Hand-held hoses and watering cans are widely used by smallholder farmers to irrigate vegetables in Cambodia and Laos. Overwatering is common. Technology change (e.g., low-pressure drip irrigation) has been used to improve irrigation efficiency but can be unaffordable for many smallholder farmers. The purpose of this study was to identify an appropriate method of predicting crop water demand, develop and field-test improved irrigation schedules for smallholder leafy vegetable farming based on that method, and then develop extension tools to communicate the schedules to smallholder farmers. Improved irrigation schedules for leafy vegetables were developed based on a crop water use prediction technique that is well established (the Penman–Monteith method) but beyond the capacity of smallholder farmers to implement without access to simple aids. Compared to conventional practice, the method approximately halved water and labour use and improved irrigation water productivity 2–3 fold in field research and demonstration trials. Simplified extension tools to assist smallholder farmers with practice change were developed. This work showed that significant efficiencies could be gained through improved irrigation scheduling without changing application technology.

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 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 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.

Diversification of food sources and agricultural production systems has potential to enhance domestic supplies and provide export market opportunities for Laos. Major constraints to agricultural productivity are related to soil management and include inefficient irrigation, poor soil structural stability, low pH and nutrient availability. An experiment at the National University of Laos (NUOL) in Vientiane assessed the effect of lime and irrigation scheduling on growth and yield of lettuce. The soil was a sandy clay loam with pH 4.89 (H2O) in the top 15 cm. Lime (CaCO3) was applied at rates of 2 and 4 tonnes per hectare (t/ha). Irrigation scheduling was based on calculated evapotranspiration (ETc) with frequencies of either twice daily, once daily or alternate days. Urea, chicken manure and rice husks were added to soil in all trial plots. The experimental design was split-plot with two treatments (lime and irrigation scheduling) and four replications. The combination of 4 t/ha lime and irrigation every second day had the highest yield (mean > 2 kg/m2). The combined treatment of irrigation once a day and no added lime showed significantly higher leaf number (p = 0.01) and plant height (p < 0.001) compared to the other treatment combinations. However, increased biomass of individual plants did not translate into increased marketable yield per square metre. The application of lime raised the pH of soil but the effect on plant growth and yield was not conclusive. Separation of the two treatments into single factor trials is needed to elucidate the effects of individual treatments in future trials.

Growing vegetables after rice harvest allows Cambodian farmers to use land that would otherwise be unproductive between rice crops. Producing vegetables on these soils is limited by low soil pH, low cation exchange capacity and limited nutrient retention capacity. Soil pH in the top 20 cm is generally low (pH 5.5 H2O) and may limit the availability of nutrients. Farm-based trials in Siem Reap and Kampot provinces assessed the effect of lime and fertiliser on leafy vegetable crop growth and yield. At lime-only sites, lime was applied at rates of 0.5, 1.0 and 2.0 tonnes per hectare (t/ha) in conjunction with farmer practice fertiliser rates. For sites with lime and fertiliser treatments, combinations of farmer practice and optimal fertiliser rates, no lime and 2.0 t/ha of lime were applied. Two consecutive crops were planted at one site to examine the residual effect of lime on soil pH and crop yield. At lime-only sites, all crops responded to lime application with yield increases of up to 100%. For sites that assessed combinations of lime and fertiliser, the treatment of lime and optimum fertiliser rates showed the highest yield increase (92%). Application of 2.0 t/ha lime increased soil pH by approximately 1.0 unit. This effect was still evident after a second crop of Bok Choy. For the 0.5 t/ha lime treatment, an initial soil pH increase of 0.4 units had reduced to 0.2 units after the second crop. The first crop yield was higher than the second crop yield. Long-term field trials are needed to examine residual lime effects.

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<0.05). Fertilizer responses for BS (WWTP2) and the two OMF products showed that about of 90% of maximum DMY can be achieved with the optimum N application rate or about 50% of the N rate required for maximum yield. For BS (WWTP1) and urea, responses showed that 80% and 85% of the maximum DMY could be achieved with the optimum N application rate, which represented, respectively, 35% and 30% of the N rate required for maximum yield. When N inputs were optimized, agronomic efficiency (kg kg-1) calculations were: 12.6 (BS WWTP1), 17.3 (OMF WWTP1), 14.7 (BS WWTP2), 15.7 (OMF WWTP2), and 20.4 (urea), respectively, and N fertilizer replacement values of OMF and BS were between 74% and 82%. The effects of BS and OMF on soil chemistry are presented and discussed by focusing upon soil phosphorus and heavy metals dynamics. There appears to be potential for further development of biosolids-derived OMF products.

Production of leafy vegetables, such as lettuce, in Lao People’s Democratic Republic (PDR) is limited by low nutrient soils. Organic fertilisers or composts made from agricultural residues may provide Lao PDR farmers with economical and environmentally sustainable alternatives to chemical fertilisers. Research is needed to increase awareness and knowledge of organic fertilisers suited to vegetable production in Lao PDR. An experiment at the Horticultural Research Centre (HRC) in Vientiane assessed the effect of four organic fertilisers on growth and yield of lettuce. Two commercially available fertilisers (fermented manure compost and an organic fertiliser) were compared with a mixture of cow manure plus rice husks, and a fourth compost made from vegetable leaves, straw and cow manure at the HRC. The experimental design was a randomised block with four replicates for each fertiliser treatment. Lettuce was grown in raised beds with 10 tonnes per hectare (t/ha) fertiliser applied before seedlings were transplanted. The fermented manure compost treatment had the highest yield (1.95 kg/m2) and was significantly higher than the other three treatments (p < 0.001). Growth rates were also highest for the fermented manure compost at all measured growth intervals (14, 28 and 45 days after transplanting). Rapid nutrient release from fertiliser is important for short-term crops. The higher growth rates and yields found for the fermented manure compost indicate that nutrients were released sooner and were more readily available compared to the other treatments. Mature compost releases nutrients more rapidly than compost that contains partially decomposed rice husks, vegetable leaves and straw.

The Australian Red Meat Processing Industry produces significant amounts of different by-products and animal wastes. One of these by-products is paunch; the stomach contents of the animal after slaughter. Between 25 and 40 kg of paunch (fresh weight) are produced per head of cattle, or approximately 4 to 6 kg paunch (dry weight). A medium-sized abattoir site processes approximately 500 head of cattle per day and produces between 60 and 90 m3 of paunch per week. This makes paunch a significant contributor (≈¼ million Mg per year) to the waste stream of Australian abattoirs. Globally, about 15 million Mg of paunch are produced by the red meat processing industry each year. Current disposal methods incur significant costs to Australian abattoirs and are increasingly regarded as non-environmentally friendly options. Recycling to farmland is relatively less expensive compared with traditional disposal methods (e.g., landfill) and is also regarded as the best practicable environmental option. Paunch waste is managed in several ways; including: (1) removal of paunch and other solids off-site, (2) composting of material on-site and use on-site, and (3) composting of material on-site and use off-site. The work reported in this study was undertaken to quantitatively assess key soil quality indicators at sites, which have received paunch as a soil amendment for several years (5 to 20 years). These quality indicators included soil physical, mechanical, chemical and hydraulic properties. Results are presented and discussed to inform management practices for soil receiving paunch as an organic amendment. Research areas that require further work, and are likely to increase the efficiency of paunch recycled to land, soil quality and nutrient recovery in crop biomass are also highlighted.

Disposal of biodegradable wastes through landfill is regarded as non-sustainable both from the environmental and resource-recovery perspectives. Agricultural recycling is considered to be the best practicable environmental option, but there are many logistic and practical difficulties that need to be overcome, including unbalanced chemical composition and physical properties not suitable for standard farm spreading equipment. Optimization of the physico-chemical properties of digestates should ensure acceptability by farmers and secure the agricultural route for disposal. Digestate from anaerobic digestion facilities is a currently underutilized source of biofertilizer for use on Australian arable land. This project sets out to firstly develop the specifications for novel, enhanced-value anaerobic digestion digestate-derived organomineral fertilizers (OMF) that meet the requirements for field application using standard farm equipment (physical properties) and nutritional needs of crop. Secondly, experimentally evaluate the proposed formulation(s) and product format; and determine the fertilizer replacement value of OMF and develop guidelines for use on crops. As a first step, this paper provides a summary of review findings undertaken on organic and inorganic fertilizers and agricultural requirement analysis to inform product specifications and provide criteria for land application. A review of national data shows that there have been no significant Australian studies conducted since the National Biosolids Program, which was conducted more than a decade ago. This highlighted the importance of performing new research, to expand that initial work, including to develop novel product formulations and to provide up to date evidence on fertilizer replacement value, crop returns and overall benefits. Key findings from the review took on two points of foci, namely 1. Understanding the nitrogen fertilizer replacement value (NFRV) and 2. Legislation and environmental concerns.

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.

Soil compaction affects soil aeration and gas diffusivity, and thus has a major impact on the release of greenhouse gases (GHGs) from fertilised soils. Controlled traffic farming (CTF) systems reduce the area of compacted soil by confining all field traffic to permanent traffic lanes, and a pilot trial at one long-term CTF site provided evidence of reduced soil emissions. We investigated the effect of CTF on soil emissions of nitrous oxide (N2O) and methane (CH4) using replicated manual chamber measurements in 3 traffic treatments; namely: non-trafficked CTF beds, permanent CT F lanes, and a single traffic pass on CTF beds to simulate the random traffic tracks of non-controlled traffic fanning. Emissions of N2O and CH4 were monitored fromm, these treatments in 15 crops over 3 years on 6 grain farms in Queensland, Victoria and Western Australia. This work has demonstrated that N2O emissions from trafficked soil were consistently and significantly greater (by an average factor of 2.2) than those from non-trafficked soil. At the same time, soil CH4 consumption was significantly increased in the CTF beds compared to random-trafficked or permanent traffic lanes, although overall CH4 fluxes were small. Permanent traffic lanes normally represent only 10%-15% of field area on controlled traffic farms, compared with similar to 50% or more trafficked area on non-controlled traffic farms. Thus, the results indicate that adoption of controlled traffic could reduce total soil emissions by 30%-50%. This demonstrates that CTF will reduce soil emissions of N2O and CH4 from mechanised crop production, while providing other agronomic, environmental and economic benefits.

This article addresses the novel dewatering process of immersion-frying of paunch and dissolved air flotation (DAF) sludge to produce high energy pellets. Literature have been analysed to address the feasibility of replacing conventional boiler fuel at meat processing facilities with high energy paunch-DAF sludge pellets (capsules). The value proposition of pelleting and frying this mixture into energy pellets is based on a Cost-Benefit Analysis (CBA). The CBA is based on information derived from the literature and consultation with the Australian Meat Processing Industry. The calorific properties of a mixture of paunch cake solids and DAF sludge were predicted from literature and industry consultation to validate the product. This study shows that the concept of pelletizing and frying paunch is economically feasible. The complete frying and dewatering of the paunch and DAF sludge mixture produces pellets with energy content per kilogram equivalent to coal. The estimated cost of this new product is half the price of coal and the payback period is estimated to be between 1.8 and 3.2years. Further research is required for proof of concept, and to identify the technical challenges associated with integrating this technology into existing meat processing plants.

The production of coal seam gas (CSG) in Australia is set to increase, driven by increasing global demand for energy and in response to the transition to a lower carbon economy through greater use of gas for electricity generation. Despite the many economic benefits delivered by the CSG industry, concerns have been raised over the potential environmental impacts associated with CSG production, particularly the long-term effects on the soil resource. Therefore, this work was conducted to: (1) assess the extent of damage to agricultural soil caused by the various elements of CSG development and (2) estimate the likely impact of soil compaction, caused during establishment of CSG infrastructure, on crop productivity. The study was undertaken using a paired-sites approach by comparing measurements conducted on selected soil properties in areas around and including well-head sites with measurements in neighboring agricultural fields. These spatial areas are referred to as "lease" and "field" areas, respectively. Measurements were used to guide parameterization and application of the Agricultural Production Systems Simulator (APSIM) model to assess the likely effects of changed soil conditions on crop productivity. To achieve this, the APSIM model was used to simulate wheat (Triticum aestivum L.) yields for 115 years on Grey Vertosols in the Darling Downs region of Queensland. Simulations were conducted with soil properties representing: (1) field area conditions not affected by CSG activities, (2) lease area conditions in which soil had been impacted by CSG activities during the development phase, and (3) lease area conditions where soils had been rehabilitated. Results showed that soil compaction within lease areas in the top 300 mm of the profile was approximately 15% higher compared with field areas (p < 0.05). The modeling work suggested that near-surface (0 to 300 mm depth) soil compaction within affected areas can lead to significant losses in crop productivity due to adverse effects on soil hydraulic properties. The simulation analyses predicted a 53% reduction in median wheat yields compared with simulated results in neighboring agricultural fields. For the bottom and top deciles, predicted relative yields were up to 60% and 32% lower, respectively. Practical solutions for management of such compaction are presented and discussed. Soil cultivation of the top 300 to 350 mm will ensure sufficient soil water storage in most years, thereby reducing the risk of crop failure. Progressive soil loosening techniques for alleviation of deeper compaction were reviewed; however, their cost-effectiveness under Australian soil conditions requires further investigation. Limit bulk density values of 1.45 and 1.60 g cm(-3) for the 0 to 350 mm and 350 to 700 mm depth intervals, respectively, are suggested as references for CSG-rehabilitated soil. These critical values may be used as guidance until further studies are undertaken. The assessment of soil chemical properties indicated that these were affected to a lesser extent by the establishment of CSG infrastructure. However, a general requirement is careful manipulation of sodium-rich subsoil and avoidance of soil blending during reinstatement operations. The dataset acquired and the simulation approach employed in this study can be used to further develop soil management guidelines relevant to the Australian CSG industry. Cost-benefit analyses of soil management practices for reinstatement, development of soil quality standards, and industry best management practices are required.

Coal seam gas (CSG) activities in the Surat and Bowen Basin areas of Queensland, Australia, cover approximately 300,000 km2 including regions of good quality agricultural lands. Without adequate knowledge of soil properties, hydrologic processes and control measures, the disturbed soil structure and landform in these regions are highly susceptible to soil degradation. The construction and installation of CSG infrastructures (e.g. roads, pipelines, hardstand and plant areas) cause various degrees of disturbance to the soil physical, chemical and biological characteristics. This disturbance may result in soil degradation through various forms including compaction, erosion processes, changes to organic carbon and soil nutrient store, exposure of potentially reactive/poor quality soils (e.g. acid sulphate soils, hyper-saline soils) or introduction of outside contaminants (poor quality water, weeds). Not only are soils directly disturbed by the footprint of the CSG operation but the surrounding soil landscape may be disturbed by secondary processes such as erosion and sedimentation. Soil compaction changes caused by CSG operations, including vehicle impacts and trench line installation, have been assessed by soil bulk density measurements. This measurement has been identified as a common impact by CSG operation and a key element of soil degradation of agricultural areas contributing poor vegetation establishment, tunnel and surface erosion processes and an ongoing decline for soil productivity. Quantifying the impacts of CSG activities on soils will inform the development of industry guidelines for impact minimisation and management of the soil resource on joint CSG-agricultural lands.

The production of coal seam gas (CSG) in Australia is set to increase driven by increasing global demand for energy and in response to the transition to a lower carbon economy through greater use of gas for electricity generation. In Queensland, the CSG industry provides approximately 90% of the gas supplies and 15% of the gas required for electricity. Despite of many economic benefits being delivered by the CSG industry, concerns have been raised over the potential environmental impacts associated with its production as well as potential long-term effects on agricultural productivity. The work reported in this paper was conducted to assess the extent of damage to agricultural soil caused by the various elements of CSG development, particularly the impact on soil compaction. The study was conducted using a paired-sites approach by comparing measurements conducted on a range of selected soil parameters in areas around and including well-head sites with measurements in neighboring agricultural fields. These spatial areas are referred to as ‘lease‘ and ‘field‘ areas, respectively. Results showed that soil compaction within lease areas was approximately 10% higher compared with fields (P<0.05), which was observed after five years or more following rehabilitation. Practical solutions to alleviation and management of such compaction are presented and discussed. Soil cultivation of the top 300 to 350 mm will ensure sufficient water storage in most years thereby reducing the risk of crop failure. Progressive soil loosening techniques for alleviation of deeper compaction were reviewed however their cost-effectiveness under Australian soil conditions requires further investigation. Threshold bulk density values of 1.45 g cm-3 for the top 350 mm of the soil profile and 1.60 g cm-3 for the 350-800 mm depth interval are suggested as reference for CSG-rehabilitated soil and may be used as guidance until further studies are undertaken. The feasibility of adopting controlled traffic should be considered to minimize additional compaction caused by standard farming operations in field areas. The assessment of soil chemical properties indicated that these were affected to a limited extent. However, a general requirement is for careful manipulation of sodium-rich subsoil, and avoidance of soil mixing and layer inversion during topsoil stripping, stockpiling and reinstatement. The dataset acquired may be used to guide parametrization of crop simulation models to enable for estimation of crop productivity losses and development of soil management practices relevant to the CSG industry in Australia. Cost-benefit analyses of techniques for soil reinstatement, development of soil quality standards and industry BMP are required.

Land that is disturbed by mining activities is required to undergo suitable rehabilitation. This study compared soils supporting grazed pasture on land that was rehabilitated after coal mining activity with that on unmined land. Pasture biomass, and soil physical and chemical properties important for pasture production and sustainability were intensively monitored on three sites that had completed rehabilitation at different times over the last 10 years, and one unmined control site. A further 18 unmined grazing sites were monitored for benchmarking purposes. Analysis of soil properties of plant available phosphorus and nitrogen, salinity and sodicity in the first year of the study suggested little difference in terms of benefits or constraints to pasture production between the rehabilitated and control sites. Plant-available phosphorus was sufficiently high in the two oldest rehabilitated sites that a fertiliser response would not be expected. Soil depth and the pasture rooting depth at the rehabilitated sites were at the shallow end of the wide range observed across the benchmark and control sites. Higher pasture biomass at the rehabilitated sites compared with the control at the initiation of the trial was attributed more to differences in grazing history than differences in soil attributes.

Acland Pastoral Company (APC), as a subsidiary of New Hope Group, are undertaking progressive rehabilitation of open cut coal mining to return to grazing pasture. As such, APC seek commercially relevant research outcomes to enable them to quantify the performance of the rehabilitation program in terms of productivity and sustainability. This report provides a progress summary of the NCEA portion of work aiming to assess the soil chemical properties, associated with fertility and structural integrity, and basic soil water properties of rehabilitated land and compare these to unmined land in order to provide independent and unbiased feedback through Outcross to APC on the potential success, or otherwise, of mine-site rehabilitation.

Land that is disturbed by mining activities is required to be suitably rehabilitated. A trial was initiated to compare the performance of livestock grazing pasture sown on land that was rehabilitated after coal mining activity with that of livestock grazing pasture on unmined land. Pasture biomass, and soil structural, nutritional and hydrological properties important for pasture production and sustainability were intensively monitored on three sites rehabilitated at different stages over the last 10 years, and one unmined Control site. A further 18 unmined grazing sites were monitored for benchmarking purposes. Preliminary results for soil ammonium, nitrate and potentially mineralisable nitrogen suggest little difference in terms of benefits or constraints to pasture production between the rehabilitated and Control sites. Plant-available phosphorus was sufficiently high in the two oldest rehabilitated sites that a fertiliser response would not be expected. Subsoil and rooting depth of the rehabilitated sites was within the range observed across the benchmark sites and shallower than in the Control site. Higher pasture biomass in the rehabilitated sites compared with the Control at the initiation of the trial was attributed more-so to differences in grazing history than differences in soil attributes. Analysis of year one monitoring data is ongoing.