Soil nitrogen balance assessment and its application for sustainable agriculture and environment

Soil nitrogen balance assessment (SNBA) serves as an effective tool for estimating the magnitude of nitrogen loss/gain of the agro-eco systems and to appraise their sustainability. SNBA brings forth awareness of soil fertility problems, besides providing information relating to the resultant release of nitrogen into the environment consequent to agricultural practices. Quantitative information relating to nitrogen escape into the environment through such exercises can be gainfully utilized for identification of causative factors, enhancing fertilizer use efficiency and formulating programmes aimed at plugging N leakages. An overview of nitrogen balance approaches and methodologies is presented. A deeper understanding and insight into the agro-eco systems provided by the SNBA exercises can lay the basis for the formulation of effective agronomic interventions and policies aimed at promoting sustainable agriculture and a benign environment.     

Soil nitrogen balance assessment and its application for sustainable agriculture and environment

Soil nitrogen balance assessment (SNBA) serves as an effective tool for estimating the magnitude of nitrogen loss/gain of the agro-eco systems and to appraise their sustainability. SNBA brings forth awareness of soil fertility problems, besides providing information relating to the resultant release of nitrogen into the environment consequent to agricultural practices. Quantitative information relating to nitrogen escape into the environment through such exercises can be gainfully utilized for identification of causative factors, enhancing fertilizer use efficiency and formulating programmes aimed at plugging N leakages. An overview of nitrogen balance approaches and methodologies is presented. A deeper understanding and insight into the agro-eco systems provided by the SNBA exercises can lay the basis for the formulation of effective agronomic interventions and policies aimed at promoting sustainable agriculture and a benign environment.     

Bioremediation of polynitrated aromatic compounds: plants and microbes put up a fight

Industrialization and the quest for a more comfortable lifestyle have led to increasing amounts of pollution in the environment. To address this problem, several biotechnological applications aimed at removing this pollution have been investigated. Among these pollutants are xenobiotic compounds such as polynitroaromatic compounds--recalcitrant chemicals that are degraded slowly. Whereas 2,4,6-trinitrophenol (TNP) can be mineralized and converted into carbon dioxide, nitrite and water, 2,4,6-trinitrotoluene (TNT) is more recalcitrant--although several microbes can use it as a nitrogen source. The most effective in situ biotreatments for TNT are the use of bioslurry (which can be preceded by an abiotic step) and phytoremediation. Phytoremediation can be enhanced by using transgenic plants alone or together with microbes.     

An exercise sequence for progression in balance training

Compared with resistance training, information concerning the progressive configuration of balance training (BT) is rare and lacks scientific validation. Therefore, a study was designed to determine participants' ability to perform balance exercises with increasing level of difficulty. The task required the participants (N = 20) to stand as stable as possible on a computerized balance platform. The experiment was performed on 3 testing days using different stance and sensory conditions. On each day, bipedal, step, tandem, and monopedal stands were performed 3 times while sensory conditions changed from firm ground, eyes opened (day 1) over foam ground, eyes opened (day 2) to firm ground, eyes closed (day 3). The results showed that total center of pressure displacements significantly increased when the use of sensory information (comparison between testing days: all p < 0.001) or when the base of support (comparison within testing days: all p < 0.001) was gradually reduced. Based on the observed pattern of increased postural sway across all testing conditions and the levels of trial variability, exercises were categorized into several stages of training. Findings indicate that balance performance decreased in response to an increased level of task difficulty introduced by narrowing the base of support and by limiting the use of sensory information. Practitioners can use the derived exercise ranking to select exercises for BT appropriate to the level of participants' balance ability and to implement progression in balance training.     

Tracing sources and pathways of dissolved nitrate in forest and river ecosystems using high-resolution isotopic techniques: a review

Nitrogen inputs into stream and river ecosystems, and the factors influencing those inputs, are important for various ecological and environmental concerns. Reliable information on where and how nitrogen compounds flow into aquatic ecosystems is indispensable to understanding the nutrient status of these ecosystems. Such information should include the biogeochemical mechanisms and hydrological controls of nutrient leaching into rivers from terrestrial systems such as forests, agricultural fields, and urbanized areas. Advancements in stable isotopomer measurements over the past two decades have expanded the variety of target substances and the precision with which they can be investigated. The high-throughput microbial denitrifier method allows for simultaneous measurement of nitrogen and oxygen isotope ratios and can provide high-resolution spatiotemporal information on both nitrate sources and biogeochemical processes. Although advanced techniques of stable isotope analysis have been used extensively to detect sources and estimate the relative contributions of multi-source systems in various rivers, there are still new horizons in investigating nitrogen transformations. For example, stable isotopes of oxygen (¹⁸O and ¹⁷O) occurring in nitrate due to atmospheric deposition can be used as natural tracers for evaluating internal nitrogen cycling; these isotopes are distinct from the oxygen within microbially generated nitrate in soils and water bodies. Another future challenge is improved use of nitrous oxide isotopomers in evaluating the relative contributions of nitrification and denitrification. Such analysis could provide insight into the nitrogen transformation that occurs under redox conditions at the boundary between terrestrial and aquatic systems, where nitrification and denitrification often occur simultaneously in soil and aquatic environments.     

Why flies? Inexpensive public engagement exercises to explain the value of basic biomedical research on Drosophila melanogaster

Invertebrate model organisms are powerful systems for uncovering conserved principles of animal biology. Despite widespread use in scientific communities, invertebrate research is often severely undervalued by laypeople. Here, we present a set of simple, inexpensive public outreach exercises aimed at explaining to the public why basic research on one particular invertebrate, the insect Drosophila melanogaster, is valuable. First, we designed seven teaching modules that highlight cutting-edge research in Drosophila genetics, metabolism, physiology, and behavior. We then implemented these exercises in a public outreach event that included both children and adults. Quantitative evaluation of participant feedback suggests that these exercises 1) teach principles of animal biology, 2) help laypeople better understand why researchers study fruit flies, and 3) are effective over a wide range of age groups. Overall, this work provides a blueprint for how to use Drosophila as a vehicle for increasing public awareness and appreciation of basic research on genetically tractable insects in particular and invertebrates in general.     

More is less: agricultural impacts on the N cycle in Argentina

Human impact on nitrogen cycling, in particular the introduction of reactive nitrogen in terrestrial and aquatic ecosystems, can be examined at multiple scales, from the global impact on atmospheric chemistry to the impact of human activities on soil organic matter and fertility at the scale of square meters. Nevertheless, anthropogenic loading of nitrogen cycling in natural and managed ecosystems can be seen most directly at the regional scale, where concentrated human activity results in disruption of the nitrogen balance, with consequences for biogeochemical cycling and their interactions. Differences in land-use and agricultural practices between North and South America, and the importance of economic drivers that determine the fate of new reactive nitrogen demonstrate a contrasting picture of human impact on N cycling when the consequences are considered at the global vs. the regional scale. In particular, in the Pampa region of Argentina, the central agricultural zone of the country, the expansion of soybean cultivation in the last 20 years and the use of synthetic fertilizers have resulted in an influx of reactive nitrogen into these systems, with unexpected consequences for the nitrogen balance. A mass balance of nitrogen for soybean demonstrates that increased nitrogen inputs from biological fixation do not compensate for losses due to seed export, such that most areas under soybean cultivation are currently experiencing a substantive net loss of nitrogen. In addition, other crops that are currently being fertilized still show a net loss of nitrogen also due to the effect of primary exports from these agroecosystems. These simple models demonstrate that socioeconomic factors in large part drive the contrasting effects of anthropogenic impact on nitrogen cycling at global vs. regional scales. The future impact on nitrogen cycling in the Americas requires an integration of both ecological factors and socioeconomic drivers that will ultimately determine human disruption of the nitrogen cycle.     

Predicting the profile of nutrients available for absorption: from nutrient requirement to animal response and environmental impact

Current feed evaluation systems for dairy cattle aim to match nutrient requirements with nutrient intake at pre-defined production levels. These systems were not developed to address, and are not suitable to predict, the responses to dietary changes in terms of production level and product composition, excretion of nutrients to the environment, and nutrition related disorders. The change from a requirement to a response system to meet the needs of various stakeholders requires prediction of the profile of absorbed nutrients and its subsequent utilisation for various purposes. This contribution examines the challenges to predicting the profile of nutrients available for absorption in dairy cattle and provides guidelines for further improved prediction with regard to animal production responses and environmental pollution.The profile of nutrients available for absorption comprises volatile fatty acids, long-chain fatty acids, amino acids and glucose. Thus the importance of processes in the reticulo-rumen is obvious. Much research into rumen fermentation is aimed at determination of substrate degradation rates. Quantitative knowledge on rates of passage of nutrients out of the rumen is rather limited compared with that on degradation rates, and thus should be an important theme in future research. Current systems largely ignore microbial metabolic variation, and extant mechanistic models of rumen fermentation give only limited attention to explicit representation of microbial metabolic activity. Recent molecular techniques indicate that knowledge on the presence and activity of various microbial species is far from complete. Such techniques may give a wealth of information, but to include such findings in systems predicting the nutrient profile requires close collaboration between molecular scientists and mathematical modellers on interpreting and evaluating quantitative data. Protozoal metabolism is of particular interest here given the paucity of quantitative data.Empirical models lack the biological basis necessary to evaluate mitigation strategies to reduce excretion of waste, including nitrogen, phosphorus and methane. Such models may have little predictive value when comparing various feeding strategies. Examples include the Intergovernmental Panel on Climate Change (IPCC) Tier II models to quantify methane emissions and current protein evaluation systems to evaluate low protein diets to reduce nitrogen losses to the environment. Nutrient based mechanistic models can address such issues. Since environmental issues generally attract more funding from governmental offices, further development of nutrient based models may well take place within an environmental framework.     

Systems biology and the heart

Understanding the logic of living systems requires knowledge of the mechanisms involved at the levels at which functionality is expressed. This information does not reside in the genome, nor even in the individual proteins that genes code for. No functionality is expressed at these levels. It emerges as the result of interactions between many proteins relating to each other in multiple cascades and in interaction with the cellular environment. There is, therefore, no alternative to copying nature and computing these interactions to determine the logic of healthy and diseased states. The rapid growth in biological databases, models of cells, tissues and organs and the development of powerful computing hardware and algorithms have made it possible to explore functionality in a quantitative manner all the way from the level of genes to the physiological function of whole organs and regulatory systems. I use models of the heart to demonstrate that we can now go all the way from individual genetic information (on mutations, for example) to exploring the consequences at a whole organ level.     

下辽河平原农业生态系统不同施肥制度的土壤养分收支

本试验是在潮棕壤上进行了10年的定位试验,研究了在养分循环再利用的基础上采取不同施肥制度下作物养分移出量,并结合施肥量计算出土壤中N,P,K养分收支。结果表明,在保持农业系统养分循环再利用的基础上,根据养分供给力设计化肥施用量,不仅可实现作物主产,而且可平衡土壤养分收支,避免土壤中肥料养分过剩（主要是N）进入环境,并揭示了我国我国在20世纪70年代以前大面积农田土壤缺P和80年代农田土壤大面积缺K的原因。     

生物脱氮中工程纳米颗粒的毒害作用及减毒措施的研究进展

氮化合物在生命代谢过程中扮演着重要的角色,但过多的无机氮会导致水体恶化进而影响人类健康,生物脱氮技术可高效去除环境中的无机氮且不引起二次污染.随着工程纳米颗粒在生活中的广泛应用,导致其大量释放到土壤及水体中,极大地阻碍了废水处理中的生物脱氮过程,因此,微生物脱氮过程中工程纳米颗粒的毒害作用及减毒措施成了近年来的研究热点...     

Coevolution of physiological systems

Coevolution is the interaction in the process of evolution of different species that are closely related biologically but do not exchange genetic information. In this paper, we address the problem of coevolution of the whole organism’s physiological systems as a process of the interrelated development of structure and function as well as their regulatory systems during the formation of living organisms. We consider the coevolution of osmoregulation and the nitrogen metabolism type, systemic and individual coevolutionary strategies of cell volume regulation in poikiloosmotic and homoiosmotic animals, coevolution of effectory organs and endocrine factors in the development of water–salt homeostasis, co-involvement of neurohypophyseal nonapeptides and glucagon-like peptide-1 in the regulation of the renal function aimed at stabilizing physico-chemical parameters of extracellular fluids which make up the internal environment of the organism.     

Integrated physiological and agronomic modelling of N capture and use within the plant

Today farmers have several constraints to take into account in managing their crops: (i) competitiveness: productivity must be maintained or increased whereas inputs must be decreased, (ii) the environmental consequences of cultural practices: pesticide and fertilizer use must be decreased, and (iii) product quality must be improved and nitrogen nutrition is an important factor in harvest quality. These new constraints sometimes conflict: maximum yield is often obtained with large amounts of N, increasing the risks of N leaching. The determination of rates and dates for nitrogen application must become more precise in this context. Tools are required for the forecasting of crop requirements, the diagnosis of N deficiencies during the crop cycle and breeding of new adapted varieties. Models and diagnosis indicators have been developed to meet these needs, but those relating to nitrogen are often based on empirical relationships. Moreover, the available models and indicators often fail to account for cultivar-specific responses. The improvement of agronomic tools and the breeding of new varieties adapted to new cropping systems should be based on a thorough understanding of the key metabolic processes involved, and the relative contributions of these processes to yield determination in conditions of fluctuating N supply. For both purposes, more information is required about plant and crop N economy. In this paper, the way in which N absorption and use within the plant and crop, plant responses to deficiencies and excesses of nitrogen are taken into account in major agronomic models is described first. The level of sophistication of the modules comprising these models depends on operational objectives. Secondly, the ways in which the most recent molecular plant physiology findings can, and indeed should, be integrated into models at the crop and crop cycle levels are described. The potential value of this approach for improving current agronomic models and diagnostic tools, and for breeding more efficient varieties is also discussed.     

The nocturnal bottleneck and the evolution of activity patterns in mammals

In 1942, Walls described the concept of a ‘nocturnal bottleneck’ in placental mammals, where these species could survive only by avoiding daytime activity during times in which dinosaurs were the dominant taxon. Walls based this concept of a longer episode of nocturnality in early eutherian mammals by comparing the visual systems of reptiles, birds and all three extant taxa of the mammalian lineage, namely the monotremes, marsupials (now included in the metatherians) and placentals (included in the eutherians). This review describes the status of what has become known as the nocturnal bottleneck hypothesis, giving an overview of the chronobiological patterns of activity. We review the ecological plausibility that the activity patterns of (early) eutherian mammals were restricted to the night, based on arguments relating to endothermia, energy balance, foraging and predation, taking into account recent palaeontological information. We also assess genes, relating to light detection (visual and non-visual systems) and the photolyase DNA protection system that were lost in the eutherian mammalian lineage. Our conclusion presently is that arguments in favour of the nocturnal bottleneck hypothesis in eutherians prevail.     

Edemagenic gain and interstitial fluid volume regulation

Under physiological conditions, interstitial fluid volume is tightly regulated by balancing microvascular filtration and lymphatic return to the central venous circulation. Even though microvascular filtration and lymphatic return are governed by conservation of mass, their interaction can result in exceedingly complex behavior. Without making simplifying assumptions, investigators must solve the fluid balance equations numerically, which limits the generality of the results. We thus made critical simplifying assumptions to develop a simple solution to the standard fluid balance equations that is expressed as an algebraic formula. Using a classical approach to describe systems with negative feedback, we formulated our solution as a "gain" relating the change in interstitial fluid volume to a change in effective microvascular driving pressure. The resulting "edemagenic gain" is a function of microvascular filtration coefficient (K(f)), effective lymphatic resistance (R(L)), and interstitial compliance (C). This formulation suggests two types of gain: "multivariate" dependent on C, R(L), and K(f), and "compliance-dominated" approximately equal to C. The latter forms a basis of a novel method to estimate C without measuring interstitial fluid pressure. Data from ovine experiments illustrate how edemagenic gain is altered with pulmonary edema induced by venous hypertension, histamine, and endotoxin. Reformulation of the classical equations governing fluid balance in terms of edemagenic gain thus yields new insight into the factors affecting an organ's susceptibility to edema.     

Quality and professionalism in health care: a review of current initiatives in the NHS.

Since the start of the 1990s the NHS and the clinical professions have made significant investments in quality management in health care, and a plethora of initiatives has been aimed at service improvement. From a patient''s perspective the extent to which these exercises have been cost effective is uncertain, although they have certainly involved great effort and enterprise on the part of many clinicians and managers. An important opportunity now exists to integrate this work into the mainstream of clinical and general service management. If clinicians can accept quality management concepts as central to their professional ethos and regulatory structures this could help them to maintain their professional authority and protect them and their patients from imposed decisions based on inadequate understanding of health care costs and benefits.     

Expanded thermodynamic true yield prediction model: adjustments and limitations

Bacterial yield prediction is critical for bioprocess optimization and modeling of natural biological systems. In previous work, an expanded thermodynamic true yield prediction model was developed through incorporating carbon balance and nitrogen balance along with electron balance and energy balance. In the present work, the application of the expanded model is demonstrated in multiple growth situations (aerobic heterotrophs, anoxic, anaerobic heterotrophs, and autolithotrophs). Two adjustments are presented that enable improved prediction when additional information regarding the environmental conditions (pH) or degradation pathway (requirement for oxygenase- or oxidase-catalyzed reactions) is known. A large data set of reported yields is presented and considered for suitability in model validation. Significant uncertainties of literature-reported yield values are described. Evaluation of the model with experimental yield values shows good predictive ability. However, the wide range in reported yields and the variability introduced into the prediction by uncertainty in model parameters, limits comprehensive validation. Our results suggest that the uncertainty of the experimental data used for validation limits further improvement of thermodynamic prediction models.     

Aerobic denitrification by novel isolated strain using NO-₂-N as nitrogen source

Biological denitrification reaction can be achieved under aerobic environment. Few aerobic denitrifiers using nitrite as sole nitrogen source were identified. Using nitrite as the sole nitrogen source, this work assessed the denitrification activity of yy7, an aerobic heterotrophic denitrifier identified as Pseudomonas sp. (94% similarity) by 16S rRNA sequencing analysis. The logistic equation describes the cell growth curve, yielding a generation time of 2.9h at an initial 18 mg l(-1)NO(-)?-N. Reduction of NO(-)?-N was primarily achieved during its logarithmic growth phase, and was accompanied by an increase in suspension pH and near complete consumption of dissolved oxygen. Three genes relating to nirK, norB, and nosZ were noted to involve in isolate strain. Isolate yy7 can survive and remove up to 40 mg l(-1)NO(-)?-N and, hence, can be applied as an effective aerobic denitrifier during simultaneous nitrification and denitrification via nitrite processes.     

Root architectural responses of Betula lenta to spatially heterogeneous ammonium and nitrate

Inorganic soil nitrogen is often heterogeneously distributed, both spatially and in form (ammonium versus nitrate). Here we present information on the architecture of black birch (Betula lenta L.) root systems exposed to homogeneous and heterogeneous nitrogen environments. The major effects on root architecture were at the whole root system level in response to heterogeneity of nitrogen form rather than the effect of local of local nitrate or ammonium supply on local root growth. In the heterogeneous treatment, plant root systems had greater link lengths and more simple branching patterns. Root architectural responses to heterogeneous nitrogen, independent of localized responses to patches, suggest that in a seedling of B. lenta whole plant integration of its environment may override local control of root growth.     

Managing agricultural phosphorus for water quality protection: principles for progress

Background

The eutrophication of aquatic systems due to diffuse pollution of agricultural phosphorus (P) is a local, even regional, water quality problem that can be found world-wide.

Scope

Sustainable management of P requires prudent tempering of agronomic practices, recognizing that additional steps are often required to reduce the downstream impacts of most production systems.

Conclusions

Strategies to mitigate diffuse losses of P must consider chronic (edaphic) and acute, temporary (fertilizer, manure, vegetation) sources. Even then, hydrology can readily convert modest sources into significant loads, including via subsurface pathways. Systemic drivers, particularly P surpluses that result in long-term over-application of P to soils, are the most recalcitrant causes of diffuse P loss. Even in systems where P application is in balance with withdrawal, diffuse pollution can be exacerbated by management systems that promote accumulation of P within the effective layer of effective interaction between soils and runoff water. Indeed, conventional conservation practices aimed at controlling soil erosion must be evaluated in light of their ability to exacerbate dissolved P pollution. Understanding the opportunities and limitations of P management strategies is essential to ensure that water quality expectations are realistic and that our beneficial management practices are both efficient and effective.