Soybean nitrogen dynamics: Nitrogen fixation, yield, and residue decomposition

Nitrogen (N) a crucial element for plant growth, often limits net primary productivity of agroecosystems. In agricultural systems it is vital to have proper management of N to secure productivity and environmental sustainability. Soybean [Glycine max (L.) Merr.] is the second most important crop in the US Corn Belt, and it can fix part of its N through biological N fixation. The overarching goal of this research was to investigate soybean N fixation dynamics in response to environmental factors, and plant tissue decomposition to understand better N cycling and improve Midwestern US N budget estimations. A long-term incubation study was conducted by using aboveground plant litter of soybean along with three other plants (maize, oats, and alfalfa), to investigate the effect of different litter amendments on mineral associated organic matter (MAOM) accumulation and stabilization. Soils amended with soybean and maize litter had more stable MAOM-N, with greater efficiency of accumulation compared to oats and alfalfa litter amendments. In my second study, I used two soybean fields to estimate N-fixation dynamics by using two methodologies (15N isotope dilution method, and isolines), and measured crop growth, soil inorganic N and weather dynamics throughout the season. On average soybean grown in Iowa fixed from 23 to 65% of total aboveground N reaching a maximum rate of 3 kg ha-1 d-1 during early seed fill period. Finally, I conducted a field experiment to test the effect of supplemental N fertilization addition to soybean at three different rates and three application timings. The experiment showed inconsistent results among years and methodologies used to determine yields, but provided evidence that high yielding soybean crops will respond to N fertilizer. Therefore, it is suggested to improve the methodologies in the near future for advanced soybean research. Overall findings from this dissertation provide novel information about soybean physiological and biological processes as a result of soil-plant-atmosphere interactions. Our results indicate that in order to boost soybean yields, there is a need to use a systematic approach that focuses on plant-environment interactions to increase available N supply either from litter mineralization, N fixation, or additional N fertilizer

On 2-group global symmetries and their anomalies

In general quantum field theories (QFTs), ordinary (0-form) global symmetries and 1-form symmetries can combine into 2-group global symmetries. We describe this phenomenon in detail using the language of symmetry defects. We exhibit a simple procedure to determine the (possible) 2-group global symmetry of a given QFT, and provide a classification of the related \u2019t Hooft anomalies (for symmetries not acting on spacetime). We also describe how QFTs can be coupled to extrinsic backgrounds for symmetry groups that differ from the intrinsic symmetry acting faithfully on the theory. Finally, we provide a variety of examples, ranging from TQFTs (gapped systems) to gapless QFTs. Along the way, we stress that the \u201cobstruction to symmetry fractionalization\u201d discussed in some condensed matter literature is really an instance of 2-group global symmetry

Enhancing Biodiversity and Multifunctionality of an Organic Farmscape in California’s Central Valley

Organic farmers in the USA increasingly manage the margins of previously monocultured farmed landscapes to increase biodiversity, e.g. they restore and protect riparian corridors, plant hedgerows and construct vegetated tailwater ponds. This study attempts to link habitat enhancements, biodiversity and changes in ecosystem functions by: 1. inventorying the existing biodiversity and the associated belowground community structure and composition in the various habitats of an organic farm in California’s Central Valley; and 2. monitoring key ecosystem functions of these habitats. Two years of inventories show greater native plant diversity in non-cropped areas. While nematode diversity did not differ between habitats, functional groups were clearly associated with particular habitats as were soil microbial communities (phospholipid fatty acid analysis). Earthworm diversity did not differ between habitats, but biomass was higher in non-cropped areas. Habitats with woody vegetation stored 20% of the farmscape’s total carbon (C), despite their relatively small size (only 5% of the total farm). Two years of monitoring data of farmscape C and nitrogen (N) through emissions, run-off and leaching showed distinct tradeoffs in function associated with each habitat. Clearly habitat restoration in field margins will increase both landscape biodiversity and the multifunctionality of the farmscape as a whole

A propeller flap for single-stage nose reconstruction in selected patients: supratrochlear artery axial propeller flap

The paramedian forehead flap is the gold standard technique for nose reconstruction. It requires two different surgical operations which prolonged the postoperative dressing and care. We present our 5-year experience with a propeller flap based on the supratrochlear artery, which allows one-stage transfer of the forehead skin to the nose without the need for pedicle division. This technique is indicated in a selected group of patients who are not suitable for multiple-stage reconstructions because they have concurrent medical conditions, reduced mobility, or live far away from specialized medical centers. We have renamed this procedure as supratrochlear artery axial propeller flap, from the acronym STAAP flap, to stress the axial, well known and constant, vascularization of the flap. In the past 5 years, we have been performing 25 STAAP flaps; full-thickness nasal reconstruction was performed in 11 cases. The patients were 16 males and 9 females, with a mean age of 79.5 years. All patients had multiple comorbidities. Complete flap survival was observed in 23 cases and healing was complete in 7 days. In two cases, there was a partial distal necrosis of the flap treated conservatively. Cosmetic results were good and the patient's satisfaction was significant. These results indicate that the STAAP flap is a reliable and useful technique in selected cases, as old or noncompliant patients who benefit from a one-stage technique of nose reconstructio