Abstract:New Zealand's pastoral agriculture faces challenges associated with increasing on-farm productivity, while minimizing the environmental footprint of farming. Soil microorganisms mediate a wide range of processes that affect plant production and also have environmental consequences. However, there has been little attempt to manage these in a farming system context. This is primarily because of difficulties in determining what microbiological resources are present in soils, how they link with soil processes and … Show more
“…There was a wide range of pH and macronutrient levels across the soils used in this study ( Table 1 ), with broad agreement between levels measured here and those by Wakelin et al (2013) from the same soils, with the exception of pH in soil 9. The northernmost soils (1 and 2) had the greatest CEC values while soil 5 was notable for a high level of Mg and soil 8 for low total N.…”
Section: Resultssupporting
confidence: 64%
“…Soil samples were collected from 10 sites previously characterized by Wakelin et al (2013) that represented a wide range of geographical locations and soil characteristics, primarily pH and nitrogen levels ( Figure 1 ). In addition, half the sites were on brown soil type and half on recent soils, while four sites were dairy farms and six were sheep and beef farms.…”
White clover (Trifolium repens) is the key legume component of New Zealand pastoral agriculture due to the high quality feed and nitrogen inputs it provides. Invertebrate pests constrain white clover growth and this study investigated rhizosphere-associated fungal controls for two of these pests and attempts to disentangle the underpinning mechanisms. The degree of suppressiveness of 10 soils, in a latitudinal gradient down New Zealand, to added Meloidogyne hapla and Costelytra zealandica scarab larvae was measured in untreated soil. Most of the soils showed no suppressive activity against these pests but two showed activity against M. hapla and two against C. zealandica. Rhizosphere fungi responsible for pest suppressive responses were elucidated via next-generation sequencing. In the M. hapla-suppressive soils nematode-trapping Orbiliomycetes fungi were present in significantly greater abundance than non-suppressive soils and their abundance increased further with addition of M. hapla. A comparison of plant growth and the rhizosphere fungal community between untreated and irradiated soil was carried out on 5 of the 10 soils using Pyronota as the scarab larvae. Soil irradiation either: reduced (by 60–70%); increased (16×) or made no difference to white clover growth across the five soils tested, illustrating the range of microbial impacts on plant production. In one of the M. hapla suppressive soils irradiation resulted in a significant increase in nematode galling suggesting that Orbiliomycetes fungi were indeed responsible for the suppressive effect. Lack of consistent changes in soil macronutrients and pH post-irradiation suggest these were not responsible for plant or invertebrate responses. The use of next generation sequencing in controlled pot trials has allowed identification of a potential biological control organism and bioindicator for M. hapla suppression.
“…There was a wide range of pH and macronutrient levels across the soils used in this study ( Table 1 ), with broad agreement between levels measured here and those by Wakelin et al (2013) from the same soils, with the exception of pH in soil 9. The northernmost soils (1 and 2) had the greatest CEC values while soil 5 was notable for a high level of Mg and soil 8 for low total N.…”
Section: Resultssupporting
confidence: 64%
“…Soil samples were collected from 10 sites previously characterized by Wakelin et al (2013) that represented a wide range of geographical locations and soil characteristics, primarily pH and nitrogen levels ( Figure 1 ). In addition, half the sites were on brown soil type and half on recent soils, while four sites were dairy farms and six were sheep and beef farms.…”
White clover (Trifolium repens) is the key legume component of New Zealand pastoral agriculture due to the high quality feed and nitrogen inputs it provides. Invertebrate pests constrain white clover growth and this study investigated rhizosphere-associated fungal controls for two of these pests and attempts to disentangle the underpinning mechanisms. The degree of suppressiveness of 10 soils, in a latitudinal gradient down New Zealand, to added Meloidogyne hapla and Costelytra zealandica scarab larvae was measured in untreated soil. Most of the soils showed no suppressive activity against these pests but two showed activity against M. hapla and two against C. zealandica. Rhizosphere fungi responsible for pest suppressive responses were elucidated via next-generation sequencing. In the M. hapla-suppressive soils nematode-trapping Orbiliomycetes fungi were present in significantly greater abundance than non-suppressive soils and their abundance increased further with addition of M. hapla. A comparison of plant growth and the rhizosphere fungal community between untreated and irradiated soil was carried out on 5 of the 10 soils using Pyronota as the scarab larvae. Soil irradiation either: reduced (by 60–70%); increased (16×) or made no difference to white clover growth across the five soils tested, illustrating the range of microbial impacts on plant production. In one of the M. hapla suppressive soils irradiation resulted in a significant increase in nematode galling suggesting that Orbiliomycetes fungi were indeed responsible for the suppressive effect. Lack of consistent changes in soil macronutrients and pH post-irradiation suggest these were not responsible for plant or invertebrate responses. The use of next generation sequencing in controlled pot trials has allowed identification of a potential biological control organism and bioindicator for M. hapla suppression.
“…Soil physicochemical properties were determined at Hill Laboratories Ltd. (Christchurch), using well characterised methods (e.g. as described in Wakelin et al 2013).…”
Section: Soil Collection and Handlingmentioning
confidence: 99%
“…Alleviation of soil biological constraints (i.e. reduction of pathogens or supply of beneficial symbionts) is identified as a key path towards achieving this goal (Wakelin et al 2013). …”
The cost to clover growth of soil-borne root disease was measured in ten New Zealand dairy pasture soils. The average increase clover growth (weight) after soil pasteurisation was 28.5 %, but ranged from a 64 % increase (Whataroa soil) to a decrease of 11.9 % (Ruakura soil). The economic cost of reduced clover growth was determined using the Farmax Dairy Pro decision support system. In Southland and Canterbury, clover root disease was estimated to cost $750 and $715 ha −1 year −1 respectively, and in the Waikato region $1506 ha −1 year −1 . DNA-based testing of the soils detected the presence of diverse fungal, oomycete and nematode pathogen populations. A significant linear relationship was found between reduction in clover growth and group F Pythium spp. (P = 0.0177). The DNA-based assay indicated that Aphanomyces trifolii, a root pathogen of subterranean clover, may be present in the dairy-pasture soils. As this pathogen is currently not recognised as present in New Zealand, a definitive determination of its presence is required. Based on the high economic costs of diseases, the control of soil-borne root pathogens in New Zealand pasture is a direct means to increase profitability.
“…For simplicity, relationships between the functional gene data and farm management were compared only for dairy vs 'other' grazing systems (see later definition) in this work. A comprehensive set of soil physicochemical properties and long-term environmental conditions from the sites (Wakelin et al 2013b) enables the assessment of the soil ecological genomics against a set of appropriate metadata, and these can be used in future studies to assess, for example, influences of intensification more precisely. Overall, the two sets enable changes in functional soil biology to be interpreted alongside soil, climatic and farm-management influences.…”
Management of soil biological resources to optimise plant production, efficiency of nutrient inputs, and system sustainability is an emerging opportunity for pastoral agriculture. To achieve these goals, suitable tools that can assess the functional state of the soil ecosystem must be developed and standardised approaches to their application adopted. Towards this end, we have undertaken comprehensive, high-density functional-gene microarray analysis (GeoChip5) of environmental DNA (eDNA) extracted from 50 pastoral soils. When combined with soil, environmental and management metadata, the information can be used to provide insights into soil biological processes spanning greenhouse gas emissions, through to natural suppression of plant root diseases. To provide an example of a structured workflow of analysis in a pastoral system context, we analysed the GeoChip data using a combination of approaches spanning routine univariate methods through to more complex multivariate and network-based analysis. Analyses were restricted to comparing effects of land-use (dairy or 'other' farming systems), and exploring relationships of the GeoChip data with the soil properties from each sample. These exemplar analyses present a pathway for the application of eDNA approaches (GeoChip or others) to deliver outcomes for pastoral agricultural in New Zealand.
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