Microbial community structure in long-term no-till and intensive-till soils

Non-Peer ReviewedConversion from intensive tillage (IT) to no-till (NT) management creates an altered habitat for soil microorganisms. We utilized four long-term tillage experiments in Saskatchewan and Alberta to compare NT and IT microbial communities. Microbial abundance increased at the soil surface (0- to 5-cm depth) in NT vs. IT soils. Differences were much less pronounced or negligible at the 5- to 10-cm and 10- to 15-cm depths. Despite increased biomass of fungi and bacteria in NT surface soils no significant shift in the relative proportion of individual groups of organisms within the community was observed. Similarly, analysis of bacterial DNA fingerprints indicated that while microbial community clusters in the 0- to 5-cm depth increment were different than those at greater depth, there was no significant effect of tillage. Our results demonstrate that depth was a stronger determinant of microbial community structure than tillage management

100 years of farming: long-term differences in cropping intensity and N fertilization impact soil microbial community structure

Non-Peer Reviewe

Assessing microbial communities in transplanted soils after 21 years

Non-Peer Reviewe

Investigation of soil microbial factors related to greater than expected residue induced N2O emissions from canola (Brassica napus L.)

Non-Peer ReviewedAbstract Oilseed residues, particularly canola (Brassica napus L.), instigate higher nitrous oxide (N2O) emissions compared to pulse and wheat crop residues. We conducted an incubation experiment (84 d) using 15N and 13C labelled residues of canola, flax, pea and wheat applied at rates equivalent to those reported for crop grown in the field in Saskatchewan to assess soil biological processes related to N2O emissions. We used a combination of molecular techniques (qPCR and PLFA) to investigate the N-cycling gene abundance and microbial abundance and community structure with each of the added residues The magnitude of nitrous oxide (N2O) emission from residue amended soils were significantly higher (p<0.05) than the control treatment (without residue addition) and differed with residue type: control < Flax < pea = Wheat < canola. Residue addition significantly (p<0.05) increased denitrification gene abundances (nirS, nirK, nosZ I and nosZ II) compared to the control. However, there was no significant (p<0.05) affect on nitrification genes (archaeal and bacterial amoA). Pearson correlation of DOC and denitrification gene abundance were significant (p<0.05) across all soils. Both canola and pea residue addition resulted in a significant increase in dissolved organic C, but only canola residue resulted in decreased dissolved organic N and NO3. This suggests an interplay between biologically available C and N that differed among residue types, affecting N2O emissions. Preliminary analysis of 15N2O and 13CO2 data suggests that the stimulatory effect of canola residues on N2O emissions is due to differences in residue C

Microbial enzyme activity in irrigated canola plots receiving different nitrogen applications

Non-Peer Reviewe

Landscape position and depth affect microbial abundance and community composition at three positions in an agricultural landscape

Non-Peer ReviewedStabilization/destabilization mechanisms of deep soil carbon are not well understood. A number of different controlling mechanisms are suggested; here we explore differences in microbial abundance and community structure as a controlling mechanism. Microbial abundance and community composition with depth was assessed at three different positions within an agricultural landscape. Microbial abundance was significantly affected by sampling depth, while differences in community structure could be attributed to depth, landscape position, and conditions found within the depositional position. Interestingly, substantial biomass existed at a depth of 81cm in a buried A horizon found in the depositional position

Soil microbial community response to buried crop residues is site-specific and depends on depth of burial

Non-Peer Reviewe

Microbial utilization of residue carbon depends on placement and differs in humid and semi-arid climates

Non-Peer Reviewe

A survey of arbuscular mycorrhizal fungi associated with spring wheat cultivars

Non-Peer ReviewedArbuscular mycorrhizal fungi (AMF) form symbiotic associations with many plants, including wheat. Typically this association benefits plant growth. This study assessed the AMF communities found in the rhizosphere of field grown spring wheat representing modern (CDC Teal), historic (Red Fife) and ancient (PI 167549) varieties. Spores of AMF were extracted from rhizosphere soil by wet sieving, decanting and sucrose density centrifugation and separated into six distinct size classes ( 53-212 um). Spore morphotypes within each size class were grouped according to visual similarity and photographed at 66X magnification under a stereomicroscope. The number of AMF spores isolated from rhizosphere soil for the wheat cultivars ranged from 328 to 464 per 50g and exhibited a variety of morphotypes. Our preliminary results suggest that historic wheat cultivars support a more numerous and diverse AMF community than modern wheat cultivars