Examining biochar as a carrier for Rhizobium spp. on legume crops

Non-Peer Reviewe

Greenhouse gas intensity of an irrigated cropping system in Saskatchewan

Non-Peer ReviewedIn response to increasing global food demands, the proportion of irrigated agricultural land within the Canadian Prairies is likely to increase. However, the implications of this with respect to the agricultural greenhouse gas (GHG) balance are not well understood. This study investigates and compares the greenhouse gas intensity of a typical irrigated and dryland cropping system in Saskatchewan, a semi-arid region of the Canadian Prairies. Compared to their dryland counterpart, irrigated cropping systems have higher GHG emissions which are a result of the energy used for pumping and larger nitrous oxide (N2O) production rates associated with higher N-fertilizer application and moist soil conditions. These emissions may be partially offset by increased carbon sequestration from the greater productivity realized through irrigation. This investigation focuses on the quantification of soil GHG emissions through chamber-based flux measurements. Factors driving these emissions have been determined through in-situ soil temperature, matric potential, and moisture measurements. The emissions associated with pumping and other crop management activities are accounted for using the Intergovernmental Panel on Climate Change (IPCC) literature and methodology. Preliminary results from the first season of study confirm that irrigated cropping systems have greater greenhouse gas intensity. Soil N2O emissions from the irrigated system were four times greater than the dryland and were the greatest source of emissions for the irrigated system. Diesel combustion used to power equipment was comparable between cropping systems. Emissions associated with pumping were notable; however, due to the wet growing season they remained smaller than could be expected most years. The information derived from this study will aid in the development of regional specific soil emission factors, improved management strategies, and will identify new approaches for mitigating emissions

Synchronizing nitrogen application with uptake using urease and nitrification inhibitors to maximize nitrogen use in forage seed stands in northeastern Saskatchewan

Non-Peer Reviewe

Does the legacy of long-term crop rotation influence crop residue decomposition dynamics and potential soil N2O flux?

Non-Peer ReviewedResearch has demonstrated that including winter wheat and under-sown red clover into corn-soybean rotations has the potential to improve soil health indices and N use efficiency. Yet, the mechanisms that explain these benefits are poorly understood. One hypothesized explanation is, that by including wheat/red clover in corn-soybean rotations, the soil N supply improves or that the soil N cycle tightens; thereby lowering potential N loss. To address this hypothesis, in Oct 2017 we collected soil cores (10 cm deep, 8 cm diam.) from the second-year corn phase of a 39-yr long-term trial where the following rotations had been maintained: corn-corn-soy-soy (CCSS) or corn-corn-soy-wheat/red clover (CCSWrc), under conventional tillage (CT) or no-till (NT). For each rotation legacy, the soil samples were sieved (2 mm) and air-dried prior to establishing 50 g soil microcosms that were amended with 15N-enriched corn stover or roots (1 and 0.2 g of dried and ground biomass, respectively). Natural abundance and unamended controls were included in the randomized complete block, replicated design. The microcosms were incubated for 14 d at 70% water-filled pore space inside 1L mason jars. Soil and gas samples were periodically collected to measure crop residue decomposition dynamics (via CO2 fluxes and 15N mineralization) and 15N2O fluxes. The results demonstrated higher residue-derived stover N mineralization, and significantly higher N2O stover emissions (by more than a twofold) from the CCSWrc vs the CCSS legacy (P=0.0075). Corn stover and root residues showed distinct N2O patterns, where corn roots (but not stover) appeared to stimulate soil-primed N2O emissions. Overall, our findings indicate that crop residues are processed differently by soil microorganisms depending on the long-term crop rotation legacy

Considering belowground nitrogen of crops grown in prairie agroecosystems

Non-Peer ReviewedGrain legumes can improve the yield of succeeding cereal crops through nitrogen and non-nitrogen benefits. Included among these is the input of symbiotically-fixed N from the remaining legume residues following grain harvest. However, the contribution of fixed-N to the soil system can be underestimated due to inadequate physical recovery of roots and unaccounted N released from living legume roots (rhizodeposition) during crop growth. This paper reports on N partitioning in pea and canola plants using 15N stable isotope methods to track N from the plant into the soil. Results illustrate the importance of accounting for below-ground N, particularly rhizodeposit N, as it accounted for more of the total N that remained in the residues compared to the above-ground residues including straw and chaff. Preliminary results also indicate different allocation of plant N between canola and pea with potential implications for N cycling between these two crops

Composted versus fresh distillers grain and solubles derived manure as nutrient source for canola

Non-Peer Reviewe

Phytoremediation of brine-affected soil with salt-tolerant plants: a screening study

Non-Peer ReviewedPhytoremediation is an attractive alternative to traditional soil remediation for brine-affected areas. Potential phytoremediation plants must possess several key characteristics including adaptation to semi-arid climate, moderate to high salt tolerance, accumulation of Na in above ground tissues and an extensive root system to obtain Na and improve soil structure. Eighteen salt-tolerant species were identified from literature and screened for sodium uptake ability in a sand culture experiment. Plants were treated with 0, 200, 400 and 600 mM NaCl and grown for 50 d. Plants were harvested and biomass analyzed for Na content. Sea blite (Suaeda calceoliformis) and salt grass (Distichlis stricta) showed promise for phytoremediation by surviving high levels of Na while developing extensive root systems. These species did not accumulate as much Na in their aboveground tissue as less tolerant plants. However, during this short screening study, cell wall integrity was maintained and a longer study would allow plants to accumulate more biomass and Na. These two species will be tested on contaminated saline sodic field soil to provide an understanding of sodium removal over the length of a Saskatchewan growing season

Nitrogen dynamics and nitrous oxide evolution in two Saskatchewan fields under irrigated and non-irrigated management

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

Temporal denitrification at the landscape scale in a Black soil

Non-Peer ReviewedLandscape scale and seasonal pattern of denitrification activity have to be incorporated in a model to estimate total N losses. A study was conducted to exam the seasonal variability of denitrification in a landscape near Blaine Lake, Saskatchewan. A 120 x 120 m sampling grid, separated by a spacing of 10 m, was established in a Black Chernozem soil. The area was surveyed, landform elements identified and from each landform element ten sampling points were further selected and sampled throughout the season for denitrification activity by the acetylene-blockage approach. Soils samples were taken seven times during the entire 1991 season before the area was prepared for seeding in the spring, following precipitation events during the growing season , and in the fall at the onset of frost. Following incubation, soil samples were analyzed for percent moisture, NH4+ and NO3-, soluble organic carbons, and total soil respiration. The distribution of denitrification activities were highly skewed and followed a distinct landscape pattern that remained consistent throughout the year. Denitrification activity increased significantly after the occurrence of a precipitation event and was further enhanced after the application of fertilizer-N, ceased toward the end of the growing season and became zero at the fall sampling. Moisture was the most dominant parameter controlling denitrification activity followed by the concentration of and NH4+ and NO3-. The highest denitrification activity occurred on the divergent and convergent footslopes, the lowest activity on the divergent shoulder and upper level landform elements, a landscape scale pattern that remained consistent throughout the year, independent of the magnitude of activity. Ambient evolution of N2O and denitrification activity followed predominantly a similar temporal and landscape scale pattern. By estimating the duration of a denitrification following a precipitation event at the various landform elements and correcting for the percentage each landform element occupies in the landscape, the total denitrification per precipitation during the early part of the season was estimated at 357 g N ha-1 cycle-1. In conclusion, results indicates that landscape scale pattern of denitrification remained constant throughout the growing season and was predominantly induced by precipitation events