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Nutrient-rich organic wastes and soil ameliorants can benefit crop performance and soil health but can also prevent crop nutrient sufficiency or increase greenhouse gas emissions. We hypothesised that nitrogen (N)-rich agricultural waste (poultry litter) amended with sorbents (bentonite clay or biochar) or compost (high C/N ratio) attenuates the concentration of inorganic nitrogen (N) in soil and reduces emissions of nitrous oxide (N2O). We tested this hypothesis with a field experiment conducted on a commercial sugarcane farm, using in vitro incubations. Treatments received 160 kg N ha−1, either from mineral fertiliser or poultry litter, with additional N (2–60 kg N ha−1) supplied by the sorbents and compost. Crop yield was similar in all N treatments, indicating N sufficiency, with the poultry litter + biochar treatment statistically matching the yield of the no-N control. Confirming our hypothesis, mineral N fertiliser resulted in the highest concentrations of soil inorganic N, followed by poultry litter and the amended poultry formulations. Reflecting the soil inorganic N concentrations, the average N2O emission factors ranked as per the following: mineral fertiliser 8.02% > poultry litter 6.77% > poultry litter + compost 6.75% > poultry litter + bentonite 5.5% > poultry litter + biochar 3.4%. All emission factors exceeded the IPCC Tier 1 default for managed soils (1%) and the Australian Government default for sugarcane soil (1.25%). Our findings reinforce concerns that current default emissions factors underestimate N2O emissions. The laboratory incubations broadly matched the field N2O emissions, indicating that in vitro testing is a cost-effective first step to guide the blending of organic wastes in a way that ensures N sufficiency for crops but minimises N losses. We conclude that suitable sorbent-waste formulations that attenuate N release will advance N efficiency and the circular nutrient economy.
Maren Westermann; Richard Brackin; Nicole Robinson; Monica Salazar Cajas; Scott Buckley; Taleta Bailey; Matthew Redding; Jitka Kochanek; Jaye Hill; Stéphane Guillou; Joao Freitas; Weijin Wang; Chris Pratt; Ryo Fujinuma; Susanne Schmidt. Organic Wastes Amended with Sorbents Reduce N2O Emissions from Sugarcane Cropping. Environments 2021, 8, 78 .
AMA StyleMaren Westermann, Richard Brackin, Nicole Robinson, Monica Salazar Cajas, Scott Buckley, Taleta Bailey, Matthew Redding, Jitka Kochanek, Jaye Hill, Stéphane Guillou, Joao Freitas, Weijin Wang, Chris Pratt, Ryo Fujinuma, Susanne Schmidt. Organic Wastes Amended with Sorbents Reduce N2O Emissions from Sugarcane Cropping. Environments. 2021; 8 (8):78.
Chicago/Turabian StyleMaren Westermann; Richard Brackin; Nicole Robinson; Monica Salazar Cajas; Scott Buckley; Taleta Bailey; Matthew Redding; Jitka Kochanek; Jaye Hill; Stéphane Guillou; Joao Freitas; Weijin Wang; Chris Pratt; Ryo Fujinuma; Susanne Schmidt. 2021. "Organic Wastes Amended with Sorbents Reduce N2O Emissions from Sugarcane Cropping." Environments 8, no. 8: 78.
The excessive application of phosphorus in agricultural lands leads to serious environmental issues. Efficient application is beneficial from an economic and environmental perspectives. Biochar can be used as a carrier for slow release of phosphate. However, its adsorption capacity is limited. In this work, biochar was prepared at different pyrolysis temperatures (350–550 °C). The biochar prepared at 550 °C had the highest adsorption capacity and was selected for modification by magnesium impregnation. Magnesium modification enhanced the adsorption capacity by 34% to a theoretical max adsorption capacity of 463.5 mg·g−1. The adsorbed phosphate can be desorbed. The desorption was bi-phasic with fast- and slow-release fractions. The distribution of the phosphate fractions was pH dependent with slow release being most prominent in neutral conditions. Mg modified biochar can be used to recover phosphate and then used as a carrier for slow release of phosphate. The bi-phasic desorption behaviour is useful as the fast release fraction can provide the immediate phosphate needed during plant establishment, while the slow-release fraction maintains steady supply over extended periods.
Laura Arbelaez Breton; Zainab Mahdi; Chris Pratt; Ali El Hanandeh. Modification of Hardwood Derived Biochar to Improve Phosphorus Adsorption. Environments 2021, 8, 41 .
AMA StyleLaura Arbelaez Breton, Zainab Mahdi, Chris Pratt, Ali El Hanandeh. Modification of Hardwood Derived Biochar to Improve Phosphorus Adsorption. Environments. 2021; 8 (5):41.
Chicago/Turabian StyleLaura Arbelaez Breton; Zainab Mahdi; Chris Pratt; Ali El Hanandeh. 2021. "Modification of Hardwood Derived Biochar to Improve Phosphorus Adsorption." Environments 8, no. 5: 41.
The surge in the use of plastic materials, its poor handling and disposal have led to an increase in microplastic pollution in terrestrial environments. Microplastic pollution in soils is of concern due to potential influences on soil properties which play a critical role in plant growth and soil fertility. Moreover, the soil environment is a key nexus linking the atmosphere, hydrosphere, biosphere and lithosphere, and thus represents a crucial conduit for pollutant migration from the anthroposphere. In this review we evaluate the effects of microplastics in the soil environment with a specific focus on physical properties and biological function in the rhizosphere. Our review reveals that agricultural sources, particularly plastic mulches and waste applications, represent the main source of soil microplastic inputs. Once in the soil environment, microplastic effects on soil properties are highly variable depending mainly on soil type and microplastic characteristics. Soil properties relating to erosion-risk (i.e., bulk density), structural integrity (i.e., aggregate stability, particularly micro-aggregate stability), and water-storage capacity (i.e., evaporation rate, desiccation) are generally adversely impacted by soil microplastic inputs. Soil microplastic effects on rhizosphere function (i.e., plant health and microbial activity) are remarkably varied with some studies revealing positive impacts, such as enhanced plant-symbiotic fungi associations, from soil plastic additions. However, all identified publications reported at least one detrimental MP-induced impact on plant responses. Finally, our review revealed associations between microplastic properties and soil functional parameters – in particular, polymer size and morphology control soil water-holding properties whereas polymer type influences plant response. These associations will be helpful in targeting future research directions on this important topic that intersects all of the Earth's spheres.
Oluchi Mbachu; Graham Jenkins; Prasad Kaparaju; Chris Pratt. The rise of artificial soil carbon inputs: Reviewing microplastic pollution effects in the soil environment. Science of The Total Environment 2021, 780, 146569 .
AMA StyleOluchi Mbachu, Graham Jenkins, Prasad Kaparaju, Chris Pratt. The rise of artificial soil carbon inputs: Reviewing microplastic pollution effects in the soil environment. Science of The Total Environment. 2021; 780 ():146569.
Chicago/Turabian StyleOluchi Mbachu; Graham Jenkins; Prasad Kaparaju; Chris Pratt. 2021. "The rise of artificial soil carbon inputs: Reviewing microplastic pollution effects in the soil environment." Science of The Total Environment 780, no. : 146569.
The agricultural sector faces looming challenges including dwindling fertiliser reserves, environmental impacts of conventional soil inputs, and increasingly difficult growing conditions wrought by climate change. Naturally-occurring rocks and minerals may help address these challenges. In this case, we explore opportunities through which the geosphere could support viable agricultural systems, primarily via a literature review supplemented by data analysis and preliminary-scale experimentation. Our objective is to focus on opportunities specifically relating to emerging agricultural challenges. Our findings reveal that a spectrum of common geological materials can assist across four key agricultural challenges: 1. Providing environmentally-sustainable fertiliser deposits especially for the two key elements in food production, nitrogen (via use of slow release N-rich clays), and phosphorus (via recovery of the biomineral struvite) as well as through development of formulations to tap into mineral nutrient reserves underlying croplands. 2. Reducing contamination from farms—using clays, zeolites, and hydroxides to intercept, and potentially recycle nutrients discharged from paddocks. 3. Embedding drought resilience into agricultural landscapes by increasing soil moisture retention (using high surface area minerals including zeolite and smectite), boosting plant availability of drought protective elements (using basalts, smectites, and zeolites), and decreasing soil surface temperature (using reflective smectites, zeolites, and pumices), and 4. mitigating emissions of all three major greenhouse gases—carbon dioxide (using fast-weathering basalts), methane (using iron oxides), and nitrous oxide (using nitrogen-sorbing clays). Drawbacks of increased geological inputs into agricultural systems include an increased mining footprint, potential increased loads of suspended sediments in high-rainfall catchments, changes to geo-ecological balances, and possible harmful health effects to practitioners extracting and land-applying the geological materials. Our review highlights potential for ‘geo-agriculture’ approaches to not only help meet several key emerging challenges that threaten sustainable food and fiber production, but also to contribute to achieving some of the United Nations Sustainable Development Goals—‘Zero Hunger,’ ‘Life on Land,’ and ‘Climate Action.’
Chris Pratt; Kate Kingston; Bronwyn Laycock; Ian Levett; Steven Pratt. Geo-Agriculture: Reviewing Opportunities through which the Geosphere Can Help Address Emerging Crop Production Challenges. Agronomy 2020, 10, 971 .
AMA StyleChris Pratt, Kate Kingston, Bronwyn Laycock, Ian Levett, Steven Pratt. Geo-Agriculture: Reviewing Opportunities through which the Geosphere Can Help Address Emerging Crop Production Challenges. Agronomy. 2020; 10 (7):971.
Chicago/Turabian StyleChris Pratt; Kate Kingston; Bronwyn Laycock; Ian Levett; Steven Pratt. 2020. "Geo-Agriculture: Reviewing Opportunities through which the Geosphere Can Help Address Emerging Crop Production Challenges." Agronomy 10, no. 7: 971.
Feed waste in pork production sheds can amount to substantial economic losses. No simple methods exist to quantify this waste, which commonly ends up in the effluent stream. Monitoring piggery effluent might offer producers a practical alert solution for feed waste losses. We investigated piggery effluent pH as a potential marker of feed waste, given that most feed substrates and breakdown products are acidic whereas effluent is alkaline. To explore this prospective relationship, we constructed simulated effluent streams comprising faeces, urine and feed. These waste components were acquired from a commercial batch grower shed, at four different times over the 12-week growth cycle. In laboratory settings (25°C) we used the collected wastes to simulate the two stages of typical flushing piggery effluent systems: (1) Faeces + urine + feed waste accumulation in flushing channels, and (2) flush water mixing with these wastes in an effluent collection sump. We repeated the exercise for a one-off sampling event at a sow facility. For all events, at the grower and sow facility, the pH of the simulated effluents yielded exponentially decreasing relationships with increasing feed waste level (P < 0.05). For the grower facility we applied each of the four laboratory-derived relationships to the farm’s sump effluent pH, which was measured during each of these sampling events. The predicted feed waste levels were commensurate with estimates of feed waste for the same facility derived from alternative, time intensive approaches reported in other studies. Further work is needed to transition the promising results uncovered here into an alert system to help farmers improve profitability and minimise waste.
Chris Pratt; Jaye Hill; Alan Skerman; Matthew Redding. pH: a promising indicator of feed waste in piggery effluent? Animal Production Science 2019, 59, 581 .
AMA StyleChris Pratt, Jaye Hill, Alan Skerman, Matthew Redding. pH: a promising indicator of feed waste in piggery effluent? Animal Production Science. 2019; 59 (3):581.
Chicago/Turabian StyleChris Pratt; Jaye Hill; Alan Skerman; Matthew Redding. 2019. "pH: a promising indicator of feed waste in piggery effluent?" Animal Production Science 59, no. 3: 581.
Clays could underpin a viable agricultural greenhouse gas (GHG) abatement technology given their affinity for nitrogen and carbon compounds. We provide the first investigation into the efficacy of clays to decrease agricultural nitrogen GHG emissions (i.e., NO and NH). Via laboratory experiments using an automated closed-vessel analysis system, we tested the capacity of two clays (vermiculite and bentonite) to decrease NO and NH emissions and organic carbon losses from livestock manures (beef, pig, poultry, and egg layer) incorporated into an agricultural soil. Clay addition levels varied, with a maximum of 1:1 to manure (dry weight). Cumulative gas emissions were modeled using the biological logistic function, with 15 of 16 treatments successfully fitted ( < 0.05) by this model. When assessing all of the manures together, NH emissions were lower (×2) at the highest clay addition level compared with no clay addition, but this difference was not significant ( = 0.17). Nitrous oxide emissions were significantly lower (×3; < 0.05) at the highest clay addition level compared with no clay addition. When assessing manures individually, we observed generally decreasing trends in NH and NO emissions with increasing clay addition, albeit with widely varying statistical significance between manure types. Most of the treatments also showed strong evidence of increased C retention with increasing clay additions, with up to 10 times more carbon retained in treatments containing clay compared with treatments containing no clay. This preliminary assessment of the efficacy of clays to mitigate agricultural GHG emissions indicates strong promise.
Chris Pratt; Matthew Redding; Jaye Hill; Grant Brown; Maren Westermann. Clays Can Decrease Gaseous Nutrient Losses from Soil-Applied Livestock Manures. Journal of Environmental Quality 2016, 45, 638 -645.
AMA StyleChris Pratt, Matthew Redding, Jaye Hill, Grant Brown, Maren Westermann. Clays Can Decrease Gaseous Nutrient Losses from Soil-Applied Livestock Manures. Journal of Environmental Quality. 2016; 45 (2):638-645.
Chicago/Turabian StyleChris Pratt; Matthew Redding; Jaye Hill; Grant Brown; Maren Westermann. 2016. "Clays Can Decrease Gaseous Nutrient Losses from Soil-Applied Livestock Manures." Journal of Environmental Quality 45, no. 2: 638-645.
Land-applied manures produce nitrous oxide (N2O), a greenhouse gas (GHG). Land application can also result in ammonia (NH3) volatilisation, leading to indirect N2O emissions. Here, we summarise a glasshouse investigation into the potential for vermiculite, a clay with a high cation exchange capacity, to decrease N2O emissions from livestock manures (beef, pig, broiler, layer), as well as urea, applied to soils. Our hypothesis is that clays adsorb ammonium, thereby suppressing NH3 volatilisation and slowing N2O emission processes. We previously demonstrated the ability of clays to decrease emissions at the laboratory scale. In this glasshouse work, manure and urea application rates varied between 50 and 150 kg nitrogen (N)/ha. Clay : manure ratios ranged from 1 : 10 to 1 : 1 (dry weight basis). In the 1-year trial, the above-mentioned N sources were incorporated with vermiculite in 1 L pots containing Sodosol and Ferrosol growing a model pasture (Pennisetum clandestinum or kikuyu grass). Gas emissions were measured periodically by placing the pots in gas-tight bags connected to real-time continuous gas analysers. The vermiculite achieved significant (P ≤ 0.05) and substantial decreases in N2O emissions across all N sources (70% on average). We are currently testing the technology at the field scale; which is showing promising emission decreases (~50%) as well as increases (~20%) in dry matter yields. This technology clearly has merit as an effective GHG mitigation strategy, with potential associated agronomic benefits, although it needs to be verified by a cost–benefit analysis.
Jaye Hill; Matthew Redding; Chris Pratt; And. A novel and effective technology for mitigating nitrous oxide emissions from land-applied manures. Animal Production Science 2016, 56, 362 .
AMA StyleJaye Hill, Matthew Redding, Chris Pratt, And. A novel and effective technology for mitigating nitrous oxide emissions from land-applied manures. Animal Production Science. 2016; 56 (3):362.
Chicago/Turabian StyleJaye Hill; Matthew Redding; Chris Pratt; And. 2016. "A novel and effective technology for mitigating nitrous oxide emissions from land-applied manures." Animal Production Science 56, no. 3: 362.
On beef cattle feed pen surfaces, fresh and decayed manure is mixed with base rock or soil (base). Quantifying this mixing has beneficial applications for aspects including nutrient and greenhouse gas budgeting. However, no practical methods exist to quantify mixing. We investigated if measuring element concentrations in: (A) fresh manure, (B) base material, and (C) pen manure offers a promising method to quantify manure/base mixing on pen surfaces. Using three operational beef feedlots as study sites, we targeted carbon (C), and silicon (Si), which are the two most abundant and easily measurable organic and inorganic elements. Our results revealed that C concentrations were strongly (>15 times) and significantly (P < 0.05) higher whereas Si concentrations strongly (>10 times) and significantly (P < 0.01) lower in fresh manure than base material at all three sites. These relative concentrations were not significantly impacted by manure decay, as determined by an 18-week incubation experiment. This suggested that both of these elements are suitable markers for quantifying base/manure mixing on pens. However, due to the chemical change of manure during decay, C was shown to be an imprecise marker of base/manure mixing. By contrast, using Si to estimate base/manure mixing was largely unaffected by manure decay. These findings were confirmed by measuring C and Si concentrations in stockpiled pen surface manure from one of the sites. Using Si concentrations is a promising approach to quantify base/manure mixing on feed pens given that this element is abundantly concentrated in soils and rocks.
Chris Pratt; Matthew Redding; Jaye Hill; And. A promising and simple method to quantify soil/manure mixing on beef feedlot pens. Animal Production Science 2016, 56, 1361 -1366.
AMA StyleChris Pratt, Matthew Redding, Jaye Hill, And. A promising and simple method to quantify soil/manure mixing on beef feedlot pens. Animal Production Science. 2016; 56 (9):1361-1366.
Chicago/Turabian StyleChris Pratt; Matthew Redding; Jaye Hill; And. 2016. "A promising and simple method to quantify soil/manure mixing on beef feedlot pens." Animal Production Science 56, no. 9: 1361-1366.