The effects of the substitution of polyacrylamide for activated carbon in the sodium bicarbonate extraction of soils for available inorganic phosphorus

Non-Peer Reviewe

Broadcast and residual P versus annual seed-placed P

Non-Peer ReviewedThe yield and nutrient uptake effects of single broadcast P treatments, annual seed-placed P treatments and their combination, were studied over five years. Maximum yield was attained from a combination of moderate levels of seed-placed and broadcast P applications. Moderate broadcast treatments (40 kg P/ha) alone produced a five-year average yield which closely approached the yield from large annual seed-placed treatments ( 20 kg P/ha/year), while larger residual treatments exceeded it. The Zn concentration in plants on plots receiving 160 kg P/ha was significantly reduced and approached levels considered deficient. After the production of five wheat crops on plots which received the broadcast application of 160 kg P/ha, the distribution of the remaining fertilizer residues among various soil P fractions was: resin-P, 35 %; NaOH-P, 30-40 %; NaHCO3-P, 15 %; HCl-P, 0-5 %; H2SO4-P, 5 %; aggregate-protected P, 5 %. Half the fertilizer residues remained in plant available forms (resin-P, NaHCO3-P)

Recent work on copper and molybdenum in pastures and soils in Saskatchewan

Non-Peer Reviewe

Residual phosphate studies

Non-Peer ReviewedData on yield and P uptake by flax and wheat is presented from the first year of an eight year residual phosphate (P) study located on the Kernen Farm of the University of Saskatchewan. Comparison of seed-placed (0, 5, 10, 20, and 40 kg P ha-1) and broadcast P (0, 40, 80, 160, and 320 kg P ha-1) treatments showed that there was a yield response to both types of P fertilizer application with maximum yields being obtained in wheat by either 40 kg P ha-1 seed-placed or by broadcast P application of 80 to 160 kg P ha-1, and in flax by 5-10 kg P ha-1 side-banded or 80 kg P ha-1 broadcast. Laboratory studies related the prediction of fertilizer P response from seed-placed treatments to broadcast treatments by use of P sorption and P extraction techniques. P sorption isotherms were run on over 300 soil samples taken from the 0-15 cm layer of cultivated fields representing the majority of the cultivated soil associations in Saskatchewan. This data would suggest that rates of P broadcast should be four to eight times higher than recommended seed-placed or side-banded rates in the same Soil Zone with the same available P content

Management effects on phosphorus transformation and implications for soil test recommendations

Non-Peer ReviewedCrop rotations and fertilizer application on long-term rotation plots at Lethbridge and Breton have dramatically affected most soil phosphorus (P) fractions. At the Lethbridge site, soil cultivation has reduced organic P (Po) levels as a result of mineralization. This has caused a significant increase in resin extractable inorganic P (Pi; most biologically available), sodium bicarbonate extractable Pi (sorbed to soil surfaces), and sodium hydroxide extractable Pi (more strongly bound to Al and Fe compounds) levels. In non-fertilized treatments, continuous wheat (CW) resulted in greater P draw-down of all labile P fractions than in wheat-wheat-fallow (WWF) and wheat-fallow (WF) rotations. The addition of P fertilizer has significantly increased Resin-Pi, Bicarb-Pi and NaOH-Pi fractions. The addition of N fertilizer has resulted in increased Bicarb-Po and NaOH-Po levels in the CW, WF, and WWF rotations. At the Breton site, continuously cropped treatments, which had not received fertilizer, resulted in greater P draw-down of all P fractions except Residual-F. Addition of fertilizer had a significant effect on all P fractions (except NaOH-Po). The added Pin the fertilizer treatments positively affected the Pi fractions and the N in the fertilizer treatment positively affected the Po fractions. Bicarb-Po levels were found to be negatively· affected by soil pH. Finally, cropping without using phosphate fertilizer has resulted in a 30 to 41 % decline in Total-P in the Breton plots. A growth chamber study was conducted to compare four routine soil test P methods with plant uptake of P. Wheat and canola were each grown in eight soils from the Lethbridge and Breton plots with different pedogenic, crop rotation and fertilizer histories. Results of the study confirm that one calibration curve to predict fertilizer P requirements for a wide range of soils and crops is virtually impossible. Future soil tests will combine a chemical extractant with a computer model prediction of Po mineralization. Much more information is needed on root rhizosphere dynamics

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Phosphorus transformations and availability under cropping and fertilization assessed by isotopic exchange

International audienc