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John D. Lea-Cox*, Andrew G. Ristvey, and David S. Ross

Many agronomic and horticultural studies on nutrient uptake and use-efficiency have indicated, in general, that agricultural crops are poor competitors for nitrogen (N) and phosphorus (P) in soil-based systems, with estimates of overall nutrient efficiency being less than 50% for N and 10% for P. Low efficiencies are due to losses from leaching, runoff, gaseous emissions and soil fixation, but uptake efficiency is also affected by rate and timing (i.e. seasonal effects) of applications. Controlled-release fertilizers (CRF's) have been promoted as a technology that can slowly release nutrients; the release rate is most often a function of prill coating and temperature. There are few data in the ornamental literature that have directly compared the total uptake efficiency of CRF's to soluble fertilizer sources. From 1999-2002, we collected three annual N and P budgetary datasets, comparing two species (Rhododendron cv. azalea and Ilex cornuta cv.`China Girl') with different growth rates and hence nutrient requirements. Plant N and P uptake efficiencies were usually less than 20% of the total applied, but all datasets included a significant soluble fertilization component. In 2003, a new study with Ilex cornuta cv.`China Girl' was initiated, where nutrients were supplied only from two CRF sources, as we want to determine whether this technology can significantly increase nutrient uptake efficiency at similar rates. A preliminary analysis of the data indicate that total N and P uptake efficiencies between different CRF sources were similar, but leaching losses between sources varied during the growing season. It appears that the primary determinant of uptake efficiency is not source material or timing, but the overall rate of nutrient application.

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Alison A. Stoven, Hannah M. Mathers, and Daniel K. Struve

The mineral nutrition requirements and fertilizer application methods for container-grown shade tree whips are not well understood. This experiment was conducted to determine the effects of fertility method (water soluble vs. controlled release) on growth, water, and N use efficiency of four taxa [(Acer ×freemanii `Jeffersred' (Autumn Blaze® maple), Cercis canadensis L. (Eastern redbud), Malus (Mill.), `Prairifire' (Prairifire crabapple), and Quercus rubra L. (red oak)] in two production environments [outdoor gravel pad vs. a retractable roof structure (RRS)]. No single fertilizer method consistently resulted in the greatest growth. In the RRS, maple and crabapple heights, and crabapple and redbud caliper were larger when whips were fertilized with controlled-release fertilizer (CRF); outdoors, CRF resulted in taller maples and larger caliper crabapples. However, in the RRS, maple whips fertilized with water-soluble fertilizer had higher production water use efficiency than those fertilized with CRF, whereas crabapple whips had higher N use efficiency when fertilized with CRF. Nitrogen use efficiency was higher for redbud and crabapple whips fertilized with CRF than with CRF. Outside, crabapple whips fertilized with CRF had higher production water use efficiency than those fertilized with water-soluble fertilizer. There were no differences in N use efficiency attributed to fertilizer method. When averaged over fertilizer application methods, height, caliper, water, and N use efficiency were greater when whips were grown in RRS than outdoors. There were two exceptions: Maple caliper and production water use efficiency were marginally higher when whips were grown outdoors. The greater growth for whips produced in the RRS was attributed to reduced ambient and substrate temperature stress.

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Geral I. McDonald

Frequency of infection, main effects and interactions among four geographic sources of white pine blister rust (WPBR) (Cronartium ribicola J.C. Fisch.) and 10 Ribes-sites (Ribes L. specie × site combinations) was investigated using leaf disk assay. Two clones, one of R. hudsonianum (Dougl.) Jancz. and one of R. viscosissimum Prush., were not infected by any sources of WPBR. One clone of R. viscosissimum that was not infected by two sources of WPBR was susceptible to the other sources. Highly significant WPBR sourc × Ribes-site analysis of variance interaction for incubation period and infection efficiency precluded testing main effects. Profile plots of incubation period interaction means showed orderly interaction by all WPBR sources and plots of infection efficiency showed that aggressively virulent WPBR from Oregon (Champion Mine) ranked near or at the bottom for infection efficiency for all Ribes-sites. Meanwhile, aggressively virulent WPBR from Idaho (Merry Creek) ranked near the bottom for infection efficiency when inoculated onto Ribes obtained from the Cascade Mountains but switched to the highest ranking when inoculated onto Ribes obtained from Idaho. Geographic interaction of white pine blister rust and Ribes for incubation period and infection efficiency may help to explain geographic patterns recently observed in WPBR molecular markers.

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William F. Lamack and Alex X. Niemiera

Studies were conducted to evaluate the effect of water application medium moisture deficit, water application rate, and intermittent application on water application efficiency {[(amount applied - amount leached)/amount applied] x 100} of spray stake-irrigated, container-grown plants. Pine bark-filled containers were irrigated to replace moisture deficits of 600, 1200, or 1800 ml; deficits were returned in single, continuous applications of 148, 220, or 270 ml·min-l. Efficiency was unaffected by application rate but decreased with increased medium moisture deficit. In the second experiment, container medium at a 600-ml deficit was irrigated with 400 or 600 ml (6570 and 100% water replacement, respectively); deficits were returned in a single, continuous application or in intermittent 100-ml applications with 30-min intervals between irrigations. Application efficiency was greater with intermittent irrigation (95% and 84% for 400- and 600-ml replacement, respectively) than with continuous irrigation (84% and 67% for 400- and 600-ml replacement, respectively). In the third experiment, pine bark was irrigated with 600 ml water (100% replacement) in 50-, 100-, or 150-ml aliquots with 20, 40, or 60 min between applications in a factorial design. Efficiency increased with decreasing application volume and increasing time between applications. Highest efficiency (86%) was achieved with an irrigation regimen of 50-ml applications with at least 40 min between applications, compared to 62% for the control treatment (a single, continuous application of 600 ml). Our results suggest that growers using spray stakes would waste less water by applying water intermittently rather than continuously.

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Yin-ming Li and W.H. Gabelman

Sixty highly homozygous tomato (Lycopersicon esculentum Mill.) strains, some selected from previous studies and some collected from known low-Ca regions, were screened under a low-Ca culture system (10 mg of Ca per plant). Four strains were selected to represent the extremes for Ca efficiency and used as parents to create a series of F1, F2, and backcross generations for inheritance studies of Ca use under low-Ca stress. Based on total plant dry weight, additive and dominance gene effects were most important for the efficiency of Ca use. Maternal control of efficiency in Ca use was not observed. Estimates of broad-sense heritability ranged from 63% to 79% for total play dry weight. Narrow sense heritabilities, determined in only two of the families, were 47% to 49$ and 68% to 75%.

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Terence L. Robinson

`Empire'/M.26 apple trees which were planted in 1978 and trained to a Y-trellis were pruned differentially from 1989-1993. Trees were dormant pruned by removing from 1-4 scaffold limbs. The annual increase in trunk cross-sectional area (TCA), and the number and length of shoots removed during summer pruning increased linearly as the severity of pruning increased. The number of shoots removed during summer pruning from the most severe pruning treatment was more than double that of the least severe treatment Cumulative fruit number and yield were reduced linearly with increasing severity of pruning while average fruit size was increased only slightly by severity of pruning. Light interception was reduced with increasing severity of pruning. Tree efficiency of converting light energy into fruit (g fruit/MJ PAR intercepted) was linearly reduced with increasing pruning severity. Most of the reduction in conversion efficiency appeared to be due to reduced partitioning of resources into fruit since partitioning index (g fruit/unit increase in TCA) was more highly correlated to pruning severity than to conversion efficiency. Conversion efficiency and partitioning index accounted for a greater portion of the yield variation than did light interception indicating that the influence of pruning on yield was more a function of changing internal physiology than reduced light interception.

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Mary Ann Rose, Mark Rose, and Hao Wang

Fertilizer recommendations for woody ornamentals suggest applying nutrients in early spring at budbreak, and in fall at the time of leaf coloration or leaf abscission. Because plants lack functional leaves at those times, there would be minimal contributions from photosynthesis to active ion absorption or from transpiration to mass flow of ions in soil towards roots. Thus, we hypothesized that fertilizer efficiency also would be low at those times. To estimate N uptake efficiency, 15N-enriched fertilizer was applied to container linden trees at one of five times during the 1998 season: at budbreak, during active growth, after terminal bud-set, before leaf abscission, and during leaf abscission. Half of the plants received 15N-nitrate-enriched ammonium nitrate on each date, and half received 15N-ammonium-enriched ammonium nitrate. Treated plants were harvested 10 days after enriched fertilizer application (29 May, 6 July, 17 Aug., 28 Sept., and 16 Nov.). Patterns of uptake were not different between plants treated with 15N-ammonium- or 15N-nitrate-enriched fertilizer. In both cases, nitrogen recovery efficiencies at budbreak and leaf abscission were much lower than at other application times. Whole-plant recovery efficiency of 15N-nitrate-enriched ammonium nitrate was 10% at budbreak, 13% at leaf abscission, and ranged from 58% to 71% for the intervening times. Recovery of 15N-ammonium-enriched ammonium nitrate was 6% at budbreak, 24% at leaf abscission, and 42% to 56% for intervening times.

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Herbert Thompson, J.M. Joshi, R.B. Dadson, and M. Nobaht

Vegetable Soybean Cultivars belonging to MG III thru V were evaluated for their Seed Yield Efficiency (SYE) and Resistance to Heliothis Zea.

This study was conducted in 1968 and 1969. Each entry was planted in a single row plot. Each plot was 5.0 m long and 0.75 m apart in a randomized complete block design with 4 replications.. All entries were evaluated for Seed Yield Efficiency by computing the ratio of seed dry matter wt. to non-seed dry matter wt. and their resistance as the percentage of damage pods.

Preliminary data indicated that cultivars kim and Oakland (MG III), Kingston and Jefferson (MG IV), Pershing and PI 416.467 (MG V) were very high in SYE while Fuji (MG III), Sanga (MG IV) and PI 417.266 (MG V) were observed to have high level of resistance to Heliothis Zea.

We hope that these cultivars could be used as parents for the development of Breeding Program in Vegetable Soybean.

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Richard C. Beeson and Thomas H. Yeager

Ligustrum japonicum, Rhododendron indica `Southern Charm' and Viburnum odoratissimum in 10-L containers were placed in a square grid pattern and overhead irrigated using impact sprinklers (30.3 L/min). Plants were irrigated with 12.5 mm with containers touching and, at 5 cm spacings, up to 50 cm between containers. Irrigation water reaching container surfaces (percent capture) increased for all species as container spacing increased. However, the increase in percent capture did not increase irrigation application efficiency because the percent of production area covered by the containers declined as spacing increased. Application efficiency declined with each increase in spacing to a low of 7%. The effects of intraand inter-canopy interference are discussed.

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Malcolm W. Smith, Mark D. Hoult, and Jeremy D. Bright

Low yields and high harvesting costs are long-standing problems in mango (Mangifera indica L.) cultivation. In an effort to increase productivity in the scion 'Kensington Pride' we examined the impact of nine different rootstocks over a 10-year period. Rootstock effects on fruit production were significant in most seasons, and cumulative yields (nine seasons of cropping) for the best treatment ('Sg. Siput') exceeded those of the poorest treatment ('Sabre') by 141%. Yield efficiencies (expressed on both a trunk cross-sectional area and canopy silhouette area basis) were also significantly affected by rootstock. Rootstock effects on yield and yield efficiency were generally consistent across seasons, despite large seasonal variations in yield. Harvest rates were also influenced by rootstock, and were poorly correlated with tree size. These results demonstrate possibilities for manipulating mango scion productivity through rootstock genotype.