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Jack W. Buxton, Wenwei Jia and Guoqiang Hou

The automatic subirrigation system consists of a capillary mat placed above a constant water level in a reservoir. The optimum mat height above the water level was established by slanting a flat surface so the difference in vertical height from one end of the surface to the other was 25 cm. A ground cover providing water movement but not root penetration was placed over the mat. The capillary mat extended beyond the lowest end of the slopped surface and into the reservoir, the mat at the lowest end of the slopped surface was at the same vertical height as the water in the reservoir and remained constantly saturated. Plug trays were placed at intervals of 2.5 cm in vertical height above the water level. An average of 96-100% germination was obtained with marigold, tomato, impatiens and pepper seed in trays placed 5-7.5 cm in vertical height above the water level. These seedlings continued to develop and reached transplanting stage quicker than other trays. The rate and % germination was less in trays placed on the surface nearer to the height of the water in the reservoir. Germination in trays above 12.5 cm was greatly reduced and seed that did germinate did not develop and eventually died.

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Prem L. Bhalla and Katherine Tozer

Plants of genus Scaevola (family, Goodeniaceae), commonly known as “fan flowers,” are mostly endemic to Australia. Commercially popular species are Scaevola aemula, S. albida, S. striata, and S. phlebopetala. These plants are used as ground covers in Australia and as hanging baskets, window boxes, and garden bed plants in Europe and America. Two aspects of in vitro culture of Scaevola are reported here; micropropagation and direct shoot regeneration. A number of commercially available cultivars of S. aemula, S. phlebopetala, S. striata and wild-collected S. phlebopetala, S. glandulifera, S. hookeri, and S. ramonissima were used for micropropagation experiments. Micropropagation medium contained salts, vitamins, L-cysteine, sucrose, and agar. Tissue-cultured shoots were rooted in hormone-free medium. A high survival percentage (>95%) was obtained when plants were transferred to soil under glasshouse conditions. Results on in vitro shoot induction and regeneration response of leaf, stem, root, node, and flower explants of two horticulturally important species of the Australian fan flower, Scaevola aemula and Scaevola striata arealso presented. Of all the explants tested, node explants of these species were the first to respond in tissue culture. Maximum number of shoot induction and regeneration was achieved from node explants of Scaevola aemula and node and stem explants of Scaevola striata. More than 95% of the regenerated shoots were rooted on the medium supplemented with 4 mg/L of IBA. The significance of above findings in assisting breeding program for new horticultural desirable cultivars of Australian fan flowers will be discussed.

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Susan M. Huslig and Michael W. Smith

Irrigation schedules were evaluated on `Cresthaven' to determine if water could be conserved without reducing fruit size or yield. Tensiometers were used to schedule trickle irrigation in 1984-88. Treatments were no irrigation or irrigation when soil matric potential reached 40 or 60 KPa 30 cm deep. When production began in 1986, trees were either irrigated until Oct. or until after harvest (1-7 Aug.). In 1989, class A pan evaporation was used to schedule irrigation by replacing 100% evaporation. Trees were irrigated from bud break to harvest or Oct., beginning at stage III fruit growth to harvest or Oct., or not irrigated. The irrigation treatments were in factorial combination with an annual ryegrass ground cover or herbicidestrip. The ryegrass was seeded in Oct., then killed at the onset of stage III fruit growth. Water application was reduced 50% when irrigation was discontinued after harvest compared to irrigation until Oct. Non-irrigated trees had smaller trunks than irrigated trees; however, there were no differences in trunk size among irrigation treatments. Non-irrigated trees yielded less total fruit and fruit over 7-cm diameter than trees irrigated until Oct., but there were no significant differences in yield among irrigated trees. Flower bud density or fruit set was not affected by treatment. The orchard floor management did not affect tree growth or yield.

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Eric L. Zeldin, Brent H. McCown, Elden Stang and John Klueh

A project to determine the comparative growth response of micropropagated (MP) and field propagated (FP) cranberry plants was conducted in field plots at a commercial cranberry marsh. Microcuttings were derived from shoot culture and rooted in either plugs or peat pots filled with peat. Replicated 1 m2 plots of MP plants and 15 cm FP cuttings were planted in June. Survival of MP plants after one month was significantly greater than that of the FP plants. Significant growth differences were observed later in the season. The MP plants produced more branches and greater runner elongation, resulting in a much greater ground cover. Many of the FP plants flowered and produced fruit, while the MP plants produced neither. Far fewer new flower buds were set in the fall on the MP plants. Potential advantages of MP cranberries include the fast, uniform establishment of new marshes and consequently earlier achievement of full productivity, and the rapid introduction of new genotypes from breeding or genetic engineering.

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Natasha R. Rice and Michael W. Smith

Legume ground covers in pecan orchards can reduce nitrogen inputs and increase beneficial insects. Preliminary data indicate that certain legumes can supply over 100 kg·ha-1 N. Additionally, certain legumes have high aphid populations which attract beneficial insects. When aphid populations on the legumes crash, beneficial insects seek alternative food sources in the pecan trees, thus reducing the necessity for pesticide applications. Preliminary studies suggest that a mixture of 'Dixie' crimson clover and hairy vetch produces high populations of beneficial insects and over 100 kg·ha-1 N. Treatments were established at four pecan orchard sites in Oklahoma, each with 5 ha of a crimson clover/vetch mixture and 5 ha of native grass sod. Additions of 0-200 kg·ha-1 N were added to the sod plots but no supplemental N was added to the legume plots. Nitrogen and biomass production by the legumes, and leaf N concentration of pecans were determined. In addition, both aphid and beneficial insect populations were monitored in the legume and grass treatments, and in the pecan trees. Results will be discussed in the presentation.

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Michael L. Parker and John R. Meyer

Peach trees (`Biscoe'/Lovell) were planted in March, 1988 in ten different ground cover management systems. The trees were planted at the Sandhills Research Station in Southeastern North Carolina on a Candor sand and Eunola sandy loam. In December, 1991 the trench profile method was used to evaluate root distribution under the six orchard floor management systems of nimblewill, bare ground control, centipedegrass, brome, bahiagrass, and weedy control. Trenches were dug parallel to the tree row 60 cm from the center of the row on both sides of the tree. Grids 1 meter square, sectioned into 10 cm squares, were placed on the profile walls and root distribution (in three size categories) was recorded for 1 meter on each side of the tree in each trench. Root numbers were greatly reduced under the vegetative covers that provided the greatest suppression of vegetative tree growth. Total root densities under the trees in the vegetative covers were ranked into three size categories which were correlated with the amount of vegetative tree growth.

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Chris A. Martin and Linda B. Stabler

Urban sprawl of the greater Phoenix metropolitan area is rapidly replacing agricultural and non-irrigated desert vegetation with an irrigated urban forest comprised of a mixture of woody ornamental plant materials. Our objective was to estimate and compare the carbon acquisition potential (CAP) of residential landscape plants to the dominate plant species found in adjacent agricultural and desert sites. Maximum shoot and leaf gas exchange measurements were made at monthly intervals for one year (Aug. 1998 to July 1999) using a portable photo-synthesis system. Concurrent diel gas exchange measurements were made seasonally. Gas exchange measurements were made on alfalfa at agricultural sites, blue palo verde, creosote bush and bur sage at desert sites, and on a mixture of 19 different woody ornamental tree, shrub and ground cover species at residential sites. A trapezoidal integration model was used to estimate daily CAP at each site based on maximum assimilation flux values and seasonally adjusted diel assimilation patterns. Annual landscape CAP was then calculated as the summation of estimates of daily CAP. Calculated annual CAP was highest at agricultural sites (159.0 mol/m2 per year), lowest at desert sites (35.3 mol/m2 per year), and intermediate at residential landscape sites (99.3 mol/m2 per year).

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H. Desilets, S. Rochefort, J. Coulombe, S. Yelle and J. Brodeur

The potential impact of propane flamers on the development and release of ascosporic inoculum of Venturia inaequalis (Cke.) Wint. from infected dead apple (Malus domestica Borkh.) leaves that overwintered on the soil of an experimental orchard was assessed. Thermal reduction of scab primary inoculum was first conducted under controlled conditions using an indoor testing facility. At the time of ascospore maturation, heavily infected leaves were submitted to temperature rises ranging from 150 to 200 °C with open-flame burners, thus reducing the number of ascospores subsequently released by 76% and 87%, respectively. During Spring 1995, thermal treatments of overwintered dead leaves were performed directly on the ground of an apple orchard with an experimental propane flamer design to generate uniform heat at ground level. Four thermal treatment strategies, involving two dates of flaming and two heat intensities, were tested. Flaming orchard ground, when performed in early May, before significant development of ground cover, reduced the number of ascopores released from infected dead leaves by half. A significant residual effect of the treatments on ascospore ejection was still observed 2 and 4 weeks after the treatments, thus indicating that ascospore maturation inside the leaves may be reduced by heat treatment. These results indicate potential for propane flamers to reduce apple scab primary inoculum in orchards.

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J.L. Sibley, D.G. Himelrick and W.A. Dozier Jr.

Poultry and coal production are two major industries concentrated in north-central Alabama. Standard surface coal mine reclamation procedures were compared to procedures utilizing poultry litter in an 3.24-ha mine site. Three 0.4-ha plots amended with litter at rates of 25, 50, and 100 mt/ha, were compared to a plot with mineral fertilizer (13N–13–P13K) at standard reclamation rates of 672 kg/ha, and a plot receiving no fertilizer or litter. All plots were amended with ground limestone and disced in 31 cm. A mix of fescue, lespedeza, rye, and clover was broadcast over all plots uniformly. Eight tree species; northern red oak, nuttall oak, willow oak, red maple, yellow poplar, royal paulownia, loblolly pine, and eastern red cedar were planted in all plots at 1482 trees/ha. Forage yields (1995–96) in litter-amended plots were two to three times higher than statewide hay production averages. High litter rates have had no negative effects on ground cover, tree survival, or ground water nitrates (NO3). This project demonstrates broiler litter use as an organic-matter amendment in a self-sustaining reclamation success.

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Cathleen A. Peterson, L. Brooke McDowell and Chris A. Martin

Heightened awareness of ecological concerns have prompted many municipalities to promote water conservation through landscape design. In central Arizona, urban residential landscapes containing desert-adapted plant species are termed xeriscapes, while those containing temperate or tropical species and turf are termed mesoscapes. Research was conducted to ascertain landscape plant species diversity, tree, shrub, and ground cover frequency; landscape canopy area coverage; and monthly irrigation application volumes for xeric and mesic urban residential landscapes. The residential urban landscapes were located in Tempe and Phoenix, Ariz., and all were installed initially between 1985 and 1995. Although species composition of xeric and mesic landscapes was generally dissimilar, both landscape types had comparable species diversity. Mesoscapes had significantly more trees and shrubs and about 2.3 times more canopy area coverage per landscaped area than xeriscapes. Monthly irrigation application volumes per landscaped surface area were higher for xeriscapes. Even though human preference for xeric landscape plants may be ecological in principle, use of desert-adapted species in central Arizona urban residential landscape settings might not result in less landscape water use compared with mesic landscapes.