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To maintain sustainable broadacre farming in the future, a better understanding of soil microbiome functions and processes associated with adapting agronomic management practices will be key. This is primarily due to the irreplaceable roles of the soil microbiome in soil and plant interactions, human health and ecosystem functions and stability. We approached this challenge by reviewing how different land management practices influence soil microbial communities. The important role that the soil microbiome plays in cropping systems is analyzed in the context of an overview of changes in land management over the past two decades using southern Australian dryland farming as a case study. Many major changes in management have occurred in this system during this time, including (i) reduction in tillage, with a corresponding increase in direct drilling and stubble retention; (ii) inclusion of oilseeds and pulses in cereal-dominated rotation systems; (iii) decrease in the pasture-dominated grain production systems; (iv) increased use of agrochemicals; (v) different soil amelioration applications and (vi) development of innovative agricultural technology. We review the overarching role of climate extremes in impacting agronomic management practices in southern Australian farming systems. In all, we demonstrate the complex interplay between land management changes and the activity, diversity and functions of the soil microbiome, with reference to changes in agronomic management practices. [ABSTRACT FROM AUTHOR]

Decomposition of mixed residues is common in many ecosystems, with residues from different species or above- and below-ground residues from the same species. Although decomposition of litter mixtures has been extensively studied, little is known about the changes in microbial biomass carbon (C) and available nitrogen (N) in the early stages of decomposition of mixtures of shoots and roots. An incubation experiment was carried out in a sandy clay loam with shoot and root residues of two grasses, annual barley (Hordeum vulgare L.), and perennial Stipa sp., added separately or as mixtures. Soil respiration was measured continuously, and soil microbial biomass C, extractable C and available N were measured by destructive sampling on days 0, 3, 6, 9, 12 and 18. Cumulative respiration and microbial biomass C concentration were higher with barley shoots alone or in mixtures than with Stipa residues alone. In the mixture of Stipa shoots and roots, which had similar decomposition rates when incubated individually, the measured cumulative respiration was greater than the expected value (average of the cumulative respiration of the individual residues), but this did not result in greater microbial biomass or changes in available N concentration compared with the individual residues. Cumulative respiration of barley shoots alone was higher than of barley root and Stipa shoot incubated individually. In the mixtures of barley shoots with barley roots or Stipa shoots, the measured cumulative respiration was either lower than the expected value or similar. Compared with barley shoots alone, microbial biomass C concentrations in the mixtures were generally lower in the first 3 days. It is concluded that mixing of residues with similar decomposition rates can stimulate microbial activity (respiration) but has little effect on microbial growth or concentrations of available N. Further, our findings provide information about extractable C and N dynamics during the early stages of decomposition of individual residue and residue mixtures. Additional keywords: available N, cumulative respiration, expected value, interaction, microbial biomass C., Introduction Microbial activity, biomass and available nutrient concentrations change rapidly after incorporation of plant residues into soil, and the extent of change is influenced by a range of factors including [...]

Abstract: Addition of clay-rich subsoils to sandy top soils is an agricultural management option to increase water and nutrient retention and may also increase organic carbon sequestration by decreasing the decomposition rates. An incubation experiment was carried out in a loamy sand top soil mixed with a clay-rich subsoil (84% clay) at 0, 10 and 30% (w/w) amended with finely ground mature shoot residues of two native perennial grasses and annual barley individually or in 1:1 mixtures of two residues. Extractable C, microbial biomass C, available N and soil pH were analysed at days 0, 3, 14 and 28. Cumulative respiration after 28days was highest with barley residue and lowest with Wallaby grass at all clay soil addition rates; 30% clay soil addition reduced cumulative respiration, especially with barley alone. In the mixture of native grasses and barley, the measured respiration was lower than expected at a clay soil addition rate of 10%. A synergistic effect (higher than expected cumulative respiration) was only found in mixture of Kangaroo grass and barley at a clay soil addition rate of 30%. Clay soil addition also decreased extractable C, available N and soil pH. The temporal change in microbial biomass C and available N in residue mixtures differed among clay addition rates. In the mixture of Wallaby grass and Kangaroo grass, microbial biomass C (MBC) decreased from day 0 to day 28 at clay soil addition rates of 0 and 10%, whereas at 30% clay MBC increased from day 0 to day 3 and then decreased. Our study shows that addition of a clay-rich subsoil to a loamy sand soil can increase C sequestration by reducing CO2 release and extractable C which are further modulated by the type of residues present individually or as mixtures. [Copyright &y& Elsevier]

Background and aims: Most studies of the relationships between the composition of soil organic matter and plant cover have been carried out at the plant genera level. However, they have largely overlooked the potential effects that plant varieties, belonging to the same genus, can have on soil organic matter.We investigated whether plant varieties belonging to different Salix species (S. dasyclados and S. viminalis) impacted the composition of organic matter using mid-infrared spectroscopy and pyrolysis GC/MS. Top-soils were taken from an 18 year-old long-term field trial where six Salix varieties were grown as short-rotation coppice under two fertilisation regimes.Significant differences in the molecular composition and diversity of the soil organic matter were observed in the fertilised plots. The effects were mostly visible at the species level, i.e. the organic matter in soil under S. dasyclados varieties had higher molecular diversity and lignin content than under S. viminalis, potentially due to differences in the amount and composition of their litter inputs. Smaller differences among varieties from the same species were also observed. No significant effects of Salix varieties were observed in the unfertilised plots. The relatively high degree of spatial variability of several soil properties found in these plots may have masked plant variety and/or species effects.This study provides evidence that the identity of Salix species or varieties can affect the molecular composition and diversity of soil organic matter. The corresponding traits should be considered in breeding programmes to enhance soil organic C accumulation and persistence.Methods: Most studies of the relationships between the composition of soil organic matter and plant cover have been carried out at the plant genera level. However, they have largely overlooked the potential effects that plant varieties, belonging to the same genus, can have on soil organic matter.We investigated whether plant varieties belonging to different Salix species (S. dasyclados and S. viminalis) impacted the composition of organic matter using mid-infrared spectroscopy and pyrolysis GC/MS. Top-soils were taken from an 18 year-old long-term field trial where six Salix varieties were grown as short-rotation coppice under two fertilisation regimes.Significant differences in the molecular composition and diversity of the soil organic matter were observed in the fertilised plots. The effects were mostly visible at the species level, i.e. the organic matter in soil under S. dasyclados varieties had higher molecular diversity and lignin content than under S. viminalis, potentially due to differences in the amount and composition of their litter inputs. Smaller differences among varieties from the same species were also observed. No significant effects of Salix varieties were observed in the unfertilised plots. The relatively high degree of spatial variability of several soil properties found in these plots may have masked plant variety and/or species effects.This study provides evidence that the identity of Salix species or varieties can affect the molecular composition and diversity of soil organic matter. The corresponding traits should be considered in breeding programmes to enhance soil organic C accumulation and persistence.Results: Most studies of the relationships between the composition of soil organic matter and plant cover have been carried out at the plant genera level. However, they have largely overlooked the potential effects that plant varieties, belonging to the same genus, can have on soil organic matter.We investigated whether plant varieties belonging to different Salix species (S. dasyclados and S. viminalis) impacted the composition of organic matter using mid-infrared spectroscopy and pyrolysis GC/MS. Top-soils were taken from an 18 year-old long-term field trial where six Salix varieties were grown as short-rotation coppice under two fertilisation regimes.Significant differences in the molecular composition and diversity of the soil organic matter were observed in the fertilised plots. The effects were mostly visible at the species level, i.e. the organic matter in soil under S. dasyclados varieties had higher molecular diversity and lignin content than under S. viminalis, potentially due to differences in the amount and composition of their litter inputs. Smaller differences among varieties from the same species were also observed. No significant effects of Salix varieties were observed in the unfertilised plots. The relatively high degree of spatial variability of several soil properties found in these plots may have masked plant variety and/or species effects.This study provides evidence that the identity of Salix species or varieties can affect the molecular composition and diversity of soil organic matter. The corresponding traits should be considered in breeding programmes to enhance soil organic C accumulation and persistence.Conclusion: Most studies of the relationships between the composition of soil organic matter and plant cover have been carried out at the plant genera level. However, they have largely overlooked the potential effects that plant varieties, belonging to the same genus, can have on soil organic matter.We investigated whether plant varieties belonging to different Salix species (S. dasyclados and S. viminalis) impacted the composition of organic matter using mid-infrared spectroscopy and pyrolysis GC/MS. Top-soils were taken from an 18 year-old long-term field trial where six Salix varieties were grown as short-rotation coppice under two fertilisation regimes.Significant differences in the molecular composition and diversity of the soil organic matter were observed in the fertilised plots. The effects were mostly visible at the species level, i.e. the organic matter in soil under S. dasyclados varieties had higher molecular diversity and lignin content than under S. viminalis, potentially due to differences in the amount and composition of their litter inputs. Smaller differences among varieties from the same species were also observed. No significant effects of Salix varieties were observed in the unfertilised plots. The relatively high degree of spatial variability of several soil properties found in these plots may have masked plant variety and/or species effects.This study provides evidence that the identity of Salix species or varieties can affect the molecular composition and diversity of soil organic matter. The corresponding traits should be considered in breeding programmes to enhance soil organic C accumulation and persistence. [ABSTRACT FROM AUTHOR]