ORCID Profile
0000-0001-9946-5008
Current Organisations
University of Reading
,
Central Queensland University
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Publisher: Springer Science and Business Media LLC
Date: 28-05-2008
Publisher: Informa UK Limited
Date: 09-2010
Publisher: Elsevier BV
Date: 03-2006
Publisher: CSIRO Publishing
Date: 2001
DOI: 10.1071/AR00092
Abstract: In earlier work, we found that the near complete defoliation of grain sorghum [Sorghum bicolor (L.) Moenchmp rsqb seedlings delayed panicle initiation and anthesis. Several aspects of the required defoliation remain unclear, however, including which parts of the seedling’s foliage need to be removed, the timing of defoliation, and what effects differing defoliation treatments have on the morphology of plants that re-form after defoliation is terminated. To answer these questions, sorghum plants (cv. Boomer) grown under natural (c. 11.5 h) or extended (14 h) photoperiods were defoliated during the vegetative development phase. Treatments removed the fully exposed leaf-blade and/or the partially exposed and still expanding leaves and were varied by commencing and ceasing defoliation at different times, by cutting the plants at different heights, and by leaving some green leaf area on the plant. All defoliation treatments, except the one in which only the fully exposed leaf-blade was removed, resulted in delays in panicle initiation and anthesis. Defoliation treatments terminating on the same date, yet commencing between the second and fifth leaf stages, the latter just prior to panicle initiation in control plants, gave the same delay to panicle initiation. Serial defoliation at 3–4-day intervals maintained the plants in a vegetative state. Subsequent plant development and growth were associated with the morphology of plants when defoliation was terminated, thus were influenced by the height at which defoliation was performed. Plants defoliated above the first ligule took longer to initiate reproductive development and re-formed bigger plants than did those defoliated above the second ligule. Defoliation did not always reduce the plant biomass at anthesis compared with that of control plants. We interpret these responses as evidence that the signal to initiate reproductive development in sorghum originates in the partially exposed expanding leaves and possibly the leaf primordia, and that removal of those leaves resets the plant’s developmental program to an earlier phase. For farmers of rain-fed crops this is an exciting result, since it now seems likely that post-sowing management, via defoliation, can be developed to control flowering time and adjust the yield potential of crops in line with the amount of in-crop rain.
Publisher: Elsevier BV
Date: 11-1996
Publisher: Elsevier BV
Date: 08-2008
Publisher: Springer Science and Business Media LLC
Date: 13-05-2011
Publisher: Elsevier BV
Date: 11-1986
Publisher: Springer Science and Business Media LLC
Date: 07-2010
Publisher: Informa UK Limited
Date: 25-07-2020
Publisher: Springer Science and Business Media LLC
Date: 07-2005
DOI: 10.1079/IVP2005649
Publisher: American Chemical Society (ACS)
Date: 07-05-2019
DOI: 10.1021/ACS.JNATPROD.8B00958
Abstract: The impact of Stevia rebaudiana leaf on feeding preferences of an insect, a mite, and a mammal was investigated. The grasshopper, Valanga irregularis of the Acrididae family, avoided feeding on S. rebaudiana leaf, as evidenced by a decrease in animal weight. Increased mortality on S. rebaudiana feed was ascribed to feeding avoidance to the point of starvation. The extent of red spider mite ( Tetranychus urticae) damage was not proportional to leaf steviol glycoside (SG) concentration, a result ascribed to a feeding mechanism that avoids chlorenchyma cells that contain SGs. Guinea pigs ( Cavia porcellus) were presented with the choice between a control feed and feed amended to contain 5% sucrose or 0.02%, 4%, or 10% (dry weight) of S. rebaudiana leaf. Feed intake increased (39% above the control) for the diet involving high levels of SG amendment of feed (10% S. rebaudiana leaf). Encouragement of general mammalian herbivory may provide ecological fitness to S. rebaudiana if it is more tolerant of grazing pressure than other plants in its environment. Improvement in feed intake may have commercial implication for use of S. rebaudiana as an additive in stock feeds.
Publisher: Informa UK Limited
Date: 08-01-2008
Publisher: Elsevier BV
Date: 11-1986
Publisher: Hindawi Limited
Date: 29-10-2020
DOI: 10.1155/2020/8856314
Abstract: There is a paucity of information on nutrient stocks and distribution in the cocoa ecosystem for the management of production sites to improve its productivity. Apart, sites with long histories of cocoa production could differ in nutrient stocks and distribution relative to recent production regions. Therefore, some existing cocoa farms in Ghana were s led on the basis of shade management (shaded and unshaded) and production site longevity (Eastern region Western North region) to determine the nutrient stock and distributions in them. Over 93% of the total ecosystems’ elementary nutrients were stored in the soil. Higher nutrient stocks occurred under shaded cocoa ecosystem. Nutrient element concentrations in cocoa tree biomasses followed the order: N Ca K Mg P S Al = Fe Zn = Mn, and mostly concentrated in leaf root = husk branch stem. On average, region as a main factor affected nutrient distributions. There was a sharp distinction between macronutrient and micronutrient accumulations in favour of Eastern region and Western North region, respectively. Therefore, the regional distinction with respect to macro- and micronutrients could be used as a guide to fertilizer recommendation for cocoa systems in the two regions.
Publisher: Elsevier BV
Date: 08-2004
Publisher: Informa UK Limited
Date: 16-08-2007
Publisher: CSIRO Publishing
Date: 2013
DOI: 10.1071/CP13348
Abstract: Australian cotton (Gossypium hirsutum L.) is predominantly grown on heavy clay soils (Vertosols). Cotton grown on Vertosols often experiences episodes of low oxygen concentration in the root-zone, particularly after irrigation events. In subsurface drip-irrigation (SDI), cotton receives frequent irrigation and sustained wetting fronts are developed in the rhizosphere. This can lead to poor soil diffusion of oxygen, causing temporal and spatial hypoxia. As cotton is sensitive to waterlogging, exposure to this condition can result in a significant yield penalty. Use of aerated water for drip irrigation (‘oxygation’) can ameliorate hypoxia in the wetting front and, therefore, overcome the negative effects of poor soil aeration. The efficacy of oxygation, delivered via SDI to broadacre cotton, was evaluated over seven seasons (2005–06 to 2012–13). Oxygation of irrigation water by Mazzei air-injector produced significantly (P 0.001) higher yields (200.3 v. 182.7 g m–2) and water-use efficiencies. Averaged over seven years, the yield and gross production water-use index of oxygated cotton exceeded that of the control by 10% and 7%, respectively. The improvements in yields and water-use efficiency in response to oxygation could be ascribed to greater root development and increased light interception by the crop canopies, contributing to enhanced crop physiological performance by ameliorating exposure to hypoxia. Oxygation of SDI contributed to improvements in both yields and water-use efficiency, which may contribute to greater economic feasibility of SDI for broadacre cotton production in Vertosols.
Publisher: Elsevier BV
Date: 11-1990
Publisher: Elsevier BV
Date: 12-1983
Publisher: Elsevier BV
Date: 2001
Publisher: Elsevier BV
Date: 1996
Publisher: Wiley
Date: 02-2009
Publisher: Cambridge University Press (CUP)
Date: 27-03-2009
DOI: 10.1017/S0007485309006774
Abstract: Cucurbit crops host a range of serious sap-sucking insect pests, including silverleaf whitefly (SLW) and aphids, which potentially represent considerable risk to the Australian horticulture industry. These pests are extremely polyphagous with a wide host range. Chemical control is made difficult due to resistance and pollution, and other side-effects are associated with insecticide use. Consequently, there is much interest in maximising the role of biological control in the management of these sap-sucking insect pests. This study aimed to evaluate companion cropping alongside cucurbit crops in a tropical setting as a means to increase the populations of beneficial insects and spiders so as to control the major sap-sucking insect pests. The population of beneficial and harmful insects, with a focus on SLW and aphids, and other invertebrates were s led weekly on four different crops which could be used for habitat manipulation: Goodbug Mix (GBM a proprietary seed mixture including self-sowing annual and perennial herbaceous flower species) lablab ( Lablab purpureus L. Sweet) lucerne ( Medicago sativa L.) and niger ( Guizotia abyssinica (L.f.) Cass.). Lablab hosted the highest numbers of beneficial insects (larvae and adults of lacewing ( Mallada signata (Schneider)), ladybird beetles ( Coccinella transversalis Fabricius) and spiders) while GBM hosted the highest numbers of European bees ( Apis mellifera Linnaeus) and spiders. Lucerne and niger showed little promise in hosting beneficial insects, but lucerne hosted significantly more spiders (double the numbers) than niger. Lucerne hosted sig-nificantly more of the harmful insect species of aphids ( Aphis gossypii (Glover)) and Myzus persicae (Sulzer)) and heliothis ( Heliothis armigera Hübner). Niger hosted significantly more vegetable weevils ( Listroderes difficillis (Germar)) than the other three species. Therefore, lablab and GBM appear to be viable options to grow within cucurbits or as field boundary crops to attract and increase beneficial insects and spiders for the control of sap-sucking insect pests. Use of these bio-control strategies affords the opportunity to minimise pesticide usage and the risks associated with pollution.
Publisher: Informa UK Limited
Date: 2012
Publisher: MDPI AG
Date: 21-11-2020
Abstract: Modern rice varieties adapted to aerobic (dryland) conditions have expanded to new rice growing systems thanks to their plasticity in adapting to rainfed and irrigated conditions. This is important because, as water becomes scarce in paddy rice regions (as it is already in Australia), there will be a move towards tropical to subtropical dryland rainfed rice with attendant problems of drought and low temperature. To assess rice adaptability in the wet season of the semi-arid subtropical conditions of coastal central Queensland, field experiments were established for a late season (in January) planting in 2014 and early season planting in November 2015 with 13 varieties developed by Australian Agriculture Technologies (AAT) Ltd were seeded in a vertisol soil. This was to assess their adaptation to rainfed conditions and their response to strategic irrigation. Water scarcity and low temperature prior to and at flowering were important factors constraining yield. Early flowering varieties in the late season planting escaped the otherwise cold and drought stress during the reproductive stage and had higher yields. In the second year, earlier planting made possible with strategic irrigation avoided the low temperature constraint on yield, but without follow-up strategic irrigation, yields were still low. The average yield of varieties increased from 1.5 times (AAT 4) to 16.3 times (AAT 15) with strategic irrigation compared with rainfed yields averaged across years. The increase in yield with strategic irrigation was associated with a greater leaf area index, spikelet fertility, and instantaneous water use efficiency during flowering. Strategic irrigation concentrated roots in the top 15 cm, but differences in yield between varieties under rainfed conditions were not related to root properties. It is important to consider variations in flowering time, yield potential, and drought patterns when developing rice varieties for rainfed semi-arid tropical conditions, as well as when quantifying the benefits of strategic irrigation.
Publisher: Springer Science and Business Media LLC
Date: 06-1991
DOI: 10.1007/BF00021244
Publisher: Wiley
Date: 06-1996
Publisher: Informa UK Limited
Date: 20-03-2018
Publisher: Oxford University Press (OUP)
Date: 19-04-2005
DOI: 10.1093/AOB/MCI151
Publisher: Elsevier BV
Date: 1980
Publisher: MDPI AG
Date: 15-03-2019
DOI: 10.3390/HORTICULTURAE5010026
Abstract: The processing of organic wastes and composts by worms results in castes and vermiliquer (i.e., vermicompost leachate). Both castes and vermiliquer contain plant available nutrients, the latter better suited to hydroponic operations, but the optimum pH for worm productivity and vermiliquer production makes the latter too alkaline for hydroponics. We show that under optimal hydroponic management practices, the growth and yield of pak choi (Brassica chinensis) based entirely on pH buffered vermiliquer collected after 8–10 weeks of vermicomposting was comparable with those treated with a conventional inorganic hydroponic fertiliser. Nitric acid proved to be a superior pH buffer compared with orthophosphoric acid. The total fresh weight in the nitric acid buffered vermiliquer treatments ranged from 70% to 98% of the total fresh weight of the control. However, the non-buffered hydroponic production of pak choi using off-line (batch) vermiliquer or direct linkage with vermifarms was not successful. There were no statistically significant differences between pak choi yields using vermiliquer from kitchen wastes or composted paunch materials. A 50% dilution of vermiliquer led to yield loss, but less proportionately than the dilution, and the use of pot hydroponics rather than nutrient film technique (NFT) hydroponics led to a better performance of pak choi under less favourable conditions. This is the first report of comparable yields between vermiliquer treatments and an inorganic nutrient source and highlights the feasibility and commercial potential of this hydroponic practice.
Publisher: Informa UK Limited
Date: 2015
Publisher: Elsevier BV
Date: 09-2011
DOI: 10.1016/J.BIORTECH.2011.06.076
Abstract: Microbially enhanced compost extracts ('compost tea') are being used in commercial agriculture as a source of nutrients and for their perceived benefit to soil microbiology, including plant disease suppression. Rumen content material is a waste of cattle abattoirs, which can be value-added by conversion to compost and 'compost tea'. A system for compost extraction and microbial enhancement was characterised. Molasses amendment increased bacterial count 10-fold, while amendment based on molasses and 'fish and kelp hydrolysate' increased fungal count 10-fold. Compost extract incubated at 1:10 (w/v) dilution showed the highest microbial load, activity and humic/fulvic acid content compared to other dilutions. Aeration increased the extraction efficiency of soluble metabolites, and microbial growth rate, as did extraction of compost without the use of a constraining bag. A protocol of 1:10 dilution and aerated incubation with kelp and molasses amendments is recommended to optimise microbial load and fungal-to-bacterial ratio for this inoculum source.
Publisher: Elsevier BV
Date: 02-2003
Publisher: Springer Science and Business Media LLC
Date: 04-1992
DOI: 10.1007/BF00035545
Publisher: CSIRO Publishing
Date: 2001
DOI: 10.1071/AR00075
Abstract: Water stress at anthesis is the major cause of yield reduction or crop failure in grain sorghum [Sorghum bicolor (L.) Moench] in central Queensland. Rainfall is difficult to predict and it is impractical to substantially alter the timing and amount of water stored in the soil, so we focussed on whether crop ontogeny could be managed, ultimately giving farmers some capability to align anthesis with in-crop rain. It is widely considered that a signal, transported from the leaf to the shoot apical meristem, is integral to the onset of panicle initiation and reproductive development. We hypothesised that modifying the leaves may interrupt the signal and cause a delay in the onset of reproductive development. Delays in sorghum anthesis associated with leaf modification treatments applied before panicle initiation were found to be a consequence of delays in panicle initiation. The longest delays in panicle initiation were obtained by twice-weekly defoliation above the second ligule (15–45 days) delays were shorter when plants were defoliated above the third ligule (10–41 days) or when only the fully exposed leaves were removed (0–13 days), depending on genotype. Although panicle initiation was delayed, leaf initiation continued, so extra leaves were produced. Defoliation of fully irrigated plants, however, generally reduced green leaf area, plant dry weight at anthesis, and grain yield, all by 30–50%. The application of ethephon also delayed anthesis, and changed the pattern but not the area of leaf produced, and did not alter grain yield. In rain-fed agriculture, where grain yields are frequently % of irrigated controls, delaying panicle initiation by 2 weeks may provide a better rainfall environment during which anthesis and grain-filling will occur. Reductions in green leaf area, although reducing yield potential, may promote a more balanced use of water between vegetative and grain growth. There was sufficient evidence to indicate that defoliation before panicle initiation could provide simple post-sowing management to achieve this scenario.
Publisher: Elsevier BV
Date: 08-2011
Publisher: Springer Science and Business Media LLC
Date: 12-2008
DOI: 10.1051/AGRO:2008034
Publisher: Cambridge University Press (CUP)
Date: 06-1990
DOI: 10.1017/S0021859600072713
Abstract: Irrigation experiments are described in which three cultivars were subjected to varying degrees of drought in the cool and hot seasons in Lima, Peru. The most severely draughted plots received, on average, 20% and 35% less water than the well-watered control plots, resulting in 20% and 52% yield reduction in the cool and hot seasons, respectively. Average fresh tuber yields ranged, according to cultivar, from 1370 to 2450 g/m 2 in the summer and from 2800 to 4450 g/m 2 in the winter, with tuber dry-matter percentages of c . 17% and 20%, respectively. The production of total dry matter per unit intercepted solar radiation (the conversion coefficient, estimated from the slope of the regression, in g/MJ) was markedly less during the hot season but, regressed on a photo thermal quotient ∑((MJ/m 2 )/(°C 4·5°C)), a common relationship across seasons was achieved. The conversion coefficient was less in draughted than in well-watered plots, more so in the hot season. Crop transpirational and evapotranspirational water use efficiencies (WUE) were less in the hot season largely because of the greater saturation vapour-pressure deficit. However, because of greater harvest index (HI) and more-efficient interception of solar radiation per unit of applied water by draughted than by well-watered plots in the summer, and despite a lower conversion coefficient, draughted plots showed greater WUE. Based on total water applied and final fresh tuber yields, WUE was, on average, 3·9 and 12·4 kg/m 3 in the hot and cool seasons, respectively, values close to the extremes of the range of published values. Low HI in the summer was, to some extent, responsible for this seasonal difference.
Publisher: Springer Science and Business Media LLC
Date: 06-1990
DOI: 10.1007/BF02987277
Publisher: Cambridge University Press (CUP)
Date: 12-2021
DOI: 10.1017/S0014479722000011
Abstract: Macadamia in Australia is traditionally grown in semi-arid climates with hot and humid summers and cool winters supporting rainfed cultivation. Recent industry expansion into more northern, drier production areas of Queensland, Australia, requires supplementary irrigation for successful macadamia production. However, ever-increasing demand for irrigation water in these areas is both competitive and regulated. Limited information is available to optimize water use efficiency for field-grown macadamia trees. We trialled a technique that employs specially designed drip tubes with push-in emitter plugs to close emitters so that transplanting can start with emitters closed distant from tree bases and open next to the trunks of each tree. Additional emitters are then gradually opened (i.e., plugs are removed) as tree canopy size increases over subsequent years. This technique was tested on single and double in-line irrigation tube configurations per row of macadamia. Temporal regulation of emitter closure significantly reduced irrigation input by 75, 50 and 25% in the first, second and third year of treatment. Hence, irrigation over the three-year establishment period was reduced to one-half that of the non-regulated crop. These early reductions of irrigation in juvenile trees had no significant negative effects on plant growth (height, canopy spread, leaf chlorophyll and leaf photosynthetic rates), nor on nut counts. Control of emitter discharge between the plants along the row in the earlier stage (i.e., before complete within-row canopy cover) also reduced weed growth between the trees in the row. Notable growth advantages of the single in-line over the double in-line tube configuration were evident, with a non-significant but sizeable benefit on nut counts too. Effects of the temporal regulation of emitters and of in-line tube configurations must be validated on cultivars with differing water requirements and for the longer-term reproductive performance and nut quality.
Publisher: Oxford University Press (OUP)
Date: 26-08-2005
DOI: 10.1093/AOB/MCI254
Publisher: Elsevier BV
Date: 11-1990
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/AR04157
Abstract: Various source–sink perturbations were employed to alter partitioning to orange flesh melon (Cucumis melo L. reticulatus group) and thus to influence fruit biomass and soluble sugar content (indexed as total soluble solids of fruit juice, % TSS), with attention given to the timing of treatment application. A strong relationship existed between harvest index and fruit mass (r2 = 0.88) in control plants, whereas the correlation with fruit TSS was poor (r2 = 0.11). Augmentation of assimilate supply to fruit early in fruit development (before approx. 21 days before harvest, DBH) resulted in more fruit set and increased fruit biomass, whereas augmentation after 21 DBH resulted in increased fruit TSS. Thus, fruit biomass was increased (1644 cf. 1442 g FW per fruit for control, P = 0.02), but not TSS, on plants in which fruit set was delayed (source biomass increased, harvest index decreased from 59% for control to 38%). Treatment of plants with a cytokinin-based vegetative growth inhibitor at 14 DBH produced fruit with higher TSS (11.3 cf. 10.7% for control). Thinning fruit to leave 1 fruit per plant 1 week before harvest increased the proportion of fruit in a population that exceeded a quality control standard of 10% TSS from 20 to 80%. Variations in plant response with timing of treatment application are interpreted in terms of fruit development (cell ision, cell expansion, and sugar accumulation phases). Although a detriment to yield (15 cf. 31 t/ha for control), the fruit thinning treatment was recommended for commercial use and a simple model was developed to calculate the required farm-gate price of fruit to make thinning economically viable.
Publisher: Springer Science and Business Media LLC
Date: 05-07-2016
Publisher: Brill
Date: 11-2003
Publisher: Elsevier BV
Date: 11-2005
Publisher: Elsevier BV
Date: 04-1988
Publisher: Informa UK Limited
Date: 1999
Publisher: Elsevier BV
Date: 2015
Publisher: Wiley
Date: 08-1997
Publisher: Elsevier BV
Date: 11-1990
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/RJ05012
Abstract: Clearing land of trees and introducing exotic pastures to enhance pasture and cattle production and hence enterprise financial performance are widely practised in Queensland. The results from many previous studies on tree clearing have emphasised the gains in pasture production, but over periods of less than 10–15 years after clearing. The present study questioned the sustainability of pasture production in cleared systems over a longer time-frame ( years of clearing). For this, three different age groups of clearing i.e. 5 year, 11–13 year and 33 year were selected in each of 3 major types of tree communities i.e. Eucalyptus populnea, E. melanophloia and Acacia harpophylla in central Queensland. Paired comparisons of cleared and uncleared (intact) pasture systems were selected for each age group of clearing. The results suggest that the initial gains in pasture production upon clearing were compatible with published studies. However, for longer periods of time since clearing, the gains in pasture production were not sustained and were accompanied by risks of land degradation and loss of pasture plant ersity. For E. populnea and A. harpophylla, the maximum benefits from clearing were achieved at 13–15 years whereas for E. melanophloia, any benefits existed only over a short period of 5–6 years. The study emphasises that each tree community exhibits a specific response with regard to the duration of increased pasture production following clearing. To estimate the total benefits from tree clearing in pasture development, it is important to consider both monetary benefits and non-monetary losses from clearing for different types of tree communities.
Publisher: Wiley
Date: 08-1995
Publisher: Elsevier BV
Date: 1982
Publisher: Springer Science and Business Media LLC
Date: 11-12-2008
Publisher: Scientific Societies
Date: 1996
DOI: 10.1094/PD-80-1367
Publisher: Springer Science and Business Media LLC
Date: 05-2004
Publisher: Cambridge University Press (CUP)
Date: 04-2004
DOI: 10.1017/S0014479703001534
Abstract: In this study, different levels of defoliation were imposed on a determinate species (maize) and a relatively indeterminate species (cotton). The aim was to quantify the effects of defoliation on plant growth and production, under either optimum or water-stressed conditions. Under well-watered conditions, 33% defoliation twice (conducted 28 and 35 days after emergence) resulted in a 16% reduction in grain yield of maize while 67% defoliation once (conducted 28 days after emergence) had no significant effect on yield. Under water stress, the grain yields of maize plants with 33% (twice) and 67% defoliation were 13.5% and 25% greater than that of non-defoliated control plants, respectively. For cotton, the reproductive yields (seed and lint) with 33% and 67% defoliation (conducted 43 days after emergence) were reduced, under well-watered conditions, by 28% and 37% of that of the non-defoliated control, respectively. Defoliated cotton plants lost less fruiting forms (squares and young bolls) than non-defoliated plants during water stress. Therefore, under water stress the harvestable product of cotton plants with 67% defoliation was double that of non-defoliated control plants. In non-defoliated cotton plants, a second flush of flowering after release from water-stress permitted further compensatory fruit set and boll harvest. Defoliated plants did not show such levels of compensation. Defoliation significantly reduced water use by maize and cotton. The relative yield advantage of defoliated plants under water-stress conditions can be attributed to defoliation-induced improvement in water status as reflected in measures of photosynthetic rate and stomatal conductance. Under anticipated drought stress, defoliation could be an important management practice to reduce drought-induced yield decrease, but this needs to be tested under field conditions.
Publisher: Elsevier BV
Date: 05-2019
Publisher: Springer Science and Business Media LLC
Date: 07-2004
Publisher: American Chemical Society (ACS)
Date: 02-11-2018
DOI: 10.1021/ACS.JNATPROD.8B00196
Abstract: Steviol glycosides (SG) (with stevioside and rebaudioside A predominating) are present in wild-type Stevia rebaudiana, at approximately 10% of dry weight (dw), prompting a consideration of the autoecological role played by these compounds in terms of energy (C) storage and/or osmoregulation. The leaf starch pool was observed to change diurnally with respect to the light cycle (from 3.29% to 0.73% of leaf dw between dusk and dawn) and also to increase under constant light treatment (from 1.53% to 6.25% of leaf dw), while SG pools were relatively constant (around 6% w/dw). A similar trend was observed during exposure to elevated CO
Publisher: Elsevier BV
Date: 09-1993
Publisher: Elsevier BV
Date: 12-2005
Publisher: Wiley
Date: 08-1994
Publisher: Informa UK Limited
Date: 22-11-2022
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-2007
Publisher: Cambridge University Press (CUP)
Date: 07-1991
DOI: 10.1017/S0014479700019025
Abstract: The influence of planting mixtures of two potato cultivars on the incidence of leafminer fly ( Liriomyza huidobrensis (Blanchard)) and on damage to potato foliage, and the effect on growth and yield, was studied in two field experiments in coastal Peru. Climatic differences between the two years of the experiments (1983 and 1984) had a greater effect than did cultivar mixtures on adult fly populations and on the numbers of feeding punctures and pupae per leaflet. Mixtures reduced the number of pupae in the tolerant cultivar, but increased it in the susceptible cultivar in contrast, mixed planting tended to decrease the adult populations and feeding punctures in the susceptible cultivar of each mixture. In neither year did mixture yields or intercepted radiation exceed those of the highest-yielding sole crop, although land equivalent ratios (LER) reached 1.19. Considering the cultivars' different maturity rates and their tuber growth curves, it is probable that the later maturing cultivar of each mixture was able to exploit available light after, and perhaps even before, senescence of the earlier cultivar. Mixed planting of potato could be beneficial but only to farmers who plant both early and late cultivars, under conditions where the early harvest commands a premium price.
Publisher: Elsevier
Date: 2005
Publisher: Springer Science and Business Media LLC
Date: 23-05-2016
Publisher: Elsevier BV
Date: 03-1995
Publisher: Springer Science and Business Media LLC
Date: 2002
Publisher: Cambridge University Press (CUP)
Date: 23-12-2015
DOI: 10.1017/S0007485315001005
Abstract: Silverleaf whitefly (SLW, Bemisia tabaci MEAM1) and aphids are sap-sucking insects, which pose a serious threat to Australian cucurbit crops and the horticulture industry. Traditional chemical control for these insect pests is becoming less effective, and there is a need to search for alternative or supplementary methods. This study aimed to manipulate the habitat of pumpkin crops in a tropical setting (Queensland, Australia), by growing pumpkins (var. Japanese pumpkin) alone and between lablab ( Lablab purpureus L. Sweet). It was hypothesized that the presence of lablab will increase the populations of natural enemies, and through their control of insect pests such as SLW and aphids, will affect pumpkin yield. The population of arthropods (natural enemies and pests of pumpkin), with a focus on SLW and aphids, were s led weekly on both lablab and pumpkin crop for a total of 21 weeks. Results showed that lablab hosted more enemies of SLW per plant than pumpkin in either treatment. In addition, adult SLW numbers were significantly higher in the pumpkin-only crop compared with the pumpkin grown between lablab, while pumpkin in the mixed plantings had significantly more ladybirds and lacewing larvae ( P 0.05). While there was no significant difference in the average fruit weight between treatments, the total weight (kg) and number of marketable pumpkins per hectare was greater ( P 0.05) for the pumpkin/lablab treatment than the pumpkin-only treatment. This study shows that growing lablab alongside a pumpkin crop may enhance natural enemies of SLW and could significantly increase the yield.
Publisher: Elsevier BV
Date: 04-1988
Publisher: CSIRO Publishing
Date: 2006
DOI: 10.1071/BT05174
Abstract: Land clearing in Queensland is often practised to enhance pasture production, and hence, increase financial returns from beef production. The benefits of clearing have been quantified in terms of short-term gains in pasture yield but have not adequately accounted for possible medium- or longer-term impediments that may be attributed to clearing. Therefore, impacts of clearing and the subsequent sowing of exotic grasses such as Cenchrus ciliaris L. on pasture composition and production were studied. To achieve this, paired sites were selected representing cleared and uncleared pastures across three different times since clearing (i.e. 5, 11–13 and 33 years since clearing) for the three dominant tree communities of central Queensland (i.e. Eucalyptus populnea F.Muell. (poplar box), E. melanophloia F.Muell. (silver-leaved ironbark) and Acacia harpophylla F.Muell. ex. Benth. (brigalow)). The results demonstrated that species ersity declined with clearing and sowing of exotic pastures. Species ersity and pasture production were negatively related. Although pasture yield was 2–3 times greater 13 years after clearing of E. populnea and A. harpohylla, the gains in pasture yield were not consistent over time, yields being only 1.5 times greater after 33 years of clearing. In E. melanophloia, an increase in the yield of only 1.5–1.8 times occurred 5 years after clearing compared with uncleared pastures, whereas 33 years after clearing, yield was 3/4 of that in uncleared pastures. The initial gains in pasture yield were accompanied by a loss of plant ersity that may affect ecosystem functions such as nutrient cycling or soil mineralisation, and the longer-term production gains.
Publisher: Elsevier BV
Date: 09-1998
Publisher: American Society of Civil Engineers (ASCE)
Date: 07-2014
Publisher: Cambridge University Press (CUP)
Date: 2006
DOI: 10.1017/S0014479705003029
Abstract: The practice and management of subsurface drip irrigation (SDI) on heavy clay soils is poorly understood. Over-irrigation can lead to excessive runoff and drainage, with associated negative environmental consequences. Experiments were conducted in 2001/2002 and 2002/2003 on cotton ( Gossypium hirsutum ) in a Vertisol in Australia to evaluate the effect of SDI at various application rates on cotton yield and quality, and the results were compared with those for conventional furrow irrigation. Irrigating with SDI that supplied 50% or 75% of daily crop evapotranspiration (ETc) maintained a dry upper soil profile throughout the season. SDI at 50% ETc could potentially capture 250mm more rain during the season compared to SDI 90% ETc, and even more than furrow irrigation. However, supplying only 50% ETc with SDI hastened the maturity of the crop by on average 25 days compared with furrow irrigation and higher SDI rates, fewer bolls were set and yields were lower than in the other treatments. Nevertheless, a shorter season, if yield sacrifice is acceptable, favours logistics when integrating winter crops with summer cotton. It also reduces the number and cost of pesticide sprays and irrigation. Yield plateaued when 75% or more of daily ETc was supplied by SDI. The two drier treatments (SDI at 50% and 75% of ETc) had consistently higher water use efficiencies (WUE) for lint production compared with those of the two wetter SDI treatments (SDI at 90% and 105/120% ETc). All SDI treatments were also more efficient in the first year in the use of water for lint production than was furrow irrigation, but improved irrigation management in the form of faster irrigation and reduction of tail water in the second year obviated the advantage of SDI. Irrigation of cotton with SDI at 75% ETc offered significant benefits in terms of saved irrigation water over wetter SDI treatments, resulted in the highest average WUE for lint production over the two years, and reduced drainage and runoff compared with higher SDI rates and furrow irrigation.
Publisher: Informa UK Limited
Date: 10-10-2014
Publisher: Elsevier BV
Date: 2017
DOI: 10.1016/J.MICRES.2016.11.006
Abstract: According to the World Health Organisation, antibiotics are rapidly losing potency in every country of the world. Poultry are currently perceived as a major source of pathogens and antimicrobial resistance. There is an urgent need for new and natural ways to control pathogens in poultry and humans alike. Porous, cation rich, aluminosilicate minerals, zeolites can be used as a feed additive in poultry rations, demonstrating multiple productivity benefits. Next generation sequencing of the 16S rRNA marker gene was used to phylogenetically characterize the fecal microbiota and thus investigate the ability and dose dependency of zeolite in terms of anti-pathogenic effects. A natural zeolite was used as a feed additive in laying hens at 1, 2, and 4% w/w for a 23 week period. At the end of this period cloacal swabs were collected to s le faecal microbial communities. A significant reduction in carriage of bacteria within the phylum Proteobacteria, especially in members of the pathogen-rich family Enterobacteriaceae, was noted across all three concentrations of zeolite. Zeolite supplementation of feed resulted in a reduction in the carriage of a number of poultry pathogens without disturbing beneficial bacteria. This effect was, in some phylotypes, correlated with the zeolite concentration. This result is relevant to zeolite feeding in other animal production systems, and for human pathogenesis.
Publisher: Elsevier BV
Date: 02-2011
DOI: 10.1016/J.BIORTECH.2010.11.087
Abstract: Physico-chemical and microbiological investigations were carried out on rumen content material composted for nine months, fresh vermicasts (obtained after passing the same compost through the guts of a mixture of three species of earthworms: Eisenia fetida, Lumbricus rubellus and Perionyx excavates) and microbially enhanced extracts derived from rumen compost, vermicast and vermicast leachate incubated for up to 48 h. Compared to composted rumen contents, vermicast was only improved in terms of microbial biomass C, while vermicast leached extract was significantly higher in NH(4)(+)-N,PO(4)(-)-P, humic acid, bacterial counts and total microbial activity compared to rumen compost extract. Although no difference between treatments was observed in genetic ersity as indicated by DGGE analysis, community level functional ersity of vermicast leached extract (Biolog™) was higher than that of composted rumen contents, vermicast and rumen compost extract indicating an enhancement of microbial activity rather than ersity due to liquid incubation.
Publisher: Elsevier BV
Date: 12-1988
Publisher: Elsevier BV
Date: 07-2000
Publisher: Informa UK Limited
Date: 2013
Publisher: JSTOR
Date: 02-1999
DOI: 10.2307/3674112
Publisher: Inderscience Publishers
Date: 2010
Publisher: Elsevier BV
Date: 02-2019
Publisher: Elsevier BV
Date: 05-2015
Publisher: Elsevier BV
Date: 1984
Publisher: Wiley
Date: 29-06-2011
DOI: 10.1002/IRD.571
Publisher: Informa UK Limited
Date: 2012
Publisher: Elsevier BV
Date: 10-1993
Publisher: Elsevier BV
Date: 06-2013
Publisher: Elsevier BV
Date: 09-1993
Publisher: Public Library of Science (PLoS)
Date: 26-04-2016
Publisher: Elsevier BV
Date: 05-2006
Publisher: Elsevier BV
Date: 12-2017
Publisher: Wiley
Date: 04-10-2007
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/FP08046
Abstract: Within-plant light and nutrient environments are spatially and temporally heterogeneous. The development of different parts of a plant is highly coordinated, which enables the efficient capture and use of resources in such heterogeneous environments. The physiological mechanisms underlying the correlative control of distantly located plant tissues and organs are still not fully understood. In this study, a mathematical model based on a self-organisation mechanism for resource allocation mediated by polar auxin transport is proposed to explain the origin of correlative effects among shoot branches. In the model, the shoot system of an in idual plant is treated as a collection of relatively independent modular subunits competing for root-derived resources. The allocation of root-derived resources to different parts of the shoot is determined by their relative vascular contacts with the root system. The development of the vascular network is specified by the polar transport of auxin produced by various parts of the shoot in response to their immediate internal and external environments. The simulation results show that, by altering the amount of auxin they release in idually in response to the local environment and modifying their relative vascular contact with the root system, subunits of a shoot are able to coordinate without a central controller and self-organise into functional and structural patterns such as light foraging and correlative dominance. This modelling study suggests that morphological dynamics at the whole-plant level can be understood as the sum of all modular responses to their local environments. The concept of self-organisation holds great promise for an in-depth understanding of the organisational laws that generate overall plant structure and functions.
Publisher: Elsevier BV
Date: 2005
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/SR03152
Abstract: In Queensland, land is cleared at high rates to develop pastures for enhanced production and the associated monetary gains. However, pasture production declines over time in cleared pastures until a new equilibrium is reached. The present study focussed on elucidating the reasons for decline in pasture production and finding the key soil properties that are affected due to clearing. Paired sites for cleared and uncleared pastures were selected to represent 3 dominant tree communities of the semi-arid tropics in central Queensland, i.e. Eucalyptus populnea, E. melanophloia, and Acacia harpophylla. The cleared pastures were chosen to represent 3 different durations of time since clearing (5, 11–13, and 33 years) to evaluate the temporal impact of clearing on soil properties. Various soil parameters were studied: macronutrients—available N (NH4+and NO3–), total N, and available P micronutrients—Cu, Fe, Zn, and Mn exchangeable cations—Ca, Mg, Na, and K (also macronutrients) pHw and electrical conductivity. Of these, pHw showed a significant response to time of clearing for all 3 tree communities. Soil pHw increased significantly at cleared sites relative to uncleared (native woodland) pastures, and the increase was highly correlated with concentrations of exchangeable Ca, Mg, and Na. The change in soil pHw and exchangeable cations was more evident at .30 m soil depth. The increase in soil pHw in cleared pastures decreased the availability of soil nutrients for plant growth and, hence, pasture productivity. The interactions of different soil properties down the profile as a result of changes caused by clearing are important when interpreting the effects of clearing on soil properties.
Publisher: Elsevier BV
Date: 11-1990
Publisher: Wiley
Date: 09-1995
Publisher: Cambridge University Press (CUP)
Date: 04-1997
DOI: 10.1017/S0014479797000070
Abstract: Four experiments were conducted in southern Taiwan to evaluate the yield and economic benefits of management practices aimed at alleviating the effects of high temperature and heavy rain on tomato production. Following tropical storms, waterlogging caused wilting which was more evident in tomatoes grown in beds 20 cm in height than in those grown in raised beds 40 cm in height. This indication of crop water stress induced by flooding was quantified by measurement of the difference between canopy surface and air temperature at a specified saturation vapour pressure deficit. Canopy heating was less on the raised beds, especially when straddled by rain shelters. Nevertheless, waterlogging stress for the low-bed treatment did not result in loss of stand. In crops which experienced heavy rain, application of a synthetic fruit-set hormone enhanced fruit numbers as did the simple transparent polyethylene rain shelters. While planting on raised beds was without yield benefit the use of fruit-set hormone improved yield by at least 10 t ha −1 . A further 4–6 t ha −1 yield was gained through the additional use of rain shelters. Partial budget analysis showed positive returns to the use of fruit-set hormone (US$6600 ha −1 ) but, unless rain shelters could be constructed with cheaper frame material or used for two tomato crops throughout the summer, their use would be uneconomical. Using existing frame material, net returns to rainshelters reached US$8000 ha −1 . The likelihood of high temperatures, tropical storms and typhoons will influence economic returns to summer tomato production. Data from this study may be subjected to economic analyses using values for inputs and tomato prices from other countries with similar climatic conditions.
Publisher: International Society for Horticultural Science (ISHS)
Date: 03-2016
Publisher: Oxford University Press (OUP)
Date: 06-12-2010
DOI: 10.1093/JPE/RTQ030
Publisher: Springer Science and Business Media LLC
Date: 1999
Publisher: Springer Science and Business Media LLC
Date: 20-04-2012
Publisher: Informa UK Limited
Date: 1997
Publisher: Cambridge University Press (CUP)
Date: 08-1992
DOI: 10.1017/S0021859600071537
Abstract: A series of experiments to quantify the response of erse potato genotypes to production and storage conditions in hot climates was carried out in 1984–87 at three sites in Peru, two of which were characterized by at least one hot season per year. Yield stability and field performance of seed tubers of six clones produced in situ , and stored in diffused light (DLS) or cold stored (CS), were compared with those of good quality seed tubers produced and stored in cool conditions. The yield potential of tubers produced in hot climates and grown as (i) a double crop per year with short DLS (1–4 months) (ii) a single crop per year with long DLS ( c. 8 months) and (iii) a single crop per year with long CS ( c. 8 months) was compared with that of seed tubers produced in cool conditions and introduced in successive crops. The first replanting of tubers produced in hot climates resulted in lower yield than that of coolproduced tubers. Yield reductions in clones ranged from 30 to 93% when replanted within 4 months, from 10 to 100% when replanted after 7–10·5 months of DLS and from 0 to 82% after similar periods of CS. Reduced yield was often due to poor plant vigour and crop growth leading to inefficient interception of solar radiation. There was, however, no evidence that the efficiency of utilization of intercepted radiation for tuber dry matter production was influenced by storage treatment. Poor sprout growth at planting reduced yield considerably for late clones in double cropping. Low dry matter content of tubers produced in hot climates did not influence emergence rate, but was related to poor plant vigour in the first replant under warmer conditions. Replanting and storage in hot climates did not enhance the initial reduction of tuber dry matter, which was evident after the first hot season. Tuber yields continued to decline, particularly under single cropping with long DLS. For the clones studied, CS would be a feasible storage method for potato production in hot climates if replanted tubers were used on an annual basis. For double cropping, short dormancy is essential however, poor plant vigour results in additional yield reductions. Our data indicate that clonal selection for maximum production in hot climates should take into account the proposed or existing production and storage schemes.
Publisher: Elsevier BV
Date: 07-2000
Publisher: Springer Science and Business Media LLC
Date: 10-2005
DOI: 10.1007/S00425-005-0133-8
Abstract: The hypothesis that hyperaccumulation of certain metals in plants may play a role in osmotic adjustment under water stress (drought) was tested in the context of nickel hyperaccumulator Stackhousia tryonii. Field-collected mature plants of S. tryonii, grown in native ultramafic soil, were pruned to soil level and the re-growth exposed to five levels of water stress (20, 40, 60, 80 and 100% field capacity FC) for 20 weeks. Water stress had significant (P<0.05) influence on growth (biomass), water potential and shoot Ni concentrations, with progressively more impact as water stress was increased from 80 to 40% FC. Shoot Ni concentration increased significantly from 3,400 microg g(-1) dry weight (at 100% FC) to 9,400 microg g(-1) dry weight (at 20% FC). Assuming that Ni is uniformly distributed through the shoot tissue, the Ni concentration could account for 100% at the 80 and 60% FC conditions, and 50% at the 40 and 20% FC conditions of plant osmotic regulation. The results are consistent with a role of Ni in osmotic adjustment and protection of S. tryonii plants against drought.
Publisher: Elsevier BV
Date: 06-2018
DOI: 10.1016/J.JENVMAN.2017.08.040
Abstract: Feeding treatments were imposed in two feeding trials involving Cobb broiler and Bond Brown layer birds. Three feed additives (biochar, bentonite and zeolite) were supplied at four rates (0, 1, 2 and 4% w/w) in feed, as previously considered in the context of animal production, was considered in the context of Excreta chemical and water retention properties and granulation characteristics of decomposed excreta (manure) were characterised. At field capacity (- 0.01 MPa), manure produced from control and 4% bentonite diets contained significantly (p = 0.001) more water (at 1.93 and 2.44% v/v water, respectively) than zeolite and biochar treatments. Manure mesoporosity was significantly (p = 0.015) higher in 2 and 4% bentonite treatments than other feed additives. Fresh excreta from layer birds on the control diet contained 6% w/dw N and 35% C, which was decreased to 2.6% N and 28% C after decomposition, with C:N ratio changing from 5.9 to 12.1. Ammonia loss was higher from biochar and zeolite manures than control or bentonite, associated with higher pH in the biochar and zeolite manures. More N was unaccounted from bentonite manure than other treatments, presumably lost as N
Publisher: Elsevier BV
Date: 09-2011
DOI: 10.1016/J.BIORTECH.2011.05.096
Abstract: A comparative study was performed on compost extracts prepared from cattle rumen content composted for three and nine months, nine month old compost inoculated with a Nutri-Life 4/20™ inoculum, and two commercial preparations (LivingSoil™ and Nutri-Life 4/20™), all incubated for 48h. Nutri-Life 4/20™ had the highest concentrations of NO(3)(-)-N and K(+)-K, while rumen compost extract had higher humic and fulvic acids concentration. The bacterial and fungal community level functional ersity of three month old compost extract and of LivingSoil™, assessed with Biolog™, were higher than that of nine month old rumen compost extract, with or without Nutri-Life 4/20™ inoculum, or Nutri-Life 4/20™. No difference in fungal ersity was observed between treatments, as indicated by Denaturing Gradient Gel Electrophoresis (DGGE) analysis, however, bacterial ersity was higher in all compost extracts and LivingSoil™ compared to the Nutri-Life 4/20™. Criteria for judging the quality of a microbially enhanced extract are discussed.
Publisher: Wiley
Date: 25-06-2009
DOI: 10.1111/J.1744-7909.2009.00837.X
Abstract: Impacts of salinity become severe when the soil is deficient in oxygen. Oxygation (using aerated water for subsurface drip irrigation of crop) could minimize the impact of salinity on plants under oxygen-limiting soil environments. Pot experiments were conducted to evaluate the effects of oxygation (12% air volume/volume of water) on vegetable soybean (moderately salt tolerant) and cotton (salt tolerant) in a salinized vertisol at 2, 8, 14, 20 dS/m EC(e). In vegetable soybean, oxygation increased above ground biomass yield and water use efficiency (WUE) by 13% and 22%, respectively, compared with the control. Higher yield with oxygation was accompanied by greater plant height and stem diameter and reduced specific leaf area and leaf Na+ and Cl- concentrations. In cotton, oxygation increased lint yield and WUE by 18% and 16%, respectively, compared with the control, and was accompanied by greater canopy light interception, plant height and stem diameter. Oxygation also led to a greater rate of photosynthesis, higher relative water content in the leaf, reduced crop water stress index and lower leaf water potential. It did not, however, affect leaf Na+ or Cl- concentration. Oxygation invariably increased, whereas salinity reduced the K+ : Na+ ratio in the leaves of both species. Oxygation improved yield and WUE performance of salt tolerant and moderately tolerant crops under saline soil environments, and this may have a significant impact for irrigated agriculture where saline soils pose constraints to crop production.
Publisher: Cambridge University Press (CUP)
Date: 02-2006
DOI: 10.1017/S0266467405003020
Abstract: The temporal impact of clearing trees on litter production, litter decomposition and on C, N and P release through decomposition of litter was examined in the pasture systems of a semi-arid zone of central Queensland. Paired sites for cleared pastures (developed from clearing woodlands) and uncleared (intact woodland) pastures were selected to represent three dominant tree communities of the region i.e. Eucalyptus populnea, E. melanophloia and Acacia harpophylla , with three different time-since-clearing (5, 11–13 and 33 y) treatments. Yearly litter production was greater at uncleared sites (1732–1948 kg ha −1 y −1 for eucalypt and 2596 kg ha −1 y −1 for acacia communities) compared with cleared sites (1038–1282 kg ha −1 y −1 for eucalypt and 1100 kg ha −1 y −1 for acacia communities averaged over three time-since-clearing treatments). Rates of litter decomposition and of release of C, N and P from decomposing litter were higher at cleared than uncleared sites for all three tree communities. The cleared and uncleared sites did not differ significantly in total amount of C and N released per year since the concentrations of C and N were greater in litter from uncleared sites but the rate of release was less than that at cleared sites. Slow but continuous release of nutrients in eucalypt and acacia woodlands may be an adaptation of these communities to maintain the nutrient cycle and to avoid leaching of nutrients in the nutrient-poor soils of the region.
Publisher: Informa UK Limited
Date: 02-01-2014
Publisher: Elsevier BV
Date: 1984
Publisher: Springer Science and Business Media LLC
Date: 24-11-2001
Publisher: Informa UK Limited
Date: 2000
Publisher: CSIRO Publishing
Date: 2000
DOI: 10.1071/EA99082
Abstract: There has been considerable effort and money spent in the development of intelligent support systems (decision support systems and expert systems) for use by farmers, but few systems appear to be adopted for regular use. An examination of the conceptual issues concerning the adoption of innovations, with particular reference to software products, identifies major factors that appear to influence the adoption of these systems by farmers. The conceptual frameworks used for this analysis include Rogers’ diffusion theory, the perceived usefulness and ease-of-use of software, software development methods with a focus on the adopter-based approach to technology, and user involvement in the development of an innovation. As a result of this approach, we argue that the low adoption rate of intelligent support systems is understandable and could have been predicted. Different approaches are needed if we are to do better in the future. These include participatory approaches, using ‘softer’ systems methodologies that acknowledge the importance of involving the user early in the development process and that pay attention to the decision-making styles and social context of potential users.
Publisher: Elsevier BV
Date: 10-2015
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for David Midmore.