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Beginning in 1986 in Bonn, trees growing in 120 liter lysimeters spaced 2.0 × 3.4 m apart were trained to either “V” - or spindle-shaped canopies. During the 4th and 5th leaf half of the trees in each training form were covered with shade fabric to reduce insolation to 42% of overhead PAR. In the 4th leaf both canopy shapes produced 26 mt apples/ha (1470 trees/ha, basis) in full sun, and shading reduced yields by 23%. But the 5th leaf yields reached 54 and 39 mt/ha under full sun in the “V”- and spindle-shaped canopies, respectively; furthermore the “V”-shaped trees under shade fabric had 25% greater yield efficiency than the spindle in full sun whereas the spindle trees under the same shade had 41% less yield efficiency than those in full sun. These differences in yield could be partially explained by differences measured in the pattern of distribution of shoots, wood and fruit in the canopies caused by tree training. Training to the “V”-shape increased dry matter partitioning to fruit on the shaded trees at the expense of the stem fraction in contrast to the opposite effect on spindle trees.
Abstract
Trees of apple [Malus domestica Borkh. cvs. Jonathan/Malling (M) 26] were summer-pruned each August from 1978-1980 by heading all shoots longer than 10 cm, and their response was compared to trees receiving only a light dormant-pruning by thinning-out cuts. Cropping treatments were a full crop or defruiting in June. Final length of shoot regrowth on summer-pruned trees was 82% and 76% less than terminal growth of control trees in 1979 and 1980, respectively, but terminal shoots produced the year following pruning were 55% and 62% longer on summer-pruned tress than on controls in 1979 and 1980, respectively. Summer-pruned trees with a full crop had 13% shorter terminal shoot length than defruited trees in 1979, but cropping had no effect in 1980. Trees with a full crop had a smaller annual increase in trunk cross-section than defruited trees, but were not affected by summer pruning. Summer pruning restricted tree canopy dimensions, resulting in 43% less canopy volume than control trees in 1979 and 1980, increased canopy openness to light penetration, and hastened flower opening. Pruning treatments did not affect fruit set. Fruit yield per tree was reduced by summer pruning, but yield per canopy volume was not affected. Fruit size was decreased by summer pruning in 1979 but was increased in 1980. Fruit soluble solids were reduced by summer pruning in 1979 and 1980, fruit color was increased in 1978 and 1980, but not in 1979. Flesh firmness was unaffected by summer pruning.
Abstract
Traditionally, the size control achieved in summer-pruned apple (Malus domestica Borkh.) trees has been attributed to the removal of shoot leaf area before it could replace the storage carbohydrate depleted during its initial growth. Therefore, tissues of young Top Red ‘Delicious’/M 9 trees grown in pots, and mature, field-grown ‘Jonathan’/M 26 trees were summer-pruned and subsequently analyzed for carbohydrate and nutrient element content. Increasing the severity of summer pruning (the length of shoot removed) did not affect the concentration of water-soluble reducing sugars (SRS) or insoluble hydrolyzable carbohydrates (IHC) in the basal shoot section of the Top Red ‘Delicious’/M 9 trees 11 weeks after pruning. Summer pruning 1) increased leaf SRS, N, K, B and stem IHC and 2) decreased leaf Ca and Mg in shoot regrowth. Levels of Fe, Ca, Zn, Al, and Na in the leaves of regrowth were not affected by summer pruning. There was no significant effect of pruning on SRS or IHC levels in the roots. A separation of the carbohydrates by gas chromatography revealed increasing glucose and fructose concentrations in the roots as pruning severity increased, but sorbitol, sucrose, and phloridzin concentrations in roots were not significantly affected. Neither previous season’s summer pruning nor fruit cropping of ‘Jonathan’/M 26 trees affected SRS or IHC of spur shoots in March or June, except that presence of fruit reduced IHC of spur leaves in June. SRS levels in roots in June were reduced by the previous year’s cropping, but not influenced by summer pruning. Root IHC was not influenced by either pruning or cropping treatments. Spur leaf N, Ca, Mg, Mn, and Al were reduced on defruited trees, with K, Ca, Mn, and Al generally being increased by summer pruning. Pruning and cropping treatments generally did not affect levels of P, Fe, B, Cu, Zn, or Na in spur leaves in June; but summer pruning increased K concentration in harvested fruit.
Abstract
Young, container-grown ‘Topred Delicious’/Malling (M) 9 apple trees (Malus domestica Borkh.) trained to a single shoot out-of-doors were summer pruned to remove 0, 25, 50 or 75% of 78 cm shoots. Net photosynthesis (Pn) and transpiration (Tr) were as much as 36% greater on older, basal leaves of trees with 50 and 75% shoot removal than on unpruned trees. These differences were present for 39 days after pruning. Basal leaves did not abscise in the 11-week period after pruning on trees with 75% shoot removal and remained longer on trees with 50% shoot removal than on unpruned trees. Leaf area removed by pruning was partially compensated by leaves on subsequent regrowth. All summer pruning treatments suppressed the area of individual leaves on regrowth by about 50% of the size of similar aged leaves on unpruned trees. Summer pruning suppressed the dry weight of basal stem sections and roots roughly in proportion to shoot removal amounts, while dry weight of shoot regrowth was less influenced. Eleven weeks after pruning, dry weight of roots on summer pruned trees with 25, 50 and 75% shoot removal was 20, 39 and 50% less, respectively, than root dry weight of unpruned trees.
The purpose of color sorting by fluorescence was to upgrade seed quality by removal of fluorescent coatings that were attributed to sinapine leakage from nonviable seeds. Nine seed lots (three seed lots each of broccoli, cabbage and cauliflower) were custom coated. Seed samples were pretreated prior to coating with or without 1.0% NaOCl for 10 minutes to enhance leakage. Fluorescence, as measured by fiber optic spectrometry, was expressed from 400 to 560 nm with peak emission being from 430 to 450 nm. A UV color sorter was employed to separate fluorescent (reject) from non-fluorescent (accept) coatings. The percent non-fluorescent coatings (averaged over seed lot and NaOCl pre-treatment) before and after sorting was 89.5 and 95.9, respectively. There was a six percent loss of non-fluorescent coatings after sorting (averaged over all treatments). An increase in the percent germination was recorded in 8 of the 9 seedlots following color sorting and the greatest improvement was obtained with seed lots of medium quality. The germination of three medium quality lots was increased from 10 to 15 percentage points. The average increase in germination with or without NaOCl pre-treatment was 8.2 and 5.5 percentage points, respectively. In conclusion, the combination of coating technology with seed conditioning by UV color sorting was effective in improving Brassica seed performance.
An interdisciplinary approach had been developed to examine the production, economic, and marketing feasibility of new crops. The methodology requires the determination of yield potential and product quality, construction of production budgets, and completion of marketing window analyses. Potential for integration of new crops into the existing farm enterprise is assessed using linear programing techniques that consider labor and equipment constraints, crop rotations and best management practices. Risk analyses consider yield, production costs, and price of both new and traditional crops. By using this method, broccoli has been identified as a potential new crop for eastern Virginia, with labor requirements and slush ice availability being the major constraints to integration into vegetable production in this area.
Color sorting was performed to upgrade seed quality by removal of fluorescent coated seeds. The fluorescent coating was attributed to sinapine leakage from nonviable seeds. Nine seedlots, three seedlots each of cabbage (Brassica oleracea L. Capitata group), broccoli, and cauliflower (B. oleracea L. Botrytis group) were custom coated. Seed samples were pretreated before coating with or without 1.0% NaOCl for 10 minutes to enhance leakage. All samples revealed a percentage of seeds with fluorescence. The light emission from selected fluorescent and nonfluorescent coated seeds was quantified by fiber-optic spectrophotometry. Fluorescence was expressed from 400 to 560 nm, with peak emission being from 430 to 450 nm. These data confirmed our visual interpretation of blue-green fluorescence. The ratio of light emission from fluorescent compared to nonfluorescent coated seeds ranged from 4.5 to 7.0 for all samples and averaged 5.7. An ultraviolet (UV) color sorter was employed to separate fluorescent (reject) from nonfluorescent (accept) coated seeds. The percentage of nonfluorescent coated seeds (averaged over seedlot and NaOCl pretreatment) before and after sorting was 89.5% and 95.9%, respectively. Therefore, color sorting was able to remove a high percentage of fluorescent coated seeds with an average loss (rejection of nonfluorescent coated seeds) of 6%. An increase in the percent germination was recorded in eight of the nine seedlots following color sorting, and the greatest improvement was obtained with seedlots of medium quality. Germination of three medium quality lots was increased by 10 to 15 percentage points. The average increase in germination with or without NaOCl pretreatment was 8.2 and 5.5 percentage points, respectively. In conclusion, the germination of Brassica seedlots could be improved by separating (removing) fluorescent from nonfluorescent coated seeds. UV color sorting technology was employed to demonstrate that seed conditioning could be conducted on a commercial basis to upgrade seed quality.
High-quality seed lots are required for successful establishment of horticultural crops. Testing methods are needed that can detect the early phases of aging prior to a significant loss in germination. Quality was assessed using both germination speed and uniformity on non-primed and primed, as well as non-aged and aged, lettuce (Lactuca sativa L.) seed. Speed and uniformity were quantified using time to 50% (T50) germination and one standard deviation (Tsd), respectively. Embryo elongation was developed as a rapid test by first soaking seeds for 2 hours, then cutting and removing the distal one-third of the seed, and finally observing the percentage of visibly elongated embryos from the seed coverings over time. The mild aging conditions employed in this study (45 °C and 50% relative humidity for up to 21 days) had little influence on viability (germination in all treatments was >98%), but reduced germination rate (increased the time for T50 and Tsd). Primed seeds aged faster than non-primed seeds under the same aging conditions. The percentage of elongated embryos was calculated at hourly intervals after cutting, and treatment differences were observed after a total hydration period of 5 hours. The embryo elongation test detected aging in both primed and non-primed treatments.
Five studies were conducted from 1997 to 1999 to determine the effects of subsoiling on root quality (i.e., root length and shape) and on yield of `Beauregard' sweetpotato. The statistical design for all five studies was a completely randomized block design with six replications (four in Goldsboro in 1997). All studies were conducted on Norfolk fine sandy loam soils. Two studies were done in 1997, one in Kinston and the other in Goldsboro, N.C.; two studies in 1998, one in Kinston and the other in Goldsboro; and one in 1999 in Kinston, N.C. Common treatments in the studies consisted of no subsoiling, V shank subsoil, 30 cm below row (56 cm from peaked ridge) and V shank subsoil, 46 cm below row (71 cm from peaked ridge). Roots were longer, had more creases, and were more misshapen due to ripping (regardless of subsoiling depth) in the 1997 Kinston test. No differences were detected in root quality due to subsoiling in the other four tests. Marketable and total yields were increased in both tests in 1997 with subsoiling; however, a similar yield increase was not obtained with subsoiling in 1998 and 1999. Jumbo yields were increased in Kinston in 1997 and Goldsboro in 1998 with subsoiling; the better response was obtained with 30-cm-depth subsoiling. Jumbo yields in 1999 were the same regardless of treatment. Canner and cull yields were similar in all tests across treatments. Yields may be increased with subsoiling in certain circumstances (i.e, drought or soils with hard pans), and can result in more off-shape roots and longer roots. It appears from these studies that yields may be increased with subsoiling; however, more off-shape roots may be produced, especially under dry conditions or where fields are not routinely subsoiled.
Legume ground covers were evaluated in pecan orchards to reduce nitrogen inputs and increase beneficial insects. Treatments were established at two sites in Oklahoma, each with 5 ha of a `Dixie' crimson clover/hairy vetch mixture and 5 ha of grass sod. Nitrogen was applied at 0-200 kg·ha-1 to the sod plots, but legume plots were not fertilized. Aphids and selected arthropods were monitored on ground covers and in the pecan canopies. Data indicated that a mixture of crimson clover/hairy vetch supplied up to 186 kg·ha-1 N to the trees. Beneficial arthropods monitored were Coccinellidae, Chrysopidae, Nabid, Syrphid, and spiders. Lady beetles, primarily Hippodamia and Coleomegilla, were the most important aphid predator in the spring, and green lacewing was the most important fall predator. There were fewer aphids infesting pecans using a crimson clover/hairy vetch ground cover than a grass sod.