Chemical and Physical Properties of Douglas Fir Bark Relevant to the Production of Container Plants

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Additional index words. aged bark, air space, dynamic physical properties, evaporative method, fresh bark, particle size, Pinus taeda, porometer, sand, static physical properties, water holding capacity Abstract. Pine bark is the primary constituent of nursery container media (i.e., soilless substrate) in the eastern United States. Pine bark physical and hydraulic properties vary depending on the supplier due to source (e.g., lumber mill type) or methods of additional processing or aging. Pine bark can be processed via hammer milling or grinding before or after being aged from £1 month (fresh) to ‡6 month (aged). Additionally, bark is commonly amended with sand to alter physical properties and increase bulk density (D b ). Information is limited on physical or hydraulic differences of bark between varying sources or the effect of sand amendments. Pine bark physical and hydraulic properties from six commercial sources were compared as a function of age and amendment with sand. Aging bark, alone, had little effect on total porosity (TP), which remained at ' '80.5% (by volume). However, aging pine bark from £1 to ‡6 months shifted particle size from the coarse (>2 mm) to fine fraction (<0.5 mm), which increased container capacity (CC) 21.4% and decreased air space (AS) by 17.2% (by volume) regardless of source. The addition of sand to the substrate had a similar effect on particle size distribution to that of aging, increasing CC and D b while decreasing AS. Total porosity decreased with the addition of sand. The magnitude of change in TP, AS, CC, and D b from a nonamended pine bark substrate was greater with fine vs. coarse sand and varied by bark source. When comparing hydrological properties across three pine bark sources, readily available water content was unaffected; however, moisture characteristic curves (MCC) differed due to particle size distribution affecting the residual water content and subsequent shift from gravitational to either capillary or hygroscopic water. Similarly, hydraulic conductivity (i.e., ability to transfer water within the container) decreased with increasing particle size.

Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 98%

mentioning

confidence: 99%

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Physical and Hydraulic Properties of Commercial Pine-bark Substrate Products Used in Production of Containerized Crops

Altland¹,

Owen²,

Jackson³

et al. 2018

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“…obser.). Chemical and physical properties of DFB, as they pertain to use in container substrates, have recently been documented by Buamscha et al (2007b). They reported nonamended DFB to have low pH (3.7 to 4.4); little or no available nitrogen (N); relatively high water-extractable phosphorus (P; 10 to 28 mgÁL -1 ) and potassium (K; 78 to 162 mgÁL -1 ); low levels of calcium (Ca), magnesium (Mg), and sulfur (S); and moderate levels of some micronutrients.…”

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confidence: 99%

Nutrient Availability from Douglas Fir Bark in Response to Substrate pH

Altland¹,

Buamscha²

2008

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Two studies were conducted to determine the influence of substrate pH on nutrient availability in Douglas fir bark. Douglas fir bark was amended with either calcium carbonate (CaCO3) or calcium hydroxide [Ca(OH)2] at 13 rates to generate substrates with low to high pH. A nonamended control was also maintained. The substrates received no other fertilizer amendments. Substrates were filled into nursery containers (2.8 L) and maintained in a nursery setting with 1.2 cm·d−1 overhead irrigation. At 1 and 6 weeks after potting, four containers of each lime treatment were harvested to determine substrate pH and availability of 13 nutrients. Substrate solutions used for analysis were obtained with the saturated media extract method. Water-extractable phosphorus and DTPA-extractable boron, iron, copper, and aluminum decreased with increasing substrate pH. Other nutrients were either nonresponsive to substrate pH or the observed response was deemed more likely caused by calcium competition on cation exchange sites.

“…In fact, the limit of a tension of 10 kPa was suggested by De Boodt and De Waele (1968) because it strongly inhibited Ficus growth; thus, the definition of water availability is species-specific. There is no exact tension at which water is unavailable to plants in general (Buamscha et al, 2007).…”

mentioning

confidence: 99%

E-values Generated from Substrate Dry-down Models as a Physical Property Measurement for Evaluating and Classifying Wetness of Root Substrates

Evans¹,

Zanin²,

Cavins³

2011

Water-holding capacity represents the volume of water retained by a substrate after a saturating irrigation and drainage, and it is often referred to as container capacity. However, water-holding capacity is a time-specific measurement that is limited to the status of the substrate immediately after saturation and drainage. It does not provide information regarding how quickly water is lost from the substrate, the substrate water status over time, or the irrigation frequency required for a substrate under specific conditions. A new procedure was developed that generated a single numeric value that described the wetness of a substrate and in so doing took into account the substrate's water-holding capacity and drying rate. This value was referred to as an E-value. For substrates included in this study, E-values ranged from a low of 6 for parboiled fresh rice hulls (PBH) to a high of 93 for the commercial substrate Metro Mix 360. The procedure was shown to generate E-values that were as would be expected for the evaluated substrates and also ranked the substrates as would have been expected. Over repeated evaluations, the procedure was demonstrated to have a maximum inherent variability of plus or minus one E-value.