Impacts of management on soil biota in Vertosols supporting the broadacre grains industry in northern Australia

Abstract

Abstract. The grain-producing regions of northern New South Wales and southern and central Queensland are characterised by cropping systems that are strongly dependent on stored soil moisture rather than in-crop rainfall, and tillage systems that are increasingly reliant on zero or minimum tillage. Crops are grown relatively infrequently and crop rotations are dominated by winter and summer grains (wheat [Triticum aestivum L.] and sorghum [Sorghum bicolor L. Moench], respectively), with smaller areas of grain legumes and cotton (Gossypium hirsutum L.). The grey, black, and brown Vertosols represent the more productive soils in the region under rainfed cropping, and are the focus of work reported in this study.Soil samples were collected from surface soils (0-0.30 m) across the region, utilising sites of long term tillage and residue management studies, fertiliser trials, and commercial fields to enable an assessment of the impact of various management practices on soil biological properties. A number of biological and biochemical parameters were measured (microbial biomass C, total organic C and labile C fractions, total C and N, microbial activity using FDA, cellulase activity, free living nematodes, total DNA and fatty acid profiles), and the response of wheat, sorghum, and chickpea (Cicer arietinum L.) to steam pasteurisation was assessed in glasshouse bioassays. The objective was to obtain an indication of the biological status of grain-growing soils and assess the impact of biological constraints in soils from different regions and management systems.Results showed that biological activity in cropped soils was consistently low relative to other land uses in northern Australia, with management practices like stubble retention and adoption of zero tillage producing relatively small benefits. In the case of zero tillage, many of these benefits were confined to the top 0.05 m of the soil profile. Fallowing to recharge soil moisture reserves significantly reduced all soil biological parameters, while pasture leys produced consistent positive benefits. Breaking a long fallow with a short duration grain or brown manure crop significantly moderated the negative effects of a long bare fallow on soil biology. Use of inorganic N and P fertilisers produced minimal effects on soil biota, with the exception of one component of the free-living nematode community (the Dorylaimida).The glasshouse bioassays provided consistent evidence that soil biota were constraining growth of both grain crops (sorghum and wheat) but not the grain legume (chickpea). The biota associated with this constraint have not yet been identified, but effects were consistent across the region and were not associated with the presence of any known pathogen or correlated with any of the measured soil biological or biochemical properties. Further work to confirm the existence and significance of these constraints under field conditions is needed.None of the measured biological or biochemical parameters consistently changed in response to management prac...

Effect of strategic tillage in soil microbial communities in Vertisols from Queensland, Australia

“…Various studies have demonstrated the impact of bulk density on enzymatic activity, soil communities and crop growth [54][55][56]. Similar to our findings, Bell, et al [57] reported the impact of different soil managements on soil biota from Hermitage fallow trial. This study revealed a marginally higher total enzymatic activity for CTSR in comparison with CTSB (P = 0.06).…”

“…The fluorescent probe binds to a complementary sequence that can therefore be detected using fluorescence microscopy. Nowadays, FISH is a widely used tool in several fields in microbiology including ecology, phylogenetics, and diagnostics [57]. For example, the presence of live bacteria was detected in root segments of Arabidopsis thaliana by CARD-FISH, which is a variation of FISH that improve its sensitivity through the use of horseradish peroxidase-labeled probes in combination with catalyzed deposition.…”

“…Generally, all treatments showed a microbial biomass C that range from 0.01 to 0.1 mg C g -1 dw soil at both sites. The percentage of microbial biomass C related to total organic C showed values from 0.1% to 1.4% (Table 1) (Saffigna et al 1989;Bell et al 2006). The differences between values may be attributed to the time of sampling.…”

Effects of strategic tillage and plant hormone treatments on wheat-associated microbial communities

“…It is likely that two-time chisel tillage could have mixed soil between depths while one-time tillage did not. FDA activity includes esterase, lipase and certain protease activities (Caldwell 2005 (Bell et al 2006). Our previous studies also used the FDA method for measuring TMA of Australian soils, which ranged from 0.52 to 1.52 µg mL -1 g -1 soil h -1 at 0-10 cm and from 0.27 to 0.73 µg mL -1 g -1 soil h -1 at 10-20 cm for a Calcisol soil, and from 0.6 to 0.8 µg mL -1 g -1 soil h -1 at 0-10 cm and from 0.3 to 0.5 µg mL -1 g -1 soil h -1 at 10-20 cm for a Vertisol soil (Liu et al 2016a,b This provides another contrast with previous results on uniform clays, and warrants further investigation into texture contrast soils.…”

“…Both MBC and MBN are simple methods for assessing the anthropogenic and environmental impacts on soil quality (Sparling et al 1997). Soil type, soil management practices and climatic conditions are important determinants in controlling soil microbial biomass (Bell et al 2006;Campbell et al 1997;Van Gestel et al 1993). Within any region, the variability between the aforementioned controlling factors underlines the importance of an extensive database to be maintained and developed.…”