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  • Author or Editor: R. P. Covey x
  • Journal of the American Society for Horticultural Science x
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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.

Open Access

Abstract

Symptoms of 2,4-D injury were observed on apple and pear trees following commercial herbicide application. This was thought to be due to absorption from the soil. 2,4-D was found to move easily into orchard soils when applied to soil columns and irrigated. Concentrations in excess of 0.5 ppm occurred. Apple trees were damaged by this concentration. 2,4-D is readily inactivated in moist soil or on a moist soil surface. Less than one week is required for deactivation. Although field observations always indicated injury occurred when both 2,4-D and paraquat were applied together, laboratory and greenhouse studies indicated that paraquat did not increase 2,4-D movement or slow its deactivation.

Open Access

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.

Open Access

Abstract

Apple trees (Malus domestica Borkh.) grown in soil fumigated with methyl bromide showed a significant increase in growth as measured by trunk circumference. The increase in trunk circumference from fumigation varied from 33 to 49% after 6 to 8 years. Fruit production increased from 2- to 4-fold during the same period. Soil pH, soil arsenic and nematode counts were not considered to be major factors in the lack of growth and fruit production for trees grown in unfumigated soil.

Open Access

Abstract

Glomus mosseae (Nicol & Gerd.) Gerd. & Trappe, inoculation increased apple (Malus domestica Borkh.) seedling growth in 3 of 5 fumigated orchard soils without supplemental phosphorous. Mycorrhizae improved seedling growth in only one soil receiving additional P. Increasing P rates up to 100–200 mg/kg improved growth in only one soil receiving additional P. Increasing P rates up to 100–200 mg/kg improved growth of nonmycorrhizal-treated apple seedlings in 4 of 5 soils tested. The 5th soil had an adequate P content, 60 mg/kg soil prior to the addition of P. Mycorrhizal root infection of seedlings growing in soil that received G. mosseae inoculum decreased with increased P rates applied. Some infection was found in seedlings from all soils inoculated with mycorrhizae at P rates of 0–400 mg/kg, and seedlings from 2 of the mycorrhizal soils had infection at the P rate of 600 mg/kg.

Open Access