School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemImpregnation of wood with stains( 2007)
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ItemMechanical properties of wood following microwave and resin modification( 2002)The influence of microwave and resin modification of wood on its density, modulus of elasticity (MOE), modulus of rupture (MOR) and surface hardness is the subject of this thesis. Microwave energy has been used in industrial processing for many years. Microwave energy is an attractive option for wood processing and drying. Recent studies have shown that microwave energy can be used to modify wood by rupturing ray cells to form a large number of cavities in its radial/longitudinal planes resulting in micro voids of various sizes throughout its cross-section. The resultant wood (`Torgvin') is more permeable and more flexible but has a lower density and mechanical properties (MOE, MOR and surface hardness) compared to the original wood. Further treatment to restore initial density and mechanical properties by addition of resin has resulted in a new timber product `Vintorg'. Initial trials of Vintorg production employed isocyanate resin. An increase in MOE, an increase in surface hardness and a 100% restoration of MOR of P. radiata heartwood was achieved. Despite being a tough adhesive, isocyanate has some drawbacks that may not make it acceptable for the production of Vintorg. This study therefore focused on melamine formaldehyde (MF) and furfuryl alcohol (FFA) resins as potential substitutes for isocyante resin in the manufacture of Vintorg. The study evaluates Vintorg produced by soaking P. radiata and E. regnans in these two resins. A factorial design is used to evaluate the effect of wood species, resin type and duration of soaking on resin uptake, resin loss, increase in density of Torgvin, density of Vintorg and mechanical properties of Vintorg. The results show that wood species and duration of soaking and resin type have significant effects on resin uptake. The increase in the density of Torgvin during the manufacture of Vintorg is found to be influenced by wood species, duration of soaking and resin type. A higher overall increase in the density of Torgvin was obtained in E. regnans compared to P. radiata. Melamine formaldehyde resin tends to have a greater effect on the increase in the density of E. regnans than P. radiata. Torgvin samples impregnated with FFA had a greater effect on increasing the density of P. radiata than E. regnans. Vintorg in the timber species tested is found to be the same or higher in MOE, much higher in density but lower in MOR than natural wood from the same species, irrespective of wood species, resin type or soaking time. Vintorg produced from P. radiata is also higher in surface hardness than natural wood from the same species irrespective of resin type and soaking time. It is interesting to note that surface hardness of Vintorg is lower in E. regnans as compared to natural wood from the same species. It is also evident that FFA and MF Vintorg are the same or higher in MOE but lower in MOR than isocyanateVintorg from the same species irrespective of wood species tested and the duration of soaking used. The FFA and MF Vintorg from are also the same or higher in surface hardness in the case of P. radiata but same or lower in the case of E. regnans. It is concluded that it may be possible to substitute the two resins for isocyanate resin in the production of Vintorg provided that a way is devised to ensure that the MOR of the resultant Vintorg is at least same or higher than that of original wood. It is recommended that further research be carried out to establish a microwave regime for optimal wood permeability and whilst minimizing the reduction in MOR, and that low cost, environmentally friendly resin systems are developed with low viscosity. These resins need to be tough enough to result in Vintorg with characteristics similar to Vintorg produced with isocyanate resin and superior to natural wood in terms of mechanical properties.
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ItemResponses of young sheep to supplements when fed low quality roughages( 1999)The morphological components of which cereal straw is composed vary in composition and nutritive value. In a survey of relevant literature, stem materials (ST) are usually found to be consumed by ruminant animals at a slower rate than leaf material (LF) from the same crop residues when these are fed alone as separated fractions. This is attributed to the higher content of cell wall constituents (CWCs) and often lower content of N of ST. Because ST and LF can vary in proportions in the roughage fed as a basal feed, the response of animals to supplements might also be expected to be variable particularly when the basal feed is offered in excess that permits selection. In particular the response to supplemental N sources varying in ruminai degradability may vary. The objective of this thesis program was to investigate the interactions between the basal roughage and supplement measured as effects on digestion and LW responses of young sheep. The overall hypothesis was that across diets made up of different proportions of LF and ST fractions of cereal straw, the response to N supplements is dependent on CWCs concentration. The program was completed through a series of experiments conducted at the Mt Derrimut Field Satation of the University of Melbourne. In all experiments the animals were fed on a basal feed of LF or ST fractions of barley straw, with supplements including (a) Bar+USS, barley grain (Bar) fortified with urea solution prepared at a ratio of 5:1 (urea plus Na,SO4). (b) USS, urea solution alone added to the basal roughage and (c) FM, fishmeal. With each basal feed one group of lambs did not receive any supplement and served as a control group (CONT). Experiment 1 (Chapter 3) was conducted to evaluate chemical and nutritional characteristics of straw fractions of Parwon cultivar barley. Straw was separated into 4 fractions - stem (ST), leaf blade (LB), leaf sheath (LS) and broken fractions plus weeds (OT). The separated fractions were analysed chemically ( van Soest, 1974) and in vitro digestibility (Tilley and Terry 1964 ) determined. ST was the largest fraction and contained a significantly higher concentration of neutral detergent fibre (NDF; p<0.01) than LB, LS and OT (83.1, 78.6, 76.8,and 71.5 g/100g respectively). ST contained less hemicellulose (HC) than LB but more than LS and OT (37.5, 39.6, 36.3, and 35.7 respectively). N content was lower in ST than in LB, LS and OT fractions (0.4, 0.9, 0.6, and 0.7 respectively). Digestibility in vitro was significantly lower (P<0.001) for ST than for other fractions (38.5, 72.7, 60.1, and 63.0 respectively) while energy required for grinding (Chenost 1966) was much higher (P<0.001) for ST than for other fractions (121, 54.6, 64.2, 56.6 respectivly). In Experiment 2 (Chapter 4) ST and LF fractions of the same Parwon barley straw were fed as the basal feed to lambs and DM intake of ST was 15% lower than for LF (403 vs 473 g/d). When LF feed was supplemented with USS and FM, DM intake was greater by 28% and 25% respectively, while supplementation with Bar+USS resulted in 10% lower LF intake. In contrast, with animals fed ST as the basal roughage, only FM led to an increase in DM intake of only 10%. Supplementation with Bar+US and USS and FM improved overall digestibility, estimated metabolisable energy intake and N intake. Low N intakes on the basal roughages supported low ruminai ammonia-N concentrations (mg/1) immediately before feeding (ST, 20.4 ; LF 35.8), but these were improved where supplements had been fed with each of ST Bar+USS, 263.7; USS, 186.7; and FM, 151) and LF (Bar+USS, 219.5; USS, 62.5; and FM, 150). Six hours after feeding, ammonia-N concentrations (mg/l)were higher for ST (99) still low for LF(35) when fed alone, reduced below the prefeeding levels by supplements of Bar+USS (ST,167; LF 173) but raised by USS (ST, 201; LF 148) and FM (ST, 114; LF, 192). The concentrations of total volatile fatty acids (VFA) in rumen fluid (mMoUl) were not significantly different for ST and LF before feeding except where FM was the supplement, or six hours after feeding except where Bar+USS or USS were fed with LF (before feeding: ST, 51; Bar+USS, 55.7; USS,46.5; FM, 56 ; LF, 42.6; Bar+USS, 53; USS, 55.5; FM, 63.6; 6h after feeding ST, 55.5; Bar+USS, 70.2; USS, 62.1; FM, 50.4 ; LF, 55.7; Bar+USS, 69.5; USS, 60.9; FM, 60.9). Lambs on ST and LF alone lost weight (ST, -105; LF -98 g/d ). Rate of liveweight loss was less when Bar+USS (ST, -32.3; LF -2.4g/d) and USS (ST, -79.8; LF -31.2 g/d) supplements were fed, while FM promoted LW gain (ST, 37.5; LF, 72.4g/d). N retention data was consistent with these LW gains, except where Bar+USS was the supplement, in which case the animals were in positive N balance though losing weight. Wool growth was significantly improved (P<0.001) only by FM on both ST (+47%) and LF (+57%) basal roughages. In Experiments 3 and 4 (Chapter . 5 and 6) the objective was to investigate the factors responsible for low feed intake and poor performance of lambs fed ST compred to those on LF. The DMI (g/d) of lambs fed ST and LF were similar to those achieved in experiment 2; and were significantly greater for LF (P<0.001). Likewise supplements of Bar+USS, USS and FM had similar effects to those reported for experiment 2_ Changes in DMI, MEI ruminai environment before feeding or 6 and:12 hours after feeding were consistent with those recorded during experiment 2. However concentration of total VFA was significantly elevated at 12 hours after feeding. Differences in ruminal environment were evident in terms of VFA concentrations and the distribution of rumen digesta particulate material in different size fractions; both variables were affected both by the basal diet and the supplement. For LF, the proportions of particles >2mm and of very fine particles (0.125 mm) were greater and for particles between 0.5 and 1 mm less those for ST in all cases. Further, the proportion of particles >2mm was less where FM was fed than for any other feeding regime. The mean retention times of rumen fluid, measured from CoEDTA dilution rate, and calculated for rumen particulate material was longer (24%, P<0.01) for ST than for LF but there was no significant effect of supplement on this (Experiment 4, Chapter 6). The mean percentage of very fine particles in the faeces of lambs fed on LF was higher than for lambs fed ST alone or with supplements. Rate of ruminai degradation of OM of ST and LF as measured by nylon bag technique ( Experiment 3, Chapter 5) was similar at 12 and 24 hours but greater for LF than for ST at 48 and 96 hours of incubation. Bar (cracked whole grain) was degraded more rapidly and extensiveley than FM; in LF fed sheep this difference was more marked. Rate of degradation of acid detergent fibre (ADF) was influenced by the kind of supplement and was greatest in lambs given FM , and least in lambs given ST with no supplement. Only the FM supplement resulted in LW gains, though rates of LW loss were least and LW gains with FM were greatest with LF as the basal roughage. The responses are interpreted as flowing from the greater proportion of ADF and lignin in the CWCs content and the greater digestibility of ADF in the LF fraction. The ST feed fraction with higher concentrations of cell wall constituents (CWCs) as NDF was eaten at a slower rate (Experiment 5, Chapter 7) and digesta particulate material and, in these experiments, the fluid phase are retained longer in the rumen. LF showed not only an advantage over ST in these respects but also in terms of a number of important digestion parameters supported a greater response to supplements, particularly N supplements of low degradability. Thus FM is these experiments interacted with the roughage component of the diet. It provided more consistent ruminai ammonia concentrations supporting a better environment for microbial activity and growth. Microbial protein together with undegraded dietary protein together provide a balance of nutrients that allows LW gains on otherwise submaintenance basal feeds. The greater enhancement of performance with LF compared to ST and the particle size measurements suggest that greater fragmentability of LF may be a major contributor . In terms of technical improvement of livestock feeding systems, providing the animal with opportunity for selection of more leaf and less stem may improve the likelihood of responses to supplements but this was not demonstrated in Experiment 5. FM was used as the experimental supplement to provide slowly degraded and undegraded dietary protein of high biological value to the animal. FM is expensive and other crop byproducts and local feed materials with properties of slow degradability of protein and good amino acid balance need to be identified. An alternative strategy would be to provide a maximum opportunity for the selection of most digestible parts. If refusals are then collected, quality could be further improved with alkali treatment and necessary supplementation. This would provide a strategy for the use of morphological fractions which could be an economical approach for the efficient utilization of roughages.
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ItemThe effect of process variables on the dimensional stability of particleboard( 1998)The work undertaken in this thesis aim at improving the dimensional stability of particleboards caused by water absorption and stress relaxation both of which often occur simultaneously in finished composite board products. Dimensional instability was quantified by measuring the board percent thickness increase resulting from: i) springbuck on press opening; ii) reversible swelling subjected to moisture or solvent absorption and, iii) irreversible swelling due to stress release The reversible swelling was measured after a complete wetting or a humidity cycle from low to high humidity levels. The irreversible swelling was assessed after a complete drying or a humidity cycle from high to low humidity levels. Chemical modification of wood aimed at reducing the reversible swelling due to moisture absorption was attempted after the sequential replacement of water in wood by solvents. P. radiata and E. Obliqua blocks saturated with water were sequentially treated with polar followed by non-polar solvents in order to replace the water in the woods. Both species showed about 30 % retention of their original (green) volume after the final stage of treatment. The partially swollen P. radiata blocks were then chemically treated with the wood cell wall-bulking and cross-linking agents, i.e. acetic anhydride and paraformaldehyde respectively. Wood thickness swell was monitored through cyclic wetting and drying tests. The results showed that the dimensional stability of neither the acetylated nor the paraformaldehyde treated sample were improved as quantified by the anti-swelling efficiency (ASE). The presence of a catalyst (ferric chloride) was necessary to enhance the cell wall cross-linking and to improve the wood dimensional stability. This work identified that a chemical reaction between the reagents and the wood is necessary for achieving dimensional stability. Stress relaxation from springbuck and irreversible recovery are inherent in wood particles which have been stressed. Much of this work focused on reducing this stress in situ during wood composite panel consolidation. Chemical conditioning of wood materials by ammonia in situ during consolidation was studied using phenolic-based resin systems. Ammonium hydroxide (source for ammonia) was found to accelerate the curing of phenol-resorcinol-formaldehyde (PRF). Accelerated curing was also found for 50:50 (w/w) mixtures of PRF and phenol-urea-formaldehyde (PUF) at low temperatures between 45 C and 75 C and in the presence of formaldehyde. The PRF:PUF (50:50) resin system showed a significantly faster cure than the PRF resin in the presence of ammonium hydroxide at all levels of temperatures investigated. The resin system also showed shorter gel times than those of the PRF at different weight portions of ammonium hydroxide additions. Preliminary chemical structural analysis of both resin systems catalysed by ammonium hydroxide using Infrared (IR) analyser showed evidence for the presence of an azomethine group which indicated that the ammonia was being incorporated into the resin structure. Single layer particleboards were manufactured at low temperatures using the PRF binder and ammonia. Gaseous injection of ammonia in situ during board consolidation was achieved by using a laboratory press fitted with perforated plattens. An optimum pressing schedule was established whereby the ammonia was injected after the mat had reaching its final thickness in a sealed press system. The effects of pressing temperature, PRF resin loading and gas pressure on board vertical density profile, MOR, MOE, IB and thickness swell were studied. The results showed that the ammonia gas-injected boards consolidated at both temperatures of 50 C and 100 C had more uniform density profiles than those of the hot-pressed boards at the temperature of 180 C, however, the MOR, MOE, IB and thickness swell were less satisfactory. The MOR, MOE, IB and thickness swell of the ammonia gas-injected boards were bench marked against the requirements for standard grade High Moisture Resistant (HIR) particleboards in accordance with the AS/NZS 1859.1: Part 1 (1997), and were found to be below the acceptable standard. Particleboards bonded with PRF:PUF 50:50 (w/w) resin catalysed by ammonia gas were also produced. The board MOR, MOE, lB and thickness swell were less superior than those bonded with PRF, although ammonia was found to accelerate the cure of both resin systems. This was thought to be attributable to a curing reaction that was too rapid between the ammonia and the resin system. The pressing time and temperature may need to be shortened and lowered respectively for board property improvement. The effect of wood particle size on the properties of ammonia gas-injected particleboards was investigated. Large size particles were found to increase the MOR and MIE irrespective of pressing methods. However, boards made from small size particles were found to have higher lB's than those of large size particles. This was thought to be due to better gas penetration. Recommendations are provided for further work to enhance the properties of ammonia-catalysed PRF boards.
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ItemDevelopment of a technique to overcome the problems associated with high dieldrin concentration in soil( 1995)Degradation of dieldrin in soils was studied in laboratory experiments. Application of powdered zinc in dilute acetic acid, nickel chloride in sodium borohydride and potassium tertiary butoxide in dimethyl sulphoxide to pots containing solonized brown soil, podzol, red brown earth, grey clay, alluvial and krasnozem soils had little effect on the rate of degradation. Application of potassium tertiary butoxide in dimethyl sulphoxide solution to soil samples containing dieldrin achieved a rapid decrease in pesticide concentration in some cases. However, the undesirable effects of these chemicals on soil fauna and flora and on soil physical properties indicate that their use in the field could not be recommended. Adsorption of dieldrin (as illustrated by the Freundlich constant) was greater in red brown earth and grey clay soils than in the solonized brown soil. The rate of dieldrin desorption from these soils was found to be in the order solonized brown soil > red brown earth > grey clay. Dieldrin uptake by plants was determined, with carrots being found to absorb the greatest quantities of dieldrin. All plant species took up considerably more dieldrin when grown on sand than on clay. Lupin translocated very little dieldrin to the plant tops. The amounts of insecticide translocated to the plant tops were not proportional to the amounts of insecticide present in soil. Brown coal was found to be a very good dieldrin adsorbent. Addition of brown coal in the proportion 4:1 soil:brown coal reduced the uptake of dieldrin by carrots from contaminated soil to acceptable levels. Both mice and sheep did not show any obvious symptoms of ill-health after being fed diets containing 10 ?g g-1 dieldrin plus 10% brown coal for 16 weeks. Animals fed diets containing 10% brown coal and 10 ?g g-1 dieldrin had lower concentrations of the insecticide in the internal organs. The concentration of dieldrin in the kidney fat of sheep fed this diet was above the maximum limit suggested to apply to animals raised for human consumption.
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ItemGrowth and yield of rice cultivars of differing growth duration in New South Wales( 1993)The growing season for rice in New South Wales is limited by low temperatures in Spring and Autumn. With current cultivars, almost all of the possible growing season is used in producing a crop. Cultivars with short growth duration have been sought by rice growers in southern New South Wales for reasons of decreased water use, increased flexibility in designing rotations and added time for rice field preparation in the event of a wet spring. This study examines the growth and yield of a short-duration cultivar compared with commercial long-duration cultivars, when subjected to a range of fertiliser applications and sowing times. Biomass accumulation of the short-duration cultivar was smaller than that of the long-duration cultivars, however yield potential was similar. This was achieved by the production of similar number of florets/m2 despite smaller biomass at flowering, and greater harvest index. Early sowing resulted in smaller yield due to restricted biomass accumulation and floret production of the short-duration cultivar. The short-duration cultivar had a greater proportion of filled grains and thus yielded more than the other cultivars when sown late. While yield of all cultivars was reduced with late sowing, the short-duration cultivar was affected least. Cultivars of this type are therefore recommended when late-sowing is unavoidable. Variation in yield was not due entirely to low-temperature damage at the critical growth stages of pollen microspore development and anthesis. Yield was also associated with growth after anthesis. A summary model of post-anthesis growth, which included the effect of low temperature on growth, predicted growth with an accuracy similar to that of the growth measurements. Thus, in determining yield, the importance of environmental conditions during grain filling was highlighted. It was concluded that the yield of short-duration cultivars may be less stable when stress occurs during grain filling, because there is less reserve available to fill the grain. Continued work on short-duration cultivars is advocated, with emphasis on faster growth to provide greater biomass production in the shorter vegetative stage. Incorporation of tolerance to low temperatures during the grain-filling stage is also suggested, to give greater yield stability.
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ItemPhosphorus and potassium sorption characteristics and their relation to seedling growth in a highly weathered kaolinite soil( 1993)P and K sorption characteristics for a highly weathered kaolinite soil are studied in this thesis and related to growth responses in a three month seedling glasshouse experiment, using E. globulus spp. pseudoglobulus. The phosphorus supplying capacity of the soil was estimated using the principle of amount sorbed versus solution concentration. P sorption characteristics were described according to the Langmuir sorption isotherm. The sorption maximum of 70.4 ?g/g was low, indicating that large applications of P fertilizers are not required to overcome unfavourable sorption of P for this soil. Exchangeable and solution potassium of the soil were characterized by Quantity/Intensity relations utilizing activity ratios. The potential buffering capacity for the soil obtained from the Q/I curve of 8.28 (me/100g)/(M/I)1 /2 was low showing the soil to be poorly buffered against potassium depletion. Seedling growth under factorial additions of P and K showed response to P but not to K addition. There was no significant interaction between P and K addition. Concentration of P in foliage, stems and roots increased with increasing P addition, with over 90% of the increase occurring at the rate of addition equivalent to the Langmuir sorption maximum (70.4 ?g/g). The soption isotherm approach was found to be of value to predicting P fertilizer requirement over the first three months of growth. K concentration in the tissues were not related to rate of K fertilizer addition.
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ItemInteractions between soil and fertilizer nitrogen( 1992)Chemical and biological interactions between soil N and alkaline-hydrolysing N fertilizers were studied in laboratory and glasshouse experiments. Chemical interactions were measured in y-irradiated soils, and biological interactions in non-irradiated or reinoculated y-irradiated samples incubated with 15 N-labelled urea, aqua ammonia or di-ammonium phosphate. The roles of NH3 fixation by soil organic matter, chemical hydrolysis and dissolution of soil organic N and transformations of solubilized organic N in influencing the availability of soil N were evaluated in laboratory experiments. The interaction between foliar application of urea and the uptake of soil N by wheat and sunflower was studied in a glasshouse experiment. Recovery of fertilizer N in the organic fraction of y-irradiated soils was due to the process of NH3 fixation. NH3 fixation varied among soils, and up to 4.6 % of aqua ammonia added at 1000 mg N kg-1 soil was fixed by soil organic matter at day 7. The amount of NH3 fixed increased with increasing rates of NH3 (aq) and urea application. More than 55 % of the total NH3 fixation measured 28 days after application of 2000 mg urea-N kg-1 soil occurred in the first week. Soil pH and NH3 fixation varied in response to N source, and increased in the order of di-ammonium phosphate < urea < aqua ammonia at equivalent N concentrations. The alkaline hydrolysis of indigenous organic N occurred simultaneously with NH3 fixation, resulting in the release of unlabelled ammonium and a real added nitrogen interaction in the majority of soils studied. The release of NH4+ in two soils initially increased up to a pH of 7.5, was inhibited between pH 8.5 and 9.0 but increased thereafter. The balance (Nbai) between NH3 fixation and deamination was positive or negative, depending on the pH, which was directly related to N source and concentration for a given soil. Organic N was measured in the extracts of unfertilized soils, but the dissolution of indigenous organic N increased with the addition of alkaline-hydrolysing N fertilizers. For a given fertilizer and rate of application, the organic N in the extracts of fertilized soils was a function of initial soil pH, cation exchange capacity, C/N ratio and soluble organic N in the extracts of the unfertilized soils. The percentage of organic N in y-irradiated soil rendered soluble by the fertilizer ranged from zero to 35 %, depending on soil type and rate of fertilizer addition. For a given soil and fertilizer source, the fertilizer-induced loss of unlabelled total N in the extracted soil increased with increasing fertilizer concentration and pH, and was linearly correlated to the pH of the fertilized soil in the range of 7.5 to 10 (r = 0.94). When several fertilizer sources were applied to a given soil at two concentrations, the relationship between fertilizer-induced organic N in the soil extracts and pH was curvilinear, and fertilizer-induced soluble organic N was not related to ammoniacal-N concentration. pH and fertilizer-induced organic N in the soil extracts decreased in the order of NH3(aq) > urea > di-ammonium phosphate > ammonium sulphate at equivalent N concentration. Recovery of fertilizer N in the organic fraction of biologically-active soil was higher than y-irradiated soil due to immobilization. Biological immobilization of labelled N was similar for urea and diammonium phosphate applications, and increased slightly with increasing N application rate or incubation time. Positive added nitrogen interactions were observed in both y-irradiated and biologically-active samples. The ANI in the biologically active soil was greater compared to sterile soil, and both increased with rate of fertilizer application and time of incubation. When added nitrogen interactions due to chemical processes and pool substitution were taken into account, a real positive ANI due to biological factors (ANI (rb)) was measured in three soils. The ANI (rb) increased with rate of fertilizer application. This increase, together with increased immobilization and a measured decrease in fertilizer-induced soluble organic N during incubation, indicated that biological activity was enhanced through increased availability of substrate. The biological availability of organic N solubilized by NH3(aq) was determined in incubation experiments using 15N-labelled and unlabelled substrates. The activity of heterotrophic microorganisms increased in response to the addition of unlabelled soluble organic N, as seen by higher gross rates of N mineralization and immobilization between day 0 and 7. However, the measured response of net mineralization was significant only when the rate of organic N addition exceeded 100 mg N kg-1 soil, or the rate of NH3(aq) addition was equal to or greater than 1500 mg N kg-1 soil. A constant proportion of approximately one-quarter of the labelled organic N added at different rates was recovered in the mineral N pool at day 14. Availability ratios calculated from net mineralization data indicated that fertilizer-induced solubilization of organic N increased its mineralization potential, and provided an explanation for the real added nitrogen interaction due to biological factors observed in N fertilized soil. The interaction between foliar application of urea to wheat and sunflower plants and the pool of available soil N accessible to plant roots was investigated in a glasshouse experiment using two soils of low and moderate N status. Fertilizer absorption was dependent on the sink size of the plant, and increased curvilinearly with the number of fertilizer applications. Dry matter production and its partitioning between tops and roots varied between soils and plants, and there was a significant soil-plant interaction. Plants grown in the N-deficient soil responded to urea application, and significant correlations between root dry matter or soil N uptake and plant N derived from fertilizer were obtained. A negative added nitrogen interaction observed for wheat sampled at day 33 in the N-deficient soil was due to less root growth as N derived from fertilizer increased. However, soil N uptake was higher in fertilized compared to unfertilized plants at 54 days after sowing due to bigger and more efficient root systems. i.e. there was a real positive added nitrogen interaction.
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ItemWood characteristics and properties of plantation mountain ash (E. regnans) and their variation( 1992)Six 15-year old Eucalyptus regnans F.Muell trees from three seedlots in a progeny trial in Narbethong, Victoria were examined in this study. Wood discs were removed from the base, breast height, 20 %, 40 %, 60 % and 80 % of the total tree height. Three methods used to demarcate the boundary between the sapwood and heartwood on the disc cross sectional surface were examined. The first method was based on the difference between sapwood and heartwood. The second method which was based on the difference in pH between sapwood and heartwood used 0.1 % methyl orange stain. The third method which was based on the presence or absence of tyloses in the vessels used a light table. Measurements were also made on the cross sectional surfaces of the discs to determine the sapwood width, heartwood percent, and the number, length and year of formation of each kino vein. The presence of decay and discolouration was also noted. Sapwood and heartwood wood blocks were cut from discs along the four cardinal directions. The basic density and moisture content of all wood blocks from the four axes and the remaining pie shaped pieces from each disc were determined. Mean basic density and moisture content based on the wood blocks from only the four axes were also computed. No difference was found in the demarcation of the sapwood-heartwood boundary between the methods based on natural colour and stain. Demarcation of the boundary using the light table method gave significantly different results to those found for the colour and stain methods. Based on the light table results, the presence of the tyloses appears to vary greatly between the base and breast height while at the 20 %, 40 and 60 heights they are more uniformly distributed. The mean sapwood width varied significantly between trees with values ranging from 24.2 mm to 28.7 mm with on average about four to five growth rings present in the sapwood zone. The mean sapwood also varied significantly with height. The lowest mean sapwood width of 21.0 mm was found at breast height and the mean sapwood width increased to 33.9 mm at the 80 height and increased from breast height to 29.9 mm at the base of the tree. The mean heartwood percent varied significantly between trees and with height. Two trees from seedlot number 13 had a mean heartwood percent of about 42 which was about 6 % lower than the mean heartwood percent of about 48 for the two trees from from seedlot number 23. The largest heartwood percent of 69.51 was found at the breast height and decreased to 0 (zero) at the 80 height and also decreased from the value at breast height to 65.75 at the base of the trees. A correlation of 0.967 was found between heartwood diameter and disc diameter. Kino veins were found in all six trees with the earliest formed vein at the tree age of 4 years. For the six trees, the total number and average length of kino veins decreased with height. The average length varied greatly between trees while the total number of kino veins was relatively uniform in five out of six trees. The presence of decay and discolouration was noted in five out of six trees. Basic density varied significantly between trees and with height but not between the sapwood and heartwood which had mean basic density values of 0.430 g/cm3 and 0.435 g/cm3 respectively. The mean basic density of 0.408 g/cm3 was lowest at breast height and highest at 80 height where the mean basic density was 0.468 g/cm3. Tree number 2 from seedlot number 13 had the highest mean density of 0.486 gm/cm3 and this was significantly greater than the lowest value of 0.422 g/cm3 found for tree number 4 from seedlot number 23. The interactions between trees and heights and between heights and axes were also found to be significant. Moisture content varied significantly between trees and with height but not between the north, south, east and west cardinal directions which had mean values of 146.98 148.47 %, 148.91 and 151.15 respectively. The mean moisture content at breast height was the highest with a value of 161.14 and the lowest value of 134.33 was found at the 80 height. Tree number 2 had the lowest mean moisture content of 127.65 and tree number 5 had the highest value of 161.05%. The interactions between heights and locations (sapwood or heartwood) and between axes and locations were significant. A correlation of -0.923 was found between moisture content and basic density. The mean basic density values and the mean moisture content values determined from blocks removed along only the four axes were strongly correlated to the weighted disc values based on virtually all the wood from each disc.