Impact of in-crop and soil residual herbicides on effective nitrogen fixation in field pea (Pisum sativum L.) and chickpea (Cicer arietinum L.)

Non-Peer ReviewedA three-year project was initiated in 2004 to examine the effects of residual herbicides and registered “in-crop” herbicides, both soil and foliar applied, on N fixation and consequent yield of field peas and chickpeas. Inoculation strategies were examined to determine if inoculant formulation (i.e., peat powder versus granular inoculant) influences the degree to which herbicides can affect N fixation. This research is ongoing and thus all results are considered preliminary. Preliminary results in field pea, suggest that where herbicides had a negative effect on N fixation, the effects occurred at relatively early growth stages (i.e., soon after herbicide application) and were typically overcome at later growth stages. In addition, granular inoculants were associated with increased N fixation as compared to peat powder inoculants, and may have mitigated any negative herbicide effects. Chickpea incurred damage from the herbicides and all treatments had significantly less N fixation than the control. In general, results suggest that N fixation may be compromised if herbicides cause significant plant damage; however, improved weed control associated with herbicide application may counter the negative impact on early N fixation

Distribution of mycorrhizal fungi in different soil zone with pyrosequencing approach

Non-Peer ReviewedWe collected 83 soil samples distributed in all five soil types of Saskatchewan, and amplified 18s rDNA as our target DNA segment with primer pairs NS1/NS4 and AMV4.5NF/AMDGR. Sequencing results show that there is rich diversity of AM and other soil fungi in summer season but fungal composition vary among different soil zones and culture management

Nitrogen cycling and budget in crop rotations as influenced by preceding crops and N fertilization

Non-Peer Reviewe

Legacy effects override soil properties for CO 2 and N 2 O but not CH 4 emissions following digestate application to soil

The application of organic materials to soil can recycle nutrients and increase organic matter in agricultural lands. Digestate can be used as a nutrient source for crop production but it has also been shown to stimulate greenhouse gas (GHG) emissions from amended soils. While edaphic factors, such as soil texture and pH, have been shown to be strong determinants of soil GHG fluxes, the impact of the legacy of previous management practices is less well understood. Here we aim to investigate the impact of such legacy effects and to contrast them against soil properties to identify the key determinants of soil GHG fluxes following digestate application. Soil from an already established field experiment was used to set up a pot experiment, to evaluate N2O, CH4 and CO2 fluxes from cattle‐slurry‐digestate amended soils. The soil had been treated with farmyard manure, green manure or synthetic N‐fertilizer, 18 months before the pot experiment was set up. Following homogenization and a preincubation stage, digestate was added at a concentration of 250 kg total N/ha eq. Soil GHG fluxes were then sampled over a 64 day period. The digestate stimulated emissions of the three GHGs compared to controls. The legacy of previous soil management was found to be a key determinant of CO2 and N2O flux while edaphic variables did not have a significant effect across the range of variables included in this experiment. Conversely, edaphic variables, in particular texture, were the main determinant of CH4 flux from soil following digestate application. Results demonstrate that edaphic factors and current soil management regime alone are not effective predictors of soil GHG flux response following digestate application. Knowledge of the site management in terms of organic amendments is required to make robust predictions of the likely soil GHG flux response following digestate application to soil

Soil and Cultivar Type Shape the Bacterial Community in the Potato Rhizosphere

The rhizospheres of five different potato cultivars (including a genetically modified cultivar) obtained from a loamy sand soil and two from a sandy peat soil, next to corresponding bulk soils, were studied with respect to their community structures and potential function. For the former analyses, we performed bacterial 16S ribosomal RNA gene-based PCR denaturing gradient gel electrophoresis (PCR-DGGE) on the basis of soil DNA; for the latter, we extracted microbial communities and subjected these to analyses in phenotype arrays (PM1, PM2, and PM4, Biolog), with a focus on the use of different carbon, sulfur and phosphorus sources. In addition, we performed bacterial PCR-DGGE on selected wells to assess the structures of these substrate-responsive communities. Effects of soil type, the rhizosphere, and cultivar on the microbial community structures were clearly observed. Soil type was the most determinative parameter shaping the functional communities, whereas the rhizosphere and cultivar type also exerted an influence. However, no genetically modified plant effect was observed. The effects were imminent based on general community analysis and also single-compound analysis. Utilization of some of the carbon and sulfur sources was specific per cultivar, and different microbial communities were found as defined by cultivar. Thus, both soil and cultivar type shaped the potato root-associated bacterial communities that were responsive to some of the substrates in phenotype arrays

Optimizing the Productivity and Resiliency of Cropping Systems in the Major Ecozones on the Canadian Prairies

Non-Peer ReviewedAgriculture faces grand challenges of meeting growing food demands and increasing profitability while reducing environmental impacts. A systems approach is required to design and manage cropping systems to meet the goal of agricultural sustainability under climate change. A 4-year rotation study was established in 2018 at seven sites across the Canadian Prairies, including Beaverlodge, Lacombe, and Lethbridge, AB; Melfort, Scott, and Swift Current, SK; and Carman MB. The objective of this project is to develop resilient cropping systems for different ecozones on the Canadian Prairies. This study tested six cropping systems consisting of 1) conventional cropping system (Control), 2) pulse- or oilseed-intensified cropping system (POS), 3) diversified cropping system (DS), 4) market-driven cropping system (MS), 5) high risk and high reward cropping system (HRHRS), and 6) green-manure incorporated soil-health focused cropping system (GMS). Each cropping system varies slightly among experimental sites (ecozones) to mimic local farming practices. Cropping system indicators such as yield, resource use efficiency, soil health, profitability, environmental impact, resiliency, and sustainability will be fully assessed at the end of rotations. The preliminary results from the first 2 years indicated that there was no single cropping system suitable for all study ecozones although POS had an above-average yield and stability among the six cropping systems. We suggest that the optimal cropping system will maximize yield in the high-yielding ecozones and stabilize yields in the low-yielding ecozones. Link to Video Presentation: https://youtu.be/VsK4RNIzaZ

Effects of past and current crop management on soil microbial biomass and activity

As soil biota is influenced by a number of factors, including land use and management techniques, changing management practices could have significant effects on the soil microbial properties and processes. An experiment was conducted to investigate differences in soil microbiological properties caused by long- and short-term management practices. Intact monolith lysimeters (0.2 m2 surface area) were taken from two sites of the same soil type that had been under long-term organic or conventional crop management and were then subjected to the same 2½-year crop rotation (winter barley (Hordeum vulgare L.), maize (Zea mais L.), lupin (Lupinus angustifolius L.) rape (Brassica napus L. ssp. oleifera)) and two fertiliser regimes (following common organic and conventional practices). Soil samples were taken after crop harvest and analysed for microbial biomass C and N, microbial activity (fluorescein diacetate hydrolysis, arginine deaminase activity, dehydrogenase activity) and total C and N. The incorporation of the green manure stimulated growth and activity of the microbial communities in soils of both management histories. Soil microbial properties did not show any differences between organically and conventionally fertilised soils, indicating that crop rotation and plant type had a larger influence on the microbial biomass and enzyme activities than fertilisation. Initial differences in microbial biomass declined, while the effects of farm management history were still evident in enzyme activities and total C and N. Links between enzyme activities and microbial biomass C varied depending on treatment indicating differences in microbial community composition