International society of sports nutrition position stand: nutrient timing
Chad M. KerksickShawn M. ArentBrad J. SchöenfeldJeffrey R. StoutBill CampbellColin WilbornLem TaylorDoug KalmanAbbie E. Smith‐RyanRichard B. KreiderDarryn S. WilloughbyPaul J. ArcieroTrisha A. VanDusseldorpMichael J. OrmsbeeRobert WildmanMike GreenwoodTim N. ZiegenfussAlan A. AragonJosé Antonio
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Sports nutrition
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Douglas fir
Soil nutrients
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Humans are modifying the availability of nutrients such as nitrogen (N) and phosphorus (P), and it is therefore important to understand how these nutrients, independently or in combination, influence the growth and nutrient content of primary producers. Using meta‐analysis of 118 field and laboratory experiments in freshwater, marine and terrestrial ecosystems, we tested hypotheses about co‐limitation of N and P by comparing the effects of adding N alone, P alone, and both N and P together on internal N (e.g. %N, C:N) and P (e.g. %P, C:P) concentrations in autotroph communities. In particular, we tested the following predictions. First, if only one nutrient was limiting, addition of that nutrient should decrease the concentration of the other nutrient, but addition of the non‐limiting nutrient would have no effect on the internal concentration of the limiting nutrient. If community co‐limitation was occurring then addition of either nutrient should result in a decrease in the internal concentration of the other nutrient. Community co‐limitation could also result in no change – or even an increase – in N concentrations in response to P addition if P stimulated growth of N fixers. Finally, if biochemically dependent co‐limitation was occurring, addition of a limiting nutrient would not decrease, and could even increase, the concentration of the other, co‐limited nutrient. We found no general evidence for the decrease in the internal concentration of one nutrient due to addition of another nutrient. The one exception to this overall pattern was marine systems, where N addition decreased internal P concentrations. In contrast, P addition increased internal N concentrations across all experiments, consistent with co‐limitation. These results have important implications for understanding the roles that N and P play in controlling producer growth and internal nutrient accumulation as well as for managing the effects of nutrient enrichment in ecosystems. Synthesis On a global scale, humans have doubled nitrogen (N) inputs and quadrupled phosphorus (P) inputs relative to pre‐industrial levels. N and P fertilization influences autotroph internal nutrient concentrations and ratios and thereby affects a variety of community and ecosystem processes, including decomposition and consumer population dynamics. It is therefore critical to understand the effects of nutrient additions on the growth and nutrient concentrations of primary producers. We used meta‐analysis to evaluate the responses of autotroph internal N and P concentrations to additions of N, P, and N+P and make inferences about limitation and co‐limitation of N and P across marine, terrestrial, and freshwater ecosystems. We found little evidence for single‐nutrient limitation, highlighting the fact that multiple nutrients generally limit primary production.
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Abstract Balanced supply of of essential nutrients is one of the most important factors in increasing crop yields. The objective of this review is to discuss interactions among major and minor nutrients in crop plants. In crop plants, the nutrient interactions are generaly measured in terms of growth response and change in concentration of nutrients. Upon addition of two nutrients, a increase in crop yield that is more than adding only one, the interaction is positive (synergistic). Similarly, if adding the two nutrients together produced less yield as compared to individual ones, the interactions is negative (antagonistic).When there is no change, there is no interaction. All the three interactions among essential plant nutrients have been reported. However, most interactions are complex. A nutrient interacting simultaneously with more than one nutrients. This may induced deficiencies, toxicities, modified growth responses, and/or modified nutrient composition. Better understanding of nutrient interactions may be useful in understanding importance of balanced supply of nutrients and consequently improvement in plant growth or yields. Acknowledgments
Essential nutrient
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Seasonality
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The merits and methodological limitations of several main approaches for determining microalgal nutrient limitation are briefly reviewed and compared. (1) The elemental ratios of microalgae can reflect the status of nutrient limitation,but the result is far from constant and easily influenced by light,CO_(2) availability and nutrient status. (2) Enrichment experiments have been commonly used to determine the nutrient limitation in phytoplankton and natural water,but it can be influenced by the species composition of the seeding inocula phytoplankton sample and addition of one macronutrient may induce limitation of other nu trients. (3) Nutrient uptake kinetics can be used for detecting microalgal nutrient limitation, as nutrient limited cells exhibit increased uptake capacity or efficiency for the specific nutrient after it is re-supplied. But the uptake rates vary with a range of factors including microalgal species, nutrient history and nutrient status. (4) Biochemical approach has been used extensively in the study of N, P and Fe deprivation, but this method entails destruction of the sample and time consuming, and complicated process. (5) Fourier-transform infrared microspectroscopie analysis can reveal dramatic spectral differences between nutrient-limited and nutrient-replete microalgal cells and represents a novel method to investigate macromolecular synthesis in response to changes in nutrient supply. But this method has the limitation of requiring bulky and expensive equipment. (6) The chlorophyll fluorescence measurements are non-destructive and highly sensitive, thus require only small volumes and low concentration of experimental samples. These characteristics make it become an increasing potential approach for exploring nutrient status of microalgae and their physiological response to varying environmental conditions.
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Theoretical considerations based on nutrition experiments suggest that nutrient ratios of terrestrial plants are similar to the Redfield ratio found in marine phytoplankton. Laboratory experiments have shown that seedlings of many different plant species have similar nutrient concentration ratios when supplied with nutrients at free access. However, at free access, nutrients are likely to be taken up in amounts in excess of a plant's requirements for growth. In further experiments, therefore, the supply rate of each nutrient was reduced so that excessive uptake did not occur. Again, similar nutrient ratios were found among the plant species tested, although the ratios differed from those found in plants given free access to nutrients. Based on the law of the minimum, we suggest that optimum nutrient ratios be defined as the ratios found in plants when all nutrients are limiting growth simultaneously. The literature on nutrient concentrations was surveyed to investigate nutrient ratios in terrestrial ecosystems. Nutrients taken into consideration were nitrogen, phosphorus, potassium, calcium and magnesium. Based on the assumption that nitrogen is either the limiting nutrient or, when not limiting, is taken up only in small excess amounts, we calculated nutrient ratios from published data. The calculated ratios corresponded closely to the ratios determined in laboratory and field experiments.
Limiting
Redfield ratio
Terrestrial plant
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Nutrient Management
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