Tolerance of four spring barley (Hordeum vulgare L.) varieties to weed harrowing

We investigated the tolerance to weed harrowing of four spring barley varieties and examined the possible interactions between varietal weed suppressive ability and two nutrient levels. Tolerance was defined as the combined effect of crop resistance (ability to resist soil covering) and crop recovery (the ability to recover in terms of yield). The weed harrowing strategy was a combination of one pre- and one post-emergence weed harrowing. In terms of yield, the four varieties responded significantly differently to weed harrowing and the response depended on nutrient level. At the lower nutrient level, weed harrowing caused an increase in yield of 4.4 hkg ha-1 for a strong competitor (cv. Otira), while there was no effect on yield at the higher nutrient level. For a weaker competitor (cv. Brazil), weed harrowing caused no change in yield at the lower nutrient level, whereas yield decreased by 6.0 hkg ha-1 at the higher nutrient level. There were marked differences between the weed suppressive ability of the four varieties when not harrowed, with less pronounced but significant differences when harrowed. Weed harrowing did not change the weed suppressive ability of a variety. Varieties that are tall at post-emergence harrowing and have increased density after pre-emergence harrowing, are the ones that benefit most from weed harrowing

Can uptake length in strams be determined by nutrient addition experiments? Results from an interbiome comparison study

Nutrient uptake length is an important parnmeter tor quantifying nutrient cycling in streams. Although nutrient tracer additions are the preierred method for measuring uptake length under ambient nutrient concentrations, short-term nutrient addition experiments have more irequently been used to estimate uptake length in streams. Theoretical analysis of the relationship between uptake length determined by nutrient addition experiments (Sw\u27) and uptake length determined by tracer additions (Sw)predicted that Sw\u27 should be consistently longer than 5, , and that the overestimate of uptake length by Sw( should be related to the level of nutrient addition above ambient concentrations and the degree of nutrient limitation. To test these predictions, we used data irom an interbiorne study of NH,- uptake length in which 15NH,- tracer and short-term NH,-a ddition experiments were performed in 10 streams using a uniform experimental approach. The experimental results largely contirmed the theoretical predictions: sw\u27 was consistently longer than Sw and Sw\u27:Sw ratios were directly related to the level of NH,- addition and to indicatvrs of N limitation. The experimentally derived Sw\u27:Sw, ratios were used with the theoretical results to infer the N limitation status of each stream. Together, the theoretical and experimental results showed the tracer experiments should be used whenever possible to determine nutrient uptake length in streams. Nutrient addition experiments may be useful for comparing uptake lengths between different streams or cliiferent times in the same stream. however, provided that nutrient additions are kept as low as possible and of similar miagnitude

Derivation of Nutrient Prices from Household level Food Expenditure Data: Methodology and Applications

In cross-country/cross-region multilateral consumer price level comparisons, differences in the mix of food items consumed in individual countries pose a major problem. Comparison of the level of prices of food items in two countries will be difficult, if the sets of food items consumed in the two countries are very different. However, if the data on average level of intake of major nutrients and some measure of the corresponding nutrient prices is available, a comparison of the level of nutrient prices is possible. At the household level, given the prices of food items actually paid and the corresponding levels of actual intake of different nutrients (from the consumption of various food items), it is possible, in principle, to work out a set of shadow prices of individual nutrients. In this context, it may be mentioned that the shadow prices of nutrients thus derived, being based on households' actual consumption information, would be influenced by the prices of food items consumed, nominal income, household attributes and other preference factors characterizing the individual households. Given such sets of household level nutrient prices and corresponding nutrient intakes for individual countries, a set of multilateral nutrient price index numbers may be worked out and a cross-country comparison of the nutrient price level performed. In this paper a regression analysis-based procedure has been proposed for estimation of household-level unit values of carbohydrates, protein and fat, using a cross-sectional household level data set on food expenditure, total consumer expenditure, quantities of nutrients consumed and related variables. The proposed procedure has been applied to the Indian household level data for the year 1999-2000 using the 55th round Consumer Expenditure Survey of the National Sample Survey Organisation, Govt. of India and subsequently analysed separately for the rural and urban sector of some selected major Indian States.Nutrients, prices, multilateral, comparisons

The influence of macronutrients on cognitive performance : effects across age and task difficulty : thesis presented in partial fulfillment of the requirements for the degree of Master of Arts in Psychology at Massey University

The effects of pure glucose, protein, and fat ingestion on tasks of paragraph recall, word recall, and mental arithmetic were examined. These effects were also investigated with regard to the age of the participant and the task difficulty level. Twelve young and twelve older adults participated in the study. Over four separate morning sessions, participants ingested one of the four drinks (glucose, protein, fat, or placebo), and completed easy and hard versions of the paragraph recall word recall, and mental arithmetic tasks. The between-group factor was Age of the participant (young or older adult). The within-group factors were type of Nutrient ingested (glucose, protein, fat, or placebo), and Difficulty Level (easy or hard). No effects of Nutrient were found in regard to overall task performance, collapsing across Age and Difficulty Level. There was no effect of Nutrient on the different performance levels of both age groups, or for the two task difficulty levels. However, post-hoc analyses did reveal a significant Nutrient x Age interaction for the elderly after ingestion of the protein drink. Trends in the data also pointed towards an enhancement effect of glucose for the paragraph recall and mental arithmetic tasks. Trends associated with performance levels after fat ingestion showed that fat tended to enhance mental arithmetic accuracy performance for the older adult age group. Protein did not appear to differ from placebo on any of the tasks, with the exception of the deficit in performance seen with the elderly on the mental arithmetic accuracy task. In addition, a post-hoc analysis of the effects of Nutrient on mood-state showed a significant Nutrient x Mood x Time interaction. These results were discussed in light of task-specific effects of nutrients and nutrient metabolism

[Corrigendum to] Effects of small-scale turbulence on lower trophic levels under different nutrient conditions [vol 32, pg 197, 2010]

Small-scale turbulence affects the pelagic food web and energy flow in marine systems and the impact is related to nutrient conditions and the assemblage of organisms present. We generated five levels of turbulence (2*10 29 to 1*10 24 W kg 21 ) in land-based mesocosms (volume 2.6 m 3 ) with and without additional nutrients (31:16:1 Si:N:P m M) to asses the effect of small-scale turbulence on the lower part of the pelagic food web under different nutrient conditions. The ecological influence of nutrients and small-scale turbulence on lower trophic levels was quantified using multivariate statistics (RDA), where nutrients accounted for 31.8% of the observed biological variation, while 7.2% of the variation was explained by small-scale turbulence and its interaction with nutrients. Chlorophyll a, primary production rates, bacterial production rates and diatom and dinoflagellate abundance were positively correlated to turbulence, regardless of nutrient conditions. Abundance of autotrophic flagellates, total phytoplankton and bacteria were positively correlated to turbulence only when nutrients were added. Impact of small-scale turbulence was related to nutrient con- ditions, with implications for oligotrophic and eutrophic situations. The effect on community level was also different compared to single species level. Microbial processes drive biogeochemical cycles, and nutrient-controlled effects of small-scale turbulence on such processes are relevant to foresee altered carbon flow in marine systems

Short-term Effects of Nutrients on a Barrier Island Grassland Community

Increased nutrient availability globally has the potential to affect community functional composition of plants in nutrient limited environments, such as coastal grassland systems. Stability of these systems are threatened worldwide by urbanization, as well as effects of sea level rise and increased frequency and intensity of storms, and atmospheric N deposition, associated with climate change. Annual net primary productivity (ANPP), species composition, and functional traits (community weighted specific leaf area (CWSLA), leaf area index (LAI), growth form and photosynthetic pathway) were measured across four treatments to assess multiple resource limitation of nitrogen (N) and phosphorus (P) and functional community response in a coastal grassland on Hog Island, VA within the Virginia Coast Reserve, Long Term Ecological Research Network (LTER) applied at a rate of 10 g m-2 yr-1 Nutrient enrichment did not alter species diversity or richness. ANPP was highest in plots receiving any type of nitrogen enrichment, and was higher than expected of low nutrient systems. CWSLA was significantly higher in NP plots, and was lower than other grasslands. P treatments were not significantly different from controls. Graminoid species, specifically C4 species responded with higher ANPP than C3 forbs or graminoids within treatments. Evidence of synergistic NP effects were seen on community level resource allocation and leaf construction, but no significant species changes occurred over a 1-year time span. These results have expanded the knowledge of functional response to increased nutrient availability in an understudied, coastal grassland, which are at high risk to being lost to sea level rise and anthropogenic development and inform community assembly processes in stressful environments

CO2 and nutrient-driven changes across multiple levels of organization in zostera noltii ecosystems

Increasing evidence emphasizes that the effects of human impacts on ecosystems must be investigated using designs that incorporate the responses across levels of biological organization as well as the effects of multiple stressors. Here we implemented a mesocosm experiment to investigate how the individual and interactive effects of CO2 enrichment and eutrophication scale-up from changes in primary producers at the individual (biochemistry) or population level (production, reproduction, and/ or abundance) to higher levels of community (macroalgae abundance, herbivory, and global metabolism), and ecosystem organization (detritus release and carbon sink capacity). The responses of Zostera noltii seagrass meadows growing in low-and high-nutrient field conditions were compared. In both meadows, the expected CO2 benefits on Z. noltii leaf production were suppressed by epiphyte overgrowth, with no direct CO2 effect on plant biochemistry or population-level traits. Multi-level meadow response to nutrients was faster and stronger than to CO2. Nutrient enrichment promoted the nutritional quality of Z. noltii (high N, low C : N and phenolics), the growth of epiphytic pennate diatoms and purple bacteria, and shoot mortality. In the low-nutrient meadow, individual effects of CO2 and nutrients separately resulted in reduced carbon storage in the sediment, probably due to enhanced microbial degradation of more labile organic matter. These changes, however, had no effect on herbivory or on community metabolism. Interestingly, individual effects of CO2 or nutrient addition on epiphytes, shoot mortality, and carbon storage were attenuated when nutrients and CO2 acted simultaneously. This suggests CO2-induced benefits on eutrophic meadows. In the high-nutrient meadow, a striking shoot decline caused by amphipod overgrazing masked the response to CO2 and nutrient additions. Our results reveal that under future scenarios of CO2, the responses of seagrass ecosystems will be complex and context-dependent, being mediated by epiphyte overgrowth rather than by direct effects on plant biochemistry. Overall, we found that the responses of seagrass meadows to individual and interactive effects of CO2 and nutrient enrichment varied depending on interactions among species and connections between organization levels.European Regional Development Fund through the COMPETE; Portuguese funds through the FCT project [PEst-C/MAR/LA0015/2011]

Nitrogen and phosphorus balances on Finnish dairy farms

The calculation of whole-farm nutrient balance is an effective and simple method for estimating the potential nutrient loading from dairy farming into the environment. In Finland, however, the published results based on larger number of farms are still lacking. In this study whole-farm nitrogen (N) and phosphorus (P) balances on Finnish dairy farms were studied based on short-cut data for the year 2002. The survey was targeted to 1260 dairy farms, located all over Finland. Of the 386 replies received, 319 were used for subsequent statistical analyses. The association between selected farm variables and nutrient balance was studied using regression analysis and a sensitivity coefficient was calculated for each regression slope. The average (± standard deviation) whole-farm nutrient balance for N and P was 109 (±41.3) and 12 (±7.2) kg ha-1, respectively. The most responsive factors affecting the nutrient balances were total nutrient and fertilizer import per ha, followed by animal density, milk export per ha and concentrate import per ha. The results suggested that nutrient surpluses could be controlled more easily in combined crop and milk than in specialised milk production. It is concluded that nutrient surplus on Finnish dairy farms is markedly lower than that on areas with intensive production in central European countries. However, when nutrient balances were extrapolated to comparable production intensity as in central Europe, the level of the surpluses was equal