Kenaf (Hibiscus cannabinus) is an alternative fiber crop being grown in Mississippi that maybe used as a tree-less fiber substitute for making paper. A by-product in this process is the pithy light-weight fiber core. The objective of this study was to examine the chemical and physical properties of kenaf fiber core as a medium component in growing woody ornamentals and compare to pine bark. Comparisons of media in which Ilex crenata `Cherokee' and Rhodoendron eirocarpum `Wakabuisi' were grown were made. The physical and chemical properties including bulk density, total pore space, water retention, pH and soluble salt concentrations were determined. Aged kenaf had lower pH values than fresh and both aged and fresh kenaf had higher pH values than pine bark. The total pore space of kenaf was lower than the pore space of pine bark. At the termination of the study, the kenaf media had considerable shrinkage, which was considered unsuitable for a long-term crop.
Physical characteristics [initial water content, surface area, surface area: volume (SA: V) ratio, cuticle weight, epicuticular wax content, and surface morphology] were examined to determine relationships between physical properties and water-loss `rate in pepper fruits. `Keystone', `NuMex R Naky', and `Santa Fe Grande' peppers, differing in physical characteristics, were stored at 8, 14, or 20C. Water-loss rate increased linearly with storage time at each temperature and was different for each cultivar. Water-loss rate was positively correlated with initial water content at 14 and 20C, SA: V ratio at all temperatures, and cuticle thickness at 14 and 20C. Water-loss rate was negatively correlated with surface area and epicuticular wax content at all temperatures. Stomata were absent on the fruit surface, and epicuticular wax was amorphous for each cultivar.
Chemical properties of unprocessed coconut husks varied significantly between 11 sources tested. The pH was significantly different between sources and ranged from 5.9 to 6.9. The electrical conductivities were significantly different between sources and ranged from 1.2 to 2.8 mS·cm–1. The levels of Na, K, P, and Cl were significantly different between sources and ranged from 23 to 88, 126 to 236, 8 to 33, and 304 to 704 ppm, respectively. The B, Cu, Fe, Ni, S, Zn, Mn, and Mo levels were all significantly different between sources and ranged from nondetectable levels to 12.7 ppm. The NH4-N, NO3-N, Ca, and Mg levels were not significantly different between sources and ranged from 0.2 to 1.8, 0.2 to 0.9, 2.9 to 7.3, and nondetectable to 4.6 ppm, respectively. Coir dust produced by screening of waste grade coir through 13-, 6-, or 3-mm screens had significantly different bulk densities, air-filled pore space, water filled pore space and water-holding capacities compared to nonscreened waste grade coir. However, total pore space and total solids were not significantly affected by screening. Screen size did not significantly affect physical properties. Compression pressures used for formation of coir dust blocks significantly affected physical properties. Additionally, coir dust age significantly affected chemical properties.
Chemical properties of unprocessed coconut (Cocos nucifera L.) husks varied significantly among 11 sources tested. The pH and electrical conductivities were significantly different among husk sources and ranged from 5.9 to 6.9 and 1.2 to 2.8 mS·cm−1, respectively. The
Physical properties differed significantly among five Philippine-produced coconut (Cocos nucifera L.) coir dust sources. Bulk densities ranged from 0.04 to 0.08 g·cm–3. Air-filled pore space, water-filled pore space, and total pore space ranged from 9.5% to 12.6%, 73.0% to 80.0%, and 85.5% to 89.5% (v/v), respectively. Total solids accounted for 10.5% to 14.5% of total volume, and water-holding capacities ranged from 750% to 1100% of dry weight. Significant differences existed in particle size distribution, with the largest differences occurring for particle sizes <8.0 mm and 0.25 to 0.50 mm in diameter. Chemical properties were determined for 12 sources from the Philippines, Sri Lanka, or Indonesia. The pH and electrical conductivities ranged from 5.6 to 6.9 and 0.3 to 2.9 mS·cm–1, respectively, and were significantly different among sources. No significant differences occurred among samples with respect to Fe, Mn, Zn, B, Cu, NH4-N, and Mg concentrations. Coir dust samples contained Fe, Mn, Zn, B, and Cu at 0.01 to 0.07 mg·L–1. The levels of NH4-N and Mg were 0.1 to 0.2 and 1.0 to 7.4 mg·L–1, respectively. Significant differences occurred between sources for Ca, Na, and NO3-N, with levels (mg·L–1) ranging from 1.0 to 24.3, from 22.3 to 88.3, and from 0.4 to 7.0, respectively. The widest ranges occurred in K (19 to 948 mg·L–1) and Cl (26 to 1636 mg·L–1). Sources differed with respect to cation exchange capacities, with values ranging from 38.9 to 60.0 meq/100 g.
In temperate regions, the vegetable growing season is short and plastic mulches are usually left in the field for an entire year when used for double cropping. This work was conducted to study the effect of weathering on the physical, optical, and thermal properties of plastic mulches during double cropping. The design was a randomized complete block with four replications. The mulches were black, grey, infrared transmitting brown (IRT-brown), IRT-green, white, and white-on-black (co-extruded white/black). Tomato was grown the first year and cucumber the following year. The grey mulch degraded substantially during double cropping (only 40% of bed was covered the second year) and showed an increase in light transmission and a decrease in heat accumulation (degree-days). The black, whiteon-black, white, IRT-brown, and IRT green mulches showed less degradation with 93%, 91%, 85%, 75%, and 61% soil cover, respectively. However, their soil warming ability was significantly reduced. These mulches could be used for double cropping to suppress weeds and to reduce inputs associated with plastic purchase, laying, and disposal. However, they may not provide adequate soil warming early in the season for the second crop.
The effects of various substrates with or without earthworm [Eisenia fetida (Savigny, 1826] castings on growth of marigolds were evaluated. In addition, the physical and chemical properties of such substrates were determined. Castings had a greater nutrient content than the remaining substrates. The 4 pine bark: 1 sand treatment (v/v) (PBS) had higher P, K, and Zn than 7 peat moss: 3 perlite (v/v) (PP). PP had the lowest nutrient content of all substrates. Castings (C) had the highest pH followed by 1 PBS: 1 C (v/v), 2 PBS: 1C (v/v) and 3 PBS: 1C (v/v). Sunshine Mix 1 and PP had the lowest pH. EC (ER) was increased by castings, which had high ER. Castings and PP had the greatest percentage pore space. Water-holding capacity was greatest for 2 PBS: 1C (v/v) compared with Sunshine Mix 1 followed by castings. Earthworm castings increased plant growth index, stem diameter, root growth, dry weight, and flower number of marigolds compared with PP, Sunshine Mix 1, and PBS. All mixtures of castings (C) with PP, PBS, except 3 PBS: 1C (v/v), increase the growth index of plants. 1 PP: 1 C (v/v), increased flower number compared with all substrates without castings. Castings alone increased number of open flowers, but did not differ from 1 PP: 1 C or 3 PP:1 C.
`Solar Set' tomatoes (Lycopersicon esculentum Mill.) were harvested at the mature-green stage of development and treated with 50 μL·L-1 ethylene at 20 °C. Breaker-stage fruit were dropped from 40 cm onto a solid surface to induce internal bruising and held along with undropped fruit at 20 °C. At the ripe stage, pericarp, locule, and placental tissues were analyzed for soluble sugars, vitamin C, pigments, titratable acidity, soluble solids content, pericarp electrolyte leakage, extractable polygalacturonase activity, and locule tissue consistency. Bruising significantly affected chemical composition and physical properties of pericarp and locule tissues, but not placental tissue. For bruised locule tissue, carotenoids, vitamin C, and titratable acidity were 37%, 15%, and 15%, lower, respectively, than unbruised fruit. For bruised pericarp tissue, vitamin C content was 16% lower than for unbruised tissue, whereas bruising increased electrolyte leakage and extractable polygalacturonase activity by 25% and 33%, respectively. Evidence of abnormal ripening following impact bruising was confined to locule and pericarp tissues and may be related to the disruption of cell structure and altered enzyme activity.
Hydration of three commercial hydrophilic polyacrylamide gels in deionized water ranged from 340 to 420 g per gram of gel. Hydration was progressively inhibited by fertilizer salt concentrations from 0 to 20 meq·liter-1. Hydration of the gels in the presence of divalent cations (Ca2+ and Mg2+) and monovalent cations (K+ and NH4 +) at 20 meq·liter-1 was reduced to ≈10% and 20% of maximum, respectively. The valence of the accompanying anion did not affect hydration. Gel hydration was unaffected by urea over the range of 2 to 20 mm. Sequential rinses of the hydrated gels with deionized water completely reversed the inhibition due to the monovalent, but not the divalent, cations. The electroconductivity (EC) of the external solution increased during gel hydration. In the presence of fertilizer salts, the physical properties of a 2 redwood sawdust : 1 sand (v/v) container mix were unaffected by hydrophilic gel additions of 1.2 and 2.4 kg·m-3 (1 × and 2 × the recommended rate, respectively).
substrate physical properties as it has on soil physical properties. Texture for soilless substrates can be defined as the distribution and proportions of particle sizes in a substrate resulting from grinding, processing, and decomposition of the parent