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  • Author or Editor: D. Sugar x
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Tree growth and productivity in 'Doyenne du Comice' ('Comice') pear were not affected by kaolin (Surround WP) treatment programs consisting of applications at 30 or 60 g·L–1 of water applied either three or six times per growing season and repeated for 3 years. In 2 of 3 years, kaolin treatment programs reduced the extent of russet on the fruit surface, although the comparative effectiveness of different concentrations or numbers of applications was not consistent. It appears that kaolin treatment programs can be used in 'Comice' pear production without adverse effects on tree growth and performance. In a relatively high density planting (1098 trees/ha), 'Comice' pear trees growing on Pyrus calleryana rootstock were less yield-efficient and had lower bloom and crop density and fruit set than trees growing on Quince A (Cydonia oblonga) rootstock. Fruit from trees growing on P. calleryana were generally smaller and had less surface russet than did fruit from trees growing on Quince A.

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A study was undertaken to determine if microsprinkler irrigation (MI) can provide sufficient water and produce similar yield and quality of pear (Pyrus communis L.) fruit as flood irrigation (FI) in a cracking (shrinking-swelling) clay soil. Soil water content and fruit quality attributes were measured under MI and FI in 2 years. Water potential of the upper 120 cm (47 inches) of soil was maintained at 0.1 to 0.3 MPa (14.5 to 43.5 lb/inch2) through most of the growing season in both MI and FI treatments. MI and FI treatments did not differ in their effect on fruit size, yield, or firmness decline during cold storage. No consistent effect on fruit susceptibility postharvest fungal decay related to irrigation treatment was observed. MI has the potential to reduce chemical and water movement to groundwater, while providing sufficient water to produce satisfactory yield and fruit quality in a cracking clay soil.

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Mature `Comice' pear trees were given 4 l of a 5% urea solution enriched in 15N (0.6 atom percentage 15N) either as a soil application (S), a foliar application with the ground covered to prevent soil contamination (F), or as a foliar application with the ground uncovered (F+S). The treatments were applied in mid-October 1990 to 6 single replicate trees each. The following spring, flower buds from trees that received either F or F+S had 38% of their N from the applied fertilizer. Trees from the S treatment had no label in their buds. In 1991, half of the trees were removed and their components analyzed for total and isotopical N to estimate N recovery. The relative enrichment of different tree parts in 15N was similar for the three modes of application. This suggests that unlike fall foliar applied N, reserve N is more uniformly distributed within the tree. N recovery depended more on tree biomass (r2 = 0.89, P = 0.001) than on the mode of fertilizer application. There was also a positive correlation between tree vigor and fruit N content.

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‘Bose’ pear fruits (Pyrus communis L.) grown in northern Oregon (NO, Hood River) and southern Oregon (SO, Medford) were harvested during the commercial harvest period and stored in either 1 % O2 with trace CO2 or in 5 other controlled atmosphere (CA) regimes, O2/CO2 at 0.5%/0%, 1.0%/0.5%, 1.5%/0.5%, 2.0/0.5%, and 2.5%/1.0%, for 6 months at −1°C in 1982, 1983, and 1984. Fruits from the NO were more susceptible to brown core (BC) disorder than those from SO. Late-harvested fruits, especially from NO, were more susceptible than early harvested ones. A low O2 concentration of <1% in CA storage without CO2 increased the potential for fruit to develop BC, and an elevated CO2 level enhanced the effect of low O2. Based on this study, it is recommended that ‘Bose’ pear fruits from NO can be safely stored in O2 not less than 1.5% with trace CO2 and those from SO in O2 as low as 1% with CO2 between 0 and 0.5% for 6 months at −1° with little probability of BC.

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