School of Agriculture, Food and Ecosystem Sciences - Research Publications
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ItemQuality assessment of the drying process for Eucalyptus delegatensis timber using greenhouse solar drying technology(Springer Verlag, 2019-01-24)The aim of this study was to investigate the process of drying Eucalyptus delegatensis in a greenhouse solar kiln. Specific objectives were to assess stress formation, moisture gradients and timber distortion, the moisture content distribution within various sections of the timber stack, and internal checking and collapse development within the boards. The maximal temperature and relative humidity (RH) during day time were set at 430C/72% RH. In the night time the temperature was at ambient condition with 90% RH. The strain measurements were undertaken before and after the samples were sliced. The timber quality at the end of drying was assessed based on Australian and New Zealand standard (AS/NZS 4787:2001). The moisture content values in the three different sections (front, middle and end) of 2400 mm long boards were compared by Analysis of Variance. The results showed that the mean compressive strain was -2 x 10-4 mm/mm in the core layers and the tensile strain was 14 x 10-4 mm/mm in the outer layers. All sample boards were within the acceptable limits for cupping, spring and bow, even though the relative humidity level did not reach the set value. However, the amount of twist in three out of twelve sample boards was above the acceptable limit. Mean moisture gradient was 0.6%. There was a significant difference in moisture content at end section compared to the front and middle sections. Internal checking, collapse and residual stress were graded as Class “C” (class A is the highest grade and D is the lowest).
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ItemDrying timber in a solar kiln using an intermittent drying schedule of conventional laboratory kiln(Taylor & Francis, 2018-10-01)The purpose of this study was to apply an intermittent drying schedule developed from a conventional kiln to a solar kiln. Implementing this experiment could help better understand the oscillation of the temperature inside a solar kiln and timber quality during drying progress. The theoretical recharge and discharge curves were used to predict the temperature inside the solar kiln using experimental data obtained previously using a solar kiln. The surface and internal checks were measured using ImageJ freeware, and the development of the Moisture Content (MC) profile was assessed by coring and slicing method for the Eucalyptus delegatensis boards during drying. The results showed that the recharge and dis-charge model can predict the temperature with less than 2 C error from the experimental data in the solar kiln. The total drying time to 12% MC was 87 days for the solar kiln. The drying rate was equivalent to the conventional kiln decreasing at an average rate of 0.2%per day. The surface check formation was found when the MC gradient between the core and the case of the board was greater than 42% at 9 days of drying in the solar kiln and conventional laboratory kiln. The applied drying schedule used in the solar kiln was success-ful and offered similar drying time. However, the oscillation of temperature in the intermittent drying will require further improvement to get closer conditions in a solar kiln.
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ItemComparing two intermittent drying schedules for timber drying quality(Taylor & Francis, 2018)Intermittent drying techniques for drying timber may provide various benefits by improving timber quality and addressing energy efficiency through saving in energy consumption. The purpose of this study was to compare two intermittent drying schedules applied in the treatment of Eucalyptus delegatensis boards, through assessing surface and internal check development, moisture content (MC) profiles during drying, and timber distortions at the end of drying. The study used identical conditions during the heating phase at 45°C/60% relative humidity (RH), except for RH during the nonheating phase (80 and 90%). The results, discussed in this paper, analyzed the timber quality during and at the end of drying. The different RH during the nonheating phase did not generate a significant difference in MC at the case boards between the two drying schedules. The assessed quality of timber at the end of drying was based on AS/NZS 4787:2001. MC gradient, drying stress residual, internal checking and collapse were graded as class “A” (class A is the highest grade and D is the lowest). Bow, cupping, and spring were under the permissible levels based on grading standard AS 2082–2007. Measured data were validated using Drytek® simulation software showing MC movement in case boards.
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ItemNo Preview AvailableApplying a GIS-based Fuzzy Method to Identify Suitable Locations for Solar Kilns(NORTH CAROLINA STATE UNIV DEPT WOOD & PAPER SCI, 2018)
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ItemAssessing the Impact of Microwave Treatment on Soil Microbial Populations(Avanti Publishers, 2015-07-28)Microwave soil treatment can kill weed plants and their seeds in the soil. It has also been demonstrated elsewhere that microwave soil treatment can kill nematodes in the soil; however few studies have considered the effect of microwave soil treatment on other key soil biota. This study explored the effect of microwave soil treatment on soil bacteria, fungi, and various protozoa. The research used a series of experiments using different techniques to verify the effect of varying degrees of microwave treatment on these soil biota. Microwave treatment reduces bacterial populations in the top layers of soil, but populations that are deeper in the soil are relatively unaffected. Bacterial populations increased significantly within a month of microwave treatment. E. coli populations experienced a 10-5 reduction in numbers in the top layer of soil by 500 J cm-2 of microwave energy; however other soil bacteria survived over 3000 J cm-2 of microwave energy applied to the soil surface, suggesting that some species are more susceptible to microwave treatment than others. No significant response of soil fungi, ciliates, amoeba and flagellates could be attributed to a microwave dose response.
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ItemThe Effect of Microwave Treatment on Ryegrass and Wild Radish Plants and Seeds(Avanti Publishers, 2015-07-28)Annual ryegrass (Lolium rigidum) and wild radish (Raphanus raphanistrum) are significant weeds in Australian winter cropping systems. These species have developed significant herbicide resistance and new control strategies need to be developed. Microwave energy has been considered for weed control for some time. The research considered the effect of varying amounts of microwave energy on plants and their seeds for each species. Several experiments explored the interaction between microwave energy and seed depth in the soil. Plant responses to microwave energy were also determined for each species. Seed treatment requires higher energy applications than plant treatment and is conceptually similar to soil fumigation treatments. Soil treatment may have application in some high value horticultural crops, which already use soil fumigation. Microwave treatment of plants requires less energy, with wild radish requiring about 60 Jcm-2 to achieve 100% mortality, while ryegrass plants require about 370 Jcm-2 to achieve 100% mortality. Microwave treatment of growing plants can be compared to the application of herbicide. Therefore control of growing plants should be the focus of developing a commercially viable microwave weed control device for cropping systems.
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ItemIntegrated Weed Management in Wheat under Subtropical Rain-Fed Conditions(Avanti, 2015-12-30)A field experiment was carried out from July, 2013 to May, 2014 at University Research Farm Chakwal Road, of Pir Mehr Ali Shah-Arid Agriculture University, Rawalpindi to evaluate the integrated weed control management strategies followed by summer green manure practices on weeds and grain yield of wheat under rain-fed conditions. The experiment was laid out in a 2-factor factorial Randomized Complete Block Design (RCBD) in strip plot arrangement with three replications of each treatment. The sorghum and sesbania crops were sown in the first week of July, 2013 and incorporated into soil as green manure at the end of August, 2013 after attaining sufficient biomass. The wheat variety "Chakwal-50" was sown with a tractor drawn rabi drill in the last week of October, 2013 with a seeding rate of 125kg ha-1. The herbicides used were buctril super @ 750ml ha-1 and isoproturon @ 1.00kg a.i. ha-1. The weeds found in the wheat crop were Fumaria indica L., Convolvulus arvensis L., Chenonpodium album L., Asphodelus tenuifolius L. The incorporation of sorghum green manuring resulted in good control to suppress the weed population and biomass. The buctril super @ 750ml ha-1 along with tharphali significantly reduced the weed density (18.8 m-2), weed biomass (12.7g m-2) and increased weed control efficiency (71.1%) followed by isoproturon applied @ 1.00kg a.i. ha-1. The highest grains yield of 3208.5kg ha-1 was recorded in the plots where weeds were controlled with buctril super @ 750ml ha-1 followed by tharphali where sorghum green manure was incorporated in summer followed by the isoproturon application @ 1.00kg a.i. ha-1(3016.1kg ha-1) in combination with tharphali in the same green manuring crop.
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ItemSimultaneous heat and moisture diffusion during microwave heating of moist wood(AMER SOC AGRICULTURAL & BIOLOGICAL ENGINEERS, 2007-03)