The use of shredded bark, wood chips, and other organic mulches to conserve water and moderate soil temperatures is a common practice in landscape maintenance. Four mulch materials (cottonseed hulls, cypress pulp, pine bark, and pine straw) were examined to determine effects on plant growth and soil conditions in annual flower beds during a 1-year rotation of warm season to cool season annuals. Inhibited plant growth was observed in pine bark treatments at the conclusion of the growing season for both plantings. Effects on soil conditions were insignificant over the year-long study in pine bark treatments. To further investigate potential phytotoxic effects of pine bark and other mulch used in the initial study, a seed bioassay was performed to determine the influence of mulch extracts in solution on germination and primary root elongation.
R.A. Mirabello, A.E. Einert, and G.L. Klingaman
M.P. Bañados, M.S. Santiago, and C. Eterovic
The main form of nitrogen reserves during overwintering are amino acids and proteins. Specific proteins called bark storage proteins (BSP) have been characterized in many tree species. To identify BSPs in `O'Henry' peach, `Angeleno' plum, and `Early Burlat' cherry trees, samples of bark were collected from January through December 1993 from trees growing under field conditions in Santiago, Chile. SDS-PAGE analyses were used to characterize the seasonal variation on the protein pattern on the bark of those Prunus species. A 60 kDa BSP was identified in the bark of all three species, which corresponds to the main protein present in the bark during the winter. This protein may play an important role as a nitrogen reserve in these fruit trees.
W.J. Foster, R.D. Wright, M.M. Alley, and T.H. Yeager
Pine bark was shown to adsorb 1.5 mg of N/g of bark when NH4 solutions were leached through the bark. Increasing pH of bark increased adsorbed NH4. At pH 3.3, only NH4 was adsorbed to bark particles when a fertilizer solution containing NH4, Ca, K, and Mg was applied. However, adsorption of NH4 and other cations increased as pH was increased from 3.8 to 5.8. These data indicate that 2 types of sites exist for the adsorption of NH4 to pine bark. One site is effective at lower pH; the other is active as pH increases. Daily application of 2.5 cm of water containing 50 ppm NH4 required 20 days for equilibration to occur so as to satisfy all binding sites. Thus, incorporation of NH4 into a pine-bark medium prior to planting may be advisable to prevent low N levels from occurring in the container solution due to NH4 binding when plants are first planted and fertilized.
J. C. Neal and D. F. Wagner
Selected physical and chemical properties of pine bark, 2 sources of coal cinders, and mixtures thereof, were evaluated as container media components. Bulk density, air-filled pore space, particle-size distribution, cation exchange capacity, and soluble salt levels were quantified. Aged and freshly combusted cinders demonstrated no major physical or chemical disadvantages when used in container media. Acid and water extracts indicated that both sources of coal cinders released significant amounts of micronutrients and heavy metals. The concentrations of certain metals were sufficiently high to warrant concern over the possibility of plant nutritional disorders; whereas, other released elements resembled those of a supplemental micronutrient fertilizer.
D. F. Wagner and J. C. Neal
Coal cinders with pine bark were evaluated as containerized plant growing medium. Rhododendron obtusum Lindl. ‘Hinodegiri’ liners were grown in several combinations of media composed of pine bark mixed with an aged and a recently combusted source of cinders. Measurements of media pH, soluble salts, NO3 − –N, NH4 + –N, and 19 extractable nutrient and metallic ions were obtained. Leaf tissue samples were analyzed for 19 elements. Top dry weight, visual growth and chlorosis ratings, and root visual ratings constituted the plant growth parameters measured. Satisfactory growth was generated in pine bark amended with up to 50% cinders from either source.
Richard Ogden and Harry Mills
Initial availability of NO3, NH4, and urea applied to limed or unlimed pine bark as well as the form of N available over a period of 21 days was determined. Nitrate was not present in significant amounts when N was supplied as either urea or NH4, and the extractable amounts of both urea and NH4 declined significantly over the course of the experiment. Urea was the least effective of the N forms in supplying N in an extractable form. With NO3 as the N source, addition of lime to pine bark resulted in significant reductions in extractable NO3. Applications of NH4 gave relatively equal amounts of extractable N as NH4 from limed and unlimed pine bark after 21 days. It was concluded that N interaction and N transformations with these N forms in pine bark would influence total available N as well as the form of N available for plant growth.
Zoran Jeknic and Tony H. H. Chen
The development of bud dormancy in poplar plants is initiated by short-day photoperiods (SD). During the development of bud dormancy, there was a gradual increase in the force required to peel off the bark from the stems. We measured the force required for bark peeling and investigated the cellular changes associated with this phenomenon. Stem samples were collected from plants which had been grown under SD for different period of time up to 10 weeks. At each sampling date, the forces required to peel off the bark were measured by a tensiometer. At the same time, samples were fixed to examine ultrastructural changes by transmission electron microscopy. We have observed that there was a significant increase in the force (in Newtons) required to peel off bark from poplar stems when the development of dormancy was initiated by SD treatment. Many ultrastructural changes were observed, including the accumulation of bark storage proteins, the break down of the central vacuole to form many small vacuoles, thickened cell walls, etc. Efforts have been made to relate ultrastructural alterations to changes in the force required for bark peeling.
Graham J. Wright and Irwin E. Smith
Composted pine bark is one of the most important substrates used in the seedling industry today. Previous work suggested the availability of inherent Potassium (K) in the bark. This research confirmed the availability of K and indicated that little or no K is needed for seedling production when pine bark is used as a substrate. Pre-enrichment rates ranged from 0 to 460 g.K.m-3, with a supplemental solution application of 0 to 200 mg.K.l-1. No evidence of K deficiencies or toxicities were detected. Three K sources, KCl, KNO3, and K2SO4 were used in the pre-enrichment of the bark. No differences were noted for top fresh mass, seedling height, root dry mass, root to shoot ratio and percentage moisture. Seedlings grown in treatments without and supplementary K showed tissue contents of 162.5 mg.K.kg-1. This research suggests the possibility of reducing the levels of-K applied to seedlings grown in a composted pine bark substrate.
Alexander X. Niemiera
Amending soilless media with micronutrients is a routine nursery practice. The objective of this research was to determine the micronutrient status of pine bark amended with two sulfate micronutrient sources and a control (unmended). Limed pine bark was unamended, amended with Ironite (1 and 2 g/l), or Micromax (1g/l). Bark was irrigated with distilled water in amounts equivalent to 30, 60, 90, and 120 irrigations (.63 cm per irrigation). Following irrigations, Cu, Fe, Mn, and Zn were extracted with a modified saturated media extract method using .001M DPTA as the extractant. Irrigation amount had no effect on Cu and Mn concentrations which were greater in the Micromax treatment than the Ironite or control treatments. A micronutrient source × irrigation interaction existed for Fe and Zn concentrations requiring regression analysis. In general, slope values indicating the decrease in micronutrient values with increasing irrigations were quite low (≤ .001) for each source. Regardless of irrigation amount, Fe and Zn concentrations were similar for amended and unamended bark.
R. A. Backhaus, R. M. Sachs, and H. Z. Hield
Morphactins, mixed with non-phytotoxic paraffinic, low molecular weight oil, were applied as bark bands and tested for growth inhibition of trees growing under field conditions. Three species were tested: Monterey pine (Pinus radiata D. Don.), olive (Olea europaea L. cv. Manzanillo) and eucalyptus (Eucalyptus globulus Labill). Shoot elongation was inhibited in all three species, but sensitivity to the treatment varied.