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Made available in DSpace on 2022-04-28T19:46:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 The water retention curve (WRC) of arable soils from the southeastern United States at different levels of compaction (no compaction, and 10 and 20% increases in soil bulk density) was estimated using the van Genuchten–Mualem (VG) model. The VG water retention parameters of the noncompacted soils were obtained first by fitting measured soil hydraulic data. To construct the WRC of the compacted soils, gravimetric values of the permanent wilting point (θgw, 1,500 kPa) and the residual (θgr) water content were assumed to remain unchanged with compaction. The VG parameter α and exponent η after compaction were estimated using two approaches. In Approach 1, α and η were estimated from saturation, the permanent wilting point, and the residual water content. In Approach 2, the value of η was assumed to remain unchanged with compaction, which allowed α to be estimated immediately from the VG equation. Approach 2 was found to give slightly better agreement with measured data than Approach 1. The effect of compaction on the saturated hydraulic conductivity (Ks) was predicted using semitheoretical approaches and the VG-WRC function. HYDRUS-1D was further used to simulate vertical infiltration into a single-layered soil profile to determine the impact of compaction on the infiltration characteristics of the soils used in our analyses. Results showed that a 10–20% increase in soil bulk density, due to compaction, reduced cumulative infiltration (Ic) at time T = Tfinal (steady-state) by 55–82%, and the available water storage capacity by 3–49%, depending upon soil type. Univ. of Southern Queensland Centre for Agricultural Engineering CSIRO Agriculture and Food Black Mountain Science and Innovation Precinct Dep. of Earth Sciences Utrecht Univ. Center for Environmental Studies São Paulo State Univ. Dep. of Agricultural and Biosystems Engineering Iowa State Univ. Engineering Dep. Harper Adams Univ. Center for Environmental Studies São Paulo State Univ.

Context The Acland Land System overlying the Walloon sandstone coal deposits in southern Queensland is generally marginal for cropping but well suited to grazing, and thus cultivated land is commonly returned to pasture. Rehabilitation of these lands after open-cut coal mining seeks to be safe, stable and self-sustaining to satisfy requirements for ecologically sustainable development. Aims The present paper evaluates the sustainability and economic viability of beef production on (a) lands retired from cultivation and then rehabilitated with sown pastures after open-cut coal mining at the New Acland mine site, and (b) similar nearby pasture lands that were not mined but were also retired from cultivation. Methods The GRASP grazing systems model was modified and calibrated with short-term (5-year) grazing trial data (soil, pasture and cattle observations), and then used with long-term (60-year) weather data to estimate effects of land type, pasture rundown, climate and grazing pressure on productivity and economic returns. The productivity of three rehabilitated sites and 15 unmined sites were evaluated, including pastures on six commercial properties. Key results Estimates of long-term mean annual growth of pastures on unmined lands retired from cultivation on three land types (Mountain Coolibah, Brigalow Uplands and Poplar Box) were 3398, 2817 and 2325 kg/ha respectively. Pasture growth was greater on rehabilitated lands; 3736 kg/ha on the site most typical of rehabilitated lands and a mean of 4959 kg/ha across three sites. Seasonal conditions had large effects on cattle liveweight gain (133–213 kg/head per year during the trial); however, pasture growth was the main driver of beef production and economic returns per hectare. In GRASP, potential nitrogen uptake was used to influence key pasture growth processes and accounted for 64% of variation in observed annual growth. The short-term lift and subsequent rundown in productivity typically associated with sown pastures was estimated to have increased mean annual pasture and cattle productivity during the 2014–2018 trial period by up to 17% and 25% respectively. Estimates of long-term mean annual beef production and economic returns for the unmined lands were less than estimated for rehabilitated lands and were 139 kg/head.year (45 kg/ha.year) and AU$154/adult equivalent. Conclusions Rehabilitated lands were found to be sustainable for beef production at grazing pressures up to 30% utilisation of annual pasture growth, and comparable with grazing systems on native and sown pastures in good condition. Pastures on unmined lands retired from cultivation had reduced productivity. Implications Overgrazing is a significant and on-going residual risk to sustainable production. Grazing regimes need to continually adjust for changes in novel landscapes, pasture condition and climate. The methods used in the present study could be applied more generally.

Context Agricultural land used for open-cut coal mining in Queensland is required by law to be returned to a safe, stable and self-sustaining state for agriculture. Aims The aim of this research was to identify whether rehabilitated pastures on post-mine soil at a site near Acland could viably support cattle production. Methods Five years of field data from Botanal pasture assessments, pasture quality, cattle liveweights and faecal observations, plus supplementary cattle liver data, were used to compare pasture and cattle performance from mined and unmined previously cultivated brigalow land. Subtropical pasture species were sown in 2007 (Rehab1, 22 ha), 2010 (Rehab 2, 32 ha) and 2012 (Rehab3, 22 ha) in three rehabilitated paddocks and in 2012 in an unmined (Control, 21 ha) paddock. The paddocks were grazed for 117–190 days of each year by Angus cattle. Key results Mean total standing dry matter in grazed pasture over the five trial years was consistently higher in Rehab 2 (5656 kg/ha) than in the other paddocks. Rehab 1 (3965 kg/ha) and Rehab 3 (3609 kg/ha) performed at an intermediate level and the Control paddock produced less pasture (2871 kg/ha). Grass leaf crude protein was higher in Rehab 2 than in the other paddocks and declined significantly (P < 0.001) across all paddocks as pasture aged. Pasture species remained perennial, palatable and productive in all paddocks; however, pasture yield, quality and composition trends over time suggested that pasture rundown occurred across all paddocks. The mean liveweight gain (LWG) per head when grazing the trial paddocks (trial LWG) was higher (P < 0.05) in the Rehab 2 cohort than the other paddock cohorts in Years 3 and 5, and trial LWG in the Control cohort was not significantly (P > 0.05) different from one or more of the rehabilitated paddock cohorts each year. Cattle production per hectare during the trial grazing periods was also consistently highest in Rehab 2 (5-year mean trial LWG 131 kg/ha) compared with the other paddocks (67–80 kg/ha). Conclusion The rehabilitated pastures in use by the mine were considered at least as productive as the surrounding unmined brigalow landscape. Implications The Acland rehabilitation process was considered successful in establishing pastures that were able to viably support cattle production.

Context New Acland coal mine in south-eastern Queensland is seeking to rehabilitate mined land to pastures that are safe, stable and sustainable for beef production. Little is known of the productivity and sustainability of grazing previously mined land in the Darling Downs study region. Additionally, information is required to specify management guidelines for sustainable grazing of regional land types retired from cultivation. Aims Identify pasture growth characteristics, rainfall use efficiencies and long-term carrying capacities of subtropical sown pastures established on lands rehabilitated after open-cut coal mining in comparison to sown pastures established on un-mined but previously cultivated lands. Methods Pasture growth and quality (% nitrogen) were observed using the Swiftsynd methodology in ungrazed exclosures with three sites on rehabilitated lands of the Acland Grazing Trial over a 5-year period (2014–2018), and 13 sites on unmined lands over periods of 2–5 years providing data for modelling pasture growth. Key results Peak pasture yield (TSDM for autumn harvests) averaged for 2017 and 2018 was greater (P < 0.1) on rehabilitated sites than unmined Poplar Box land type sites (5957 and 2233 kg/ha respectively) but similar to Brigalow Uplands and Mountain Coolibah land type sites (3946 and 3413 kg/ha respectively). Pasture rundown was evident, with pasture N uptake decreasing over 5 years at some sites. Soil mineral N supply (potentially mineralisable N and mineral N) in spring was a useful indicator of N uptake over the following growing season. Simulations using the GRASP pasture growth model for the grazing trial period predicted rainfall use efficiencies of 12.0, 7.0, 9.1 and 4.8 kg/ha.mm rainfall for rehabilitated sites and unmined sites on Brigalow Uplands, Mountain Coolibah and Poplar Box land types respectively. Long-term carrying capacities based on estimates of long-term median pasture growth and 30% utilisation were 4.39, 3.58 and 5.92 ha/adult equivalent respectively for the unmined land types, and 2.45 ha/adult equivalent for the rehabilitated lands. Conclusions Rehabilitated land can be as productive as unmined but previously cultivated land. Implications Grazing management plans for sustainable management of mined and unmined lands can be developed using data from the present study. The plans will assist with the transition of rehabilitated lands to commercial agriculture.

The Australian Red Meat Processing (RMP) industry is challenged with ever increasing environmental pressures to reduce their environmental footprint. Wastewater is high strength and requires qualit...

Ensiling of sugarcane trash (SCT) and sugarcane stalks (SCS) was studied to assess the effects of molasses (MOL) and lactic acid bacteria (LAB) inoculant on methane potential. The experiment was run for 70 days and monitoring parameters were analyzed at days 0, 5, 15 and 70. Biochemical methane potential (BMP) tests performed with fresh and ensiled material at day 70 showed an increase in methane potential by 24.0%, 23.4%, 1.7% and 71.1% for SCSctr, SCTctr, SCTmol and SCTmol + lab, respectively. Such improved performance is explained by the formation of organic acids (mostly acetate and lactate) which were able to decrease the pH of the silages from 5.7–5.9 to 3.8–4.2 for all SCT treatments and from 5.9 up to 3.4 for SCS treatment. Thus, the ensiling process provided similar effects to a pre-treatment at low acid concentrations, which in turn improved the digestibility of the cellulosic biomass for methane production.

A key environmental sustainability requirement for the treatment of organic waste via anaerobic digestion (AD) is the prevention of unwanted methane emissions in the production chain whenever possible. Identifying and quantifying these emissions has been frequently investigated, particularly in Europe. However, the challenges of climate change are also becoming vitally important in Australia. This novel study presents the results from emission measurement campaigns carried out at two biogas plants and one landfill site in Australia. An on-site approach consisting of leakage detection and emission quantification by a static chamber method was applied. Twenty-nine leakages were detected predominantly on the digesters (gastight covered anaerobic lagoons) of the biogas plants. Ten emission hot spots were found on the surface cover of a landfill site. Methane emission rates of 9.9 ± 2.3 kg h−1 (10.5 ± 2.4% CH4) for biogas plant A, 3.0 ± 1.9 kg h−1 (8.1 ± 5.2% CH4) for biogas plant B and 41–211 g h−1 for the two largest emission hot spots from the landfill were measured. Since not every single leakage or hot spot could be quantified separately, the stated overall emission rates had to be extrapolated. Importantly, the emission rates from the landfill should be interpreted carefully due to the limited overall area which could be practicably investigated. Leakages occurred at common components of the covered anaerobic lagoons such as the membrane fixation or concrete walls. Repairing these parts would increase the plant safety and mitigate negative environmental effects.

This paper reports on the validation of two numerical approaches that were developed to determine the effect of compaction on the soil water retention curve (WRC). The proposed approaches satisfactorily expanded the applicability of the van Genuchten (1980) model. In Approach 1, an optimization problem was solved to enable the van Genuchten model parameters α and η to be estimated for a range of soil bulk densities, based on the WRC of the corresponding non-compacted soil and the estimated saturation, residual, and permanent wilting-point (-1500 kPa) water contents of the compacted soil. In Approach 2, the parameter η was assumed to be unaffected by changes in soil bulk density. Subsequently, the parameter α was determined using an equation especially developed by this study. Compared with measured data, Approach 2 yielded slightly better predictions of the WRC than Approach 1. However, both numerical approaches may be used with confidence in a wider range of scenarios than those presented in this study. Across all soils, our analyses showed that relatively small increments in soil bulk density, due to compaction, can result in significant reductions in the available water storage capacity (AWSC) of soils; the effect being dependent on soil type and the relative increase in soil bulk density. Mechanization systems that mitigate, or where possible avoid, soil damage due to compaction (coupled with management practices that reduce loss of soil organic carbon) are encouraged. Quantification of the benefits of compaction avoidance, in terms of improved infiltration, soil water retention and water-use efficiency, as well as better predictions of the hydrology of compacted soils, may be possible through the application of the models reported in this study.

The work reported in this article was conducted to determine thin layer drying rates and equilibrium moisture contents of abattoir paunch waste. The equilibrium moisture content of paunch varied from 7.14% to 13.12% for drying in air between 35 and 55 °C, and at 40–80% relative humidity. A predictive equilibrium moisture content equation based on the Chung-Pfost model was developed with the constants A found to be 586.72, B (27.461), and C (28.913) with a standard error of ±0.0035. These values were comparable to the published values for wheat and barley. The thin layer drying constant, k, varied from 0.00023 to 0.0029 min -n with an average time exponent, n, value of 1.42 for air temperatures in the range of 35–55 °C. The variation in drying rates demonstrated a significant sensitivity to humidity.

The micrometeorological factors driving variation in litter moisture (GWClit) at the landscape scale are poorly understood, particularly in areas with heterogeneous vegetation and complex terrain. In this research we seek to quantify how climate and eco-hydrology contribute to variation in litter moisture and potential evaporation at the forest floor. Research sites were established at 12 locations in southeast Australia with variable precipitation, solar exposure, and drainage position. We measured solar radiation, air temperature, relative humidity, litter moisture, and litter temperature. Spatial patterns of GWClit, examined during two drying phases, show that moisture in the litter and its rate of evaporation are closely linked to vegetation density, which is largely a function of aridity. This creates a pattern whereby aridity-related differences in vegetation structure controls the spatial variation in GWClit, with regional effects being driven by precipitation while local effects are caused by variation in solar exposure and drainage position. By parametrising a model of daily potential evaporation (Ep) at the forest floor we explore how vegetation and topography influence evaporative demand above the litter layer. The model shows that Ep is driven primarily by net radiation and that the role of vapour pressure deficit is almost negligible due to high moisture content within the sub-canopy air mass and high aerodynamic resistance. In dry forests the net radiation is directly related to shortwave radiation and Ep remains high despite low temperatures. In the tall wet forests, commonly found at high elevations, along drainage lines and on slopes with polar-facing aspects, the long-wave radiation (i.e. temperature) was just as important for Ep as the shortwave radiation. Low energy inputs to the forest floor in these tall forests means that a significant rainfall event results in surface fuels that remain wet for much longer than fuels in the dry open forest. This leads to a spatial pattern of flammability whereby surface fuels in densely vegetated areas are more often less likely to burn than those in the open forests. These wet compartments limit landscape-scale fire activity by creating dis-connectedness in the available fuel. Heatwaves and the duration of dry spells determine the degree with which these wet compartments persist as barriers to fuel connectivity through a fire season. Elsewhere in the landscape, however, the large inputs of shortwave radiation to the forest floor means that surface fuels reach flammable conditions within several hours or days after rainfall and are therefore flammable for much of the fire season.

In Australia, recycling of paunch waste to farmland has been suggested as a cost-effective and practicable environmental option, but little is known about its agronomic value. Experimental work was undertaken to assess potential risks due to weed seed contamination, determine the agronomic response of ryegrass ( L.) to soil incorporation of paunch, and investigate short-term greenhouse gas (GHG) emissions. Five types of paunch with compost ages between 2 and 16 weeks were compared with urea (46% N) and applied at field equivalent rates of 0 (control), 150, and 300 kg ha-1 N. The risk of weed contamination from paunch applied to soil appeared to be negligible; however, techniques that enable seed viability to be determined may be required to fully discard such risk. Average dry matter yield with paunch was ~30% higher than untreated grass, but ~35% lower than with urea. Dry matter yield in paunch-treated grass was between 2500 and 3250 kg ha-1 over five cuts conducted at 25-day intervals. Paunch N responses were between 1.12 and 3.25 kg DM kg-1 N depending on compost age, but lower than with urea N (~6.5 kg DM kg-1 N). Nitrogen use efficiency of paunch ranged between 3% and 20%, compared to about 35% with urea. Nitrogen fertilizer replacement value (NFRV) of paunch was highest in the 6-week-old compost (~60%) and ranged between 20% and 55% across all other organic materials. Short-term N2O emissions were similar (p > 0.05) with both mineral and organic amendments; however, CH4 emissions were higher (p < 0.05) from paunch compared with urea-treated soil. Overall, there appears to be potential for paunch-derived products to be used as a source of C and nutrients in crop production. Industry quality specifications for compost are available, but they need to be expanded to incorporate guidelines relevant to paunch. There is a requirement for the value proposition to industry to be determined, including reduced cost of paunch disposal via gate fees. Keywords: Byproducts, Composting, Fertilizer replacement value, Nutrient recovery, Nutrient use efficiency, Recycling of abattoir-derived waste.

Fuel moisture is a key driver of forest flammability as it influences ignition likelihood, fire intensity and resultant fire severity. Changes to forest canopy cover following disturbances like wildfire or logging may alter forest flammability by changing the microclimatic conditions that influence fine fuel moisture. Wet forests dominated by Mountain Ash (Eucalyptus regnans) are highly valued for their flora and fauna, timber, carbon and water. Wildfires are an important part of the lifecycle of these forests, but too frequent fire can threaten post-fire regeneration. With large tracts of Mountain Ash forest recovering from recent wildfires (in 2009 and 1983) there is a need to understand the mechanisms driving flammability in these forests, particularly as the forest structure changes following fire. This study sought to understand the effects of fire history on the flammability of Mountain Ash forests by specifically considering fuel moisture for different times since fire and fire severities. We measured canopy cover (plant area index) and fuel moisture within 8 forest sites last burnt between 7 and 200 years ago by wildfires of low or high severity. Fuel moisture and fuel availability (i.e. number of days when fine fuels are dry enough to ignite and sustain spreading fire) were strongly associated with canopy cover; with denser canopied forests having higher fuel moisture. The largest differences in canopy cover occurred between the recently burnt high and low severity forests. For the longer-unburnt forests there were no systematic differences evident in canopy cover with time since fire or fire severity. The fuel moisture was higher and fuels only available to burn on one day in the forest recently burnt by high severity fire (in association with a dense canopy). In contrast, fuels were drier and available to burn on 238 days in the forest recently burnt by low severity fire (in association with a sparser canopy). For the longer-unburnt forests (33 or more years since fire) there were no clear trends between fuel moisture and time since fire and fire severity suggesting that fires do not have a lasting impact on fuel moisture within these wet forests. Overall, this study shows that wildfires have immediate impacts on fuel moisture in Mountain Ash forests but as the time since fire increases, moisture appears to be more a function of canopy properties than fire history.

Organomineral fertilizers (OMF) derived from treated sewage sludge (biosolids) were produced using a novel technique that enables addition of nitrogen (N) to biosolids (BS) to increase the N:P ratio of the sludge and improve its agronomic suitability. Two OMF products (OMF WWTP1 and OMF WWTP2) were formulated and tested in a glasshouse facility on pot-grown ryegrass (Lolium perenne L.). The agronomic performance of OMF was compared with urea and two types of biosolids (BS WWTP1 and BS WWTP2) sourced from different wastewater treatment plants located in southern Queensland, Australia. The fertilizer materials had the following N:P2O5 compositions: 5:12.5 (BS WWTP1), 5.5:6 (BS WWTP2), ≈15:10 (OMF WWTP1), ≈15:5 (OMF WWTP2), and urea (46:0), respectively. Cubical-shaped particles (median size: ≈5x5x5 mm) of BS and OMF, and granular urea were applied to soil (Red Ferrosol) in pots at field-equivalent rates ranging from 0 (control) to 750 kg N ha-1 at regular increments of 75 kg N ha-1, and six grass cuts performed at intervals of 30 days. Results showed that cumulative dry matter yield (DMY) was between 13% and 21% higher with OMF and BS compared with urea, depending on fertilizer type and rate (P

Rehabilitation of mined land intends to support food and biomass production, with open cut mines required to return the land to a safe, stable and productive state in Queensland, Australia. The aim of this investigation was to assess the potential for soil that was previously farmed, then mined and rehabilitated to support pasture for commercial cattle production. The study was focussed on abiotic properties of the rehabilitated soils, in comparison to properties of a range of unmined soil profiles supporting pastures within the immediate vicinity. Three hypotheses were tested: 1) the abiotic properties of rehabilitated soils would fall within the range of those from nearby unmined soils; 2) that rehabilitated soils would support viable pasture production; and 3) that the mine-spoil would restrict root function. The mine was situated near Acland, Queensland, with rehabilitated land sown to pasture 1, 3 and 6 years prior to the initiation of the study in 2013. The investigation followed these rehabilitated sites, in comparison to a Control site, and 18 proximal unmined sites, through a five year period. All sites were used to support cattle grazing, with soil nutrients, structural condition and pasture growth (8 sites) monitored. Evidence from pasture production and root exploration obtained through soil pit investigations demonstrated that the mine spoil was capable of supporting root growth beyond the replaced soil layer. There were few differences between the Control and rehabilitated sites with regard to benefits or constraints to pasture production, with exception that two rehabilitated sites had simillar or higher plant-available phosphorus and nitrogen. It was concluded that: 1) abiotic properties of rehabilitated soils fell within the range of unmined soils; 2) viable pasture production was achieved from the rehabilitated sites; and 3) both the replaced soil layer and the mine spoil supported root exploration and pasture production.

The moisture content of dead leaves, twigs and bark on the forest floor is a key determinant of fire behaviour. The microclimate inside forests, which drive the moisture content of these dead fuel components, is typically measured at screen height (150 cm). However, in some forest types, the surface fuel at ground level may be subject to additional sheltering from low shrubs, ferns and grasses, which could alter the microclimate near the surface (hereafter near-surface). In such cases, screen height measurements may not adequately represent the near-surface conditions that determine dead fuel moisture contents. We sought to quantify the effect of understorey vegetation on near-surface microclimate. We measured in-forest temperature, relative humidity and solar radiation in eucalypt forests over two fire seasons at both screen height and the near-surface using weather stations at 25 sites. The sites encompassed wet eucalypt forest (n=18) with a dense, mesic understorey and dry eucalypt forest (n=7) with a sparser, scleromorphic understorey. Wet forests with dense understorey vegetation had near-surface air temperatures that averaged 1.3°C lower, relative humidities that averaged 13.1% higher and total solar radiation that was 0.84 MJ less per day compared with those measured at screen height. These microclimate differences led to predicted fuel moistures which averaged 4.7% higher at the near-surface compared with screen height – this was statistically significant. In contrast, dry forests with less understorey vegetation, had near-surface air temperatures that averaged 4.2°C higher, and relative humidities that averaged 3.1% lower compared to screen height. These differences were not large enough to translate into statistically significant differences in predicted fine fuel moisture between heights. Overall, these findings show that understorey vegetation plays an important role in moderating near-surface microclimate in some forest types and this needs to be taken into consideration when predicting fuel moisture.

In this review, the use of MESe are evaluated in the monitoring of volatile fatty acids (VFAs) during the anaerobic digestion of high strength wastewater, with a focus on slaughterhouse wastewater. VFAs are identified as a key intermediary in anaerobic digestion, hence their accumulation could be used to infer possible process instability of anaerobic digesters. Current sample measurement for VFAs through off-line laboratory analysis can be costly, time consuming, and require specialist skills. Consequently, microbial electrochemical sensors (MESe) are currently being investigated as a low-cost alternative method for in-line VFA measurement. In this paper, the fundamental operation of MESe is summarised, including the exploration of several factors that would impact the operation of MESe in real wastewater applications. It is found that, in the context of wastewater sensing, MESe technology has been unable to bridge the gap between the laboratory and real-world anaerobic digesters effectively. Important issues surrounding biofouling, sensitivity, and detection range are explored and prioritised in this review, and an overview of potential research pathways is provided. These include the potential to further explore alternate electrode materials, use of ion exchange membranes, and development of other sensor components, as further described in the review.

On-farm, intensive feed and processing sectors from Australian red meat, dairy and pork industries produce significant quantities of waste. The management of these wastes is a significant cost for these industries exceeding AUD100-200 (≈USD75-150) million per year. In addition, primary production and processing costs are rising and there is an ongoing need to improve productivity to maintain future industry profitability and environmental performance. Understanding key information gaps on waste composition and quantities in these industries is a fundamental step to fully realizing the opportunities in unlocking new revenue streams to produce energy products, fertilizers, feeds and chemicals for use in agriculture. One of the key strategies for ensuring the development of viable commercial outcomes from this research program is to underpin the work with research into the waste resources available in Australia and opportunities to aggregate the waste resources that can lead to new business models for adoption. This paper will provide a literature review of the work undertaken in this area. The critical evaluation scoped out available information, and data was collated from these various sources and synthesized. This process has confirmed that beef, pork and dairy industries all have varying information available on waste resources and overall there is a lack of high-resolution data available. This activity presents an opportunity to assist industries in waste resource recovery by achieving higher resolution data, through collaborations with Australian Biomass for Bioenergy Assessment (ABBA), Rural Research and Development Corporations (RDCs), industry stakeholders and regulatory bodies to garner specific information on co-digestion opportunities and interest in high value add products.

Agriculture and the related primary industry is an increasingly energy demanding sector. Energy is needed to different extent in all the stages of the agri-food chain. In many cases, energy cost may represent a significant proportion of the total agricultural production cost, including the cost of manufacturing and transportation of various chemicals and fertilisers. A modified and standardized energy analysis and benchmarking process is described in this paper. It is shown that energy use in agriculture varies considerably, depending on the cropping enterprise and the farming systems. Opportunities to reduce energy use and costs and greenhouse gas emissions in agriculture are discussed.

Rainfall simulator trials were conducted on sugar cane paddocks across dry-tropical and subtropical Queensland, Australia, to examine the potential for spot spraying to reduce herbicide losses in runoff. Recommended rates of the herbicides glyphosate, 2,4-D, fluoroxypyr, atrazine, and diuron were sprayed onto 0, 20, 40, 50, 70, or 100% of the area of runoff plots. Simulated rainfall was applied 2 days after spraying to induce runoff at one plant cane and three ratoon crop sites. Over 50% of all herbicides were transported in the dissolved phase of runoff, regardless of the herbicide's sediment-water partition coefficient. For most sites and herbicides, runoff herbicide concentrations decreased with decreasing spray coverage and with decreasing herbicide load in the soil and cane residues. Importantly, sites with higher infiltration prior to runoff and lower total runoff had lower runoff herbicide concentrations.

There have been recent developments in (1) sensing and perception, (2) variable rate technologies, and (3) machine optimization in agriculture. Such automated systems have potential for use in agricultural production and consist of multiple functional components that enable them to perform pre-determined tasks. Developments include optical guidance systems, vision-based systems, automation and process monitoring, and the precision application of fertilizer, herbicide, and seeding. Optical guidance systems use either laser or machine vision to enable better positioning of the tractor relative to the crop. Vision-based systems increase situational awareness of the tractor operator and thereby improve safety. Sensors for process monitoring include grain yield and protein sensors which make georeferenced measurements to provide maps of yield and protein variability in the crop. These data can be used with a number of precision agriculture (PA) techniques. New variable rate technologies use section control of functional implements to reduce seeding or herbicide overlap. A communication Standard (ISO 11783) has been developed through collaboration between tractors and implement manufacturers. Engineering performance and optimization of tractors has taken various elements of tractor operation that are typically performed by a human operator and turned them toward automation, resulting in improved fuel efficiency and reduced wear on the vehicles. The essential functions of the new developments in automation and their commercial availability are discussed and reviewed, from which recommendations for future research were developed.

Crop nitrogen (N) management is one of many important agricultural applications that can benefit from crop sensing. The technologies in this field are advancing rapidly, including: (1) sensor-carrying platforms, (2) the sensors themselves, and (3) the analytical techniques used to derive actionable information from the data. A review of commercially and semi-commercially available platforms was undertaken to inform sensor mounting, with particular focus on unmanned aerial vehicle (UAV) sensor platforms and unmanned ground vehicle (UGV) sensor platforms. The UAV and UAG platforms provide indirect and direct measurements for crop monitoring and N mapping with the goals of being low-cost, on-site, and versatile. Optical crop sensing techniques and systems for N management are also discussed, because destructive sampling and laboratory analyses are expensive and often not practical for site-specific management of N. The optical properties of the plant are significant because they are related to water content, leaf senescence, disease, and nutrient status, which can inform farming decisions. Additionally, Red, Green and Blue (RGB) imaging can provide a plant height assessment for multiple measurements, including: yield potential, biomass, density, uniformity, and planter skips. The work reported in this paper includes a comparison of various optical sensors for plant measurements, including: vis-NIR, Machine Vision, and 3D-imaging, with camera varieties such as multispectral, fluorescence, hyperspectral, thermal, and visible. Key recommendations have been provided for the development of data aggregation and decision support tools including the data sources to be used in development of machine learning models, software/data standardization efforts, and corporate collaborations regarding big data. In conjunction with the sensors and their platforms, this advancing field of management technology can provide intelligent sensing and intelligent decisions.

Operations at meat processing plants result in the production of a range of solid and liquid wastes. Traditional solid waste management practices in Australia include rendering of offal, bones and blood into saleable products (example bone meal), composting (on-site and off-site) and off-site disposal whereas wastewater is treated on-site using anaerobic lagoons. The last decade has seen considerable interest in alternative technologies for the treatment of solid and liquid waste driven by a range of factors including rapidly increasing energy and fertilizer costs, increasing costs of disposal, odor emission and urban encroachment onto traditional rural areas and the potential for improved regulatory compliance. This work provides an overview of closed-loop opportunities for the production of bioenergy and bioproducts using solid and liquid waste at Australian red meat processing facilities. Our investigations undertaken at one of Australia’s largest processing plants have centered on developing tools and practices that better manage waste streams. This work will present results on biogas process optimization of a covered high rate anaerobic lagoon including addition of trace elements and investigation of crust management strategies. The use of solid organic waste in co-digestion and investigations into the reuse of paunch as a fertilizer are also provided. In addition, a review of value added products in the form of blood products was carried out to identify new opportunities in this area.

Farming has recently experienced increasing automation, and further development is likely to include systems of multiple robots. Such systems will require development in machine-to-machine communication, telematics and infield communication, and data infrastructure for more sophisticated autonomy and decision support. Machine-to-machine communication technologies involve direct radio links between vehicles and are used to improve logistics and efficiency of multiple vehicle operation. Additionally, this type of communication enables the sharing of coverage maps and guidance lines to coordinate operations such as seeding, nutrient application and spraying, and grain unloading during harvest. Within machine-to-machine communication there are two major groupings: leader-follower technologies, and multi-robot systems. Within the multi-robot systems grouping are three sub-groupings: multi-robot interaction, multi-robot guidance, and control architecture. A number of telematics and infield communication solutions have been developed by tractor manufacturers, but it is unclear how open these communication platforms are and how well multiple systems are able to interact. Recent emergence of cloud-based farm management platforms (e.g., OnFarm®), which aim to integrate data from multiple sensors, vehicles, weather, and other sources across multiple manufacturers, and also to include decision support systems, could provide a more versatile data infrastructure in the future. This paper reviews and discusses the current state of communication systems, including patents, and the required improvements for universal commercial viability.

Developments in agricultural machinery navigation include tractor guidance and steering control systems, machine operation and path planning systems. Tractor guidance and steering control technologies have been in commercial use for two decades. These systems enable tractors to be positioned precisely in the field or relatively to the crop with minimal driver interaction. This reduces driver fatigue, frees the driver to better monitor implement and machine operations, and with suitable position accuracy, which differs based on the underlying positioning technology (e.g., real time kinematic (RTK) GNSS, crop sensors), more advanced agronomic techniques such as inter-row seeding are therefore feasible. One of the primary benefits of guidance technology is the reduction in overlap during seeding, spraying, fertilizing and harvesting, which optimizes both input costs and machine efficiency. All major tractor manufacturers offer some form of guidance and automated steering control, and systems are also available from companies that specialize in tractor guidance systems. Developments in machine operation and path planning include systems that better coordinate implement and tractor operations. In some cases, fully automating procedures such as end turns where a seeding implement is raised, the vehicle performs a 180 degree turn and aligns correctly for the next pass. Implement guidance products are also available that control the steering and position of the tractor to achieve accurate positioning of the implement, rather than the tractor itself. The availability and distinguishing factors of these varying navigation technologies are presented and discussed per manufacturer, as well as their significant recent developments.

In this study, a simulation was carried out using BioWin 3.1 to test the capability of the software to predict the biogas potential for two different anaerobic systems. The two scenarios included: (1) a laboratory-scale batch reactor, and (2) an industrial-scale anaerobic continuous lagoon digester. The measured data related to the operating conditions, the reactor design parameters and the chemical properties of influent wastewater were entered into BioWin. A sensitivity analysis was carried out to identify the sensitivity of the most important default parameters in the software’s models. BioWin was then calibrated by matching the predicted data with measured data and used to simulate other parameters that were unmeasured or deemed uncertain. In addition, statistical analyses were carried out using evaluation indices, such as the coefficient of determination (R-squared), the correlation coefficient (r) and its significance (p-value), the general standard deviation (SD) and the Willmott index of agreement, to evaluate the agreement between the software prediction and the measured data. The results have shown that after calibration, BioWin can be used reliably to simulate both small-scale batch reactors and industrial-scale digesters with a mean absolute percentage error (MAPE) of less than 10% and very good values of the indexes. Furthermore, by changing the default parameters in BioWin, which is a way of calibrating the models in the software, as well, this may provide information about the performance of the digester. Furthermore, the results of this study showed there may be an over estimation for biogas generated from industrial-scale digesters. More sophisticated analytical devices may be required for reliable measurements of biogas quality and quantity.

This paper combines data from soil moisture capacitance probes and a cosmic-ray neutron probe in a fuzzy inference system to estimate spatially variable soil moisture in a ∼28 ha circular area at an hourly interval in northeast Tasmania, Australia. The technique uses hourly counts of cosmic-ray neutrons, a network of 25 capacitance probes measuring soil moisture at half hourly intervals and at five depths (0-50 cm), and a multiple adaptive neuro-fuzzy inference system. We quantified soil moisture in the top portion of the soil during wet and dry periods for training and testing periods. After training, the technique provided reliable estimates of temporal pattern of soil moisture at 10- and 20-cm depths during a wet period using input data only from the cosmic-ray neutron probe. There was overprediction of soil moisture during a dry period, which suggests a longer training period representative of the full range of likely conditions might be required. Spatial maps of soil water content produced from the single cosmic-ray neutron probe were similar to those of the capacitance probe

Covered anaerobic ponds offer significant advantages to the red meat processing industry by capturing methane rich gas as a fuel source for bioenergy while reducing greenhouse gas emissions (GHG). This paper presents the results of a novel-designed anaerobic pond system at an Australian abattoir in relation to pond performance and potential biogas production. Key findings in assessing the effectiveness of the system revealed that the covered ponds are capable of efficient wastewater decomposition and biogas production. The primary issue with the covered ponds at the abattoir was the build-up of fat/crust that prevented the accurate measurement of biogas and effective use of the cover. In the absence of field biogas data the novel application of the computer modelling software BioWin® was carried out to simulate chemical oxygen demand(COD) removal rates and subsequent biogas yield. The unique parameter used to fit field data was the fraction of the inlet COD due to a superficial crust which did not follow anaerobic digestion. Field data effluent COD removal rates were matched to simulated rates predicted by BioWin when measured influent COD was reduced to 30%. Biogas modelling results suggest significant variation in the economic benefit of biogas energy, with the quantity of biogas potentially varying tenfold (from 328 m3/d to 3284 m3/d) depending on site factors such as pond efficiency, pond configuration and operational practices.

Due to the high strength nature of abattoir wastewater, the accumulation of crusts on anaerobic ponds is a systemic problem in the red meat processing industry in Australia and can limit the ability to accurately obtain biogas measurements. In this study, BioWin was used to simulate chemical oxygen demand (COD) removal rates and subsequent biogas production rate based on field data from two abattoirs where crust accumulation was an issue. BioWin is a Microsoft Windows-based simulator developed by EnviroSim Associates Ltd, which has seen use in the design and optimisation of wastewater treatment plants. In assessing overall anaerobic decomposition efficiency it was hypothesised that a large percentage of influent COD was present as a surface crust which remained largely unbiodegradable. Field data effluent COD removal rates were matched to simulated rates predicted by BioWin when measured influent COD was reduced to 30% (absolute relative error of 11–14%), thus supporting the notion that a significant portion of COD is not taking part in the anaerobic digestion process. The simulation provides a preliminary assessment of pond performance in terms of COD removal rates and also subsequent biogas production rates. BioWin was able to predict approximate biogas production rates ranging between 113 to 173 m3/d and 52 m3/d for the two abattoirs investigated. Further work to validate simulation using BioWin includes obtaining actual biogas measurements and performing COD measurement of crust.

This study was designed to improve our understanding of, and mechanistically simulate, nitrate (NO3) dynamics in a steep 9.8 ha rural headwater catchment, including its production in soil and delivery to a stream via surface and subsurface processes. A two-dimensional modelling approach was evaluated for (1) integrating these processes at a hillslope scale annually and within storms, (2) estimating denitrification, and (3) running virtual experiments to generate insights and hypotheses about using trees in streamside management zones (SMZs) to mitigate NO3 delivery to streams. Total flow was mathematically separated into quick- and slow-flow components; the latter was routed through the HYDRUS software with a nitrogen module designed for constructed wetlands. Flow was monitored for two years. High surface-soil NO3 concentrations started to be delivered to the stream via preferential subsurface flow within two days of the storm commencing. Groundwater NO3-N concentrations decreased from 1.0 to less than 0.1 mg l−1 from up-slope to down-slope water tables, respectively, which was attributed to denitrification. Measurements were consistent with the flushing of NO3 mainly laterally from surface soil during and following each storm. The model accurately accounted for NO3 turnover, leading to the hypotheses that denitrification was a minor flux (

Churchill Abattoir Pty Ltd (CA) is a beef abattoir and rendering facility that has operated for 43 years as a government entity, and for the past 11 years as a private enterprise. Since the changeover, there have been significant improvements in CA's environmental performance. In response to improving waste treatment and minimisation, CA has developed a novel covered anaerobic pond design for the treatment of abattoir wastewater. This design consists of five smaller ponds arranged in a cell configuration which has been driven by a number of factors including, manageability (for desludging ponds) and ease of removing and applying covers. Industry design and management standards are based on generalised metrics for anaerobic ponds rather than industry specific data. To inform pond design, an intensive study of pond behaviour was performed on the covered anaerobic ponds. This paper gives an overview of the literature reported on the use of anaerobic ponds in the treatment of high-strength wastewater and outlines the key findings in the preliminary assessment of the behaviour and performance of these novel anaerobic ponds. The use of five smaller ponds instead of one larger pond has proven successful in terms of crust and sludge removal. The primary issue with the covered ponds at Churchill, however, was the build-up of fat/ crust that prevented the capture of biogas and effective use of the cover. Despite the operational difficulties in relation to fat/crust accumulation, results indicate that satisfactory, stable operation has been achieved for the smaller five-pond system, notwithstanding the higher than desired organic loading rate of the two primary ponds.

In Australia, the red meat processing industry actively seeks approaches to improve the management of solid waste from processing operations and enhance the environmental performance. Recycling of paunch waste to farmland could be a cost-effective and practicable environmental option. However, little is known about the agronomic value of fresh and composted paunch, and the associated requirements for land application. Therefore, a short-term experimental work was undertaken to assess potential risks due to weed seed contamination and determine the agronomic response of ryegrass (Lolium perenne L.) to soil incorporation of paunch. The risk of weed contamination from soil application of paunch appeared to be low; however, methods that account for viability of seeds may be required to fully discard such a risk. Soil application of paunch at field equivalent rates of 150-300 kg ha-1 of N increased dry matter yield by ≈30% on average compared with untreated grass, but was approximately 35% lower than a mineral fertilizer treatment applied at the same rates. Dry matter yield of paunch-treated grass was between 2000 and 3000 kg per ha over four consecutive cuts at 25-day intervals. Nitrogen use-efficiency of paunch was approximately 10% (range: 3% to 20%, depending on paunch type), and total N in harvested plant material showed values, which were between 2% and 3%. Overall, there appears to be potential for paunch-derived products to be used as a source of carbon and nutrients in crop production. Areas that merit a research priority within this space are also outlined in this paper. Such work is required to inform soil-, climate- and crop-specific land application rates, optimize agronomic performance, and minimize environmental concerns. There is also a requirement for the value proposition to industry to be determined, including reduced cost of disposal of material via gate fees and fertilizer replacement value.

Ginning is an energy intensive process. This paper evaluates the energy usage inside the cotton gins in Australia. Benchmark electricity use is found to range between 44 and 66 kWh per bale, with average being 52.3 kWh. The electricity consumption for different gins is nearly linearly correlated with bale numbers produced. The electricity network charge is a significant cost in cotton ginning operations. All gins monitored had an overall power factor of higher than 0.85. It is found that drying gas usage is strongly influenced by the cotton moisture reduction and regulated drying temperature. Overall, electricity and gas usage comprises about 61% and 39% respectively of total energy use (GJ/bale). 60.38 kg of CO2 are emitted for ginning each bale of cotton. A method for detailed monitoring of energy performance in cotton gins is developed and described. Detailed monitoring and analysis are carried out at two gin sites. It is found that changes in trash content in the module, degree of moisture and lint quality produced do not have significant influence on electricity usage, while the cotton variety is shown to affect the energy usage. Overall, cotton handling is found to be the largest energy user and it takes up to nearly 50% of power use in both gins. Packaging and handling together use some 70% of total power required.

Herbicide usage in weed control represents a significant economic cost and environmental risk in Australian sugarcane production. Weed spot spraying has potential to increase sugarcane production while reducing chemical usage and environmentally damaging runoff. However, weed spot spraying is traditionally a laborious manual task. This paper reports on a precision machine vision system that was developed to automatically identify and target the difficult to control weed Panicum spp. (Guinea Grass) in sugarcane crops. The infield machine vision system comprised a camera and artificial illumination to enable day and night trials. Image analysis algorithms were developed to discriminate Guinea Grass and sugarcane based on colour and textural differences between the species. A positive weed identification from the image analysis activated solenoid-controlled spray nozzles. Evaluations of the system in a sugarcane crop established that the image analysis algorithm parameters required frequent recalibration during the day but that the requirement for recalibration was reduced at night with constant artificial illumination. The algorithm was only effective at detecting mature Guinea Grass. The developed technology is considered a viable alternative to manual spot spraying of mature Guinea Grass in sugarcane at night. A cost benefit analysis of the new weed control system indicated potential grower savings of $170/ha by adopting the technology.

Within highly mechanised agricultural productions systems such as the Australian cotton industry, operational energy inputs represent a major cost to the growers. In this paper, a framework to assess the operational energy inputs of various production systems and the relative performance of a grower within an adopted system is developed. It divides energy usage of cotton production into six broadly distinct processes, including fallow, planting, in-crop, irrigation, harvesting and post harvest. This enables both the total energy inputs and the energy usage of each production processes to be assessed. This framework is later implemented and incorporated into an online energy assessment tool (EnergyCalc). Using the developed software, seven farm audits are conducted. It is found that overall, depending on the management and operation methods adopted, the total energy inputs for these farms range from 3.7 to 15.2 GJ/ha of primary energy, which corresponds to $80–310/ha and 275–1404 kg CO 2 equivalent/ha greenhouse gas emissions. Among all the farming practices, irrigation water energy use is found to be the highest and is typically 40–60% of total energy costs. Energy use of the harvesting operation is also significant, accounting for approximately 20% of overall direct energy use. If a farmer moves from conventional tillage to minimum tillage, there is a potential saving of around 10% of the overall fuel used on the farm. Compared with cotton, energy uses by other crops are generally much smaller, due to less intensive management practices, and reduced irrigation requirements.

On-farm energy efficiency is becoming increasingly important in the context of rising energy costs and concerns over greenhouse gas (GHG) emissions. Energy audits are a crucial part of the overall energy and environmental management process. In this paper, the results of six on-farm energy audits are presented. It is shown that energy uses for these farms varied significantly, ranging from 1.29 GJ/ha for dryland sorghum production to 43.06 GJ/ha for avocado production. In some cases, nearly 80% of operational energy was expended on water harvesting and irrigation. The research shows that there is currently a strong need to develop standardised energy assessments and reporting protocols so that effective and widespread energy audits in agriculture can take place. It is further suggested that an energy audit in agriculture in the future may best start from irrigation, as it also consumes a considerable proportion of on-farm energy cost.

Limited water availability in dry cane growing regions poses a challenge to sugarcane farmers. Water allocations tend to be lower at the beginning of the water season, and are increased during the season when inflows are captured. Probabilistic information reflecting the likelihood of specified increases in water allocation is not available to sugarcane farmers. The present paper describes how seasonal climate forecasts were used to provide this information for the 2001/2002 season as part of a case study involving sugarcane farmers in Bundaberg, Australia. Water allocation forecasts were then supplied to an irrigation simulation scheduling system to provide guidance about when and how much water could be applied. This research was underpinned by a cross-institutional collaboration that engaged industry, extension officers, engineers from the water authority and scientists from agriculture and climatology. The key findings from this investigation were 2-fold: the participatory approach (1) contributed to the development of information needed by industry, and (2) demonstrated the potential usefulness of climate forecasting models, hydrological models and cropping system simulators to contribute to enhancing knowledge about water availability and application. Additional investigations are required before this technology can be operationalised.

We undertook a study to test the hypothesis that fertiliser application would moderate the effects of insect herbivory on stem growth of plantation-grown Eucalyptus globulus Labill. Three-year-old E. globulus with damage from the Eucalypt weevil ( Gonipterus scutellatus ) ranging from 0–50% loss of total crown leaf area were fertilised with either nitrogen (N), phosphorus (P) or the combination of N + P. Stem growth and crown condition were monitored for 12 months. Applications of N or N + P increased diameter and height increment for both treatments, suggesting nutrient limitations at the site. In the absence of fertiliser, diameter and height increment were significantly reduced when defoliation was more than 10%. The application of N + P or N alone increased diameter increment in all defoliation classes to at least the level of unfertilised trees with minimal defoliation. Application of P did not. While there was an overall improvement in crown condition over the experimental period, trees in the N only treatment displayed a greater improvement in crown condition, and less trees per plot had poorer crown condition, than did trees in the other treatments. It was concluded that fertilising with N offers a management tool to eucalypt growers concerned with loss of productivity following insect defoliation.

Defoliation from herbivores can reduce growth of affected plants, and this has been demonstrated for plantation-grown Eucalyptus globulus. We undertook a field study to examine: (1) the influence of severity, pattern and frequency of defoliation on E. globulus stem growth, (2) whether fertiliser application influences growth responses to defoliation and (3) whether rate or timing of fertiliser application is important in determining growth responses. Two rates of nitrogen (N) (100 or 300 kg ha−1) were applied either pre- or post-defoliation or both. Defoliation treatments examined the effects of pattern, frequency and severity of defoliation on growth. In the absence of fertiliser, removal of 25% of leaf area from throughout the crown reduced diameter and height increment over the following 20 months. Removal of all leaf area from the upper 50% of crown had a much more dramatic effect on stem growth than did removal of all leaf area from the lower 50% of crown. More frequent defoliation increased the effect of defoliation on stem growth, and there was more of an effect following defoliation of the upper rather than lower crown. While there was no fertiliser response in undefoliated trees at the site, pre-defoliation fertiliser application maintained diameter and height increment of defoliated trees at a level similar to that of undefoliated trees. The growth response to fertiliser following defoliation was greater with pre- than post-defoliation applications of N, although there was still a significant response to post-defoliation applications. While foliar N content increased with rate of N application in undefoliated trees, defoliation generally reduced foliar N content and total phenolics. It was concluded that fertilising with N, even on sites with no discernible N deficiency, is a potential management tool for dealing with defoliation events. Management implications of the results are discussed.

The effect of a high rate of fertiliser addition, (900 kg ha −1 nitrogen (N):150 kg ha −1 phosphorus (P)) on pruning associated decay was investigated at two N and P deficient sites in Tasmania, Australia. Decay infections from pruned stubs were found to be more common in trees that received additions of fertiliser N and P, but fertiliser addition was not found to have an effect on basic density, lignin or the concentrations of extractives. Crown depth, and branch size were greater, and kino production reduced on trees that received fertiliser N and P. The incidence of decay infections in the pruned branch stubs increased with the frequency of living and large branches. Hence, improved tree nutrition increased the longevity and size of branches, thereby leading to an increased incidence of decay infections.

Low nitrogen (N) availability commonly limits the growth of Eucalyptus nitens plantations on ex-forest sites in Tasmania, Australia. We summarise here a decade of mechanistic and empirical research that has improved the basis for N management of these plantations. Twenty-two fertiliser experiments were used to define relationships between tree growth and methods of N fertilisation, i.e. timing, frequency, form, rate and placement. Pools and fluxes of mineral N were monitored at five sites. Potential deficiencies of N between planting and 10 years of age were indicated by the concentrations of soil NH4, NO3, total N and total phosphorus (P). Appropriate timing of N fertilisation depended on when N demand started to exceed supply from soil reserves, and was indicated by soil total N. Plantations on low-N sites experienced N deficiency during the first few years of growth, but others experienced it later or not at all. High cumulative rates of N fertilisation (at least 500 kg N ha−1) were needed to maximise growth at many sites, but there is no evidence to suggest that any individual application in excess of 200 kg N ha−1 is warranted. Hence, multiple applications will be needed to maximise growth. Urea was the preferred form of N, because it was relatively cheap and at least as effective as other N forms. Limiting N application to the crown drip line of 6-year-old trees with small crowns did not increase growth compared to a totally broadcast application. Soil N availability increased for 1–2 years following most N-fertiliser applications. Tree growth rates increased significantly for the same period followed by several years of less significant responses during which re-applications promoted a more sustained response in growth. This research has fostered an increase in the use of N fertilisers to increase productivity, and it should improve the basis for evaluating the economics of options for N fertilisation. Although applications of N fertilisers at rates up to 200 kg N ha−1 and at intervals of several years are unlikely to be a threat to water quality, especially if urea is used, research is needed to determine the environmental risks associated with long-term and higher intensity uses.

Fertigation can be a more efficient means of applying crop nutrients, particularly nitrogen (N), so that nutrient application rates can be reduced in fertigated crops. However, there is little information on the extent of the possible reduction in N application rate for fertigated sugarcane, one of the major row crops grown under trickle irrigation, nor the fate of N in fertigated sugarcane systems if N application rates are not reduced. An experiment was established to determine the response of cane and sugar production to different N rates (0–240 kg ha−1 year−1) spanning that recommended for conventional irrigation systems (160 kg ha−1 year−1). As well as yield, N removed in the crop and changes in soil mineral N were determined annually for four crops (a plant and three ratoon crops). δ15N values were also measured in selected treatments at selected times to assess possible N inputs to the experiment via biological N fixation (BFN). Yields of cane and sugar responded to application of N fertiliser in the three ratoon crops, but they were not significantly increased by applying more than 80 kg ha−1 of N. There were no N responses in the plant crop, as there was >200 kg ha−1 of soil mineral N (SMN) to 2 m depth at the site prior to planting, and much of this SMN was depleted in the treatment receiving no N. There was no evidence of N input from BFN in the experiment. During the 4-year study period, net removal of N from the treatment with no applied N totalled 207 kg ha−1. When 80 or 120 kg ha−1 year−1 of N was applied to ratoon crops, outputs of N from the harvested crop approximately balanced inputs from fertiliser and depletion of SMN during the experiment. Inputs clearly exceeded output at higher N application rates. Assuming that the net removal of N from the treatment with no applied N was the same as the net mineralisation of N from soil organic matter in all treatments in the experiment, 204–639 kg ha−1 of N was unaccounted for in the treatments with applied N over the duration of the experiment. While some of this N (e.g. 45 kg ha−1) may have resulted in small (and undetectable) increases in total soil N, much of it would have been lost to the environment. We suggest that the high soil water contents maintained with daily application of irrigation water through the trickle system promotes mineralisation of soil organic matter and hence losses of N to the environment. Thus, particular care is required to avoid over-application of N in fertigated sugarcane.

Leaf area index (LAI) is a key driver of water and nutrient use, carbon balance, and the rate of growth of plantation forests, but these interactions can be environment-dependent. Our aim was to determine the relationship between LAI and stem growth in four 5–8-year-old Eucalyptus nitens plantations and its dependence on site and fertilization. Fertilizers were applied at various intervals between planting and age 6 years at cumulative rates that ranged from 0 to 1600 kg N ha−1 and 0 to 700 kg P ha−1. Stem growth and LAI were monitored for 2 years. Values of LAI ranged from 1.4 to 9.6, and temporal variations in LAI were small. Fertilization increased LAI by up to 3.1 units. There was a strong relationship across all sites and treatments between initial LAI and growth, and predictions using LAI were more precise than those using basal area as the independent variable.

This study combines soil moisture capacitance probes and cosmic-ray neutron probe with a Fuzzy Inference System to estimate variability of soil moisture in a ~28 ha circle over time. The technique demonstrates that the cosmic-ray neutron probe's average neutron count and a network of capacitance probes may be useful for estimating spatial and temporal variability in soil moisture patterns within the probe's footprint.

Soil moisture has important effects on fuel availability, but is often assessed using drought indices at coarse spatial resolution, without accounting for the fine-scale spatial effects of terrain and canopy variation on forest floor moisture. In this study, we examined the spatial variability of air temperature, litter temperature and near-surface soil moisture (θ, 0–100 mm) using data from field experiments at 17 sites in south-east Australia, covering a range of topographic aspects and vegetation types, within climates from semiarid to wet montane. Temperatures and θ in mountainous environments were found to vary at much finer spatial scales than typical drought index grid dimensions (several kilometres). Using terrain elevation, local insolation ratio and plant area index, we developed semi-empirical microclimate models for air and litter temperatures, then used modelled temperatures as input into calculations of the Keetch–Byram Drought Index, a widely used index of soil moisture deficit. Drought index results based on predicted litter temperature were found to explain 91% of the spatial variation in near-surface soil moisture at our experimental sites. These results suggest the potential for routine hillslope-scale predictions of forest floor moisture status, which may be useful in the management of fire, particularly prescribed burning, in complex terrain.

Purpose In Australia, farmers and natural resource managers are striving to enhance environmental outcomes at farm and catchment scales by planting streamside management zones (SMZs) on farms with trees and other perennial vegetation. Lack of sound information on and funding for establishing and managing trees in SMZs is hindering wide-scale adoption of this practice. Australian Codes of Forest Practice discourage or prevent harvesting of trees in SMZs of perennial streams. One concern is the potential effect of tree harvesting in SMZs on delivery of sediment to adjacent streams. The aims of this paper were to summarize the literature relevant to this concern and, in one case study in an agricultural context, to determine the effects on turbidity of harvesting a SMZ plantation.