Browsing by Author "Peng, Wei"

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    Improving Nitrogen Management in Corn- Wheat-Soybean Rotations Using Site Specific Management in Eastern Virginia
    Peng, Wei (Virginia Tech, 2001-09-21)
    Nitrogen (N) is a key nutrient input to crops and one of the major pollutants to the environment from agriculture in the United States. Recent developments in site-specific management (SSM) technology have the potential to reduce both N overapplication and underapplication and increase farmers' net returns. In Virginia, due to the high variability of within-field yield-limiting factors such as soil physical properties and fertility, the adoption of SSM is hindered by high grid﷓sampling cost. Many Virginia corn-wheat-soybean farms have practiced generating yield maps using yield monitors for several years even though few variable applications based on yield maps were reported. It is unknown if the information generated by yield monitors under actual production situations can be used to direct N management for increased net returns in this area. The overall objective of the study is to analyze the economic and environmental impact of alternative management strategies for N in corn and wheat production based on site-specific information in eastern Virginia. Specifically, evaluations were made of three levels of site-specific information regarding crop N requirements combined with variable and uniform N application. The three levels of information are information about the yield potential of the predominant soil type within the field, information about yield potentials of all soils within the field (soil zones), information about yield potentials of smaller sub-field units which are aggregated into functional zones. Effects of information on expected net returns and net N (applied N that is not removed by the crop) were evaluated for corn-wheat-soybean fields in eastern Virginia. Ex post and ex ante evaluations of information were carried out. Historical weather data and farm-level yield data were used to generate yield sequences for individual fields. A Markov chain model was used to describe both temporal and spatial yield variation. Soil maps were used to divide a field into several soil management units. Cluster analysis was used to group sub﷓field units into functional zones based on yield monitor data. Yield monitor data were used to evaluate ex post information and variable application values for 1995-1999, and ex ante information and variable application values for 1999. Ex post analysis results show that soil zone information increased N input but decreased net return, while functional zone information decreased N input and increased net returns. Variable application decreased N input compared with uniform application. Variable application based on soil zone information reduced net return due to cost of overapplication or underapplication. Variable application based on functional information increased net return. Ex ante results show that information on spatial variability was not able to increase farmers?net return due to the cost of variable N application and information. Variable rate application decreases N input relative to uniform application. However, imprecision in the spatial predictor makes the variable application unprofitable due to an imbalance between costs of under- and over-application of N. Sensitivity analysis showed that value of information was positive when temporal uncertainty was eliminated. The ex post results of this study suggest there is potential to improve efficiency of N use and farmers?net returns with site specific management techniques. The ex ante results suggest that site specific management improvements should be tested under conditions faced by farmers including imperfect information about temporal and spatial yield variability.
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    miRNA-1-3p is an early embryonic male sex-determining factor in the Oriental fruit fly Bactrocera dorsalis
    Peng, Wei; Yu, Shuning; Handler, Alfred M.; Tu, Zhijian Jake; Saccone, Giuseppe; Xi, Zhiyong; Zhang, Hongyu (2020-02-18)
    Regulation of male sexual differentiation by a Y chromosome-linked male determining factor (M-factor) is one of a diverse array of sex determination mechanisms found in insects. By deep sequencing of small RNAs from Bactrocera dorsalis early embryos, we identified an autosomal-derived microRNA, miR-1-3p, that has predicted target sites in the transformer gene (Bdtra) required for female sex determination. We further demonstrate by both in vitro and in vivo tests that miR-1-3p suppresses Bdtra expression. Injection of a miR-1-3p mimic in early embryos results in 87-92% phenotypic males, whereas knockdown of miR-1-3p by an inhibitor results in 67-77% phenotypic females. Finally, CRISPR/Cas9-mediated knockout of miR-1-3p results in the expression of female-specific splice variants of Bdtra and doublesex (Bddsx), and induced sex reversal of XY individuals into phenotypic females. These results indicate that miR-1-3p is required for male sex determination in early embryogenesis in B. dorsalis as an intermediate male determiner.
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    Risk Analysis of Adopting Conservation Practices on a Representative Peanut-Cotton Farm in Virginia
    Peng, Wei (Virginia Tech, 1997-09-26)
    The objective of this study is to evaluate the costs of reducing pesticide, nitrogen, phosphorus, and sediment losses of a representative risk-neutral and risk-averse peanut-cotton farmer in Southeast Virginia. Five currently popular rotations and eight alternative conservation rotations are evaluated for the representative farm. The Erosion-Productivity Impact Calculator (EPIC) model is used to simulate pesticide, nitrogen, phosphorus, and soil loss from each rotation using actual rainfall and temperature data from the study area. A Target-MOTAD mathematical programming model, REPVAFARM, is developed and solved with GAMS. The objective of the farmer is to maximize expected net return, while meeting a target income with certain allowable expected shortfall from the income target. The farmer is also constrained by land, labor, peanut quota, and levels of pesticide, nitrogen, phosphorus, and soil losses. Major findings of this study are: reducing pesticide, nitrogen, phosphorus, and soil losses imposes costs to the farmer regardless of his risk attitude, with costs ranking from high to low in the order of reducing all pollutant losses, reducing nitrogen losses, reducing phosphorus losses, reducing soil losses, and reducing pesticide losses. Costs of reducing pollutant losses are higher for more risk-averse farmers than for less risk-averse and risk-neutral farmers implying that risk-aversion is an obstacle to the adoption of alternative conservation practices. Reducing pesticide losses has little impact on other pollutants. Reducing pesticide and nitrogen losses simultaneously achieves similar reductions in soil loss and phosphorus loss.
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    Self-compensating fiber optic flow sensor having an end of a fiber optics element and a reflective surface within a tube
    (United States Patent and Trademark Office, 2006-05-16)
    A flow rate fiber optic transducer is made self-compensating for both temperature and pressure by using preferably well-matched integral Fabry-Perot sensors symmetrically located around a cantilever-like structure. Common mode rejection signal processing of the outputs allows substantially all effects of both temperature and pressure to be compensated. Additionally, the integral sensors can individually be made insensitive to temperature.