ORCID Profile
0000-0002-3889-7058
Current Organisation
Murdoch University
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Publisher: Springer International Publishing
Date: 2022
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/CP08448
Abstract: In Mediterranean-type climates, dryland soil water storage and evaporation during the hot and dry summer are poorly understood, particularly for sandy-textured soils. Continued evaporation during summer, and any effects of crop stubble management, could have a significant impact on annual components of the water balance and crop yield. In this research, the effect of wheat stubble management on summer evaporation and soil water storage was investigated for a sandy soil in south-western Australia, during the summers of 2005–06 and 2006–07. Treatments comprised: retained standing stubble retained flattened stubble removed stubble and removed stubble followed by burying the crowns with topsoil from an adjacent area. Under ‘dry’ conditions, evaporation continued at ~0.2 mm/day. In contrast to previous results for finer textured soil types, stubble retention did not decrease the rate of evaporation, but marginally (10–30%) increased evaporation on 7 out of 14 days when measurements were taken. Significant differences due to stubble management were observed in two successive summers, but only for relatively dry soil conditions. There were no significant differences observed for several days after irrigation or rainfall. Under dry conditions in the absence of rainfall, total decrease in water storage during a 90-day summer period could be ~20 mm, but differences attributable to stubble management are likely to be a few mm.
Publisher: Elsevier BV
Date: 07-2003
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/EA03254
Abstract: Rain-fed cotton production can be a significant proportion (average 17%) of the Australian Cotton Industry. One of the management techniques that rain-fed cotton growers have is to modify row configuration. Configurations that have entire rows missing from the sowing configuration are often referred to as ‘skip row’. Skip configurations are used to: increase the amount of soil water available for the crop, which can influence the potential lint yield reduce the level of variability or risk associated with production enhance fibre quality and reduce input costs. Choosing the correct row configuration for a particular environment involves many, often complex, considerations. This paper presents an examination of how rain-fed cotton production in Australia is influenced by row configuration with different management and environmental factors. Data collated from field experiments and the cotton crop simulation model OZCOT, were used to explore the impact of agronomic decisions on potential lint yield and fibre quality and consequent economic benefit. Some key findings were: (i) soil water available at sowing did not increase the advantage of skip row relative to solid configurations (ii) reduced row spacing (75 cm) did not alter lint yield significantly in skip row crops (iii) skip row, rain-fed crops show reasonable plasticity in terms of optimum plant spacing within the row (simular to irrigated cotton) (iv) sowing time of rain-fed crops would appear to differ between solid and skip row arrangements (v) skip row configurations markedly reduce the risk of price discounts due to short fibre or low micronaire and this should be carefully considered in the choice of row configuration and (vi) skip configurations can also provide some savings in variable costs. In situations where rain-fed cotton sown in solid row configurations is subject to water stress that may affect lint yield or fibre quality, skip row configurations would be a preferential alternative to reduce risk of financial loss.
Publisher: Elsevier
Date: 2012
Publisher: CSIRO Publishing
Date: 2011
DOI: 10.1071/FP11031
Abstract: There is little consensus on whether having a large root system is the best strategy in adapting wheat (Triticum aestivum L.) to water-limited environments. We explore the reasons for the lack of consensus and aim to answer the question of whether a large root system is useful in adapting wheat to dry environments. We used unpublished data from glasshouse and field experiments examining the relationship between root system size and their functional implication for water capture. In idual root traits for water uptake do not describe a root system as being large or small. However, the recent invigoration of the root system in wheat by indirect selection for increased leaf vigour has enlarged the root system through increases in root biomass and length and root length density. This large root system contributes to increasing the capture of water and nitrogen early in the season, and facilitates the capture of additional water for grain filling. The usefulness of a vigorous root system in increasing wheat yields under water-limited conditions maybe greater in environments where crops rely largely on seasonal rainfall, such as the Mediterranean-type environments. In environments where crops are reliant on stored soil water, a vigorous root system increases the risk of depleting soil water before completion of grain filling.
Publisher: Wiley
Date: 05-2010
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/AR07423
Abstract: Recently, genetically engineered (transgenic) cottons expressing genes from Bacillis thuringiensis (Bt) have been made available to cotton growers throughout the world. In Australia, cotton growers have access to Bt cotton that contains genes expressing the insecticidal proteins Cry1Ac and Cry2Ab (Bollgard II®). Bollgard II offers significant potential to reduce pesticide use for the control of major Lepidopteran pests (particularly Helicoverpa spp. in Australia). As a consequence of the improved insect control, retention of squares (flower buds) and young bolls is higher in Bollgard II varieties than in non-Bollgard varieties. A concern raised by Australian cotton growers is that in some regions, yield potential for Bollgard II may be limited because the demands of earlier high fruit retention reduce resources for continued growth and fruiting, thus leading to earlier maturity and reduced yield. Non-Bollgard crops with high early retention are known to mature earlier sometimes reducing yield. Three field experiments over three seasons, which varied sowing date and compared non-Bollgard II and Bollgard II cotton cultivars, were conducted to test the hypothesis that delaying sowing date in Bollgard II will increase canopy size (without delaying crop development) and alleviate the potential concerns for the effect of higher fruit retention reducing canopy size and the time to maturity, limiting the yield of Bollgard II. In non-Bollgard II crops, larger canopies resulting from early loss of fruit or apical meristem damage can support more fruit growth for longer, provided season length allows fruit to mature. Results showed that delayed sowing did not increase the yield of the Bollgard II cultivar through increased leaf area index at flowering compared with normal sowing dates. However, in comparison with the conventional cultivar, which had yields that became lower with later sowings, Bollgard II maintained its yield presumably through the shorter fruiting cycle (because of its consistently higher earlier fruit retention), allowing time to support growth of the same number of bolls as earlier sowings. Improvements in fibre quality were also recorded with later sowings for both cultivars. Varying sowing dates for Bollgard II in different production regions may offer opportunities for Australian growers to help optimise yield, fibre quality, and reduce risks associated with poor crop establishment when crops are sown too early.
Publisher: MDPI AG
Date: 07-03-2023
Abstract: Incursion and establishment of an exotic pest may threaten natural habitats and disrupt ecosystems. On the other hand, resident natural enemies may play an important role in invasive pest control. Bactericera cockerelli, commonly known as the tomato-potato psyllid, is an exotic pest, first detected on mainland Australia in Perth, Western Australia, in early 2017. B. cockerelli causes direct damage to crops by feeding and indirectly by acting as the vector of the pathogen that causes zebra chip disease in potatoes, although the latter is not present in mainland Australia. At present, Australian growers rely on the frequent use of insecticides to control B. cockerelli, which may lead to a series of negative economic and environmental consequences. The incursion of B. cockerelli also provides a unique opportunity to develop a conservation biological control strategy through strategically targeting existing natural enemy communities. In this review, we consider opportunities to develop biological control strategies for B. cockerelli to alleviate the dependence on synthetic insecticides. We highlight the potential of existing natural enemies to contribute toward regulating populations of B. cockerelli in the field and discuss the challenges ahead to strengthen the key role they can play through conservation biological control.
Publisher: Elsevier BV
Date: 10-2009
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/AR03221
Abstract: Regression analysis of field data has indicated that minimum daily temperatures below 11°C delay the development of cotton (Gossypium hirsutum L.) seedlings beyond what would be expected based on the accumulated degree-day sum. In Australian cotton production systems, events where the minimum daily temperature falls below this value are referred to as ‘cold shocks’. The number of cold shocks is used by growers and advisors in assessing retardation of crops in their areas. However, this effect has not been tested explicitly. The aim of this work was to empirically assess effects of cold shock on pre-flower development of cotton plants. Cotton seedlings were grown in controlled-temperature glasshouses. Plants were transferred to cold chambers ranging from 5 to 22°C during the night period for durations from 3 to 10 days. Negative effects were not seen until plants had been exposed to at least 10 nights at 10°C, or for at least 5 nights at 5°C. When differences were generated it did not delay development to first square any more than 4 days, nor was the effect consistent. These differences translated into delays to first flower, but had little effect on plant morphology, or on dry weight measured soon after flowering. In one experiment, a significant reduction in leaf photosynthesis was measured at two times of day on the day after cold shock at 5°C. Improving understanding of the effects of temperature extremes on cotton growth and development will help in developing more functional decision-support tools and field management strategies.
Publisher: MDPI AG
Date: 13-01-2023
Abstract: Storing potato tubers at cold temperatures, either for transport or continuity of supply, is associated with the conversion of sucrose to reducing sugars. When cold-stored cut tubers are processed at high temperatures, with endogenous asparagine, acrylamide is formed. Acrylamide is classified as a carcinogen. Potato processors prefer cultivars which accumulate fewer reducing sugars and thus less acrylamide on processing, and suitable processing cultivars may not be available. We used CRISPR-Cas9 to disrupt the genes encoding vacuolar invertase (VInv) and asparagine synthetase 1 (AS1) of cultivars Atlantic and Desiree to reduce the accumulation of reducing sugars and the production of asparagine after cold storage. Three of the four guide RNAs employed induced mutation frequencies of 17–98%, which resulted in deletions, insertions and substitutions at the targeted gene sites. Eight of ten edited events had mutations in at least one allele of both genes for two, only the VInv was edited. No wild-type allele was detected in both genes of events DSpco7, DSpFN4 and DSpco12, suggesting full allelic mutations. Tubers of two Atlantic and two Desiree events had reduced fructose and glucose concentrations after cold storage. Crisps from these and four other Desiree events were lighter in colour and included those with 85% less acrylamide. These results demonstrate that multiplex CRISPR-Cas9 technology can generate improved potato cultivars for healthier processed potato products.
Publisher: CSIRO Publishing
Date: 1992
DOI: 10.1071/EA9920071
Abstract: Great brome (Bromus diandrus) is a common weed in wheat and can be expected as a weed in lupin crops (Lupinus angustifolius L.), particularly those in rotation with wheat. Although chemical control of brome in lupin is available, those plants escaping control compete with the lupin. This competition has been investigated by comparing the growth of lupin (cv. Yandee) in monoculture with its growth in the presence of 2 densities of brome, and with the growth of brome in monoculture. Each of the 4 treatments was grown with high and low fertiliser applications, to see how the competition was modified by nutrient availability. Water was not limiting. Daily measurements were made of lupin growth rates and the development of leaf area, and light interception and radiation use efficiencies were calculated (g DM assimilated per MJ intercepted photosynthetically active radiation). Radiation use efficiency changed with the phase of development of lupin, increasing to over 3 g/MJ at 95 days after sowing. It was higher in the high fertiliser treatments and in the presence of brome, particularly before 95 days after sowing. Changes in unit leaf rate (i.e. net assimilation rate) of lupin due to brome were small, but these, and changes in radiation use efficiencies, may have played a minor role in the depression of crop growth rates, more important during early lupin growth than later when leaf area indices had reached % of their maximum values. Depressions of the crop growth rate of lupin caused by the presence of brome were linearly related to changes in leaf area indices of lupin. The decrease in lupin seed yield per plant was due to a decrease in pod number per plant, not to a change in the number of seeds per pod or single seed weight. The number of pods was linearly related to the number of axes per plant (i.e. branches plus main stem).
Publisher: Elsevier BV
Date: 10-2000
Publisher: Elsevier BV
Date: 10-2004
Publisher: Oxford University Press (OUP)
Date: 07-1997
Publisher: Elsevier BV
Date: 12-2022
Publisher: CSIRO Publishing
Date: 1996
DOI: 10.1071/AR9960997
Abstract: A study was undertaken to identify improved management strategies for barley (Hordeum vulgare L.), particularly in relation to time of planting, location, and frost risk in the variable climate of north-eastern Australia. To achieve this objective, a crop growth simulation model (QBAR) was constructed to integrate the understanding, gained from field experiments, of the dynamics of crop growth as influenced by soil moisture and environmental variables. QBAR simulates the growth and yield potential of barley grown under optimal nutrient supply, in the absence of pests, diseases, and weeds. Genotypic variables have been determined for 4 cultivars commonly grown in the northern cereal production areas. Simulations were conducted using long-term weather data to generate the probabilistic yield outcome of cv. Grimmet for a range of times of planting at 10 locations in the north-eastern Australian grain belt. The study indicated that the common planting times used by growers could be too late under certain circumstances to gain full yield potential. Further applications of QBAR to generating information suitable for crop management decision support packages and crop yield forecasting are discussed.
Publisher: Wiley
Date: 09-08-2022
DOI: 10.1002/AGJ2.21086
Abstract: Key management recommendations for cotton ( Gossypium hirsutum L.) management require estimates of the timing of crop phenology. Most commonly growing day degree (DD) (thermal time) approaches are used. Currently, across many cotton production regions, there is no consistent approach to predicting first square and flower timing. Day degree approaches vary considerably, with base thresholds different (12.0–15.6 °C) with no consistency using an optimum temperature threshold (i.e., temperature where development ceases to increase). As cotton is grown in variable and changing climates, and cultivars change, there is a need to ensure the accuracy of this approach for predicting timing of flowering for assisting cotton management. In this study new functions to predict first square and first flower were developed and validated using data collected in multiple seasons and regions (Australia and the United States). Earlier controlled environment studies that monitored crop development were used to assess in more detail how temperatures were affecting early cotton development. New DD functions developed predicted first square and first flower better than the existing Australian and U.S. approaches. The best performing functions had base temperatures like those of existing U.S. functions (15.6 °C) and an optimum threshold temperature of 32.0 °C. New universal DD targets for first square (343 DD [°C]) and first flower (584 DD) were developed. Controlled environment studies supported this base temperature outcome however, it was less clear that 32.0 °C was the optimum threshold temperature from these data. Precise predictions of cotton development will facilitate accurate growth stage assessments and hence better cotton management decisions.
Publisher: Wiley
Date: 03-11-2023
DOI: 10.1002/PS.7247
Abstract: The tomato potato psyllid, Bactericera cockerelli (Šulc) is a new invasive pest in Western Australia, which may disperse across the whole of Australia within a few years and cause significant economic losses. Chemical control is the most widely used approach to manage B. cockerelli , but insect resistance, chemical residue and effects on non‐target species have become an increasing concerned. Therefore, in this study, the biocontrol potential of variegated lady beetle, Hippodamia variegata (Goeze) was investigated. The impact of utilizing B. cockerelli as a food source on the predator's development and reproduction was assessed by formulating age‐stage, two sex life tables. The predatory potential of H. variegata on B. cockerelli nymphs was assessed in a closed arena and the effects of releasing H. variegata for the control of B. cockerelli were then evaluated. H. variegata could successfully develop and oviposit when feeding on B. cockerelli . However, both survival and the rate of development were higher for H. variegata feeding on Myzus persicae (Sulzer) than B. cockerelli or a mixed population of B. cockerelli and M. persicae . A type II functional response was observed for H. variegata . In the greenhouse, the releases of H. variegata larvae reduced the number of B. cockerelli nymphs by up to 66% and adults by up to 59%, which positively influenced the plant chlorophyll content and biomass. This study demonstrated the potential of the resident generalist predator, H. variegata as a biocontrol agent for the invasive pest, B. cockerelli , which may help improving current management strategies. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
Publisher: Elsevier BV
Date: 2013
Publisher: Elsevier BV
Date: 2008
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/FP13143
Abstract: Genotypic differences in early growth and nitrogen (N) uptake among 24 wheat (Triticum aestivum L.) genotypes were assessed in a field trial. At late tillering, large genetic variation was observed for shoot biomass (23–56 g m–2 ground area) and N uptake (1.1–1.8 g m–2 ground area). A strong correlation between aboveground biomass and N uptake was observed. Variation around this relationship was also found, with some genotypes having similar N uptake but large differences in aboveground biomass. A controlled environment experiment was conducted to investigate the underlying mechanisms for this variation in aboveground biomass using three vigorous genotypes (38–19, 92–11 and CV97) and a non-vigorous commercial cultivar (Janz). Vigorous genotypes had lower specific leaf N in the youngest fully expanded leaf than Janz. However, there was no difference in chlorophyll content, maximum Rubisco activity or the rate of electron transport per unit area. This suggests that Janz invested more N in non-photosynthetic components than the vigorous lines, which could explain the higher photosynthetic N use efficiency of the vigorous genotypes. The results suggest that the utilisation of wheat genotypes with high early vigour could improve the efficiency of N use for biomass production in addition to improving N uptake during early growth.
Publisher: CSIRO Publishing
Date: 1995
DOI: 10.1071/AR9950845
Abstract: A model to simulate leaf area development for barley at the whole plant level was constructed. Data for leaf area development in the absence of soil water stress were collected from irrigated field trials grown at Hermitage Research Station, near Warwick, Queensland, in 1990. The response of leaf area expansion to soil water status was measured in a glasshouse trial. In the model, green leaf area per plant (GPLA) is derived as the difference between total leaf area produced per plant (TPLA) and senesced leaf area (SPLA). TPLA and SPLA are described by logistic functions of thermal time. Two types of senescence are included: that due to ageing of the whole plant (ontogenetic senescence) and senescence associated with the development of large canopies (light-induced senescence). The onset of ontogenetic senescence is linked to anthesis, whereas light-induced senescence occurs if the leaf area index of the crop exceeds 5.5. Leaf expansion of plants in pots varying in the fraction of transpirable soil water available (FTSW) was compared with leaf expansion of those in well-watered pots three times per week. The relationship between relative leaf expansion (RLE) and FTSW was described by a logistic function (r2 = 0.96). A 50% reduction in RLE occurred when FTSW = 0.34. Similarly, a logistic function described the relationship between relative transpiration (RT) and FTSW (r2 = 0.96). A 50% reduction in RT occurred when FTSW = 0.17. Potential leaf expansion as predicted by the non-stressed model was reduced in response to moisture stress via a r function relating RLE to RT. The model gave an unbiased prediction of the leaf area dynamics for 21 rainfed and irrigated crops of barley grown in southern Queensland between 1986 and 1993 (RMSD = 1.09 m2 m-2, r2 = 0.75, n = 76). Precision may have been reduced by the lack of information available on parameters for soil water balance when barley is grown on a range of soil types.
Publisher: Informa UK Limited
Date: 06-07-2022
Publisher: Elsevier BV
Date: 08-2004
Publisher: Elsevier BV
Date: 08-2014
Publisher: Elsevier BV
Date: 08-2006
Publisher: Elsevier BV
Date: 06-2019
Publisher: Oxford University Press (OUP)
Date: 03-2001
Publisher: Elsevier BV
Date: 04-2004
Publisher: Elsevier BV
Date: 06-2019
Publisher: Elsevier BV
Date: 09-2009
Publisher: Springer Science and Business Media LLC
Date: 2017
Publisher: CSIRO Publishing
Date: 1993
DOI: 10.1071/AR9931351
Abstract: Dry matter production and utilization of photosynthetically active radiation (PAR) was studied for barley (Hordeurn vulgare L.) in the field at Hermitage Research Station, Qld. In 1990, four cultivars (Gilbert, Tallon, Grimmett, Skiff) were sown at three times and grown with non-limiting soil moisture. In 1991, soil moisture limitations were imposed on one sowing of the cultivar Grimmett. The radiation extinction coefficient (k) was 0.41�0.02 and did not vary with cultivar, time of sowing or soil moisture availability. Radiation use efficiency (RUE) (based on absorbed PAR and above-ground dry matter) did not change with time of sowing but did vary between cultivars. RUE was highest for Gilbert (2.90�0.10 g MJ-1), while the other three cultivars averaged 2.60�0.04 g MJ-l. RUE of Grimmett was significantly lower in 1991 (1.48�0.07 g MJ-1) than in 1990 (2.60�0.07g MJ-1), but soil moisture differences in 1991 did not significantly affect RUE. Several factors with possible links with RUE were examined and discussed. Of the variables examined those which showed the strongest relationships with RUE were average daily vapour pressure deficit and average daily minimum temperature.
Publisher: Elsevier BV
Date: 07-2013
Publisher: Elsevier BV
Date: 08-1996
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/CP13352
Abstract: This study investigated the effects of predicted changes in rainfall distribution in marginal (≤325 mm annual rainfall) parts of the south-west Australian wheatbelt and options for management and adaptation of the wheat crop. Field experiments with rain-out shelters and irrigation were conducted in 2008 and 2009 to investigate the interactions of rainfall distribution, row spacing, genotype and timing of nitrogen application on growth, water use and grain yield of spring wheat. Water storage before seeding showed potential to maintain or increase yields despite lower in-season rainfall. Widening row spacing reduced biomass and slowed water use but did not increase grain yield, because of increased soil evaporation and water left in the soil at crop maturity. The Agricultural Production Systems Simulator (APSIM) wheat model was used to investigate the effects of recent and projected climate change on yield in relation to row spacing, phenology and nitrogen. Two climate-change scenarios were applied to historical climatic data to create two plausible future climates (‘optimistic’ and ‘pessimistic’) for the year 2030. None of the strategies tested increased wheat yield under the predicted climate scenarios. Simulated yields at wider row spacings were consistently lower due to insufficient biomass, increased soil evaporation and the inability of the crop to use all of the available water before maturity. Simulated yields of short-season genotypes were always greater than yields of longer season genotypes. Nitrogen regimes had little effect in this study. This study points to several genotypic traits that could improve the performance of wheat grown at wider row spacings. These include early vigour to reduce soil evaporation and increase competition with weeds, greater tillering/biomass to reduce limitation by sink size, and a vigorous root system with appropriate lateral spread and growth to depth to access available soil water.
Publisher: Elsevier BV
Date: 08-2012
Publisher: Elsevier BV
Date: 06-2008
Publisher: Springer Science and Business Media LLC
Date: 02-03-2011
Publisher: Springer Science and Business Media LLC
Date: 10-09-2009
Publisher: Elsevier BV
Date: 02-1993
Publisher: Wiley
Date: 14-02-2020
DOI: 10.1111/JAC.12391
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/FP15215
Abstract: Shoot and root system size influences N uptake in wheat (Triticum aestivum L.). Previously, we showed that four wheat genotypes with different biomass had similar N uptake at tillering. In the present study, we determined whether the similarity in N uptake in these genotypes was associated with genotypic differences in the affinity of the root system for NO3– uptake. Kinetic parameters of NO3– uptake were measured in hydroponic seedlings of vigorous and nonvigorous early growth wheat genotypes by exposing them to solutions with differing concentrations of K15NO3 for 15 min. In the low concentration range, the high-affinity transport system of the nonvigorous cultivar Janz showed a higher maximum influx rate than the three vigorous lines and a higher affinity than two of the three vigorous lines. At high NO3– concentrations, where the low-affinity transport system was functional, the responsiveness of NO3– uptake to external concentrations was greater in Janz than in the vigorous lines. Both the high- and low-affinity transport systems were inducible. The genotypic variation in the kinetic parameters of NO3– uptake was large enough to offset differences in morphological traits and should be considered in efforts to improve N uptake. In a field trial, the growth and N uptake performance of the four wheat genotypes was investigated over the winter–spring growing season (June–November of 2010). The field trial showed that although early N uptake was disproportionately large relative to biomass accumulation, the differences in uptake at tillering can be changed by subsequent patterns of uptake.
Publisher: Elsevier BV
Date: 03-2013
No related grants have been discovered for Stephen Milroy.