Economic assessment of weed management strategies in rice is dependent upon a quantitative estimate of the yield impact of a given weed population. To assist rice producers in making such assessments, a mathematical model was developed to predict rice yield reduction as a function of weed density and duration of interference. The nonlinear empirical model was a unique 3-dimensional adaptation of the Richards equation with 4 parameters. Using published data, individual parameter values were fitted for each of 6 weed species interfering with either conventional or semi-dwarf statured rice cultivars. The functional form of the equation produced surfaces that were qualitatively consistent with available data and experience regarding rice-weed biology. Hence, predictions from the model should be useful and reliable in assessing the economic impact of weeds and in determining the feasibility of alternative weed control treatments for various field scenarios.
Core Ideas Nutrient concentrations are low at Big Creek relative to expected biological‐response thresholds. Nutrient concentrations at Big Creek are typical of streams draining watersheds with similar land use. Flow‐adjusted nutrient concentrations at Big Creek have not increased over the short‐term. Nutrient concentrations in streams increase as watershed land area in pasture and urban uses increases. Nutrient concentrations in several streams of the Boston and Ozark Mountains region of Arkansas, including the Buffalo National River and its tributaries, have garnered tremendous interest. In particular, Big Creek has been the center of attention within the Buffalo River watershed because of a permitted concentrated animal feeding operation (CAFO). The objectives of this paper were to put nutrient concentrations of Big Creek into the context of the stream nutrient and watershed land‐use relationship and develop a framework to evaluate regional land‐use impacts on regional water quality. Nutrient concentrations in streams draining the Boston and Ozark Mountains region were related to the intensity of watershed land use. Concentrations in Big Creek were similar to other watersheds in the ecoregion with similar land use, suggesting limited impact of the CAFO on Big Creek at the present time. However, this does not preclude future impacts, and longer‐term monitoring continues.
The coronavirus disease 2019 pandemic has turned into a global healthcare challenge, causing significant morbidity and mortality. Healthcare workers (HCWs) who are on the frontline of the COVID-19 outbreak response face an increased risk of contracting the disease. Some common challenges encountered by HCWs include exposure to the pathogen, psychological distress, and long working hours. In addition, HCWs may be more prone to develop mental health issues such as anxiety, depression, suicidal thoughts, post-traumatic stress disorder (PTSD), sleep disorders, and drug addictions compared to the general population. These issues arise from increased job stress, fear of spreading the disease to loved ones, and potential discrimination or stigma associated with the disease. This study aims to review the current literature to explore the effects of COVID-19 on healthcare providers' physical and mental well-being and suggest interventional strategies to combat these issues. To that end, we performed a literature search on Google Scholar and PubMed databases using combinations of the following keywords
Phosphorus distribution in pasture soils underlain with karst geology was determined on a 0.10-ha grid in 2014, 2016, and 2018. Two fields (Fields 1 and 12) received swine slurry from a concentrated animal feeding operation, whereas another (Field 5) received mineral fertilizer. All fields were grazed by cattle and periodically hayed. Mean Mehlich-3 extractable P in the top 10 cm increased (p ≤ .05 level) for Fields 1 (59-91 mg kg −1) and 12 (63-122 mg kg −1) between 2014 and 2018, with little change for Field 5 (45-47 mg kg −1). Over the 5-yr monitoring period, P and N runoff averaged a respective 1.0 and 2.4 kg ha −1 yr −1 from Fields 1 and 12 or 1.4 and 2.5% of P and N applied in swine slurry. Field 5 P and N runoff averaged a respective 1.9 and 2.8 kg ha −1 yr −1 or 6.6 and 4.4% of that applied as mineral fertilizer. Findings confirmed that long-term application of P, as fertilizer or manure, in excess of pasture uptake, result in a rapid accumulation of P near the soil surface, and thus, increase nutrient loss via surface runoff. Mehlich-3 P increased in the top 10 cm of soil (143-255 mg kg −1) in edge-of-field buffer zones of 30 m on Fields 1 and 12, where no manure was applied. This illustrates the complexity of cattle grazing areas as additional nutrient sources that must be managed to minimize off-site nutrient transport that are particularly important in karst watersheds. 1 INTRODUCTION An increase in the concentration of P at the surface of pasture soils that receive P as mineral fertilizer or manure in amounts exceeding plant uptake has been widely Abbreviations: AFO, animal feeding operation; CAFO, concentrated animal feeding operation; CNMP, comprehensive nutrient management plan; ICAP-AES, inductively coupled plasma-atomic emissions spectrometer; M3P, Mehlich-3 extractable soil phosphorus; NMP, nutrient management plan. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
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