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Factors affecting fertilizer decisions made by grain growers are changing in the context of changing climatic conditions and growing volatility in global fertilizer and grain markets. To ensure sustainable development of grain industries in light of this uncertainty, research, development, extension, and adoption activities associated with growers' fertilizer decisions need to be focused on factors to which they are most sensitive. The aim of this paper is to understand the factors that have the greatest influence on grain producer's fertilizer strategies, how these factors have changed over recent years, and what is the relative importance of agronomic, socioeconomic, and logistical factors affecting these strategies. A telephone survey of 425 grain-growing businesses in Western Australia was conducted, and survey results were analyzed statistically. We show for the first time that grain growers' fertilizer decisions are most sensitive to agronomic factors (especially the amount and distribution of rainfall). Logistic factors (such as difficulties fertilizing increasing areas in short periods of time) are growing in influence as farm size, cropping areas, and the number of fertilizer applications within seasons increase. Fertilizer decisions have become less sensitive to socioeconomic factors over the last 10 to 15 years. To ensure sustainable development of grain production, research through to adoption activities should focus on agronomic issues (such as seasonal forecasting) and logistic issues (such as improving planning, organizational, and technical capacity for developing and implementing fertilizer strategies). [ABSTRACT FROM AUTHOR]

Abstract: Semi-arid lands represent one fifth of the global land area but our understanding of greenhouse gas fluxes from these regions is poor. We investigated if inclusion of a grain legume and/or lime in a crop rotation altered greenhouse gas emissions from an acidic soil. Nitrous oxide (N2O) and methane (CH4) fluxes were measured from a rain-fed, cropped soil in a semi-arid region of Australia for two years on a sub-daily basis. The randomised-block design included two cropping rotations (lupin–wheat, wheat–wheat) by two liming treatments (0, 3.5tha−1) by three replicates. The lupin–wheat rotation only received N fertilizer during the wheat phase (20kgNha−1), while the wheat–wheat received 125kgNha−1 during the two year study. Fluxes were measured using soil chambers connected to a fully automated system that measured N2O and CH4 by gas chromatography. Nitrous oxide fluxes were low (−1.4 to 9.2gN2O-Nha−1 day−1), and less than those reported for arable soils in temperate climates. Including a grain legume in the cropping rotation did not enhance soil N2O; total N2O losses were approximately 0.1kgN2O-Nha−1 after two years for both lupin–wheat and wheat–wheat rotations when averaged across liming treatment. Liming decreased cumulative N2O emissions from the wheat–wheat rotation by 30% by lowering the contribution of N2O emissions following summer–autumn rainfall events, but had no effect on N2O emissions from the lupin–wheat rotation. Daily CH4 fluxes ranged from −14 to 5g CH4-Cha−1 day−1. Methane uptake after two years was lower from the wheat–wheat rotation (601gCH4-Cha−1) than from either lupin–wheat rotations (967gCH4-Cha−1), however liming the wheat–wheat rotation increased CH4 uptake (1078gCH4-Cha−1) to a value similar to the lupin–wheat rotation. Liming provides a strategy for lowering on-farm greenhouse gas emissions from N fertilised soils in semi-arid environments via decreased N2O fluxes and increased CH4 uptake. [Copyright &y& Elsevier]

Understanding nitrous oxide (NO) fluxes from grain-legume crops in semiarid and arid regions is necessary if we are to improve our knowledge of global terrestrial NO losses resulting from biological N fixation. NO fluxes were measured from a rain-fed soil, cropped to a grain-legume in a semiarid region of southwestern Australia for 1 year on a subdaily basis. The site included plots planted to narrow-leafed lupin ( Lupinus angustifolius; 'lupin') and plots left bare (no lupin). Fluxes were measured using soil chambers connected to a fully automated system that measured NO by gas chromatography. Daily NO fluxes were low (−0.5 to 24 g NO-N ha day) and not different between treatments, culminating in an annual loss of 127 g NO-N ha. Greatest daily NO fluxes occurred from both treatments in the postharvest period, and following a series of summer and autumn rainfall events. At this time of the year, soil conditions were conducive to soil microbial NO production: elevated soil water contents, increased inorganic nitrogen (N) and dissolved organic carbon concentrations, and soil temperatures generally > 25 °C; furthermore, there was no active plant growth to compete for mineralized N. NO emissions from the decomposition of legume crop residue were low, and approximately half that predicted using the currently recommended IPCC methodology. Furthermore, the contribution of the biological N fixation process to NO emissions appeared negligible in the present study, supporting its omission as a source of NO from the IPCC methodology for preparing national greenhouse gas inventories. [ABSTRACT FROM AUTHOR]

Abstract: We contrasted oribatid species richness and the distribution of carbon (C) and nitrogen (N) in organic matter (OM) density and size fractions in agricultural fields with the closest area of native vegetation at three locations in the Western Australian wheat belt. Few studies have quantified oribatid richness in WA soils and none has investigated the impact of agriculture on these animals. A total of 22 oribatid species was identified from the samples, of which 8 were found in agricultural fields. A maximum of 5 species was found in individual agricultural fields, and a minimum of 11 species was found in the individual native vegetation areas. There were few differences in the mass of C and N in OM fractions between native and agricultural areas, and no correlation between mite abundance and mass of C in the density and size fractions of soil OM assessed. Therefore, soil disturbance, and not soil OM levels per se, is the likely cause of the low species richness at the agricultural sites. [Copyright &y& Elsevier]