Recent research shows that 7.7% of individuals who use indoor tanning beds do so in private homes,1 but little is known about this group. This study evaluated the tanning practices, reasons for tanning, and association with tanning addiction of adults who use tanning beds in private residences.

The use of artificial ultraviolet (UV) indoor tanning (IT) beds increases the risk of skin cancer. The IT industry claims IT devices provide users with control over the amount of UV radiation exposure and thus reduces risks of sunburn (i.e., skin erythema) when tanning. This study aims to establish the prevalence and predictors of IT-related erythema using diary data. Six bimonthly diary surveys were administered to 198 female college IT users. Diaries assessed IT use and IT-related erythema. Among participants who used IT, 66 % experienced at least one episode of erythema and nearly one in five IT sessions resulted in skin erythema. Those who reported the most frequent IT use prior to the study were less likely to experience an IT-related erythema on a given IT session compared to the least experienced IT users. Perceived susceptibility to burns from IT use was positively associated with risk of erythema. Erythema was a frequently reported experience among IT users. Implications for policy makers and behavioral medicine practitioners are discussed

The potential for relay intercropping and double cropping was assessed in field trials over three consecutive years at Gatton, Queensland. The rationale was to use controlled traffic technology to facilitate relay and double cropping and thus research a cropping system that could exploit late winter crop rainfall. In Field Trial I, grain sorghum and sunflower, broadacre crops already grown within the Southern and Darling Downs regions of Queensland and New South Wales were intercropped into wheat; sunflower was intercropped with wheat in Field Trial II. Sole summer plantings were made at the same time as intercrops were planted. The wheat crop was cut and stubble removed to facilitate this. Various planting dates (three for Field Trial I; four for Field Trial II) for the relayed summer crops were used to determine if an optimum planting time existed. Plant height, tiller number, light interception, grain yield, soil moisture and economic return were used as parameters to compare the intercrop with sole plantings in Field Trial I. Grain yield, soil moisture, rainfall infiltration and economic return were measured in Field Trial II. Research also involved the modification and testing of a tractor to carry out the sowing of the intercrop. In Field Trial I, light interception was shown to vary at different stages of the wheat crop and the use of these stages to determine optimum planting dates of the relay crop is suggested. In both trials, no differences were recorded in the grain yield between intercropped and sole cropped wheat treatments suggesting the trafficking of the plot did not affect the wheat. As neither sorghum or sunflower established as intercrops, competition was not a factor in affecting wheat yields. Moisture readings in both trials showed little change below a depth of 100 cm; however some treatment differences were present at shallower depths. In Field ii Trial I, sole summer sorghum, especially the first planting date, showed reduced water capture/ higher soil evaporation due to wheat removal initially and later transpiration loss due to crop growth and increased weed pressure. Sole wheat treatments showed increased moisture storage after harvest due to lack of water use by the crop and increased infiltration/reduced runoff due to stubble retention. Improved soil moisture recharge after rainfall events was apparent in double cropped treatments suggesting not only improved water utilisation but also improved capture and storage is possible within this system. Sorghum, commonly used throughout south eastern Queensland as a summer crop option, proved unsuitable for relay intercropping in Field Trial I for Planting Dates 1 and 2. Minimum soil temperatures for these plantings were marginal as they were close to the 15o Celsius level recommended for sorghum. However, even though establishment was poor for the intercropped plantings, it was higher for sole sorghum plantings. Wheat allelopathic effects may be involved. To avoid the temperature limitations of sorghum, sunflower was selected as an alternative intercrop in the later planting dates of Field Trial I and all dates for Field Trial II. Reasons for the poor establishment and yield of sunflowers in the earlier intercrop planting dates compared to sole plantings remain unknown but also may be related to allelopathic effects from intercropped wheat. Low soil temperature was not a factor affecting establishment Yields for planting dates were recorded in the intercropped sunflower treatments for Field Trial II and the optimal planting time for sunflowers in a wheat/sunflower relay intercrop was identified as when physiological maturity of the wheat had occurred. This may relate to the wheat crop stage. In Field Trial II, no significant differences in soil moisture were recorded between treatments from overall water use for the trial period. There were differences in water use between intercropped and sole cropped treatments for iii some rainfall events. Three rainfall events were chosen for closer study in each of the field trials conducted. Each event varied in the length and time as well as the duration and intensity of the rain that fell for the period. For the first rainfall period the moisture content of the first planting date of the sole summer treatment and to a lesser extent the second planting date of the same treatment increased, most likely due to wheat removal. In the third rainfall period the double cropped sunflower treatment with stubble tended to store less moisture and this may be due to the active crop growth at this time. It was evident in both field trials of the need for an effective weed control program in the intercrop plots. Weeds were controlled in wheel tracks by glyphosate sprays. Cultural methods may help but a herbicide suitable for both components of the intercrop would be very useful. A tractor was successfully modified to a 3 metre wheelspace and a clearance of 70 cm. This proved sufficient for planting the relay intercrop in Field Trial II without negatively affecting the yield of the standing crop. The row spacing of 18 cm for wheat in a 3 metre fixed bed and wheeltrack configuration assisted with guidance and interplanting of the relay crop. The relay crop was sown as single alternating rows.

Solid propellant gas generators that have high gas capacity are used for fast pressurization of inflatable devices or elastic shells. However, many applications such as control surface actuation, air bottle pressurization in rocket engines and safety systems of automobiles (airbags) require exit gases at near ambient temperature. A scheme suitable for short duration applications is passive cooling of gas generator gases by using a packed bed as compact heat exchanger. A study indicated that the mass flow rates of solid propellant gas generators for applications such as air bottle pressurization and control system actuators were of the order of 1 kg/s. Since pressure and enthalpy drop correlations for packed beds with mass flow rates (~1 kg/s) and packing sphere based Reynolds number (Red) ~ 9X104 were unavailable in open literature, an experimental investigation was deemed necessary. The objectives of the present study were (a) characterization of packed beds for pressure and enthalpy drop, (b) develop Euler and Nusselt number correlations at Red~105 and (c) evolve an engineering procedure for estimation of packed bed pressure and enthalpy drop. An experimental test facility with a hydrogen-air combustor was designed and fabricated for this purpose to characterize a variety of packed beds for pressure drop and heat transfer. Flow through separate packed beds consisting of 9.5mm and 5mm steel spheres and lengths ~200mm and ~300mm were studied in the sphere based Reynolds numbers (Red) range of 0.4X104 to 8.5X104. The average porosity (є) of the randomly packed beds was ~0.4. The ratios of packed bed diameter to packing diameter for 9.5mm and 5mm sphere packing were ~ 9.5 and 18 respectively. The inlet flow temperature was unsteady and a suitable arrangement using mesh of spheres was used at either ends to eliminate flow entrance and exit effects. Stagnation pressures were measured at entry and exit of the packed beds. The pressure drop factor fpd, (ratio of Euler number (Eu) to packed bed dimensions) for packed bed with 9.5mm spheres exhibited an asymptotically decreasing trend with increasing Reynolds number, and a correlation for the pressure drop factor is proposed as, fpd=Eu/ [6(1-є) (L/dp)] =125.3 Red-0.4; 0.8X104 < Red < 8.5X104 (9.5mm sphere packing). However, for packed beds with 5mm spheres the pressure drop factor fpd, was observed to increase in the investigated Reynolds number range. The correlation based for pressure drop factor is proposed as, fpd= Eu/ [6(1-є) (L/dp)] =0.0479 Red0.37; 0.4X104 < Red < 3.9X104 (5mm sphere packing). The pressure drop factor was observed to be independent of the inlet flow temperature. Gas temperatures were measured at the entry, exit and at three axial locations along centerline in the packed beds. The solid packing temperature was measured at three axial locations in the packed bed. At Red~104, the influence of gas phase and solid phase thermal conductivity on heat transfer coefficient was found to be negligible based on order of magnitude analysis and solid packing temperature data obtained from the experiments. Evaluation of sphere based Nusselt number (Nud) at axial locations in the packed bed indicated a length effect on the heat transfer coefficient, which was a function of Reynolds number and size of spheres used in packing. The arithmetic average of Nusselt numbers at different axial locations in the packed bed were correlated as Nud=3.85 Red0.5; 0.5X104 < Red < 8.5X104. The Nusselt numbers obtained in the experiments were consistent with corresponding literature data available at lower Reynolds numbers. In this experimental study Euler number correlations for pressure drop and Nusselt number correlations for heat transfer were obtained for packed beds at Red~105. An engineering model for estimation of packed bed pressure and enthalpy drop was evolved, which is useful for sizing of packed bed heat exchanger in solid propellant gas generation systems.

Modern, small-scale wastewater treatment faces a twofold challenge: On the one hand requirements from legal authorities regarding removal of eutrophying substances have become more demanding. On the other hand high-quality phosphorus reserves are dwindling, which has raised calls for increased recycling. The problem is acute in the county of Stockholm where about 34 000 households are identified to not possess adequate wastewater treatment facilities. In this master’s thesis, four treatment systems, of which three had some phosphorus recycling potential, were compared using life cycle assessment methodology. The small-scale treatment systems analyzed were infiltration, filter beds with Filtralite® P and Filtra P respectively as filter material and a chemical precipitation system. The system boundaries included the extraction of raw materials, production of materials and components, the construction and operation of the systems as well as deconstruction and recycling of the treatment plants. Apart from impacts on human health and acidification potential, which both proved to be of less relevance to the final results, energy usage, consumption of abiotic resources, global warming potential and eutrophication potential were taken into account in this study. The infiltration system attained the most favourable results in all impact categories save eutrophication potential, which was due to both the low usage of energy and resources as well as the system’s high life expectancy. The filter bed system using Filtralite® P demonstrated the best performance in reduction of eutrophying substances. However, the system’s energy demand and emissions of greenhouse gases by far exceeded the other systems’ results in these categories. Both the filter bed system using Filtra P and the chemical precipitation system fared relatively equal in the overall analysis, with moderate impacts in all categories. The nutrient recycling potential was shown to be limited by the waste products’ relatively high heavy metal content. Sludge from chemical precipitation had higher potential for replacement of fertilizer than filter bed material. The chemical precipitation system fared best in the overall assessment. Its technical immaturity and limited data foundation put the alternative using Filtra P into second place. The infiltration system’s limited treatment performance and inexistent recycling potential put this alternative into third place. The alternative using Filtralite® P was ruled out entirely because of its high impact on fossil fuel consumption and global warming. Based on this ranking recommendations were made. Even though the filter bed materials in this study showed excellent phosphorus removal capacity, further research into alternative filter bed materials will have to be made due to the materials’ environmental impacts in other areas. Focus should be on waste material and natural products (such as shell sand) with low environmental impacts from production. Ways of separating heavy metals from plant nutrients need to be explored if nutrient recycling is to be an aim. This study showed that good phosphorus removal characteristics can lead to an increase in other environmental impacts, which in some cases even may outweigh the positive effects of decreased eutrophication. / Modern, småskalig avloppsreningsteknik står inför två utmaningar. Å ena sidan har kraven från lagstiftaren på rening av eutrofierande ämnen ökat. Problemet är akut i Stockholms län där det finns ca. 34 000 hushåll som inte anses uppfylla reningskraven. Å andra sidan minskar fosforförekomsterna av hög kvalitet i allt större takt, vilket har väckt krav på ökad återföring av växtnäring. I detta examensarbete undersöktes fyra olika reningstekniker, varav tre har en viss återföringspotential, med hjälp av metodik från livscykelanalys. Systemen som undersöktes var infiltration, filterbäddar dels med Filtralite® P och dels med Filtra P som filtermaterial, samt ett kemikaliefällningssystem. Systemgränserna omfattade extraktion av råmaterial, produktion av anläggningsmaterial och –komponenter, uppförande och drift av systemen samt avveckling av anläggningarna och återföring av restmaterial. Förutom påverkan på mänsklig hälsa och försurningspotential, som visade sig vara mindre relevanta för slutresultaten, omfattade analysen även en undersökning av energianvändning, förbrukning av abiotiska resurser, potential för global uppvärmning och eutrofieringspotential. Infiltrationslösningen fick de mest fördelaktiga resultatvärden i alla kategorierna förutom eutrofieringspotential, vilket kan förklaras med systemets låga energi- och resursbehov samt dess höga livslängd. Filterbädden med Filtralite® P som filtermaterial uppvisade den största förmågan att reducera eutrofierande substanser. Systemets energibehov och utsläpp av växthusgaser översteg dock de andra systemens resultat i dessa kategorier kraftigt. Både anläggningen med Filtra P och kemikaliefällningslösningen fick liknande resultat, med måttlig påverkan i alla kategorier. Systemens återföringspotential visade sig vara begränsad av restprodukternas höga tungmetallhalt. Kemikaliefällt slam hade högre återföringspotential än filterbäddsmaterial. Kemikaliefällning klarade sig totalt sett bäst i studien. Den relativt obeprövade tekniska utformning och det osäkra dataunderlaget ledde till att Filtra P hamnade i rangordningen efter kemikaliefällning. Infiltrationssystemets begränsade reningsförmåga och den obefintliga återföringspotentialen ledde till att alternativet hamnade näst sist. Filtralite® P-alternativet blev placerat sist i rangordningen på grund av dess stora påverkan på förbrukning av fossila bränslen och global uppvärmning. Baserat på rangordningen utfärdades rekommendationer. Trots att filtermaterialen som undersöktes i denna studie har en utmärkt fosforreningsförmåga, kommer det att krävas fler studier med avseende på alternativa filtermaterial, eftersom materialens användning av icke-förnybara energikällor är mycket stor vid tillverkningen. Fokus borde ligga på återvunna eller naturliga material (som t.ex. snäcksand) med låg miljöpåverkan vid tillverkning. Om återföring av växtnäring ska bli ett mål inom småskalig avloppsvattenrening, måste effektiva sätt att separera tungmetaller från växtnäringsämnen utforskas. Denna studie visade att goda fosforavskiljningsegenskaper kan medföra att andra typer av miljöpåverkan ökar, vilket i vissa fall kan leda till att de negativa konsekvenserna överväger nyttan av minskad eutrofiering. / Moderne, dezentrale Abwassertechnik steht zwei großen Herausforderungen gegenüber. Zum einen sind die Ansprüche von Seiten des Gesetzgebers gestiegen, die effektivere Abwasserreinigungstechniken erfordern. Zum andern werden Phosphorvorkommen von hoher Qualität zunehmend knapper, was Rufe nach verstärkter Rückführung von Phosphor hat laut werden lassen. Im Verwaltungsbezirk Stockholm, in dem es ungefähr 34 000 Haushalte mit unzureichender Abwasserreinigung gibt, ist das Problem von besonderer Bedeutung. In dieser Diplomarbeit wurden vier Abwasserreinigungssysteme, wovon drei ein gewisses Potential für Phosphorrückführung haben, mit Hilfe einer Ökobilanzierung untersucht. Folgende Systeme wurden untersucht: Eine Infiltrationsanlage, zwei Filterbettsanlagen, eine mit Filtralite® P und eine mit Filtra P als Filtermaterial sowie ein System mit Chemikaliefällung. Die Systemgrenzen umfassten die Gewinnung und Verarbeitung von Rohstoffen, das Errichten der jeweiligen Anlage, deren Betrieb sowie Rückgewinnung und Entsorgung von Restmaterialien. Neben Auswirkungen auf die menschliche Gesundheit und Versauerungspotential, die sich im Nachhinein als weniger relevant erwiesen, wurden Energiebedarf, Verbrauch abiotischer Resourcen, Potential für globale Erwärmung und Eutrophierungspotential untersucht. Die niedrigsten Resultate in allen Kategorien außer Eutrophierungspotential wurden vom Infiltrationssystem erreicht. Filtralite® P erwies sich als am leistungsstärksten, was die Reduktion von eutrophierenden Substanzen angeht. Der Energiebedarf und die Emissionen von Treibhausgasen dieser Alternative überstieg die Ergebnisse der anderen Alternativen in diesen Kategorien doch bei weitem. Filtra P und Chemikaliefällung erzielten moderate Auswirkungen in allen Kategorien. Das Potential für die Rückführung von Pflanzennährstoffen wird, wie die Ergebnisse zeigen, vom relativ hohen Schwermetallhalt in den Restprodukten begrenzt. Chemikaliefällung ist in dieser Studie die beste Alternative. Filtra P zeigte sich als technisch noch zu wenig ausgereift und die Datenunterlage als zu unvollständig, weswegen diese Alternative an zweiter Stelle steht. Die begrenzte Reinigungsfähigkeit des Infiltrationssystemes und das nicht vorhandene Potential für Rückführung von Phosphor führten dazu, dass diese Lösung an dritter Stelle steht. Das System mit Filtralite® P als Filtermaterial wurde wegen seines großen Verbrauchs von fossilen Brennstoffen für wenig brauchbar befunden und steht damit an letzter Stelle. Trotz ihrer hervorragenden phosphorreduzierenden Eigenschaften, wird weitere Forschung im Bereich alternativer Filtermaterialien notwendig werden. Hierbei sollten natürliche Materialien (wie Muschelsand) oder Restprodukte im Mittelpunkt des Interesses stehen, um die Umweltauswirkungen gering zu halten. Wenn die Rückführung von Phosphor ein Ziel der Abwasserreinigung sein soll, müssen Lösungen, Schwermetalle von Pflanzennährstoffen zu trennen, gefunden werden. Diese Studie hat gezeigt, dass gute phosphorreduzierende Eigenschaften zu verstärkten Umweltauswirkungen in anderen Bereichen führen können, welche in manchen Fällen sogar die Vorteile einer verringerten Eutrophierung übersteigen können.

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The potential for relay intercropping and double cropping was assessed in field trials over three consecutive years at Gatton, Queensland. The rationale was to use controlled traffic technology to facilitate relay and double cropping and thus research a cropping system that could exploit late winter crop rainfall. In Field Trial I, grain sorghum and sunflower, broadacre crops already grown within the Southern and Darling Downs regions of Queensland and New South Wales were intercropped into wheat; sunflower was intercropped with wheat in Field Trial II. Sole summer plantings were made at the same time as intercrops were planted. The wheat crop was cut and stubble removed to facilitate this. Various planting dates (three for Field Trial I; four for Field Trial II) for the relayed summer crops were used to determine if an optimum planting time existed. Plant height, tiller number, light interception, grain yield, soil moisture and economic return were used as parameters to compare the intercrop with sole plantings in Field Trial I. Grain yield, soil moisture, rainfall infiltration and economic return were measured in Field Trial II. Research also involved the modification and testing of a tractor to carry out the sowing of the intercrop. In Field Trial I, light interception was shown to vary at different stages of the wheat crop and the use of these stages to determine optimum planting dates of the relay crop is suggested. In both trials, no differences were recorded in the grain yield between intercropped and sole cropped wheat treatments suggesting the trafficking of the plot did not affect the wheat. As neither sorghum or sunflower established as intercrops, competition was not a factor in affecting wheat yields. Moisture readings in both trials showed little change below a depth of 100 cm; however some treatment differences were present at shallower depths. In Field ii Trial I, sole summer sorghum, especially the first planting date, showed reduced water capture/ higher soil evaporation due to wheat removal initially and later transpiration loss due to crop growth and increased weed pressure. Sole wheat treatments showed increased moisture storage after harvest due to lack of water use by the crop and increased infiltration/reduced runoff due to stubble retention. Improved soil moisture recharge after rainfall events was apparent in double cropped treatments suggesting not only improved water utilisation but also improved capture and storage is possible within this system. Sorghum, commonly used throughout south eastern Queensland as a summer crop option, proved unsuitable for relay intercropping in Field Trial I for Planting Dates 1 and 2. Minimum soil temperatures for these plantings were marginal as they were close to the 15o Celsius level recommended for sorghum. However, even though establishment was poor for the intercropped plantings, it was higher for sole sorghum plantings. Wheat allelopathic effects may be involved. To avoid the temperature limitations of sorghum, sunflower was selected as an alternative intercrop in the later planting dates of Field Trial I and all dates for Field Trial II. Reasons for the poor establishment and yield of sunflowers in the earlier intercrop planting dates compared to sole plantings remain unknown but also may be related to allelopathic effects from intercropped wheat. Low soil temperature was not a factor affecting establishment Yields for planting dates were recorded in the intercropped sunflower treatments for Field Trial II and the optimal planting time for sunflowers in a wheat/sunflower relay intercrop was identified as when physiological maturity of the wheat had occurred. This may relate to the wheat crop stage. In Field Trial II, no significant differences in soil moisture were recorded between treatments from overall water use for the trial period. There were differences in water use between intercropped and sole cropped treatments for iii some rainfall events. Three rainfall events were chosen for closer study in each of the field trials conducted. Each event varied in the length and time as well as the duration and intensity of the rain that fell for the period. For the first rainfall period the moisture content of the first planting date of the sole summer treatment and to a lesser extent the second planting date of the same treatment increased, most likely due to wheat removal. In the third rainfall period the double cropped sunflower treatment with stubble tended to store less moisture and this may be due to the active crop growth at this time. It was evident in both field trials of the need for an effective weed control program in the intercrop plots. Weeds were controlled in wheel tracks by glyphosate sprays. Cultural methods may help but a herbicide suitable for both components of the intercrop would be very useful. A tractor was successfully modified to a 3 metre wheelspace and a clearance of 70 cm. This proved sufficient for planting the relay intercrop in Field Trial II without negatively affecting the yield of the standing crop. The row spacing of 18 cm for wheat in a 3 metre fixed bed and wheeltrack configuration assisted with guidance and interplanting of the relay crop. The relay crop was sown as single alternating rows.

The potential for relay intercropping and double cropping was assessed in field trials over three consecutive years at Gatton, Queensland. The rationale was to use controlled traffic technology to facilitate relay and double cropping and thus research a cropping system that could exploit late winter crop rainfall. In Field Trial I, grain sorghum and sunflower, broadacre crops already grown within the Southern and Darling Downs regions of Queensland and New South Wales were intercropped into wheat; sunflower was intercropped with wheat in Field Trial II. Sole summer plantings were made at the same time as intercrops were planted. The wheat crop was cut and stubble removed to facilitate this. Various planting dates (three for Field Trial I; four for Field Trial II) for the relayed summer crops were used to determine if an optimum planting time existed. Plant height, tiller number, light interception, grain yield, soil moisture and economic return were used as parameters to compare the intercrop with sole plantings in Field Trial I. Grain yield, soil moisture, rainfall infiltration and economic return were measured in Field Trial II. Research also involved the modification and testing of a tractor to carry out the sowing of the intercrop. In Field Trial I, light interception was shown to vary at different stages of the wheat crop and the use of these stages to determine optimum planting dates of the relay crop is suggested. In both trials, no differences were recorded in the grain yield between intercropped and sole cropped wheat treatments suggesting the trafficking of the plot did not affect the wheat. As neither sorghum or sunflower established as intercrops, competition was not a factor in affecting wheat yields. Moisture readings in both trials showed little change below a depth of 100 cm; however some treatment differences were present at shallower depths. In Field ii Trial I, sole summer sorghum, especially the first planting date, showed reduced water capture/ higher soil evaporation due to wheat removal initially and later transpiration loss due to crop growth and increased weed pressure. Sole wheat treatments showed increased moisture storage after harvest due to lack of water use by the crop and increased infiltration/reduced runoff due to stubble retention. Improved soil moisture recharge after rainfall events was apparent in double cropped treatments suggesting not only improved water utilisation but also improved capture and storage is possible within this system. Sorghum, commonly used throughout south eastern Queensland as a summer crop option, proved unsuitable for relay intercropping in Field Trial I for Planting Dates 1 and 2. Minimum soil temperatures for these plantings were marginal as they were close to the 15o Celsius level recommended for sorghum. However, even though establishment was poor for the intercropped plantings, it was higher for sole sorghum plantings. Wheat allelopathic effects may be involved. To avoid the temperature limitations of sorghum, sunflower was selected as an alternative intercrop in the later planting dates of Field Trial I and all dates for Field Trial II. Reasons for the poor establishment and yield of sunflowers in the earlier intercrop planting dates compared to sole plantings remain unknown but also may be related to allelopathic effects from intercropped wheat. Low soil temperature was not a factor affecting establishment Yields for planting dates were recorded in the intercropped sunflower treatments for Field Trial II and the optimal planting time for sunflowers in a wheat/sunflower relay intercrop was identified as when physiological maturity of the wheat had occurred. This may relate to the wheat crop stage. In Field Trial II, no significant differences in soil moisture were recorded between treatments from overall water use for the trial period. There were differences in water use between intercropped and sole cropped treatments for iii some rainfall events. Three rainfall events were chosen for closer study in each of the field trials conducted. Each event varied in the length and time as well as the duration and intensity of the rain that fell for the period. For the first rainfall period the moisture content of the first planting date of the sole summer treatment and to a lesser extent the second planting date of the same treatment increased, most likely due to wheat removal. In the third rainfall period the double cropped sunflower treatment with stubble tended to store less moisture and this may be due to the active crop growth at this time. It was evident in both field trials of the need for an effective weed control program in the intercrop plots. Weeds were controlled in wheel tracks by glyphosate sprays. Cultural methods may help but a herbicide suitable for both components of the intercrop would be very useful. A tractor was successfully modified to a 3 metre wheelspace and a clearance of 70 cm. This proved sufficient for planting the relay intercrop in Field Trial II without negatively affecting the yield of the standing crop. The row spacing of 18 cm for wheat in a 3 metre fixed bed and wheeltrack configuration assisted with guidance and interplanting of the relay crop. The relay crop was sown as single alternating rows.

The potential for relay intercropping and double cropping was assessed in field trials over three consecutive years at Gatton, Queensland. The rationale was to use controlled traffic technology to facilitate relay and double cropping and thus research a cropping system that could exploit late winter crop rainfall. In Field Trial I, grain sorghum and sunflower, broadacre crops already grown within the Southern and Darling Downs regions of Queensland and New South Wales were intercropped into wheat; sunflower was intercropped with wheat in Field Trial II. Sole summer plantings were made at the same time as intercrops were planted. The wheat crop was cut and stubble removed to facilitate this. Various planting dates (three for Field Trial I; four for Field Trial II) for the relayed summer crops were used to determine if an optimum planting time existed. Plant height, tiller number, light interception, grain yield, soil moisture and economic return were used as parameters to compare the intercrop with sole plantings in Field Trial I. Grain yield, soil moisture, rainfall infiltration and economic return were measured in Field Trial II. Research also involved the modification and testing of a tractor to carry out the sowing of the intercrop. In Field Trial I, light interception was shown to vary at different stages of the wheat crop and the use of these stages to determine optimum planting dates of the relay crop is suggested. In both trials, no differences were recorded in the grain yield between intercropped and sole cropped wheat treatments suggesting the trafficking of the plot did not affect the wheat. As neither sorghum or sunflower established as intercrops, competition was not a factor in affecting wheat yields. Moisture readings in both trials showed little change below a depth of 100 cm; however some treatment differences were present at shallower depths. In Field ii Trial I, sole summer sorghum, especially the first planting date, showed reduced water capture/ higher soil evaporation due to wheat removal initially and later transpiration loss due to crop growth and increased weed pressure. Sole wheat treatments showed increased moisture storage after harvest due to lack of water use by the crop and increased infiltration/reduced runoff due to stubble retention. Improved soil moisture recharge after rainfall events was apparent in double cropped treatments suggesting not only improved water utilisation but also improved capture and storage is possible within this system. Sorghum, commonly used throughout south eastern Queensland as a summer crop option, proved unsuitable for relay intercropping in Field Trial I for Planting Dates 1 and 2. Minimum soil temperatures for these plantings were marginal as they were close to the 15o Celsius level recommended for sorghum. However, even though establishment was poor for the intercropped plantings, it was higher for sole sorghum plantings. Wheat allelopathic effects may be involved. To avoid the temperature limitations of sorghum, sunflower was selected as an alternative intercrop in the later planting dates of Field Trial I and all dates for Field Trial II. Reasons for the poor establishment and yield of sunflowers in the earlier intercrop planting dates compared to sole plantings remain unknown but also may be related to allelopathic effects from intercropped wheat. Low soil temperature was not a factor affecting establishment Yields for planting dates were recorded in the intercropped sunflower treatments for Field Trial II and the optimal planting time for sunflowers in a wheat/sunflower relay intercrop was identified as when physiological maturity of the wheat had occurred. This may relate to the wheat crop stage. In Field Trial II, no significant differences in soil moisture were recorded between treatments from overall water use for the trial period. There were differences in water use between intercropped and sole cropped treatments for iii some rainfall events. Three rainfall events were chosen for closer study in each of the field trials conducted. Each event varied in the length and time as well as the duration and intensity of the rain that fell for the period. For the first rainfall period the moisture content of the first planting date of the sole summer treatment and to a lesser extent the second planting date of the same treatment increased, most likely due to wheat removal. In the third rainfall period the double cropped sunflower treatment with stubble tended to store less moisture and this may be due to the active crop growth at this time. It was evident in both field trials of the need for an effective weed control program in the intercrop plots. Weeds were controlled in wheel tracks by glyphosate sprays. Cultural methods may help but a herbicide suitable for both components of the intercrop would be very useful. A tractor was successfully modified to a 3 metre wheelspace and a clearance of 70 cm. This proved sufficient for planting the relay intercrop in Field Trial II without negatively affecting the yield of the standing crop. The row spacing of 18 cm for wheat in a 3 metre fixed bed and wheeltrack configuration assisted with guidance and interplanting of the relay crop. The relay crop was sown as single alternating rows.

The potential for relay intercropping and double cropping was assessed in field trials over three consecutive years at Gatton, Queensland. The rationale was to use controlled traffic technology to facilitate relay and double cropping and thus research a cropping system that could exploit late winter crop rainfall. In Field Trial I, grain sorghum and sunflower, broadacre crops already grown within the Southern and Darling Downs regions of Queensland and New South Wales were intercropped into wheat; sunflower was intercropped with wheat in Field Trial II. Sole summer plantings were made at the same time as intercrops were planted. The wheat crop was cut and stubble removed to facilitate this. Various planting dates (three for Field Trial I; four for Field Trial II) for the relayed summer crops were used to determine if an optimum planting time existed. Plant height, tiller number, light interception, grain yield, soil moisture and economic return were used as parameters to compare the intercrop with sole plantings in Field Trial I. Grain yield, soil moisture, rainfall infiltration and economic return were measured in Field Trial II. Research also involved the modification and testing of a tractor to carry out the sowing of the intercrop. In Field Trial I, light interception was shown to vary at different stages of the wheat crop and the use of these stages to determine optimum planting dates of the relay crop is suggested. In both trials, no differences were recorded in the grain yield between intercropped and sole cropped wheat treatments suggesting the trafficking of the plot did not affect the wheat. As neither sorghum or sunflower established as intercrops, competition was not a factor in affecting wheat yields. Moisture readings in both trials showed little change below a depth of 100 cm; however some treatment differences were present at shallower depths. In Field ii Trial I, sole summer sorghum, especially the first planting date, showed reduced water capture/ higher soil evaporation due to wheat removal initially and later transpiration loss due to crop growth and increased weed pressure. Sole wheat treatments showed increased moisture storage after harvest due to lack of water use by the crop and increased infiltration/reduced runoff due to stubble retention. Improved soil moisture recharge after rainfall events was apparent in double cropped treatments suggesting not only improved water utilisation but also improved capture and storage is possible within this system. Sorghum, commonly used throughout south eastern Queensland as a summer crop option, proved unsuitable for relay intercropping in Field Trial I for Planting Dates 1 and 2. Minimum soil temperatures for these plantings were marginal as they were close to the 15o Celsius level recommended for sorghum. However, even though establishment was poor for the intercropped plantings, it was higher for sole sorghum plantings. Wheat allelopathic effects may be involved. To avoid the temperature limitations of sorghum, sunflower was selected as an alternative intercrop in the later planting dates of Field Trial I and all dates for Field Trial II. Reasons for the poor establishment and yield of sunflowers in the earlier intercrop planting dates compared to sole plantings remain unknown but also may be related to allelopathic effects from intercropped wheat. Low soil temperature was not a factor affecting establishment Yields for planting dates were recorded in the intercropped sunflower treatments for Field Trial II and the optimal planting time for sunflowers in a wheat/sunflower relay intercrop was identified as when physiological maturity of the wheat had occurred. This may relate to the wheat crop stage. In Field Trial II, no significant differences in soil moisture were recorded between treatments from overall water use for the trial period. There were differences in water use between intercropped and sole cropped treatments for iii some rainfall events. Three rainfall events were chosen for closer study in each of the field trials conducted. Each event varied in the length and time as well as the duration and intensity of the rain that fell for the period. For the first rainfall period the moisture content of the first planting date of the sole summer treatment and to a lesser extent the second planting date of the same treatment increased, most likely due to wheat removal. In the third rainfall period the double cropped sunflower treatment with stubble tended to store less moisture and this may be due to the active crop growth at this time. It was evident in both field trials of the need for an effective weed control program in the intercrop plots. Weeds were controlled in wheel tracks by glyphosate sprays. Cultural methods may help but a herbicide suitable for both components of the intercrop would be very useful. A tractor was successfully modified to a 3 metre wheelspace and a clearance of 70 cm. This proved sufficient for planting the relay intercrop in Field Trial II without negatively affecting the yield of the standing crop. The row spacing of 18 cm for wheat in a 3 metre fixed bed and wheeltrack configuration assisted with guidance and interplanting of the relay crop. The relay crop was sown as single alternating rows.