Effect of cultivation on the activity of some soil enzymes

Non-Peer Reviewe

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

Non-Peer Reviewe

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

A growth chamber study on the effects of metribuzin on the rhizobium-lentil symbiosis

Non-Peer Reviewe

The impact of inoculation on the tripartite association between pulse crops, rhizobia, and arbuscular mycorrhizal fungi

Non-Peer Reviewe

Root-associated bacterial communities in flax (Linum usitatissimum) and their response to arbuscular mycorrhizal (AM) inoculation

Non-Peer Reviewe

Survival of a genetically engineered Pseudomonas putida strain in soil and its potential to conjugatively transfer genes to indigenous soil bacteria

Non-Peer ReviewedThere is an interest in releasing genetically engineered bacteria into the environment as biofertilizers, biological control agents or to remediate contaminated soil. However, there is little information available on the factors affecting the persistence of genetically engineered bacteria or their potential to transfer genes to indigenous soil microorganisms. This study assessed the survival of a genetically engineered Pseudomonas putida strain CR30RNS (pADPTel) in bulk and rhizosphere soil and its ability to transfer genes for atrazine degradation and tellurite resistance to indigenous soil bacteria. The P. putida strain survived for ten weeks in bulk and rhizosphere soil at approximately 106 cfu per g soil. After the plants were harvested, the population of the P. putida strain declined to undetectable levels. However, upon the addition of water and a nutrient solution containing atrazine, the P. putida CR30RNS (pADPTel) population in the rhizosphere soil rebounded to a density of ca. 105 cfu per g soil while the population in bulk soil remained undetectable. The frequency of conjugative gene transfer to indigenous soil bacteria was assessed under laboratory conditions by the use of filter matings. Under optimal conditions a range of 1-10-2 transconjugants per recipient was observed. Recipient bacteria were identified by FAME analysis as Rahnella aquatilis strains. The results indicate that the genetically engineered bacteria survived better in the rhizosphere of canola than in bulk soil, and had the potential to transfer genes to indigenous soil bacteria

The use of large undisturbed cores to assess soil quality-yield relationships in the greenhouse

Non-Peer ReviewedLarge undisturbed cores were taken from different landscape positions (divergent shoulders, DSH, and convergent footslopes, CFS) at two sites in the Black soil zone. The soils are classified as belonging to the Oxbow association and have been cultivated for 15 and 82 years. The cores were used in a greenhouse experiment to study the effect of soil quality on yield of spring wheat (var. Katepwa) at three levels of simulated growing season precipitation: low (123 mm season-1), mid (189 mm season-1), and high (332 mm season-1). Grain yields in the DSH cores increased with increasing precipitation for both the 15- and 82-year soils. Moreover, the 15-year DSH cores out-yielded their 82-year counterparts by 50, 76, and 85% at the low, mid, and high water levels, respectively. Cores from the CFS positions were watered only at the mid-water level. Grain yields in the 15- and 82-year CFS cores and the 15-year DSH cores were not significantly different (P < 0.05). The results of this study indicate that soil quality is a relatively minor factor when water is limiting but assumes a much greater role in years of normal or above normal growing season precipitation. These initial results also suggest that large cores are a feasible and cost-effective means of studying soil-plant relationships in the greenhouse or growth chamber

Phytoremediation of hydrocarbon-contaminated soil using native plants

Non-Peer ReviewedPhytoremediation of hydrocarbon-contaminated soil involves plants and their associated microorganisms. However, few cold-tolerant plants have been identified for reclamation in the native grasslands and woodlands of Canada. We assessed 35 native grasses, legumes and forbs, and seven exotic grasses and legumes for their ability to germinate and survive in crude oil contaminated soil. Based on germination, survival, growth rate, and above and below ground biomass five native (Artemisia frigida, Bromus ciliatus, Glycyrrhiza lepidota, Potentilla pensylvanica, and Psoralea esculenta) and three exotic (Medicago sativa, Melilotus officinalis and Trifolium repens) plants exhibited phytoremediation potential. The ability of these species to degrade specific hydrocarbons and mixtures of hydrocarbons is currently being assessed

Influence of urease and nitrification inhibitors on ammonium and nitrate supply and the soil microbial population in western Canadian soils

Non-Peer ReviewedImproving nitrogen use efficiency and limiting losses of N from the soil system is important both economically and environmentally. This study assessed the potential of using a urease inhibitor, Agrotain®, or a nitrification inhibitor, nitrapyrin, to create a slow release effect similar to that found in sulfur coated urea in western Canadian soils of the Brown and Black soil zones. The nitrapyrin significantly reduced the cumulative NO3- supply to the point of inhibition of nitrification for 21d in the Brown soil, but had little effect on the Black soil. Nitrapyrin had little effect on the supply of NH4+ in both soils. The Agrotain® had some effect on NO3- supply and significantly reduced the NH4+ supply for 14d in the Brown soil. Differences between the two soils were consistent with results in other studies and attributed to pH and organic matter content differences. The total heterotrophic and Nitrosomonas microbial populations were enumerated using spread plates and most probable number assays. It was concluded that Agrotain® had little effect on the microbial population, where as nitrapyrin reduced Nitrosomonas populations and increased total heterotrophic counts in both soils. Similarity between the results in this study and the literature suggest that the soils in Western Canada have similar responses to inhibitors as those characterized by the literature. Therefore, whether improved nitrogen use efficiency from the use of inhibitors in wheat in Western Canada would be large enough to justify the used of inhibitors will depend on whether local soil properties are conducive to promote volatilization, leaching and denitrification losses of N