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- Author or Editor: R. E. Worley x
`Oconee' is a `Schley' × `Barton' cross from the USDA pecan breeding program and was tested as selection 56-7-72. It first bore in its 5th leaf and yields increased each succeeding year except year 11. Yields exceeded 23 kg/tree in year 10 and 12 and nut quality has been excellent each year. Percentage kernel averaged 56 with 26% (of inshell nut) grading fancy and 2% grading amber. `Oconee' is large with nuts averaging 9.7 g in wt. and 13 cc in volume with 71% 2.54 cm or larger in diameter. After mechanical cracking, nuts are easily shelled into large unbroken kernel halves. `Oconee' will pollinate `Cape Fear', `Stuart', `Desirable', `Kiowa' and `Sumner'. It is pollinated by `Sumner', `Stuart', `Maramek', `Kiowa', `Gloria Grande' and `Forkert'. `Oconee' should make an excellent temporary tree. More years data are needed to assess its merits as a permanent tree.
Fungicides, dodine, fentin hydroxide, captafol, and benomyl, gave adequate control of pecan scab caused by Fusicladium effusum Wint., using a 3-week spray schedule beginning April 22 and concluding August 5. Massive applications of dodine and captafol at bud break to replace the first 3 scheduled applications failed to give equivalent control of scab.
Leaf scorch symptoms are described. Control was excellent using any of the fungicides tested. Leaves of checks were severely damaged by scorch. It is suggested that 1 or more fungi are associated with the cause(s) of this malady. Fungicides increased quality by increasing percentage of edible kernel, reducing shuck damage, and increasing wt of nuts.
An Mg-N formulation (RES-20482) used as a 0.25 or 0.50% spray solution or when trunk injected at 5 ml/2.54 cm of trunk circumference did not significantly increase leaf Mg of pecan (Carya illinoensis (Wang.) K. Koch).
Three out of many pecan cultivars (Gloria, Pabst, & Stuart) were examined over long periods of time. The latter two cultivars have been planted since 1921 when the first pecan orchard was established. One tree of each of these cultivars were removed because of overcrowding. Gloria and Pabst were planted in 1954. Best production practices known were used until 1962. Fertilization and insecticide sprays were adopted. In 1970, spraying for disease was adopted. In 1974, drip irrigation and selective limb pruning were adopted. GrowSeason (GS) [(Year-Planted+l)-mean GS] was used in a linear (L), quadratic (Q), or cubic (C) model where the best model was chosen (significant F-test). Yield was expressed as cumulative yield. Older trees tended to produce more after 1962 (C trend), mid-aged trees more after 1970 (Q/C trend), and younger trees more after 1974 (L/Q trend). Younger trees had the greatest average yearly cumulative yield.
Pressure trunk injection of Zn sulfate solutions rapidly increased leaf Zn levels of Zn deficient trees in pecan (Carya illinoensis (Wang.) K. Koch). Injection of 2270 g/tree killed foliage and twig terminals within one week. New foliage growth appeared normal but was high in Zn. Injected Rhodamine B dye indicates that solutions move rapidly to the extremities of the tree. Injected wood preservative “Osmose” killed trees within 10 days.
Concentration of pecan roots in the 15-45 cm layer of soil and lower soil pH, P, and K in the 15-30 cm layer than in adjacent layers indicate that pecan trees are feeding primarily in this zone. Fertilization with N-containing complete fertilizers or NH4NO3 reduced soil pH gradually, and continued annual application gradually affected deeper soil layers. Phosphorus and K applications affected soil pH very little.
Continued annual applications of P gradually built up residual soil P (measured one year later) to high levels at all layers sampled for old trees over a 10-year period. When P applications were based on topsoil P levels, subsoil P level was not affected over a 5-year period.
Applications of K usually increased residual soil K, but rate effects were slow to appear in old trees and were often erratic. Rates of K were readily reflected in residual soil K levels at depths to 70 cm when rates were based on topsoil K level.
Magnesium sulfate applied as a soil amendment (34 kg Mg/ha annually for 3 years or a single application of 224 kg Mg/ha) increased leaf Mg 5 years after initial application. Dolomite increased soil pH and soil test Mg but not leaf Mg. Sulfate of potash magnesia and MgO increased soil test Mg and slightly, though insignificantly, increased leaf Mg. Single foliar sprays of MgSO4 and Mg(NO3)2 did not affect leaf Mg.
Mature pecan, Carya illinoensis (Wang.) Koch., grove management systems of 1) rotational summer grazing, 2) clean cultivation + winter legume, 3) winter or spring intercropping + summer cultivation, and 4) closely mowed sod affected yields differently in different years, but did not affect total yield or tree growth significantly over a 10-year period. Kernel quality, nuts/kg count, nut size, and tree growth were not affected consistently by management systems. Extra fertilization, particularly N, applied to grazed and intercropped plots reduced soil pH and residual soil K; but treatments affected soil P very little. Leaf Zn and Mn were also high for these treatments. Applied N, or N from legumes, was reflected in higher leaf N. Leaf K, Mg, Fe, B, Cu, Al, Mo, and Sr were not affected significantly by management treatment.
Carbon dioxide assimilation and ribulose-l,5-bisphosphate (RuBP) carboxylase activity were measured in 3 cultivars of pecan (Carya illinoensis (Wang) K. Koch cvs. Brooks, Stuart, and Mobile). Optimum leaf temperatures (27°C) and saturating irradiances (675 μEm−2s−1) were uniform among cultivars. Carbon dioxide assimilation was significantly higher in ‘Brooks’ and ‘Stuart’ than in ‘Mobile’ between April and June, but no differences were apparent among cultivars for the remainder of the season. The maximum rate observed was 13.5 mg CO2 dm−2hr−1. A lower rate occurred between mid-August and mid-September, which may limit available carbohydrate reserves for the following growing season. A significant decrease in RuBP carboxylase activity between May and August may have been a result of leaf senescence.