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Abstract

An equation for predicting bulk density (BD) of pine bark and sand potting media was devised using BD data from laboratory analysis of individual components. BD values calculated from the predictive equation and actual values obtained from potting medium samples were compared. Actual and predicted BD increased linearly with each incremental increase in percentage sand in the medium. Actual and predicted BD values were not significantly different. The devised equation is applicable to media other than bark and sand.

Open Access

Abstract

Gasifier residue (GR) had less than half the vertical shrinkage of pine bark or 2-bark : 1-peat : 1-sand medium. Little change in particle size distribution occurred in gasifier residue or 2-GR : 1-peat : 1-sand medium over 9 months. Particle breakdown occurred in bark, 2-bark : 1-peat : 1-sand and 3-GR : 1-peat media. In the upper Vs samples of the vertical profile, no change occurred in the water tension points of all media; however, in the lower ⅓ samples, the moisture of both 2B : IP : IS and 3GR : IP increased. Total pore space of all media tested varied initially but did not change over time. Bark gained easily available water and water buffer capacity, and lost air space. Gasifier residue lost easily available water but was stable in all other measured factors. The 2-bark : 1-peat : 1-sand medium lost air space over time but gained easily available water and water buffer capacity, thus increasing in moisture. The 2-GR : 1-peat : 1-sand medium retained its initial air space and water buffer capacity, but lost easily available water. The 3-GR : 1-peat medium similarly lost easily available water over time.

Open Access

In the southeastern United States, inconsistent pine bark (PB) supplies and overabundance of cotton gin by-products warrant investigation about the feasibility of replacing PB with cotton gin compost (CGC) for container horticultural plant production. Most research on the use of composted organic substrates for horticultural plant production has focused on shoot growth responses, so there is a need to document the effect of these substrates on root growth. In 2004, `Blitz' tomato (Lycopersicon esculentum), `Hot Country' lantana (Lantana camara `Hot Country'), and weeping fig (Ficus benjamina) were placed in Horhizotrons to evaluate root growth in 100% PB and three PB:CGC substrates containing, by volume, 60:40 PB:CGC, 40:60 PB:CGC, and 0:100 PB:CGC. Horhizotrons were placed in a greenhouse, and root growth in all substrates was measured for each cultivar. Physical properties (total porosity, water holding capacity, air space, and bulk density) and chemical properties (electrical conductivity and pH) were determined for all substrates. Physical properties of 100% PB were within recommended guidelines and were either within or above recommended ranges for all PB:CGC substrate blends. Chemical properties of all substrates were within or above recommended guidelines. Root growth of all species in substrates containing CGC was similar to or more enhanced than root growth in 100% PB.

Free access

Pine bark-filled containers periodically fertilized with NH4-N were heated from 21C to 28, 34, 40, 46, or 52C for daily exposures of 1, 2, 4, 6, or 24 hours over 20 days. Concentrations of NH4-N and NO3-N in medium solution extracts were determined every 5 days. Medium solution NH4-N concentration was higher at constant (24 hours) exposure to 40C than at lower temperatures or exposure times. There was a similar increase in NH4-N concentration for a 2-hour·day–1 exposure to 46C, with further increases in NH4-N for longer exposure times. By day 10, NH4-N concentration was highest after 1 hour·day–1 exposure to 52C. Decreases in medium solution NO3-N concentration generally coincided with the increases in NH4-N. These results indicate that container medium thermal periods, similar to those observed in nurseries of the southern United States, may inhibit nitrification, thereby influencing NH4-N: NO3-N ratios in the medium solution of plants fertilized with predominantly ammoniacal N sources.

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Abstract

A high incidence of longitudinal trunk bark cracking was observed in an apple planting with 4 scion cultivars and 9 rootstocks between Nov., 1969 and Feb., 1972. The injury, occurring mostly in late Nov., was related to scion and rootstock. Almost no cracking occurred on ‘Wellspur’ and ‘Red King’ trunks. More cracking occurred on ‘Golden Delicious’ than ‘Goldspur’ on 3 rootstocks. With these 3 rootstocks, 96% cracking occurred with ‘Golden Delicious’/‘M 7’ and ‘MM 106’ and 52% with trees on ‘M 26’. With ‘Goldspur’ on 9 different rootstocks, the highest incidence of cracking was with trees on ‘M 7’ (85%) and ‘MM 106’ (82%) while 30% cracking occurred with trees on domestic seedling, and 4% with trees on ‘M 25’ No cracking was observed with ‘Goldspur’/‘M 26’. The greatest no. of cracks occurred on the S sector of the trunks with moderate amounts on the SE and E sectors with fewer cracks on all other sectors. The cracking appears to be low temp induced and the effect of rootstocks appears to be an effect on fall maturity of the scion.

Open Access

Paclobutrazol, a triazole growth regulator, effectively regulates pecan vegetative growth when applied as a soil or trunk drench. However, its absorption and subsequent biological activity in leaves and shoot tissue is not well understood. Terminal shoots from scaffolds of 8-yr-old `Chickasaw' pecan trees were treated with paclobutrazol after leaf flush in mid-May of 1988. Treatments included painting a mixture of 10 mg a.i. paclobutrazol and 1 ml distilled water onto either 1-yr-old wood, green wood, or the abaxial leaf surface. Shoot growth measurements and nut counts were taken in October of 1988 and 1989 on the treated shoots and all shoots arising from them. Paclobutrazol significantly increased the number of nuts per shoot in 1988, but did not affect shoot growth. More nuts were found on shoots from the 1-yr-old wood and leaf treatments than from the control and green wood treatments. In 1989, shoot growth was significantly less in the 2 former than the 2 latter treatments. These data indicate that paclobutrazol was absorbed through the bark of 1-yr-old wood and abaxial leaf tissue and sub-sequently translocated to areas of shoot growth.

Free access

Pine bark-filled containers periodically fertilized with a (NH4)2SO4 solution were heated from 21°C to one of 5 temperatures (28°, 34°, 40°, 46°, or 52°C) for a daily exposure duration of 1, 2, 4, 6, or 24 hours. Medium solution extracts were analyzed for NH4-N and NO3-N every 5 days for 20 days. Treatment temperature of at least 40°C and a daily exposure duration of 24 hours was necessary to inhibit nitrification, thereby increasing NH4-N concentration in the medium solution. Similar increase in NH4-N was found for a 2 hr/day exposure to 46°C, with further increases in NH4-N at longer exposure times. By day 10, the maximum level1 of NH4-N concentration in medium extracts was found after a 1 hr/day exposure to 52°C. Decreases in medium solution NO3-N concentration generally coincided with the increases in NH4-N. Results indicate that high container temperatures may increase the ratio of NH4-N to NO3-N in the medium solution of plants fertilized with predominantly ammoniacal N.

Free access

In response to environmental cues plants undergo changes in gene expression that result in the up- or down-regulation of specific genes. To identify genes in peach [Prunus persica (L.) Batsch.] trees whose transcript levels are specifically affected by low temperature (LT) or short day photoperiod (SD), we have created suppression subtractive hybridization (SSH) libraries from bark tissues sampled from trees kept at 5 °C and 25 °C under short day (SD) photoperiod or exposed to a night break (NB) interruption during the dark period of the SD cycle to simulate a long day (LD) photoperiod. Sequences expressed in forward and reverse subtractions using various subtracted combinations of temperature and photoperiod treatments were cloned, sequenced, and identified by BLAST and ClustalW analysis. Low temperature treatment resulted in the up-regulation of a number of cold-responsive and stress-related genes and suppression of genes involved in “housekeeping” functions (e.g., cell division and photosynthesis). Some stress-related genes not observed to be up-regulated under LT were increased in response to SD photoperiod treatments. Comparison of the patterns of expression as a consequence of different temperature and photoperiod treatments allowed us to determine the qualitative contribution of each treatment to the regulation of specific genes.

Free access

Cotoneaster dammeri Schneid. `Skogholm' liners were potted into combinations of pine bark (PB), horticultural rockwool (RW), composted municipal yardwaste (CYW), composted turkey broiler litter (TBL) and washed builders sand (S). The objective of the study was to characterize the physical and chemical properties, subsequent plant growth and foliar tissue levels of the resultant substrates. Of the physical parameters tested the three component substrates PB:RW:CYW and PB:RW:TBL (70:20:10 by v) appeared to have the most consistent favorable physical properties. Electrical conductivity (EC) was extremely high the first day after initiation in the substrates containing TBL but was not different for other sampling dates. Leachate pH initially ranged from 4.9 to 6.1 but through most of the study ranged from 5.2 to 5.8. As with EC all nutrient levels were very high one day after initiation. Leachate phosphate levels were maintained at recommended levels in the substrates containing TBL throughout most of the study while other substrates were generally deficient. The same was true for foliar tissue phosphate levels. The greatest top dry weight was yielded in the PB:RW:TBL (70:20:10, by v) substrate and least in the PB:S (80:20) substrate.

Free access

Container-grown Viburnum plicatum Thunb. var. tomentosum (Thunb.) Miq. were transplanted on May 1 into tilled plots, tilled plots amended with aged pine bark, and untilled unamended plots (control) within a greenhouse. Plants were irrigated weekly for three months prior to drought initiation. Root growth, shoot growth, leaf water status, and leaf expansion rates were measured to determine whether tilling or site amending enhanced drought stress resistance. Prior to drought initiation amended treatments had the greatest new root length. New root dry weight of amended plots was 57% greater than controls and 32% greater than tilled plots. Mean root system diameter was 111 cm, 87 cm, and 61 cm for amended, tilled, and control plots, respectively. The mean ratio of new root length (cm) to leaf area (cm2) was 5.3:1 in amended plots, 2.2:1 in tilled plots, and 1.7:1 in controls. During the drought, midday relative leaf water content was lowest in controls, while the rate of leaf expansion was greatest in tilled plots. Changes in soil moisture were monitored using time domain reflectometry. Control plots had higher volumetric water content; however, moisture release curves suggest that tilled and amended plots contained more plant available water.

Free access