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 (Db). 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 Db while decreasing AS. Total porosity decreased with the addition of sand. The magnitude of change in TP, AS, CC, and Db 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.
Funding for this work was provided, in part, by the Virginia Agricultural Experiment Stations, Agricultural Research Service, and the Hatch Programs of the National Institute of Food and Agriculture, U.S. Department of Agriculture.
Trade or brand names used in this publication do not constitute a guarantee or warranty of the products by Virginia Polytechnic Institute and State University, U.S. Department of Agriculture, North Carolina State University, or Louisiana State University and do not imply their approval to the exclusion of other products or vendors that may also be suitable.
BilderbackT.E.2000Pine bark handling and storage. North Carolina State Department of Horticultre Science Nursery Crops. <http://www.nurserycropscience.info/substrates/manage-inventory/extension-pubs/pine-bark-storage-and-handling.doc/view>
BilderbackT.BoyerC.ChappellM.FainG.FareD.GilliamC.JacksonB.E.Lea-CoxJ.LeBudeA.V.NiemieraA.OwenJ.RuterJ.TiltK.WarrenS.WhiteS.WhitwellT.WrightR.YeagerT.2013Best management practices: Guide for producing nursery crops. 3rd ed. Southern Nurs. Assn. Acworth GA
BilderbackT.E.WarrenS.L.OwenJ.S.JrAlbanoJ.P.2005Healthy substrates need physicals too!HortTechnology15747751
Bilderback,T.E.Warren,S.L.Owen,J.S.JrAlbano,J.P.2005Healthy substrates need physicals too!15747751)| false
FieldsJ.S.OwenJ.S.JrScogginsH.L.2017The influence of substrate hydraulic conductivity on plant water status of an ornamental container crop grown in suboptimal substrate water potentialsHortScience5214191428
Fields,J.S.Owen,J.S.JrScoggins,H.L.2017The influence of substrate hydraulic conductivity on plant water status of an ornamental container crop grown in suboptimal substrate water potentials5214191428)| false
JacksonB.E.WrightR.D.BarnesM.C.2010Methods of constructing a pine tree substrate from various wood particle sizes, organic amendments, and sand for desired physical properties and plant growthHortScience45103112
Jackson,B.E.Wright,R.D.Barnes,M.C.2010Methods of constructing a pine tree substrate from various wood particle sizes, organic amendments, and sand for desired physical properties and plant growth45103112)| false
KaderabekL.E.2017Effects of aging on the physical chemical and hydrologic properties of pine bark substrates. North Carolina State Univ. Raleigh NC Thesis
Lea-CoxJ.D.SmithI.E.1997The interaction of air-filled porosity and irrigation regime on the growth of three woody perennial (Citrus) species in pine bark substratesProc. Southern Nurs. Assoc. Res. Conf. 42169174
Lea-Cox,J.D.Smith,I.E.1997The interaction of air-filled porosity and irrigation regime on the growth of three woody perennial (Citrus) species in pine bark substrates42169174)| false