended plots.