This study examined the role of olfactory and visual cues in host finding of the pine bark beetles Hylastes ater and Hylurgus ligniperda and the burnt pine longhorn beetle Arhopalus ferus. The ultimate aim of this research was to provide new information on attractant and repellent (such as non-host leaf volatiles) stimuli to improve monitoring methods and reduce the attack by wood-boring and bark beetle species. A field trapping trial of visual and olfactory cues near Nelson caught 7842 H. ater, 274,594 H. ligniperda and 16,301 A. ferus adults. There were significant effects of both visual (colour and sihoutte) and olfactory (host and non-host volatiles) cues for all three species. The highest catches were in black (host mimicking), panel flight intercept traps baited with attractant (α-pinene and ethanol) and the lowest in clear or white (non-host mimicking) control traps. The repellent, green leaf volatiles (GLV) ((E)-2-hexen-1-ol & (Z)-3-hexen-1-ol) when present on traps with attractant reduced catches significantly but modestly in H. ater and H. ligniperda, but had no significant effect on A. ferus. A field trial near Christchurch found that GLV applied as a topical repellent halved the number of beetles attacking Pinus radiata logs. This reduction was significant in H. ligniperda, but not quite (P = 0.07) in H. ater. Placing logs among broadleaved plants (natural sources of non-host volatiles) significantly reduced attack of H. ligniperda by about 75% compared to logs in the open, but had no effect on H. ater. Attack by H. ater was found on 4% of 500 P. radiata seedlings in a field trial near Dunedin. Treatment of seedlings with GLV significantly affected the severity and proportion of seedlings attacked by H. ater, compared with insecticide-treated and control seedlings, but the treatment effect was apparently driven by an unexpected direct damaging effect of GLV on the health of seedlings. It is recommended that future research explores the use of non-host volatiles from natural sources that influence host finding in wood–boring and bark beetle species for the protection of plantation forests in New Zealand.

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.

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.

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.