D'Annunzio sulla scena lirica: libretto o "Poema"?

Australia Direct Action climate change policy relies on purchasing greenhouse gas abatement from projects undertaking approved abatement activities. Management of soil organic carbon (SOC) in agricultural soils is an approved activity, based on the expectation that land use change can deliver significant changes in SOC. However, there are concerns that climate, topography and soil texture will limit changes in SOC stocks. This work analyses data from 1482 sites surveyed across the major agricultural regions of Eastern Australia to determine the relative importance of land use vs. other drivers of SOC. Variation in land use explained only 1.4% of the total variation in SOC, with aridity and soil texture the main regulators of SOC stock under different land uses. Results suggest the greatest potential for increasing SOC stocks in Eastern Australian agricultural regions lies in converting from cropping to pasture on heavy textured soils in the humid regions

Minimising nitrogen losses to improve use efficiency in summer crops

As reliance on N fertilizer increases, getting good crop recovery of applied N is essential. Crop N recovery is most efficient when N is distributed through the root volume. Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum. Ensuring fertilizer N is in the crop or deeper in the soil profile is the best defence against loss. Controlled release fertilizers can reduce denitrification but are rarely economic; legume N is effectiv

An economic approach to soil fertility management for wheat production in north-eastern Australia

Soil fertility decline and soil management for crop production are important economic issues for grain growers in north-eastern Australia. In that region, there is evidence of soil fertility decline which is attributed to past crop management practices. The questions addressed in this article are first, whether components of soil fertility can be improved by better management and second, by how much soil fertility would change. Soil fertility for crop production is considered in terms of soil organic carbon and nitrogen. A stochastic dynamic economic analysis of soil fertility management for wheat production is presented. A sequential analysis of first deriving the optimal nitrogen stock and application rates is followed by an assessment of tillage, stubble, and fertilizer strategies to obtain an optimal level of soil organic carbon. The recommended management practices are consistent with emerging management trends in the region. The derivation of optimal levels of soil fertility for agricultural purposes has other policy implications, which we discuss

Greenhouse gas emission reductions in subtropical cereal-based cropping sequences using legumes, DMPP-coated urea and split timings of urea application

To contribute to national greenhouse gas emissions (GHG) reduction targets, grain growers need strategies that minimise emissions associated with grain production. We used life cycle assessments (LCAs) with field-measured production inputs, grain yields and proteins, legume nitrogen (N₂) fixation, and soil nitrous oxide (N₂O) and methane (CH4) emissions, to explore mitigation strategies in 3-year crop sequences in subtropical Australia. The sequences were: canola plus 80 kg/ha fertiliser nitrogen (80N)-wheat 85N-barley 65N (CaNWtNBaN), chickpea 0N-wheat 85N-barley 5N (CpWtNBa), chickpea 0N-wheat 5N-chickpea 5N (CpWtCp), and chickpea 0N-sorghum 45N (CpSgN). We also assessed the impacts of split fertiliser N application and urea coated with DMPP, a nitrification inhibitor, on the LCA for the CaNWtNBaN sequence. Total pre-farm plus on-farm GHG emissions varied between 915 CO₂-e/ha (CpSgN) and 1890 CO₂-e/ha (CaNWtNBaN). Cumulative N₂O emitted over the 3-year study varied between 0.479kg N₂O-N/ha (CpWtCp) and 1.400 kg N₂O-N/ha (CaNWtNBaN), which constituted 24-44% of total GHG emissions. Fertiliser production accounted for 20% (CpSgN) to 30% (CaNWtNBaN) of total emissions. An extra 4.7 kg CO₂-e/ha was emitted for each additional kg N/ha of applied N fertiliser. Three-year CH4 emissions ranged from 1.04 to 0.98 kg CH4-C/ha. Split N and DMPP strategies could reduce total GHG emissions of CaNWtNBaN by 17 and 28% respectively. Results of the study indicate considerable scope for reducing the carbon footprint of subtropical, dryland grains cropping in Australia

An economic approach to soil fertility management for wheat production in north-eastern Australia

Soil fertility decline and soil management for crop production are important economic issues for grain growers in north-eastern Australia. In that region, there is evidence of soil fertility decline which is attributed to past crop management practices. The questions addressed in this article are first, whether components of soil fertility can be improved by better management and second, by how much soil fertility would change. Soil fertility for crop production is considered in terms of soil organic carbon and nitrogen. A stochastic dynamic economic analysis of soil fertility management for wheat production is presented. A sequential analysis of first deriving the optimal nitrogen stock and application rates is followed by an assessment of tillage, stubble, and fertilizer strategies to obtain an optimal level of soil organic carbon. The recommended management practices are consistent with emerging management trends in the region. The derivation of optimal levels of soil fertility for agricultural purposes has other policy implications, which we discuss. Copyright 2008 International Association of Agricultural Economists.

The current status of nitrogen fertiliser use efficiency and future research directions for the Australian cotton industry

Fifty years of sustained investment in research and development has left the Australian cotton industry well placed to manage nitrogen (N) fertiliser. The average production in the Australian cotton industry today is greater than two tonnes of lint per hectare due to improved plant genetics and crop management. However, this average yield is well below the yield that would be expected from the amount of N fertiliser used. It is clear from the recent studies that across all growing regions, conversion of fertiliser N into lint is not uniformly occurring at application rates greater than 200–240 kg·hm− 2 of N. This indicates that factors other than N availability are limiting yield, and that the observed nitrogen fertiliser use efficiency (NFUE) values may be caused by subsoil constraints such as sodicity and compaction. There is a need to investigate the impact of subsoil constraints on yield and NFUE. Gains in NFUE will be made through improved N fertiliser application timing, better targeting the amount of fertiliser applied for the expected yield, and improved soil N management. There is also a need to improve the ability and confidence of growers to estimate the contribution of soil N mineralisation to the crop N budget. Many Australian studies including data that could theoretically be collated in a meta-analysis suggest relative NFUE values as a function of irrigation technique; however, with the extensive list of uncontrolled variables and few studies using non-furrow irrigation, this would be a poor substitute for a single field-based study directly measuring their efficacies. In irrigated cotton, a re-examination of optimal NFUE is due because of the availability of new varieties and the potential management and long-term soil resilience implications of the continued removal of mineralised soil N suggested by high NFUE values. NFUE critical limits still need to be derived for dryland systems

Cotton strip assay detects soil microbial degradation differences among crop rotation and tillage experiments on Vertisols

The cotton strip assay (CSA) is a simple and inexpensive method of evaluating management effects on soil mi-crobial decomposition. The average loss of tensile strength of cotton strips buried 3 to 35 days in soils from two long-term tillage and crop-rotation experiments was of the order: cotton-wheat rotation > minimum-tillage cotton monoculture > maximum-tillage cotton monoculture. The study suggests CSA can be an effective indi-cator to delineate microbial activity, soil organic carbon or crop biomass as influenced by agricultural practices in cotton fields. minimum-tillage cotton monoculture > maximum-tillage cotton monoculture. The study suggests CSA can be an effective indi-cator to delineate microbial activity, soil organic carbon or crop biomass as influenced by agricultural practices in cotton fields. maximum-tillage cotton monoculture. The study suggests CSA can be an effective indi-cator to delineate microbial activity, soil organic carbon or crop biomass as influenced by agricultural practices in cotton fields

Relating particulate organic matter-nitrogen (POM-N) and non-POM-N with pulse crop residues, residue management and cereal N uptake

Particulate organic matter nitrogen (POM-N) was evaluated as an indicator of crop residue source (pulse versus cereal) and residue management (no-tillage [NT], stubble burned [SB] or stubble mulched [SM]) on soil quality and subsequent crop productivity in a continuous cropping experiment in northern New South Wales (NSW), Australia. The relative contributions to POM of pulse versus cereal, and shoots versus roots, were studied using in situ $^{15}$N shoot labelling. Under NT, a greater proportion of organic N was found in POM-N $>$ 250 $\mu$m (5.5% versus 3.5% [SM] and 2.7% [SB]) and POM-N $>$ 53 $\mu$m (10.3% versus 9.7% [SM] and 8.7% [SB]). Pulse residues (particularly roots) contributed 2-7 times more N to POM and 2-4 times more N to non-POM-N than barley ($^{15}$N data), but this increased contribution was not detectable with non-isotopic analysis. POM-N was sensitive to residue management, but was not a reliable measure of N inputs from pulse versus cereal residues, nor a useful tool for predicting subsequent crop N uptake.Relation entre la matière organique azotée particulaire et non particulaire et les résidus de culture de légumineuses, leur gestion et le prélèvement d'azote par les céréales. La matière organique particulaire POM-N a été évaluée comme indicateur des sources des résidus de cultures (légumineuses ou céréales) et de la gestion des résidus (non-labour [NT], brûlage des pailles [SB], mulch de paille [SM]) sur la qualité du sol et la productivité induite des cultures dans une expérience continue de culture sans le Nord des New South Wales en Australie. Les contributions relatives des POM des légumineuses par rapport à celles des céréales et des tiges par rapport aux racines ont été étudiées en utilisant des tiges marquées à l'azote $^{15}$N in-situ. Sous NT, une plus grande proportion de l'azote organique a été trouvé dans la fraction POM-N $>$ 250 $\mu$m (5,5 % par rapport à 3,5 % pour [SM] et 2,7 % pour [SB]) et POM-N $>$ 53 $\mu$m (10,3 % par rapport à 9,7 % pour [SM] et 8,7 % [SB]). Les résidus de légumineuses (particulièrement les racines) ont apporté 2 à 7 fois plus d'azote sous forme POM et 2 à 4 fois plus d'azote sous forme non particulaire que l'orge (données de $^{15}$N) mais cette contribution accrue n'était pas détectable avec une analyse non isotopique. POM-N était sensible à la gestion des résidus mais n'était pas une mesure fiable pour les apports d'azote à partir des légumineuses comparativement aux résidus de céréales ni un outil utile pour prédire le prélèvement induit d'azote par la culture