A Comparison of Tillage Techniques on Selected Soil Microbes Within the Rhizosphere of Wheat

Abstract

This thesis reports on the implications of Conventional tillage regimes with a focus upon Arbuscular Mycorrhizal (AM) fungi for their contribution to soil chemical, physical and biological attributes, including aggregation, abundance and contribution to organic material. Soil inversion of conventional tillage (CT) treatments was compared with soil management practices involving zero tillage (ZT) for the growing season between September 2018 and September 2019 within Hertfordshire, UK, focusing upon alterations to AM fungal relationships between glomalin and soil aggregation, host-fungal symbiosis, and interactions with rhizobacteria. Identified sites, matched on similarities of crop histories and fertiliser type and application, were sampled in grid formats to maximum soil depths of 40cm. Sampled soils of both applied tillage practices indicated variances in soil glomalin and soil aggregation with sampling depth as well as between tillage regimes. Top soil (<10cm) glomalin and aggregation was seen to be homogenised throughout the zone of tillage in CT soils, whereas ZT soils varied with sampling depth. Correlations between glomalin and soil aggregates were seen to diminish in CT managed soils, accompanied by reductions to quantified fungal biomass, when compared with ZT treatments which did not produce such reductions. Examined root sections of winter wheat, grown under each tillage treatment, indicated reduced AM fungal symbiosis in CT managed soils compared with ZT soils. Further investigations were able to indicate glyphosate application in ZT treatments may have produced profound reductions to AM fungal symbiosis. Furthermore, the type of fertiliser was seen to influence the degree to which AM fungi associated with wheat root tissues. Application of Selected rhizobacterial inoculants (Bacillus spp.) to sampled soils from each tillage practice, with planted Zulu winter wheat, affected AM fungal symbiosis in stained root tissues as well as influencing above and below ground wheat biomass. Monitoring of selected rhizobacteria by qPCR gave further indications to the persistence of select Bacillus spp. rhizobacteria in wheat producing soils.