Late-Season Nitrogen Applications Increase Soybean Yield and Seed Protein Concentration

Low seed and meal protein concentration in modern high-yielding soybean [Glycine max L. (Merr.)] cultivars is a major concern but there is limited information on effective cultural practices to address this issue. In the objective of dealing with this problem, this study conducted field experiments in 2019 and 2020 to evaluate the response of seed and meal protein concentrations to the interactive effects of late-season inputs [control, a liquid Bradyrhizobium japonicum inoculation at R3, and 202 kg ha−1 nitrogen (N) fertilizer applied after R5], previous cover crop (fallow or cereal cover crop with residue removed), and short- and full-season maturity group cultivars at three U.S. locations (Fayetteville, Arkansas; Lexington, Kentucky; and St. Paul, Minnesota). The results showed that cover crops had a negative effect on yield in two out of six site-years and decreased seed protein concentration by 8.2 mg g−1 on average in Minnesota. Inoculant applications at R3 did not affect seed protein concentration or yield. The applications of N fertilizer after R5 increased seed protein concentration by 6 to 15 mg g−1, and increased yield in Arkansas by 13% and in Minnesota by 11% relative to the unfertilized control. This study showed that late-season N applications can be an effective cultural practice to increase soybean meal protein concentration in modern high-yielding cultivars above the minimum threshold required by the industry. New research is necessary to investigate sustainable management practices that increase N availability to soybeans late in the season

The Effects of Brassica Cover Crops on Weed Dynamics

Concerns about the health and environmental impacts of herbicide use have led farmers and researchers to seek alternative methods of weed management. One such alternative is the use of allelopathic cover crops, which release chemicals into the soil environment that can contribute to weed management through suppression of weed seed germination, seedling emergence and establishment, and seedling growth, in addition to providing other soil quality benefits to farmers. Brassicas, or members of the Brassicaceae, contain glucosinolates, sulfur-containing molecules that degrade to form compounds toxic to a variety of organisms. Glucosinolate content varies between brassicas grown as cover crops; mustards typically have very high glucosinolate content, whereas others, including canola and rapeseed, contain lower amounts. Brassica residues have strong phytotoxic effects; weed density and biomass has been observed to be lower in crops following incorporation of brassica residue. In addition to a literature review, this thesis describes two experiments that investigated the mechanisms behind this observed weed suppression by brassicas. The first experiment examined seedling establishment following incorporation of brassica residues and residues of other short-season cover crops. We hypothesized that all cover crop residues would decrease and delay seedling emergence compared to fallow and that emergence following the brassica residues would be lowest and slowest, particularly following the high-glucosinolate mustard. Based on the theory that smaller seeds are more susceptible to stress such as those imposed by allelopathic cover crops, we expected that smaller-seeded species would be affected more than larger-seeded ones. While average emergence was indeed lower following all of the cover crop residues compared to fallow, emergence was similar following the brassicas and following the other cover crop residues. Seed size was a poor predictor of species emergence following the cover crops. While emergence was slower following all the cover crop residues, emergence rates were generally similar between the brassicas and the other cover crops, although delayed emergence following mustard was observed in one year. The second experiment examined the effects of mustard and canola on the growth of established redroot pigweed and green bean plants and, in turn, on interspecific competition. Redroot pigweed and green bean, both alone and in mixture, were seeded into incorporated mustard and canola residues and fallow plots; plants were sampled throughout the season to assess the effects of the cover crop residues on growth. We hypothesized that growth of the smaller-seeded redroot pigweed would be harmed by the brassica residues, particularly early in the season, but that growth of the larger-seeded green bean would not be affected. In turn, we expected that the brassica residues would mediate interspecific competition, through differential effects on growth, thereby conferring a competitive edge to green bean plants growing with redroot pigweed. As expected, brassica cover crop residues did not affect green bean height, biomass, leaf area, relative growth rate, or final marketable yield. Contrary to expectations, these parameters for redroot pigweed were also unaffected. While the presence of competition reduced growth of both species, no interaction with cover crop residue was found

Comparison of virus concentration methods for the RT-qPCR-based recovery of murine hepatitis virus, a surrogate for SARS-CoV-2 from untreated wastewater

There is currently a clear benefit for many countries to utilize wastewater-based epidemiology (WBE) as part of ongoing measures to manage the coronavirus disease 2019 (COVID-19) global pandemic. Since most wastewater virus concentration methods were developed and validated for nonenveloped viruses, it is imperative to determine the efficiency of the most commonly used methods for the enveloped severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Municipal wastewater seeded with a human coronavirus (CoV) surrogate, murine hepatitis virus (MHV), was used to test the efficiency of seven wastewater virus concentration methods: (A–C) adsorption-extraction with three different pre-treatment options, (D–E) centrifugal filter device methods with two different devices, (F) polyethylene glycol (PEG 8000) precipitation, and (G) ultracentrifugation. MHV was quantified by reverse-transcription quantitative polymerase chain reaction and the recovery efficiency was calculated for each method. The mean MHV recoveries ranged from 26.7 to 65.7%. The most efficient methods were adsorption-extraction methods with MgCl2 pre-treatment (Method C), and without pre-treatment (Method B). The third most efficient method used the Amicon® Ultra-15 centrifugal filter device (Method D) and its recovery efficiency was not statistically different from the most efficient methods. The methods with the worst recovery efficiency included the adsorption-extraction method with acidification (A), followed by PEG precipitation (F). Our results suggest that absorption-extraction methods with minimal or without pre-treatment can provide suitably rapid, cost-effective and relatively straightforward recovery of enveloped viruses in wastewater. The MHV is a promising process control for SARS-CoV-2 surveillance and can be used as a quality control measure to support community-level epidemic mitigation and risk assessment