ORCID Profile
0000-0002-4699-0957
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Publisher: Springer Science and Business Media LLC
Date: 28-07-2012
Publisher: Elsevier BV
Date: 2012
Publisher: Elsevier BV
Date: 2017
Publisher: Elsevier BV
Date: 11-2011
Publisher: CSIRO Publishing
Date: 2010
DOI: 10.1071/CP09157
Abstract: In eastern Australia, latitudinal gradients in vapour pressure deficit (VPD), mean temperature (T), photosynthetically active radiation (PAR), and fraction of diffuse radiation (FDR) around the critical stage for yield formation affect wheat yield and crop water-use efficiency (WUE = yield per unit evapotranspiration). In this paper we combine our current understanding of these climate factors aggregated in a normalised phototermal coefficient, NPq = (PAR· FDR)/(T · VPD), with a shire-level dynamic model of crop yield and water use to quantify WUE of wheat in 245 shires across Australia. Three measures of WUE were compared: WUE, the ratio of measured yield and modelled evapotranspiration WUEVPD, i.e. WUE corrected by VPD and WUENPq, i.e. WUE corrected by NPq. Our aim is to test the hypothesis that WUENPq suits regional comparisons better than WUE or WUEVPD. Actual median yield at the shire level (1975–2000) varied from 0.5 to 2.8 t/ha and the coefficient of variation ranged from 18 to 92%. Modelled median evapotranspiration varied from 106 to 620 mm and it accounted for 42% of the variation in yield among regions. The relationship was non-linear, and yield stabilised at ~2 t/ha for evapotranspiration above 343 mm. There were no associations between WUE and rainfall. The associations were weak (R2 = 0.09) but in the expected direction for WUEVPD, i.e. inverse with seasonal rainfall and direct with off-season rainfall, and strongest for WUENPq (R2 = 0.40).We suggest that the effects of VPD, PAR, FDR, and T, can be integrated to improve the regional quantification of WUE defined in terms of grain yield and seasonal water use.
Publisher: Proceedings of the National Academy of Sciences
Date: 28-12-2015
Abstract: We collated a unique dataset covering land use and production data of more than 13,000 smallholder farm households in 93 sites in 17 countries across sub-Saharan Africa. The study quantifies the importance of off-farm income and market conditions across sites differing strongly in agroecology and derives generally applicable threshold values that determine whether farm households have enough food available to feed their families. These results show there is a strong need for multisectoral policy harmonization and incentives and improved interconnectedness of people to urban centers and ersification of employment sources, rather than a singular focus on agricultural development of smallholder farmers in sub-Saharan Africa.
Publisher: Elsevier BV
Date: 10-2016
Publisher: CSIRO Publishing
Date: 2006
DOI: 10.1071/AR04133
Abstract: The APSIM-Wheat module was used to investigate our present capacity to simulate wheat yields in a semi-arid region of eastern Australia (the Victorian Mallee), where hostile subsoils associated with salinity, sodicity, and boron toxicity are known to limit grain yield. In this study we tested whether the effects of subsoil constraints on wheat growth and production could be modelled with APSIM-Wheat by assuming that either: (a) root exploration within a particular soil layer was reduced by the presence of toxic concentrations of salts, or (b) soil water uptake from a particular soil layer was reduced by high concentration of salts through osmotic effects. After evaluating the improved predictive capacity of the model we applied it to study the interactions between subsoil constraints and seasonal conditions, and to estimate the economic effect that subsoil constraints have on wheat farming in the Victorian Mallee under different climatic scenarios. Although the soils had high levels of salinity, sodicity, and boron, the observed variability in root abundance at different soil layers was mainly related to soil salinity. We concluded that: (i) whether the effect of subsoil limitations on growth and yield of wheat in the Victorian Mallee is driven by toxic, osmotic, or both effects acting simultaneously still requires further research, (ii) at present, the performance of APSIM-Wheat in the region can be improved either by assuming increased values of lower limit for soil water extraction, or by modifying the pattern of root exploration in the soil profile, both as a function of soil salinity. The effect of subsoil constraints on wheat yield and gross margin can be expected to be higher during drier than wetter seasons. In this region the interaction between climate and soil properties makes rainfall information alone, of little use for risk management and farm planning when not integrated with cropping systems models.
Publisher: Elsevier BV
Date: 10-2009
Publisher: Elsevier BV
Date: 11-2011
Publisher: IOP Publishing
Date: 25-02-2014
Publisher: Springer Science and Business Media LLC
Date: 1999
Publisher: Wiley
Date: 11-1999
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 12-2012
Publisher: Elsevier BV
Date: 03-2013
Publisher: Elsevier BV
Date: 12-2002
Publisher: Springer Science and Business Media LLC
Date: 07-2006
Publisher: Elsevier BV
Date: 05-2017
Publisher: Elsevier BV
Date: 05-2017
Publisher: Elsevier BV
Date: 10-2007
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/AR05035
Abstract: This work addresses the need for meaningful spatial indices of the physiological condition of field crops for site-specific management and variable rate application in precision agriculture. Precision agriculture is designed to target crop inputs according to within-field requirements to increase profitability while protecting the environment. The objectives of this work were to (a) develop a canopy physiological stress index with spatial resolution commensurate with the needs of site-specific management, and (b) test the physiological meaning of this index by exploring its association with key processes and variables at leaf and crop levels. We report results from a single-year field experiment where different levels of irrigation, wheat crop density, and nitrogen supply were applied to increase the expression of within-season variability. We defined a canopy stress index (CSI) as the difference between canopy (Tc), and air temperature (Ta), normalised by vapour pressure deficit (VPD): CSI = (Tc – Ta)/VPD. A novel method to extract canopy temperatures (Tc) from complex digital thermal images was developed, thus allowing for the spatial characterisation of CSI. CSI is expected to be positive and high if the capacity of the canopy to dissipate heat is reduced as when stomata close. CSI accounted for 80% of the variation in growth rate and yield, compared with 46–49% explained by the normalised difference vegetation index (NDVI). Most of the variation in crop response variables was related to water supply. The physiological meaning of this index was reinforced by its significant association with gas exchange variables measured at the leaf-level. The potential for the use of digital thermal imaging in precision agriculture is discussed.
Publisher: Wiley
Date: 05-2001
Publisher: Elsevier
Date: 2020
Publisher: Elsevier BV
Date: 04-2014
Publisher: Elsevier BV
Date: 2021
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/CP16027
Abstract: This paper reviews the interactions between water and nitrogen from physiological, agronomic, economic, breeding and modelling perspectives. Our primary focus is wheat we consider forage crops, sorghum and legumes where relevant aspects of water–nitrogen interactions have been advanced. From a physiological perspective, we ask: How does nitrogen deficit influence the water economy of the crop? How does water deficit influence the nitrogen economy of the crop? How do combined water and nitrogen deficit affect crop growth and yield? We emphasise synergies, and the nitrogen-driven trade-off between the efficiency in the use of water and nitrogen. The concept of nitrogen–water co-limitation is discussed briefly. From agronomic and economic perspectives, the need to match supply of nitrogen and water is recognised, but this remains a challenge in dryland systems with uncertain rainfall. Under-fertilisation commonly causes gaps between actual and water-limited potential yield. We discuss risk aversion and the role of seasonal rainfall forecasts to manage risk. From a breeding perspective, we ask how selection for yield has changed crop traits relating to water and nitrogen. Changes in nitrogen traits are more common and profound than changes in water-related traits. Comparison of shifts in the wheat phenotype in Australia, UK, Argentina and Italy suggests that improving yield per unit nitrogen uptake is straightforward it requires selection for yield and allowing grain protein concentration to drift unchecked. A more interesting proposition is to increase nitrogen uptake to match yield gains and conserve protein in grain. Increased stomatal conductance is a conspicuous response to selection for yield which partially conflicts with the perception that reduced conductance at high vapour pressure deficit is required to increase water- use efficiency but high stomatal conductance at high vapour pressure deficit may be adaptive for thermal stress. From a modelling perspective, water and nitrogen are linked in multiple ways. In crops where water limits growth, reduced biomass reduces nitrogen demand. Reciprocally, nitrogen limitation during crop expansion reduces leaf area index and increases the soil evaporation : transpiration ratio. Water–nitrogen interactions are also captured in the water-driven uptake of nitrogen by mass flow and diffusion and in the water-driven processes of nitrogen in soil (e.g. mineralisation). The paper concludes with suggestions for future research on water-nitrogen interactions.
Publisher: Springer Science and Business Media LLC
Date: 02-02-2018
DOI: 10.1038/S41598-018-20628-2
Abstract: Expected increases in food demand and the need to limit the incorporation of new lands into agriculture to curtail emissions, highlight the urgency to bridge productivity gaps, increase farmers profits and manage risks in dryland cropping. A way to bridge those gaps is to identify optimum combination of genetics (G), and agronomic managements (M) i.e. crop designs (GxM), for the prevailing and expected growing environment (E). Our understanding of crop stress physiology indicates that in hindsight, those optimum crop designs should be known, while the main problem is to predict relevant attributes of the E, at the time of sowing, so that optimum GxM combinations could be informed. Here we test our capacity to inform that “hindsight”, by linking a tested crop model (APSIM) with a skillful seasonal climate forecasting system, to answer “What is the value of the skill in seasonal climate forecasting, to inform crop designs?” Results showed that the GCM POAMA-2 was reliable and skillful, and that when linked with APSIM, optimum crop designs could be informed. We conclude that reliable and skillful GCMs that are easily interfaced with crop simulation models, can be used to inform optimum crop designs, increase farmers profits and reduce risks.
Publisher: Elsevier BV
Date: 11-2015
Publisher: Elsevier BV
Date: 12-2003
Publisher: Springer Science and Business Media LLC
Date: 1998
Publisher: CSIRO Publishing
Date: 2006
DOI: 10.1071/AR05361
Abstract: We tested the capacity of several published multispectral indices to estimate the nitrogen nutrition of wheat canopies grown under different levels of water supply and plant density and derived a simple canopy reflectance index that is greatly independent of those factors. Planar domain geometry was used to account for mixed signals from the canopy and soil when the ground cover was low. A nitrogen stress index was developed, which adjusts shoot %N for plant biomass and area, thereby accounting for environmental conditions that affect growth, such as crop water status. The canopy chlorophyll content index (CCCi) and the modified spectral ratio planar index (mSRPi) could explain 68 and 69% of the observed variability in the nitrogen nutrition of the crop as early as Zadoks 33, irrespective of water status or ground cover. The CCCi was derived from the combination of 3 wavebands 670, 720 and 790 nm, and the mSRPi from 445, 705 and 750 nm, together with broader bands in the NIR and RED. The potential for their spatial application over large fields addocks is discussed.
Publisher: Wiley
Date: 08-1994
Publisher: Springer Science and Business Media LLC
Date: 1998
Publisher: CSIRO Publishing
Date: 2007
DOI: 10.1071/AR06376
Abstract: We investigated the influence of rainfall patterns on the water-use efficiency of wheat in a transect between Horsham (36°S) and Emerald (23°S) in eastern Australia. Water-use efficiency was defined in terms of biomass and transpiration, WUEB/T, and grain yield and evapotranspiration, WUEY/ET. Our working hypothesis is that latitudinal trends in WUEY/ET of water-limited crops are the complex result of southward increasing WUEB/T and soil evaporation, and season-dependent trends in harvest index. Our approach included: (a) analysis of long-term records to establish latitudinal gradients of amount, seasonality, and size-structure of rainfall and (b) modelling wheat development, growth, yield, water budget components, and derived variables including WUEB/T and WUEY/ET. Annual median rainfall declined from around 600 mm in northern locations to 380 mm in the south. Median seasonal rain (from sowing to harvest) doubled between Emerald and Horsham, whereas median off-season rainfall (harvest to sowing) ranged from 460 mm at Emerald to 156 mm at Horsham. The contribution of small events (≤ 5 mm) to seasonal rainfall was negligible at Emerald (median 15 mm) and substantial at Horsham (105 mm). Power law coefficients (τ), i.e. the slopes of the regression between size and number of events in a log-log scale, captured the latitudinal gradient characterised by an increasing dominance of small events from north to south during the growing season. Median modelled WUEB/T increased from 46 kg/ha.mm at Emerald to 73 kg/ha.mm at Horsham, in response to decreasing atmospheric demand. Median modelled soil evaporation during the growing season increased from 70 mm at Emerald to 172 mm at Horsham. This was explained by the size-structure of rainfall characterised with parameter τ, rather than by the total amount of rainfall. Median modelled harvest index ranged from 0.25 to 0.34 across locations, and had a season-dependent latitudinal pattern, i.e. it was greater in northern locations in dry seasons in association with wetter soil profiles at sowing. There was a season-dependent latitudinal pattern in modelled WUEY/ET. In drier seasons, high soil evaporation driven by a very strong dominance of small events, and lower harvest index override the putative advantage of low atmospheric demand and associated higher WUEB/T in southern locations, hence the significant southwards decrease in WUEY/ET. In wetter seasons, when large events contribute a significant proportion of seasonal rain, higher WUEB/T in southern locations may translate into high WUEY/ET. Linear boundary functions (French-Schultz type models) accounting for latitudinal gradients in its parameters, slope, and x-intercept, were fitted to scatter-plots of modelled yield v. evapotranspiration. The x-intercept of the model is re-interpreted in terms of rainfall size structure, and the slope or efficiency multiplier is described in terms of the radiation, temperature, and air humidity properties of the environment. Implications for crop management and breeding are discussed.
Publisher: Elsevier BV
Date: 12-2015
Publisher: CSIRO Publishing
Date: 2007
DOI: 10.1071/AR06135
Abstract: In the wheatbelt of eastern Australia, rainfall shifts from winter dominated in the south (South Australia, Victoria) to summer dominated in the north (northern New South Wales, southern Queensland). The seasonality of rainfall, together with frost risk, drives the choice of cultivar and sowing date, resulting in a flowering time between October in the south and August in the north. In eastern Australia, crops are therefore exposed to contrasting climatic conditions during the critical period around flowering, which may affect yield potential, and the efficiency in the use of water (WUE) and radiation (RUE). In this work we analysed empirical and simulated data, to identify key climatic drivers of potential water- and radiation-use efficiency, derive a simple climatic index of environmental potentiality, and provide an ex le of how a simple climatic index could be used to quantify the spatial and temporal variability in resource-use efficiency and potential yield in eastern Australia. Around anthesis, from Horsham to Emerald, median vapour pressure deficit (VPD) increased from 0.92 to 1.28 kPa, average temperature increased from 12.9 to 15.2°C, and the fraction of diffuse radiation (FDR) decreased from 0.61 to 0.41. These spatial gradients in climatic drivers accounted for significant gradients in modelled efficiencies: median transpiration WUE (WUEB/T) increased southwards at a rate of 2.6% per degree latitude and median RUE increased southwards at a rate of 1.1% per degree latitude. Modelled and empirical data confirmed previously established relationships between WUEB/T and VPD, and between RUE and photosynthetically active radiation (PAR) and FDR. Our analysis also revealed a non-causal inverse relationship between VPD and radiation-use efficiency, and a previously unnoticed causal positive relationship between FDR and water-use efficiency. Grain yield (range 1–7 t/ha) measured in field experiments across South Australia, New South Wales, and Queensland (n = 55) was unrelated to the photothermal quotient (Pq = PAR/T) around anthesis, but was significantly associated (r2 = 0.41, P 0.0001) with newly developed climatic index: a normalised photothermal quotient (NPq = Pq . FDR/VPD). This highlights the importance of diffuse radiation and vapour pressure deficit as sources of variation in yield in eastern Australia. Specific experiments designed to uncouple VPD and FDR and more mechanistic crop models might be required to further disentangle the relationships between efficiencies and climate drivers.
Publisher: Wiley
Date: 2013
Publisher: Elsevier BV
Date: 02-2017
Publisher: Elsevier BV
Date: 08-2000
Publisher: Informa UK Limited
Date: 11-1995
Publisher: Society of Petroleum Engineers (SPE)
Date: 30-04-2014
DOI: 10.2118/167016-PA
Abstract: The rapid expansion of the coal-seam-gas (CSG) sector in Queensland has fueled debate on the sector's contributions to community sustainability in a rural economy dominated by the farming of food and cotton, cattle grazing, coal mining, and a modest level of tourism. For ex le, will the impacts of CSG extraction on surface and groundwater have sustained negative impacts on the growing of grain, and if so, what should one expect of the CSG industry today? The intensity of debate is accompanied by an array of operating conditions placed on CSG projects by the state government, extensive media coverage, and a focus on what it takes to maintain a “social license to operate.” Such a context is a challenge for resource companies committed to sustainability principles and to contributing to the social, economic, and institutional development of the communities in which they operate as well as to the conservation of bio ersity and integrated approaches to land-use planning. In this context, our research explored perceptions of the social and environmental impacts in two local government areas of rural Queensland. We surveyed and interviewed stakeholders affected by—and/or influential in—decision making and the management of mining, CSG extraction, and agriculture in these areas. We asked their views on the state of the environment, the economy, social fabric, human capital, and local infrastructure, comparing today to 5 years ago. Their responses reveal how this contested arena harbors “wicked” problems: issues that are hard to formulate in simple terms and in which every potential solution has irreversible consequences. Our findings suggest further that the successful coexistence of multiple industries and a social license to operate for CSG companies depend on effective management by resource companies, and by regulators, of operating practices, off-site impacts, and the distribution of benefits.
Publisher: Elsevier BV
Date: 09-2020
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/AR07061
Abstract: Reliable seasonal climate forecasts are needed to aid tactical crop management decisions in south-eastern Australia (SEA). In this study we assessed the quality of two existing forecasting systems, i.e. the five phases of the Southern Oscillation Index (SOI) and a three phase Pacific Ocean sea-surface temperatures (SSTs), to predict spring rainfall (i.e. rainfall from 1 September to 31 November), and simulated wheat yield. The quality of the forecasts was evaluated by analysing four attributes of their performance: their reliability, the relative degree of shift and dispersion of the distributions, and measure of forecast consistency or skill. Available data included 117 years of spring rainfall and 104 years of grain yield simulated using the Agricultural Production Systems Simulator (APSIM) model, from four locations in SEA. Average values of spring rainfall were 102–174 mm with a coefficient of variation (CV) of 47%. Average simulated wheat yields were highest (5609 kg/ha) in Albury (New South Wales) and lowest (1668 kg/ha) in Birchip (Victoria). The average CV for simulated grain yields was 36%. Griffith (NSW) had the highest yield variability (CV = 50%). Some of this year-to-year variation was related to the El Niño Southern Oscillation (ENSO). Spring rainfall and simulated wheat yields showed a clear association with the SOI and SST phases at the end of July. Important variations in shift and dispersion in spring rainfall and simulated wheat yields were observed across the studied locations. The forecasts showed good reliability, indicating that both forecasting systems could be used with confidence to forecast spring rainfall or wheat yield as early as the end of July. The consistency of the forecast of spring rainfall and simulated wheat yield was 60–83%. We concluded that adequate forecasts of spring rainfall and grain yield could be produced at the end of July, using both the SOI and SST phase systems. These results are discussed in relation to the potential benefit of making tactical top-dress applications of nitrogen fertilisers during early August.
Publisher: Elsevier BV
Date: 02-2018
Publisher: Elsevier
Date: 2015
Publisher: Elsevier BV
Date: 09-2010
Publisher: Elsevier BV
Date: 04-2014
Publisher: Informa UK Limited
Date: 1993
Publisher: Elsevier BV
Date: 04-2010
Publisher: FapUNIFESP (SciELO)
Date: 05-2018
Publisher: Springer International Publishing
Date: 2016
Publisher: Informa UK Limited
Date: 1996
Publisher: Elsevier BV
Date: 02-2016
Publisher: Informa UK Limited
Date: 14-12-2015
Publisher: Elsevier BV
Date: 08-2015
Publisher: Elsevier BV
Date: 11-2011
Publisher: Springer Science and Business Media LLC
Date: 1998
Location: No location found
Location: Australia
No related grants have been discovered for Daniel Rodriguez.