University of Minnesota, Waseca

BACKGROUND AND METHODS: The Program on the Surgical Control of the Hyperlipidemias (POSCH), a randomized clinical trial, was designed to test whether cholesterol lowering induced by the partial ileal bypass operation would favorably affect overall mortality or mortality due to coronary heart disease. The study population consisted of 838 patients (417 in the control group and 421 in the surgery group), both men (90.7 percent) and women, with an average age of 51 years, who had survived a first myocardial infarction. The mean follow-up period was 9.7 years. RESULTS: When compared with the control group at five years, the surgery group had a total plasma cholesterol level 23.3 percent lower (4.71 +/- 0.91 vs. 6.14 +/- 0.89 mmol per liter [mean +/- SD]; P less than 0.0001), a low-density lipoprotein cholesterol level 37.7 percent lower (2.68 +/- 0.78 vs. 4.30 +/- 0.89 mmol per liter; P less than 0.0001), and a high-density lipoprotein cholesterol level 4.3 percent higher (1.08 +/- 0.26 vs. 1.04 +/- 0.25 mmol per liter; P = 0.02). Overall mortality and mortality due to coronary heart disease were reduced, but not significantly so (deaths overall [control vs. surgery], 62 vs. 49, P = 0.164; deaths due to coronary disease, 44 vs. 32, P = 0.113). The overall mortality in the surgery subgroup with an ejection fraction greater than or equal to 50 percent was 36 percent lower (control vs. surgery, 39 vs. 24; P = 0.021). The value for two end points combined--death due to coronary heart disease and confirmed nonfatal myocardial infarction--was 35 percent lower in the surgery group (125 vs. 82 events; P less than 0.001). During follow-up, 137 control-group and 52 surgery-group patients underwent coronary-artery bypass grafting (P less than 0.0001). A comparison of base-line coronary arteriograms with those obtained at 3, 5, 7, and 10 years consistently showed less disease progression in the surgery group (P less than 0.001). The most common side effect of partial ileal bypass was diarrhea; others included occasional kidney stones, gallstones, and intestinal obstruction. CONCLUSIONS: Partial ileal bypass produces sustained improvement in the blood lipid patterns of patients who have had a myocardial infarction and reduces their subsequent morbidity due to coronary heart disease. The role of this procedure in the management of hypercholesterolemia remains to be determined. These results provide strong evidence supporting the beneficial effects of lipid modification in the reduction of atherosclerosis progression.

Antibiotics are commonly added to animal feed as supplements to promote growth of food animals. However, absorption of antibiotics in the animal gut is not complete and as a result substantial amounts of antibiotics are excreted in urine and feces that end up in manure. Manure is used worldwide not only as a source of plant nutrients but also as a source of organic matter to improve soil quality especially in organic and sustainable agriculture. Greenhouse studies were conducted to determine whether or not plants grown in manure-applied soil absorb antibiotics present in manure. The test crops were corn (Zea mays L.), green onion (Allium cepa L.), and cabbage (Brassica oleracea L. Capitata group). All three crops absorbed chlortetracycline but not tylosin. The concentrations of chlortetracycline in plant tissues were small (2-17 ng g(-1) fresh weight), but these concentrations increased with increasing amount of antibiotics present in the manure. This study points out the potential human health risks associated with consumption of fresh vegetables grown in soil amended with antibiotic laden manures. The risks may be higher for people who are allergic to antibiotics and there is also the possibility of enhanced antimicrobial resistance as a result of human consumption of these vegetables.

Diversifying cropping systems improves environmental health and has the potential to reduce risk from climate-change-related threats, but empirical evidence remains sparse. In this study, we found that maize yields were higher during adverse weather, including droughts, when maize was grown as part of a more diverse rotation. Rotation diversification also increased maize yields over time and under better growing conditions. Policies that support more diversified cropping systems could help reduce risk from increasingly stressful weather.

Subsurface tile drainage from row-crop agricultural production systems has been identified as a major source of nitrate entering surface waters in the Mississippi River basin. Noncontrollable factors such as precipitation and mineralization of soil organic matter have a tremendous effect on drainage losses, nitrate concentrations, and nitrate loadings in subsurface drainage water. Cropping system and nutrient management inputs are controllable factors that have a varying influence on nitrate losses. Row crops leak substantially greater amounts of nitrate compared with perennial crops; however, satisfactory economic return with many perennials is an obstacle at present. Improving N management by applying the correct rate of N at the optimum time and giving proper credits to previous legume crops and animal manure applications will also lead to reduced nitrate losses. Nitrate losses have been shown to be minimally affected by tillage systems compared with N management practices. Scientists and policymakers must understand these factors as they develop educational materials and environmental guidelines for reducing nitrate losses to surface waters.

Of the 20 amino acids, the precise function of methionine (Met) remains among the least well understood. To establish a determining characteristic of methionine that fundamentally differentiates it from purely hydrophobic residues, we have used in vitro cellular experiments, molecular simulations, quantum calculations, and a bioinformatics screen of the Protein Data Bank. We show that approximately one-third of all known protein structures contain an energetically stabilizing Met-aromatic motif and, remarkably, that greater than 10,000 structures contain this motif more than 10 times. Critically, we show that as compared with a purely hydrophobic interaction, the Met-aromatic motif yields an additional stabilization of 1-1.5 kcal/mol. To highlight its importance and to dissect the energetic underpinnings of this motif, we have studied two clinically relevant TNF ligand-receptor complexes, namely TRAIL-DR5 and LTα-TNFR1. In both cases, we show that the motif is necessary for high affinity ligand binding as well as function. Additionally, we highlight previously overlooked instances of the motif in several disease-related Met mutations. Our results strongly suggest that the Met-aromatic motif should be exploited in the rational design of therapeutics targeting a range of proteins.

Despite the use of best management practices for nitrogen (N) application rate and timing, significant losses of nitrate nitrogen (NO3(-)-N) in drainage discharge continue to occur from row crop cropping systems. Our objective was to determine whether a autumn-seeded winter rye (Secale cereale L.) cover crop following corn (Zea mays L.) would reduce NO3(-)-N losses through subsurface tile drainage in a corn-soybean [Glycine mar (L.) Merr.] cropping system in the northern Corn Belt (USA) in a moderately well-drained soil. Both phases of the corn-soybean rotation, with and without the winter rye cover crop following corn, were established in 1998 in a Normania clay loam (fine-loamy, mixed, mesic Aquic Haplustoll) soil at Lamberton, MN. Cover cropping did not affect subsequent soybean yield, but reduced drainage discharge, flow-weighted mean nitrate concentration (FWMNC), and NO3(-)-N loss relative to winter fallow, although the magnitude of the effect varied considerably with annual precipitation. Three-year average drainage discharge was lower with a winter rye cover crop than without (p = 0.06). Over three years, subsurface tile-drainage discharge was reduced 11% and NO3(-)-N loss was reduced 13% for a corn-soybean cropping system with a rye cover crop following corn than with no rye cover crop. We estimate that establishment of a winter rye cover crop after corn will be successful in one of four years in southwestern Minnesota. Cover cropping with rye has the potential to be an effective management tool for reducing NO3(-)-N loss from subsurface drainage discharge despite challenges to establishment and spring growth in the north-central USA.

ABSTRACT Acquiring argumentative reading and writing practices reflects a key component of recent curricular reforms in schools and universities throughout the United States and the world as well as a major challenge to teachers of reading and writing in K‐12 and college writing classrooms. In this review, we consider the contributions of two research perspectives, cognitive and social, that researchers have employed in the study of the teaching and learning of argumentative reading and writing. We address two basic questions: How do these perspectives with their own disciplinary frameworks and logics of inquiry interactively inform how researchers study argumentative reading and writing, and consequently, how have these orientations informed pedagogical knowledge that may support teachers' understanding of what argumentation is and how it may be taken up in the educational contexts? We analyze relevant conceptual and empirical studies by considering assumptions underlying the cognitive and social disciplinary perspectives, especially in terms of the warrants that those perspectives assume. We also interrogate how these perspectives' logics of inquiry reveal assumptions about the transfer of learning as supported by instruction and other practices, such as classroom discussion, computer‐supported collaborations, and other forms of instructional support. Using empirical studies of the teaching and learning of argumentative reading and writing conducted in grades K‐12 and college writing classrooms, we delineate the assumptions that drive the two perspectives and their instructional consequences, arguing that researchers and teachers need an understanding of their assumptions about knowledge and transfer in order to establish a clear and coherent relationship between theory and practice. We offer a vision for research that integrates the cognitive and social perspectives to argue that the work of literacy research is to reveal cognitive processes and instructional practices that teachers can promote and students can employ for learning how to do argumentative reading and writing. إن الحصول على ممارسات قراءة وكتابة جدلية يعكس عنصرا رئيسيا للإصلاحات الأخيرة في المناهج الدراسية في المدارس والجامعات في جميع أنحاء الولايات المتحدة الأمريكية والعالم، وكذلك تحديا كبيرا لمعلمي القراءة والكتابة في الفصول الأخيرة من المدرسة الثانوية وفصول الكتابة في الجامعة. في هذه الدراسة، ندرس مساهمات منظوريْن لأبحاث معرفية واجتماعية استخدمها الباحثون في دراسة تعليم وتعلم القراءة والكتابة الجدلية. علينا بمعالجة مسألتين أساسيتين: كيف يخبرنا هاذين المنظورين مع أطرهما التأييدية الخاصة بهما، ومنطق البحث بصورة متفاعلة كيف يدرس الباحثون القراءة والكتابة الجدلية، وبناء على ذلك، كيف عرّفتنا هذه التوجهات بالمعرفة التربوية التي بوسعها أن تدعم فهم المعلمين عن الجدلية وعن كيفية تبنيها في السياقات التعليمية؟ نحلل الدراسات المفاهيمية والتجريبية ذات الصلة بالموضوع، وذلك بدراسة الفرضيات التي تقوم عليها المنظورات التأييدية الاجتماعية والمعرفية، ولاسيما من حيث الضمانات التي تفترضها تلك المنظورات. ونتساءل كذلك كيف يكشف منطق بحث المنظورات عن الفرضيات بشأن انتقال التعلم عندما يكون مدعما بالتعليم وممارسات أخرى مثل المناقشات في الفصول الدراسية وأوجه التعاون المدعومة بالحاسوب وأشكال أخرى من الدعم التعليمي. بعدما استخدمنا الأبحاث التجريبية لتعليم وتعلم القراءة والكتابة الجدلية التي تجرى في الصفوف الأخيرة من المدرسة الثانوية وفصول الكتابة في الجامعة، استطعنا وصف وتحديد الفرضيات التي تدفع المنظوريْن ونتائجهما التعليمية، محاولين أن نبرهن أن الباحثين والمعلمين يحتاجون إلى فهم هذه الفرضيات بشأن المعرفة والانتقال من أجل إقامة علاقة واضحة ومتجانسة بين النظرية والتطبيق. نقدم رؤيا لبحث يدمج المنظوريْن المعرفي والاجتماعي لنبرهن أن وظيفة أبحاث القراءة والكتابة هو كشف العمليات المعرفية والممارسات التعليمية التي يمكن أن يعززها المعلمون ويوظفها التلاميذ من أجل تعلم كيفية القيام بالقراءة والكتابة الجدلية. 培养议论文读写能力的教学实践，是近今在美国及世界各地学校及大学课程改革的一个关键组成部分，也是从幼儿园、小学到中学的阅读与写作教师，以至大学的写作教室中所面对的一项重大挑战。在本文献回顾中，作者考虑研究人员从认知与社会这两个角度研究议论文读写教学的贡献。作者讨论两个基本问题：（1）这两个角度与研究人员自己的学科框架及探究逻辑，如何以交互方式影响研究人员对研究读写议论文所采用的方法？（2）这些方向因此如何影响给予教师的教育知识内容，以帮助教师理解什么是议论文及在教学环境中怎样学习议论文？作者分析相关的概念及实证研究时，考虑到认知及社会学科观点的基本假设，特别是支持这些观点的根据。作者亦调查这两个观点的探究逻辑，如何揭示学习转移的假设，如何利用教学和其他教学实践例如课堂讨论、电脑支援的协作及其他形式的教学支援来促进学习转移。作者使用幼儿园、小学、中学的议论文读写教学及大学写作教室的实证研究，藉以说明推动这两个观点的假设及其教学后果，并建议为了建立明确和一致的理论与实践关系，研究人员及教师需要了解他们对知识和转移所持的假设。作者更提供一个结合认知及社会观点的研究设想，论证读写文化研究工作是要揭示认知过程及教学实践，让教师可以用以促进议论文读写教学，学生可以用以学习如何阅读和写作议论文。 L'acquisition de pratiques argumentatives en lecture et en écriture est le reflet d'une composante clé des récentes réformes des programmes dans les écoles et les universités d'un bout à l'autre des Etats‐Unis et dans le monde, ainsi qu'un défi majeur pour ceux qui enseignent la lecture et l'écriture du jardin d'enfants au lycée et dans les classes d'écriture de premier cycle à l'université. Dans cette revue de question, nous examinons les apports des deux perspectives de recherche, cognitive et sociale, que les chercheurs ont utilisées pour étudier l'enseignement et l'apprentissage de l'argumentation en lecture et en écriture. Nous nous intéressons à deux questions de base: Comment ces perspectives avec leurs spécificités de structures disciplinaires et de logique d'enquête indiquent interactivement comment les chercheurs étudient le discours argumentatif et, par voie de conséquence, comment ces orientations ont informé les connaissances pédagogiques qui peuvent sous‐tendre la compréhension qu'ont les enseignants de la compréhension et comment elle peut être appréhendée dans les contextes pédagogiques. Nous avons analysé les études théoriques et empiriques pertinentes en considérant les présupposés sous‐jacents aux perspectives disciplinaires cognitive et sociale, en particulier en termes de garanties assumées par ces perspectives. Nous avons aussi interrogé comment les logiques d'enquête de ces disciplines révílent des présupposés en ce qui concerne le transfert d'apprentissage que suppose l'enseignement, et d'autres pratiques comme les discussions en classe, le travail en coopération avec l'aide d'un ordinateur, et d'autres formes d'apport pédagogique. En utilisant des études empiriques de l'enseignement et de l'apprentissage de l'argumentation en lecture et en écriture dans les classes du jardin d'enfants au lycée et les classes d'écriture du premier cycle universitaire, nous avons circonscrit les présupposés qui pilotent les deux perspectives et leurs conséquences pédagogiques, et soutenu que les chercheurs et les enseignants ont besoin de comprendre leurs présupposés au sujet des connaissances et du transfert de façon à établir une relation claire et cohérente entre théorie et pratique. Nous présentons une conception de la recherche qui intígre les perspectives cognitive et sociale et soutenons que le travail de recherche en littératie est de mettre en évidence les processus cognitifs et les pratiques pédagogiques que les enseignants peuvent promouvoir et que les élíves peuvent employer pour apprendre comment lire et écrire de façon argumentée. Недавние реформы учебных планов в школах и университетах США и других стран мира были связаны с введением аргументированного чтения и письма. Однако подобная практика по‐прежнему вызывает сложности у преподавателей в старшей школе и колледжах. В данном обзоре рассматриваются два подхода – когнитивный и социальный – к исследованию чтения и письма. Первый вопрос: как эти подходы с присущими им дисциплинарными рамками и логикой исследовательского поиска интерактивно информируют о том, как происходит освоение аргументированного чтения и письма? Второй вопрос производный от первого: как эти подходы формируют знание учителей о том, что такое аргументация и как она может использоваться в образовательном контексте? В статье анализируются значимые концептуальные и эмпирические исследования, лежащие в основе когнитивного и социального подходов к изучению различных дисциплин, особенно в плане их потенциальных возможностей. Мы также рассматриваем, каким образом поисковая логика каждого из этих подходов обнажает различные представления об обучении как о различных формах сотрудничества учеников и поддерживающего их педагога, а именно: прямая передача знаний на уроке, учебная дискуссия, общение через компьютер и т.д. Используя эмпирическое исследование процессов обучения чтению и письму в старших классах и колледже, авторы рассматривают внутренние посылки обоих подходов и их возможные академические последствия и доказывают, что и исследователям и преподавателям необходимо определиться с собственными установками о знании и способах его передачи, чтобы установить ясные и последовательные отношения между теорией и практикой. Авторы предлагают объединить познавательный и социальный подходы к исследованию грамотности и утверждают, что цель подобных исследований состоит в сочетании осознанных когнитивных процессов с учебными методами, которые могут использовать преподаватели и учащиеся для аргументированного чтения и письма. Adquirir prácticas argumentativas en la lectura y la escritura refleja un componente importante de las recientes reformas hechas en escuelas y universidades en los Estados Unidos y el mundo además de un reto importante para los maestros de lectura y escritura en ambos centros docentes. En esta evaluación veremos las contribuciones de dos perspectivas de investigación, cognitivo y social, que han sido usadas por los investigadores al estudiar la enseñanza y el aprendizaje de la lectura y la escritura argumentativa. Nos enfocamos en dos preguntas básicas: Qué información se saca de cada una de estas perspectivas con sus propios marcos disciplinarios y lógica de cuestionar sobre como los investigadores estudian la lectura y la escritura argumentativa, y, de ahí, cómo estas orientaciones informan el conocimiento pedagógico que podría apoyar lo que los maestros entienden por argumentación y cómo se podría presentar la argumentación en un contexto docente. Analizamos estudios concept

The intestinal homeostasis is an orchestrated dynamic equilibrium state composed of the coexistence and interactions among the nutrients, microbial flora, and immune system. The intestinal balance disorder can trigger a series of diseases, such as inflammatory bowel disease (IBD). Many of tryptophan (Trp) metabolites, such as kynurenine and indole, generated under a series of endogenous enzymes or microbial metabolism, have been reported enable to bind and activate the aryl hydrocarbon receptor (AhR), this series of process is termed the Trp-AhR pathway. The activated Trp-AhR pathway can induce the expression of downstream cytokines such as interleukin-22 (IL-22) and interleukin-17 (IL-17), thereby regulating the intestinal homeostasis. This review highlights the advance of Trp-AhR pathway in the regulation of intestinal homeostasis and provides some insights for the clinical strategies that expect to effectively prevent and treat gut diseases via intervening the Trp-AhR pathway.

Four experiment stations (IL, KS, MN, and MO) conducted experiments to determine effects of introducing a CIDR (controlled internal device release) into an ovulation control program for postpartum suckled beef cows. Five hundred sixty cows were assigned randomly to two treatments: 1) 100 microg of GnRH (i.m.) followed in 7 d with 25 mg of PGF2alpha, followed in 48 h by a second injection of GnRH and one fixed-time insemination (Cosynch; n = 287) or 2) Cosynch plus one CIDR during the 7 d between the first injection of GnRH and PGF2alpha (Cosynch+P; n = 273). Cows at three stations were inseminated at the time of the second GnRH injection (n = 462), whereas 98 cows at the fourth station were inseminated 16 to 18 h after that injection. Blood samples were collected at d -17, -7, 0, and 2 relative to PGF2alpha to determine concentrations of progesterone. Ultrasonography was used to monitor follicle diameter on d 2 and to determine the presence of an embryo at 30 to 35 d after insemination. Pregnancy rates were greater (P < 0.05) for Cosynch+P- (58%) than for Cosynch-treated (48%) cows. No station x treatment interaction occurred; however, cows at MO (62%) and KS (60%) had greater (P < 0.05) pregnancy rates than those at IL (47%) and MN (44%). Cows that had follicles > 12 mm on d 2 had greater (P < 0.01) pregnancy rates than those with follicles < or = 12 mm regardless of treatment. Pregnancy rates were similar between Cosynch and Cosynch+P treatments when cycling cows had elevated concentrations of progesterone at d 0, but pregnancy rates were greater (P < 0.05) in the Cosynch+P (79%) than in the Cosynch (43%) treatment when cycling cows had low concentrations of progesterone on d 0 (at PGF2alpha injection). Similarly, among noncycling cows, pregnancy rates were greater (P < 0.05) in the Cosynch+P (59%) treatment than in the Cosynch (39%) treatment. Cows in greater body condition at the onset of the breeding season experienced improved (P < 0.001) overall pregnancy rates. Pregnancy rates for cows that calved > 50 d before the onset of the breeding season were greater (P < 0.01) than those for cows that calved < or = 50 d. Thus, treatment of suckled cows with Cosynch yielded acceptable pregnancy rates, but addition of a CIDR improved pregnancy rates in noncycling cows. Body condition and days postpartum at initiation of the breeding season affected overall efficacy of the Cosynch and Cosynch+P protocols.

This study investigated the prevalence and correlates of personal growth and distress following romantic relationship breakups. Causal attributions for why the relationship declined and ended, personality factors, gender, and initiator status were examined as correlates of growth and distress in 92 undergraduates who had experienced a recent romantic relationship breakup. In regard to the prevalence of growth, respondents reported, on average, five types of personal growth they thought might improve their future romantic relationships. Correlates of self–reported growth included causal attributions to environmental factors and the personality factor of Agreeableness. Women reported more growth than did men. Factors related to higher levels of distress included causal attributions to the ex–partner and to environmental factors surrounding the previous relationship. The importance of assessing growth following relationship breakups and of accounting for the environmental context of close relationships is discussed.

Abstract There are numerous reports of the beneficial effects of rotating corn ( Zea mays L.) and soybean [ Glycine max (L.) Merr.]. However, few studies have been specifically designed to document the important corn‐soybean rotation effect. The objective of this study was to determine the impact of various corn and soybean cropping patterns on the yield of both crops. The 9‐year field study conducted at two locations was managed for maximum production. Cropping sequences consisted of: continuous monoculture with the same cultivar; continuous monoculture with cultivars alternated; annual rotation of the two crops; and 1, 2, 3, 4, and 5 yr of monoculture following 5 yr of the other crop. Annually rotated corn yielded 10% better, and first‐year corn yielded 15% better than corn under monoculture. Annually rotated soybean yielded 8% better, and first year soybean yielded 17% better than soybean under monoculture. With monoculture of either crop, alternating two different cultivars annually resulted in the same yield as continuous cropping of just one cultivar. There were differences in the response of the two crops to increasing years of monoculture: the lowest corn yield was from second year corn; the lowest soybean yield was from extended monoculture. Total corn dry weight was affected by cropping sequence but soybean dry weight was not. Our data suggest that, from a yield standpoint, a superior cropping sequence for Minnesota would include at least three, and possibly more crops.

Soil organic carbon (SOC) is closely tied to soil health. However, additional biological indicators may also provide insight about C dynamics and microbial activity. We used SOC and the other C indicators (potential C mineralization, permanganate oxidizable C, water extractable organic C, and β-glucosidase enzyme activity) from the North American Project to Evaluate Soil Health Measurements to examine the continental-scale drivers of these indicators, the relationships among indicators, and the effects of soil health practices on indicator values. All indicators had greater values at cooler temperatures, and most were greater with increased precipitation and clay content. The indicators were strongly correlated with each other at the site-level, with the strongest relationship between SOC and permanganate oxidizable C. The indicator values responded positively to decreased tillage, inclusion of cover crops, application of organic nutrients, and retention of crop residue, but not the number of harvested crops in a rotation. The effect of decreased tillage on the C indicators was generally greater at sites with higher precipitation. The magnitude and direction of the response to soil health practices was consistent across indicators within a site but measuring at least two indicators would provide additional confidence of the effects of management, especially for tillage. All C indicators responded to management, an essential criterion for evaluating soil health. Balancing the cost, sensitivity, interpretability, and availability at commercial labs, a 24-hr potential C mineralization assay could deliver the most benefit to measure in conjunction with SOC.

Lung infections caused by the opportunistic pathogen Pseudomonas aeruginosa can present as a spectrum of clinical entities from a rapidly fatal pneumonia in a neutropenic patient to a multi-decade bronchitis in patients with cystic fibrosis. P. aeruginosa is ubiquitous in our environment, and one of the most versatile pathogens studied, capable of infecting a number of diverse life forms and surviving harsh environmental factors. It is also able to quickly adapt to new environments, including the lung, where it orchestrates virulence factors to acquire necessary nutrients, and if necessary, turn them off to prevent immune recognition. Despite these capabilities, P. aeruginosa rarely infects healthy human lungs. This is secondary to a highly evolved host defence mechanism that efficiently removes inhaled or aspirated pseudomonads. Many arms of the respiratory host defence have been elucidated using P. aeruginosa as a model pathogen. Human infections with P. aeruginosa have demonstrated the importance of the mechanical barrier functions including mucus clearance, and the innate immune system, including the critical role of the neutrophilic response. As more models of persistent or biofilm P. aeruginosa infections are developed, the role of the adaptive immune response will likely become more evident. Understanding the pathogenesis of P. aeruginosa, and the respiratory host defence response to it has, and will continue to, lead to novel therapeutic strategies to help patients.

Nitrate nitrogen (NO3-N) losses from agriculture into groundwater are a continuing concern for society. The agricultural community must begin to reduce these losses to be responsible stewards of soil and water resources, to improve crop N-use efficiency and farm profitability, and to respond to society's expectations. A general feature common to many agricultural watershed N budgets is that the largest N03-N losses are associated with sites that receive excess N inputs. This chapter reviews N budget concepts and develops a N-screening model that will estimate field-scale N budgets to quickly identify N-rich sites where potential NO3-N losses to groundwater may be extensive. The first step in constructing a N budget is a clear statement of goals. Specific N budget goals may be to identify knowledge gaps, to identify dominant processes, or to study the interaction of specific N cycle processes.

Abstract Information is lacking on the long‐term impact of tillage systems on NO 3 losses to surface and groundwater. An 11‐yr (1982–1992) study was conducted to assess NO 3 losses to subsurface, tile drainage for corn ( Zea mays L.) grown with continuous conventional tillage (CT) and no tillage (NT) on a poorly drained Webster clay loam soil (fine‐loamy, mixed, mesic Typic Haplaquoll) at Waseca, MN. Nitrogen was applied at an annual application rate of 200 kg ha −1 . Mean annual subsurface drain flow during the 11‐yr period was 35 mm higher for NT (315 ram) compared with CT (280 mm). Flow‐weighted nitrate‐nitrogen (NO 3 ‐N) concentrations increased dramatically in the wet years (1990 and 1991) following the dry period of 1987 to 1989. Flow‐weighted NO 3 ‐N concentrations during the 11‐yr period averaged 13.4 and 12.0 mg L −1 for CT and NT, respectively. Although subsurface drain flow was 12% higher with NT, NO 3 ‐N losses were about 5% higher with CT mainly due to higher NO 3 ‐N concentrations with CT in the last 2 yr. Corn grain yields and N removal were significantly higher in 6 out of 11 yr with CT compared with NT with no difference between tillage systems in the other 5 yr. Grain yields averaged 8.6 Mg ha −1 with CT and 7.3 Mg ha −1 with NT during the 11‐yr period. Multiple regression equations showed that annual flow‐weighted NO 3 ‐N concentration is best predicted from residual soil NO 3 in the 0‐ to 1.2‐m profile and spring rainfall while NO 3 ‐N flux can be predicted well from May and June rainfall. Results from this long‐term study indicate that on this poorly drained soil, CT had a positive effect on corn grain yield and N removal compared with NT, but tillage systems had minimal impact on NO 3 losses to subsurface drain flow. Higher drain flow with NT does not necessarily result in higher NO 3 ‐N fluxes lost via subsurface drainage.

Seed dispersal, interacting with environmental disturbance and management across heterogeneous landscapes, results in irregular weed spatial distributions. Describing, predicting, and managing weed populations requires an understanding of how weeds are distributed spatially and the consequences of this distribution for population processes. Semivariograms and kriged maps of weed populations in several fields have helped describe spatial structure, but few generalizations can be drawn except that populations are aggregated at one or more scales. Limited information is available on the effect of weed arrangement, pattern, or field location on weed population processes. Because weeds are neither regular nor uniform in distribution, mean density alone is of limited value in estimating yield loss or describing population dynamics over a whole field. Sampling strategies that account for spatial distribution can increase sampling efficiency. Further research should focus on understanding processes that cause changes in spatial distributions over time to help predict rates of invasion and potential extent of colonization.

Abstract The development of cropping systems that use N efficiently requires methods that evaluate system differences in N use. A procedure, based conceptually on soil and plant processes that affect N use, was developed to evaluate differences in N use efficiency among cropping systems. The method uses measurements of yield, grain N, aboveground plant N, applied N, and postharvest inorganic soil N to partition cropping system differences in yield and grain N into N efficiency components. The components consist of N supply, available N efficiency, available N uptake efficiency, N utilization efficiency, grain Naccumulation efficiency, and N harvest index. The N efficiency component analysis was demonstrated for a field study with hard red spring wheat ( Triticum aestivum L. ‘WB 906R’) where conventional tillage had a greater yield and grain N than no‐tillage. At low N rates, 78% of the difference in yield between the two was attributed to N supply and available N efficiency components. At high levels of applied N, 88% of the yield difference was attributed to the N utilization efficiency component. Differences in grain N were attributed to N supply and available N efficiency components, whereas components of grain N accumulation efficiency, available N uptake efficiency, and N harvest index were nonsignificant. Overall, this new approach transcends empirical analyses and provides insight into underlying mechanisms of cropping system differences in N use.

ABSTRACT Defining the baseline bacterial microbiome is critical to understanding its relationship with health and disease. In broiler chickens, the core microbiome and its possible relationships with health and disease have been difficult to define, due to high variability between birds and flocks. Presented here are data from a large, comprehensive microbiota-based study in commercial broilers. The primary goals of this study included understanding what constitutes the core bacterial microbiota in the broiler gastrointestinal, respiratory, and barn environments; how these core players change across age, geography, and time; and which bacterial taxa correlate with enhanced bird performance in antibiotic-free flocks. Using 2,309 samples from 37 different commercial flocks within a vertically integrated broiler system and metadata from these and an additional 512 flocks within that system, the baseline bacterial microbiota was defined using 16S rRNA gene sequencing. The effects of age, sample type, flock, and successive flock cycles were compared, and results indicate a consistent, predictable, age-dependent bacterial microbiota, irrespective of flock. The tracheal bacterial microbiota of broilers was comprehensively defined, and Lactobacillus was the dominant bacterial taxon in the trachea. Numerous bacterial taxa were identified, which were strongly correlated with broiler chicken performance across multiple tissues. While many positively correlated taxa were identified, negatively associated potential pathogens were also identified in the absence of clinical disease, indicating that subclinical dynamics occur that impact performance. Overall, this work provides necessary baseline data for the development of effective antibiotic alternatives, such as probiotics, for sustainable poultry production. IMPORTANCE Multidrug-resistant bacterial pathogens are perhaps the greatest medical challenge we will face in the 21st century and beyond. Antibiotics are necessary in animal production to treat disease. As such, animal production is a contributor to the problem of antibiotic resistance. Efforts are underway to reduce antibiotic use in animal production. However, we are also challenged to feed the world's increasing population, and sustainable meat production is paramount to providing a safe and quality protein source for human consumption. In the absence of antibiotics, alternative approaches are needed to maintain health and prevent disease, and probiotics have great promise as one such approach. This work paves the way for the development of alternative approaches to raising poultry by increasing our understandings of what defines the poultry microbiome and of how it can potentially be modulated to improve animal health and performance.

Utilizing conservation tillage practices and increasing fertilizer N use efficiency for corn ( Zea mays L.) are necessary for optimizing growers' profits and for minimizing loss of sediment and nutrients to the environment. A 3‐yr study was conducted on a Nicollet clay loam (fine loamy, mixed, mesic, Aquic Hapludoll)–Webster clay loam (fine loamy, mixed, super active, Typic Endoquoll) soil complex in southern Minnesota to determine the effects of four tillage systems (no tillage, strip tillage, one‐pass field cultivate, and chisel plow) and two N application times on corn production following soybean [ Glycine max (L.) Merr.]. Anhydrous ammonia was applied at 123 kg N ha −1 either in late October when soil temperatures at 15 cm were generally below 10°C or in April before planting. Tillage system had a statistically significant effect on corn production but showed no interaction with the N timing treatments. Maximum differences among tillage systems were 4.3% for grain yield, 5.1% for silage yield, and 8.6% for total N uptake. In 1 yr, when April and May were wet and warm, grain yield and total N uptake were reduced 20 and 27%, respectively, with fall N. Apparent N recovery was reduced from 87% for spring N to 45% for fall N. Corn production was not affected by time of N application in the other 2 yr. Relative leaf chlorophyll, measured by a SPAD meter at the V10, R1, and R3 growth stages, was highly correlated to relative corn grain yield, and could be used as a diagnostic tool at the V10 stage to determine sidedress N needs under non‐irrigated conditions. Because the risk of N loss is greater with fall N application, N should be applied in the spring on these soils to minimize risk and optimize profitability regardless of tillage system.

Efficient fertilizer placement is attracting increasing interest as tillage systems change, economic profitability becomes tighter, environmental awareness increases, and improvements are made in application equipment. Efficacy of various placement methods for fertilizer P and K is highly dependent on soil test level, crop, soil texture, tillage system, and climatic conditions. At high soil test levels, crop yield response differences due to placement methods are rare. At low soil test levels, corn ( Zea mays L.) yields obtained from band (2 × 2 in.) placement are seldom surpassed by other placement methods. Surface strip and deep subsurface bands (6 to 8 in.) have outperformed broadcast applications, particularly in years when precipitation is insufficient, soil test levels are low, or reduced tillage is used. Placement of fertilizer directly with the corn seed is not recommended on sandy soils if seed‐zone soil moisture is low. Soybean ( Glycine max L.) has responded more consistently to broadcast than to band applications in limited studies. Small grains generally have responded better to band applications with the seed or knifed in to a 4‐ to 5‐in. depth, especially under drier conditions. When soil tests are low, soil moisture and/or precipitation is limiting, or land is rented, and when fertilizer efficiency and economic return are to be maximized, localized placement methods giving a zone of high fertilizer concentration within the effective rooting area should be strongly considered for corn and small grains.