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Nutrient Balance (nutrient + balance)
Selected AbstractsCan management compensate for atmospheric nutrient deposition in heathland ecosystems?JOURNAL OF APPLIED ECOLOGY, Issue 4 2006WERNER HÄRDTLE Summary 1Atmospheric nutrient deposition has contributed to widespread changes in heathlands throughout Europe. As a consequence, management is now being considered as a potential tool with which to compensate for increased nutrient loads. Currently, only limited information is available on the extent to which management measures could compensate for atmospheric nutrient deposition. We hypothesized that low-intensity management measures are not sufficient to counterbalance current nutrient inputs, particularly of nitrogen (N). 2In order to improve heathland management schemes, we evaluated the effectiveness of different management measures in reducing the impact of ongoing atmospheric nutrient loads. We compared the effects of mowing, prescribed burning (low-intensity management) and sod-cutting (high-intensity management) on heathland nutrient budgets [N, calcium (Ca), potassium (K), magnesium (Mg) and phosphorus (P)] in the Lueneburg Heath nature reserve (north-west Germany). Nutrient balances were calculated by analysing the present-day input, the output as a result of the removal of biomass/humus horizons, and changes in leaching rates. 3Nutrient losses by increased leaching following management measures were negligible compared with nutrient losses caused by the removal of above-ground biomass or humus horizons. The total quantities of nutrients removed by sod-cutting were equivalent to between 37 and 176 years of atmospheric input (for N, 89 years). 4In contrast, the quantities of N removed by mowing and prescribed burning were equivalent to only 5 years of atmospheric input. Thus, heathlands subjected to such treatments will accumulate N in the long term. In addition, output,input ratios for phosphorus (P) exceeded those for N in the mowing and sod-cutting experiments. It is therefore likely that heathlands currently (co-) limited by N will shift to being more P-limited in the long term. This will promote species that are well adapted to P-limited sites (e.g. Molinia caerulea). 5Synthesis and applications. This study shows that low-intensity management cannot compensate for atmospheric N loads in the long term. Consequently, high-intensity management measures are an indispensable tool in preserving a long-term balanced N budget in heathlands. In order to maintain a diverse structure, managers need to combine low- and high-intensity management measures. Prescribed burning proved to be the best means of avoiding an increasing P shortage, because this measure causes very low P outputs. [source] Linking above-ground and below-ground effects in autotrophic microcosms: effects of shading and defoliation on plant and soil propertiesOIKOS, Issue 3 2000Juha Mikola Although factors affecting plant growth and plant carbon/nutrient balance , e.g., light availability and defoliation by herbivores , may also propagate changes in below-ground food webs, few studies have aimed at linking the above-ground and below-ground effects. We established a 29-week laboratory experiment (,one growing season) using autotrophic microcosms to study the effects of light and defoliation on plant growth, plant carbon/nutrient balance, soil inorganic N content, and microbial activity and biomass in soil. Each microcosm contained three substrate layers , mineral soil, humus and plant litter , and one Nothofagus solandri var. cliffortioides seedling. The experiment constituted of the presence or absence of two treatments in a full factorial design: shading (50% decrease in light) and artificial defoliation (approximately 50% decrease in leaf area in the beginning of the growing season). At the end of the experiment a range of above-ground and below-ground properties were measured. The shading treatment reduced root and shoot mass, root/shoot ratio and leaf production of the seedlings, while the defoliation treatment significantly decreased leaf mass only. Leaf C and N content were not affected by either treatment. Shading increased NO 3,N concentration and decreased microbial biomass in humus, while defoliation did not significantly affect inorganic N or microbes in humus. The results show that plant responses to above-ground treatments have effects which propagate below ground, and that rather straightforward mechanisms may link above-ground and below-ground effects. The shading treatment, which reduced overall seedling growth and thus below-ground N use and C allocation, also led to changes in humus N content and microbial biomass, whereas defoliation, which did not affect overall growth, did not influence these below-ground properties. The study also shows the carbon/nutrient balance of N. solandri var. cliffortioides seedlings to be highly invariant to both shading and defoliation. [source] Effects of hunger level and nutrient balance on survival and acetylcholinesterase activity of dimethoate exposed wolf spidersENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2002Lars-Flemming Pedersen Abstract The influence of two nutritional factors (food quantity and quality) on the responses of a wolf spider, Pardosa prativaga (L.K.), to a high dose of the insecticide dimethoate, was investigated in a fully factorial experimental design. Spider groups with different (good and bad) nutrient balance were created by feeding them fruit flies of either high or low nutrient content for 28 days. Both groups were then split into satiated and 14 days starved subgroups. Each of these was further divided into insecticide treated and control halves. Survivorship and acetylcholinesterase (AChE) activity measured on the survivors were used as response variables. Survivorship after topical dimethoate exposure (LD50; 48 h) was influenced by spider body weight, nutrient balance, and starvation. Furthermore, AChE activity was significantly inhibited by dimethoate exposure. A significant interaction between nutrient balance, starvation, and dimethoate exposure revealed synergistic effects of starvation and nutrient imbalance on AChE inhibition by dimethoate in surviving spiders. These results show that the tolerance of non-target arthropods to dimethoate may vary depending on the nutritional history of the animal. [source] Challenges and opportunities in soil organic matter researchEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2009R. Lal Summary Soil organic matter (SOM) can be a source or sink for atmospheric CO2 depending on land use, and management of soil, vegetation and water resources. SOM is a source of atmospheric CO2, with the use of extractive farming practices that lead to a negative nutrient balance and exacerbate soil degradation. The historic loss of C from the SOM pool between the 1850s and 2000 is estimated at 78 ± 12 Gt compared with the emission of 270 ± 30 Gt from fossil fuel combustion. Despite its numerous direct and ancillary benefits, enhancing the SOM pool is a major challenge, especially in impoverished and depleted soils in harsh tropical climates. In addition to biophysical factors, there are also numerous social, economic and political constraints that limit increase in SOM pools. Conversion of plough-tillage to no-till farming, an important practice to enhance the SOM pool, is constrained by the limited access to herbicides and seed drill, and the competing uses of crop residues. Yet, enhancing the SOM pool is essential to restoring degraded soils, advancing food security and improving the environment. Important subjects among researchable topics include: assessing the rate of SOM accretion for a wide range of land use and management practices with reference to a baseline; evaluating the importance of biochar; measuring and predicting SOM at landscape and extrapolation to regional scale; establishing relationships between SOM and soil quality and agronomic productivity; determining on- and off-site effects of crop residues removal for ethanol/biofuel production; determining the fate of C in SOM translocated by erosional processes; evaluating nutrient requirements for increasing SOM in croplands; validating predictive models in tropical environments; and developing methodology for trading C credits. [source] Nutritional value of cannibalism and the role of starvation and nutrient imbalance for cannibalistic tendencies in a generalist predatorJOURNAL OF ANIMAL ECOLOGY, Issue 1 2006DAVID MAYNTZ Summary 1Cannibalism is considered an adaptive foraging strategy for animals of various trophic positions, including carnivores. However, previous studies on wolf spiders have questioned the high nutritional value of cannibalism. We therefore analysed two different aspects of nutritional quality of conspecifics in the wolf spider Pardosa prativaga: their value for survival, growth and development; and the growth efficiency of feeding on conspecifics. We also measured the propensity for cannibalistic attacks and the consumption rate of conspecifics in an experiment where hunger level and nutrient balance were manipulated. In all experiments, cannibalism was compared with predation on fruit flies as control prey. 2The growth experiment gave ambiguous results regarding the nutritional quality of conspecifics. Spiders on pure cannibalistic diets split into two distinct groups, one performing much better and the other much worse than spiders on fruit fly diets. We discuss the possibility that the population is dimorphic in its cannibalistic propensity, with the latter group of individuals showing a high level of inhibition against cannibalistic attacks in spite of a high nutritional value of cannibalism. 3The food utilization experiment confirmed the high nutritional quality of conspecifics, as cannibalistic spiders had the same growth rate as spiders fed insect prey in spite of a much lower consumption rate. 4Inhibition against cannibalistic attacks was demonstrated in medium-sized juveniles: only half of the spiders attacked a prescribed victim of 50% the size of their opponents, and the latency for those that did attack was more than half an hour, compared with a few minutes for spiders fed fruit flies. 5Nutrient-imbalanced spiders utilized an alternative insect diet less efficiently than balanced spiders, whereas no difference was present in efficiency of utilizing conspecifics. This result indicates that spiders can remedy at least part of a nutrient imbalance through cannibalism. 6As spiders can escape nutritional imbalance as well as restore energy reserves through cannibalism, we predicted both nutrient imbalance and hunger to stimulate cannibalism. This prediction was confirmed only with respect to hunger. Nutrient-imbalanced spiders had reduced cannibalistic consumption, perhaps due to lowered predatory aggressiveness as a result of bad condition. [source] The effect of advice to walk 2000 extra steps daily on food intakeJOURNAL OF HUMAN NUTRITION & DIETETICS, Issue 4 2006A.-A. Koulouri Abstract Background, It is currently unclear how physical activity and diet interact within the ranges of activity seen in the general population. This study aimed to establish whether a small, acute, increase in physical activity would lead to compensatory change in energy intake and nutrient balance, and to provide power analysis data for future research in this field. Method, Twelve participants were studied over 7 days of habitual activity and 2 weeks after instruction to increase physical activity by 2000 steps per day. Physical activity was assessed using a diary, the ,activPAL' activity monitor and a pedometer. Dietary analyses from prospective food diaries were compared between the first and third weeks. Results, Participants increased step-counts (+2600 steps per day, P = 0.008) and estimated energy expenditure (+300,1000 kJ day,1, P = 0.002) but did not significantly change their energy intake, dietary composition or number of meals per day. From reverse power analysis 38 participants would be needed to exclude a change in energy intake of 400 kJ day,1 with 90% power at P < 0.05; 400 kJ day,1 would compensate for a 2000 steps per day increase in physical activity. Conclusion, These results did not demonstrate any compensatory increase in food consumption when physical activity was increased by walking an average of 2600 additional steps per day. Power analysis indicates that a larger study (n = 38) will be necessary to exclude such an effect with confidence. [source] Nutrient losses from rain-fed bench terraced cultivation systems in high rainfall areas of the mid-hills of NepalLAND DEGRADATION AND DEVELOPMENT, Issue 5 2007G. P. Acharya Abstract Between the elevations of 1000 and 2000,m in the mid-hills of Nepal, over 12 million people subsist on land-holdings of less than 0·5,ha. These farmers have limited access to commercial inputs such as fertilisers and are reliant on organic manures for soil fertility maintenance. Participatory research was conducted with farmers on bari land (upper slope rain-fed crop terraces) in the hill community of Landruk (bench terraces 0,5° slope, 3000,3500,mm annual rainfall, which aimed to develop soil and water management interventions that controlled erosion without resulting in high leaching, and so were effective in minimising total nutrient losses. Interventions tested were the control of water movement through diversion of run-on and planting fodder grasses on terrace risers on bench terraces. The interventions were effective in reducing soil loss from the bari land in comparison with existing farmer practices, but no effect was observed on nutrient losses in solution form through runoff and leaching. Losses of NO3 -N in leachate ranged from 17·3 to 99·7,kg,ha,1,yr,1, but only 0·7 to 5·6,kg,ha,1,yr,1 in runoff. The overall nutrient balance suggests that the system is not sustainable. Fertility is heavily dependent on livestock inputs and if the current trends of declining livestock numbers due to labour constraints continue, further losses in productivity can be expected. However, farmers are interested in interventions that tie ecosystem services with productivity enhancement and farmers' priorities should be used as entry points for promoting interventions that are system compatible and harness niche opportunities. Copyright © 2007 John Wiley & Sons, Ltd. [source] Soil carbon sequestration in China through agricultural intensification, and restoration of degraded and desertified ecosystems,LAND DEGRADATION AND DEVELOPMENT, Issue 6 2002R. Lal Abstract The industrial emission of carbon (C) in China in 2000 was about 1,Pg,yr,1, which may surpass that of the United States (1,84,Pg,C) by 2020. China's large land area, similar in size to that of the United States, comprises 124,Mha of cropland, 400,Mha of grazing land and 134,Mha of forestland. Terrestrial C pool of China comprises about 35,60,Pg in the forest and 120,186,Pg in soils. Soil degradation is a major issue affecting 145,Mha by different degradative processes, of which 126,Mha are prone to accelerated soil erosion. Total annual loss by erosion is estimated at 5,5,Pg of soil and 15,9,Tg of soil organic carbon (SOC). Erosion-induced emission of C into the atmosphere may be 32,64,Tg,yr,1. The SOC pool progressively declined from the 1930s to 1980s in soils of northern China and slightly increased in those of southern China because of change in land use. Management practices that lead to depletion of the SOC stock are cultivation of upland soils, negative nutrient balance in cropland, residue removal, and soil degradation by accelerated soil erosion and salinization and the like. Agricultural practices that enhance the SOC stock include conversion of upland to rice paddies, integrated nutrient management based on liberal use of biosolids and compost, crop rotations that return large quantities of biomass, and conservation-effective systems. Adoption of recommended management practices can increase SOC concentration in puddled soil, red soil, loess soils, and salt-affected soils. In addition, soil restoration has a potential to sequester SOC. Total potential of soil C sequestration in China is 105,198,Tg,C,yr,1 of SOC and 7,138,Tg,C,yr,1 for soil inorganic carbon (SIC). The accumulative potential of soil C sequestration of 11,Pg at an average rate of 224,Tg,yr,1 may be realized by 2050. Soil C sequestration potential can offset about 20 per cent of the annual industrial emissions in China. Copyright © 2002 John Wiley & Sons, Ltd. [source] Farmland degradation in the mountains of Nepal: a study of watersheds ,with' and ,without' external interventionLAND DEGRADATION AND DEVELOPMENT, Issue 6 2002G. B. Thapa Abstract Amidst growing concerns about farmlands conservation, this paper examines the status of farmlands in two mountain watersheds ,with' and ,without' external intervention, located in the western hills of Nepal. Information was obtained from a household survey and group discussions conducted during April to September 1999. The severity of soil erosion from farmers' perspectives, density of landslides, soil nutrient balance and change in crop yield have been adopted as indicators of the status of the land. Results of the analysis indicate that land resources in both watersheds are undergoing degradation, though the causes and extent of degradation vary from one type of land to another. Upland crop terraces, locally called bari, are undergoing degradation most seriously under the combined influence of severe soil erosion, landslide and the depletion of soil nutrients. In particular, soil erosion has severely affected nearly half of the upland crop terraces in both watersheds due to a number of natural and anthropogenic factors ranging from weak geological structure to arable agriculture. Landslide and nutrient depletion have affected all types of farmlands except homesteads in both watersheds. Overall, the extent and intensity of land degradation is relatively high in the non-project area, as farmers were not provided with necessary technical and financial support. A broad strategy has been outlined for effective conservation of farmlands. Copyright © 2002 John Wiley & Sons, Ltd. [source] Theory of plant defensive level: example of process and pitfalls in development of ecological theoryOIKOS, Issue 3 2003N. Stamp Several hypotheses appear regularly in the literature as explanations for the level of plant defense, i.e. why some plants are so well defended and others are not. These hypotheses include optimal defense, carbon: nutrient balance, growth rate and growth-differentiation balance. However, there is considerable dissatisfaction with the progress with the plant defense hypotheses. At least part of the dissatisfaction with the hypotheses and research framed by them arises from the nature of the development of theory. Progress toward a mature stage requires attention to how theory develops (e.g. clearly distinguishing between the theoretical domain and the subset that can be tested, establishing criteria of robustness, properly accounting for discrepancies). In addition, part of the dissatisfaction with the development of the theory stems from inadequate approaches, such as failure to identify and test assumptions in experimental designs, confusing the hypotheses and their predictions, choosing a subsystem (e.g. plant age or part) that may be inappropriate for the test, and defaulting to a less precise hypothesis for explanation of the results. [source] Determinants of polyphagy by a woolly bear caterpillar: a test of the physiological efficiency hypothesisOIKOS, Issue 2 2001Michael S. Singer The physiological efficiency hypothesis argues that the physiological efficiency of food utilization determines feeding habits of herbivorous insects. Although relatively unsuccessful at explaining dietary specificity, it may explain the food-mixing habit of individually polyphagous herbivores because they may opportunistically increase physiological efficiency by optimizing nutrient balance or diluting toxins in the course of feeding on multiple host-plant species. This study tests two predictions of the physiological efficiency hypothesis with the woolly bear caterpillar, Grammia geneura (Strecker) (Lepidoptera: Arctiidae). Namely, both herbivore performance (survival, developmental rate, pupal mass) and growth efficiency should be better on mixed-plant diets than on single-plant diets. In a series of three laboratory experiments, I found that larval survival and developmental rate on mixed-plant diets were superior to performance on single-plant diets in only one of four cases. In all other cases, mixed-plant diets were either inferior (female pupal mass) to single-plant diets or not detectably different from them. Larval growth efficiency on mixed-plant diets was never superior to that on single-plant diets. In mixed-plant treatments, caterpillars often selected a diet that included plant species of relatively low suitability alone, thereby suffering reduced performance and growth efficiency. These results contradict predictions of the physiological efficiency hypothesis, indicating the limitations of the conventional focus on the physiological constraints on food utilization as an explanation for both individual polyphagy and dietary specificity in herbivorous insects. [source] Balancing fertility management and economics in organic field vegetable rotationsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 15 2007Ulrich Schmutz Abstract BACKGROUND: Organic field-scale vegetables are among the most profitable enterprises in organic farming systems. They are also some of the most nutrient-demanding crops, and many organic arable systems with field-scale vegetables are stockless. Without livestock manure inputs, nutrient supply depends on fertility-building crops, which generate only costs and no income. Different strategies of fertility management were compared on a central England research farm. Fertility management treatments consisted of different lengths of fertility building with green waste compost additions. Outputs and inputs in terms of nutrients and economics were monitored for 31 rotations during 1996,2002. RESULTS: N, P and K rotational nutrient balances, as well as C inputs, showed a negative relationship with rotational gross margins. Variable and allocated fixed costs of fertility building were low, between 2 and 5% of variable costs (£0.5,2 ha,1 for 1 kg N ha,1 supplied to the rotation). The intensity of vegetable cropping in these rotations was moderate (25,40% vegetable crops in the rotation) and balancing of fertility management and economics was possible at this intensity without livestock manure or other permitted fertiliser additions. CONCLUSION: Completely stockless systems (in analogy may be called vegan) are possible in organic vegetable production without compromising on fertility or economics. However, for a higher vegetable-cropping intensity (up to 90%) a more sophisticated mix of short-term fertility-building and N-trapping crops will be needed and such rotations may require further external addition of green waste or livestock manure. Copyright © 2007 Society of Chemical Industry [source] Nitrogen, phosphorus and potassium utilization and their cycling in a beef-forage production systemANIMAL SCIENCE JOURNAL, Issue 4 2009Yusuke TABATA ABSTRACT The objective of this study was to quantify nitrogen (N), phosphorus (P) and potassium (K) utilization and their cycling in a beef-forage production system. A survey was conducted at the Kyoto University experimental farm in Kyoto Prefecture, Japan, and included 9.5 ha of meadow and about 160 head of beef cattle. Forages cultivated on the meadow were ensiled and offered to breeding cows. The whole farm was regarded as a beef-forage production system. The system consisted of three components: animals, manure and soil/crop. Nutrient inputs, flows through the soil-plant-animal pathway and outputs were quantified for 2 periods for the whole farm. Nutrient utilization was evaluated by nutrient balances, utilization efficiencies (ratio of nutrient export to nutrient input) and cycling index. The average nutrient balances of N, P and K for the whole farm (kg/year/ha) were 435.7, 136.3, and 262.8, and the average nutrient utilization efficiencies were 0.08, 0.06, and 0.01, respectively. The characteristics of nutrient balances and utilization efficiencies for each component differed among the nutrients. The average cycling indices for N, P and K were 0.19, 0.17 and 0.49, respectively. This study illustrates the importance of internal nutrient cycling for improving nutrient utilization in beef production systems. [source] Substrate oxidation and retention in pigs and poultryANIMAL SCIENCE JOURNAL, Issue 2 2002André CHWALIBOG ABSTRACT A model combining data from gas exchange measurements with nutrient balances, demonstrating energy transfer between the pools of protein, carbohydrate and fat and their partition in the body, is described. Data from energy metabolism experiments with growing pigs and laying hens is incorporated into the model in order to illustrate methods of calculations and interpretations of the model. The experiments with pigs were carried out with growing pigs (20,100 kg) measured alternately on high (ad libitum) and low (near maintenance) feed levels on diets with low or high fat concentration. When energy intake from digested carbohydrate covered the requirements for growth, heat from oxidation of carbohydrate contributed 85,90% to the total heat production, while there was no net oxidation of fat. When the intake of digested carbohydrate was not sufficient to cover requirements, fat was mobilized from the body and oxidized. Energy from oxidation of carbohydrate was in all measurements below the energy in the carbohydrate pool, indicating transfer of energy from carbohydrate to fat metabolism in the process of de novo lipogeneis. The experiments with hens were carried out with 62 hens during the laying period from 26 to 47 weeks of age. The hens originated from two strains (A and B); they were kept in battery cages either individually or 3 hens/cage and fed ad libitum with an identical commercial diet. The partition of the protein pool between oxidation and retention was not influenced by the housing system. However, the genetic origin of hens effected protein utilization with relatively lower oxidation and higher retention in Strain B. The main part of the carbohydrate pool was oxidized (45,60%), but the hens kept individually oxidized more carbohydrate than those kept 3 hens/cage. Further, there were significant differences between the strains. Generally, about half of the fat pool originated from de novo lipogenesis from carbohydrate, indicating the importance of this process for fat retention in eggs. Fat oxidation depended on the energy supply from carbohydrate, hence with higher use of carbohydrate for oxidation in Strain B less fat was oxidized and more was used for fat synthesis. The presented results indicate that by combining results from gas exchange measurements with nitrogen and energy balances it is possible to evaluate the contribution of nutrients to the oxidative processes and the energy transfer between substrate pools. [source] Role of nutrient supply on cell growth in bioreactor design for tissue engineering of hematopoietic cellsBIOTECHNOLOGY & BIOENGINEERING, Issue 7 2005Pragyansri Pathi Abstract In the present study, a dynamic mathematical model for the growth of granulocyte progenitor cells in the hematopoietic process is developed based on the principles of diffusion and chemical reaction. This model simulates granulocyte progenitor cell growth and oxygen consumption in a three-dimensional (3-D) perfusion bioreactor. Material balances on cells are coupled to the nutrient balances in 3-D matrices to determine the effects of transport limitations on cell growth. The method of volume averaging is used to formulate the material balances for the cells and the nutrients in the porous matrix containing the cells. All model parameters are obtained from the literature. The maximum cell volume fraction reached when oxygen is depleted in the cell layer at 15 days and is nearly 0.63, corresponding to a cell density of 2.25 × 108 cells/mL. The substrate inhibition kinetics for cell growth lead to complex effects with respect to the roles of oxygen concentration and supply by convection and diffusion on cell growth. Variation in the height of the liquid layer above the cell matrix where nutrient supply is introduced affected the relative and absolute amounts of oxygen supply by hydrodynamic flow and by diffusion across a gas permeable FEP membrane. Mass transfer restrictions of the FEP membrane are considerable, and the supply of oxygen by convection is essential to achieve higher levels of cell growth. A maximum growth rate occurs at a specific flow rate. For flow rates higher than this optimal, the high oxygen concentration led to growth inhibition and for lower flow rates growth limitations occur due to insufficient oxygen supply. Because of the nonlinear effects of the autocatalytic substrate inhibition growth kinetics coupled to the convective transport, the rate of growth at this optimal flow rate is higher than that in a corresponding well-mixed reactor where oxygen concentration is set at the maximum indicated by the inhibitory kinetics. ©2005 Wiley Periodicals, Inc. [source] | |||||||||||||