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Abstract
Apple trees (Malus domestica Borkh.) grown in soil to which As was added decreased in size with each As addition to a total of 100 ppm, above which there was no growth. Trees grown in As-contaminated field soils tolerated much higher soil As levels, indicating about 60% of the soil As was not available. Correlation between tree growth and soil As was poor, with an “r” value of about 0.35. Greenhouse trials with corn on these soils indicated a much closer relationship, with an “r” value of about 0.70. Factors other than As in contaminated field soils probably have more influence on apple tree growth retardation than soil As.
Abstract
‘Golden Delicious’ apple trees (Malus domestica Borkh.) growing in gravel culture required a minimum of 0.088% P in mature leaves for continued shoot growth. Immature leaves were found to be a better index of P nutrition than mature leaves. A correlation of r = 0.959 was obtained between growth as indicated by increase in trunk circumference and percentage P over the range of 0.05 to 0.35% P in immature leaves and r = 0.84 over the range 0.055 to 0.188% P for mature leaves.
Abstract
Zinc fertilization (5 ppm) of apple seedlings (Malus sp.) grown in chloropicrin-fumigated soil increased shoot weight slightly and Zn concentration significantly after 70 days. Inoculation of seedling with vesicular-arbuscular mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, or G. fasciculatus (Thaxter) Gerd. & Trappe without Zn fertilization increased shoot weight but not plant Zn concentration. Zinc fertilization plus mycorrhizal inoculation increased shoot weight and Zn concentration. Total Zn uptake was increased 7 fold by combined Zn fertilization and G. fasciculatus inoculation. G. mosseae was slightly less effective than G. fasciculatus in promoting seedling growth.
Abstract
‘Golden Delicious’ apple trees sprayed with 50 ppm 2,3,5-triiodobenzoic acid (TIBA) 28 days after bloom had pitted fruit at harvest, but comparable control trees had none. The appearance of the pits on the fruit was similar to bitter pit. TIBA decreased the fruit Ca content and increased fruit B content. Decrease in Ca content by TIBA probably caused the development of bitter pit on the fruit.
Abstract
The growth of apple seedlings (Malus domestica Brokh.) is negatively correlated with soil arsenic and zero growth occurs at about 450 ppm total arsenic. Soil arsenic concentrations less than 150 ppm, which are frequently found in orchard soils, contribute less to the replant problem than biological factors. Growth of apple trees was increased 50% or more by preplant soil fumigation with methyl bromide or trichloronitromethane (chloropicrin) in 87.5% of the trials in 17 apple orchard soils tested. Non-specific plant pathogens in orchard soils attack cereals as well as apple seedlings, but apple orchard soils also contain an entity that specifically affects apples. This is probably the same unknown entity that is responsible for specific apple replant disease in Europe, Australia, and elsewhere.
Abstract
In early September 1963, extensive leaf drop on Winesap apple trees was reported from an orchard in Yakima County, Washington. Later a high percentage of fruit dropped prematurely, and the remaining fruit failed to color and mature normally.