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1
Güsewell, Sabine. "N : P ratios in terrestrial plants: variation and functional significance". New Phytologist 164, n. 2 (20 settembre 2004): 243–66. http://dx.doi.org/10.1111/j.1469-8137.2004.01192.x.
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Qaim, S. M., M. Ibn Majah, R. Wölfle e B. Strohmaier. "Excitation functions and isomeric cross-section ratios for theZr90(n,p)90Ym,gandZr91(n,p)91Ym,gprocesses". Physical Review C 42, n. 1 (1 luglio 1990): 363–67. http://dx.doi.org/10.1103/physrevc.42.363.
3
Karchi, Zvi, e Daniel J. Cantliffe. "GROWTH OF CONTAINERIZED TRANSPLANTS SUPPLEMENTED WITH VARYING N AND P RATIOS". HortScience 26, n. 2 (febbraio 1991): 101b—101. http://dx.doi.org/10.21273/hortsci.26.2.101b.
4
Bakhshiyan, T. M. "Discussion of isomeric ratios in (p, n) and (d, 2n) reaction". Physics of Atomic Nuclei 79, n. 1 (gennaio 2016): 38–43. http://dx.doi.org/10.1134/s1063778816010051.
5
Simonne, E. H., J. N. McCrimmon, H. L. Scoggins-Mantero e H. A. Mills. "254 KJELDAHL N:DUMAS N RATIOS FOR SELECTED CROPS". HortScience 29, n. 5 (maggio 1994): 466b—466. http://dx.doi.org/10.21273/hortsci.29.5.466b.
Abstract (sommario):
With recent advances in N analyzers, the Dumas method becomes more attractive as a replacement for Kjeldahl N. Kjeldahl N (K_N):Dumas N (D_N) ratios were determined for anthurium (A), orchid (O), fern (F) and turf (T). Dry tissues were ground to pass a 20-mesh seive. D_N was determined using 0.2 g of sample and a Leco FP-428. K_N was determined by digesting 0.4 g tissue with a CuO/TiO/K2SO4 catalyst and 10 mL H2SO4 at 450°C for 2 hr. Ammonium in the digest was assayed by colorimetry (Lachat analyzer). Overall (n=397 obs.), D_N was a good estimator of K_N: K_N = 0.90(p<0.01) D_N + 0.09(p=0.03), R2=0.93, over the 0.4-6.6 N range. K_N:D_N ratio was significantly (p<0.01) affected by plant type. Ratios of 0.85 for A, 0.92 for T, 0.99 for O, and 1.00 for F may be used to estimate K-N from D-N for the diagnosis of N nutrition, along with existing interpretative data.
6
Kraus, H. T., S. L. Warren, G. J. Bjorkquist, A. W. Lowder, C. M. Tchir e K. N. Walton. "Nitrogen:Phosphorus:Potassium Ratios Affect Production of Two Herbaceous Perennials". HortScience 46, n. 5 (maggio 2011): 776–83. http://dx.doi.org/10.21273/hortsci.46.5.776.
Abstract (sommario):
A series of experiments were undertaken to determine the effects of nitrogen (N), phosphorus (P), and potassium (K) concentrations and N:P:K ratio on flowering and vegetative growth of two herbaceous perennials, Hibiscus moscheutos L. (hibiscus) and Rudbeckia fulgida var. sullivantii Ait. ‘Goldsturm’ (rudbeckia). Plant growth and flowering of both hibiscus and rudbeckia were influenced by concentration and ratio of N, P, and K. When N was held constant at 100 mg·L−1, 4:1 N:K (25 mg·L−1 K) and 16:1 N:P (6.3 mg·L−1 P) were optimal for growing hibiscus, whereas higher K concentration (1:2 N:K, 200 mg·L−1 K) and lower P concentration (32:1 N:P, 3.1 mg·L−1 N) were required for optimal growth of rudbeckia. However, when holding N constant at 100 mg·L−1 and varying both P and K in the fertilizer solutions, higher P and K concentrations and a 2:1:2 (50 mg·L−1 P, 100 mg·L−1 K) N:P:K ratio best supported hibiscus growth, whereas 3:1:2 (33 mg·L−1 P, 66 mg·L−1 K) N:P:K was needed for growth of rudbeckia. Finally, when both N concentration and N:P:K ratio were altered, optimum growth of both hibiscus and rudbeckia was achieved at similar and lower P and K concentrations (25 mg·L−1 P and 50 mg·L−1 K) and 200 mg·L−1 N. An 8:1:2 N:P:K ratio was optimum for production of both hibiscus and rudbeckia, although 12:1:2 N:P:K (200 mg·L−1 N, 17 mg·L−1 P, 33 mg·L−1 K) produced similar growth of rudbeckia. Based on results of these two herbaceous perennials, it appears herbaceous perennials have N requirements similar to annual plants and P and K requirements similar to woody plants. Furthermore, the two herbaceous perennials used in this study required nutrients in the fertilizer solution at a higher N:P:K ratio than either annual or woody plants. Foliar concentrations of 2.2% N, 0.4% P, and 1.9% K were adequate for growth of hibiscus, whereas 2.4% N, 0.2% P, and 2.6% K were required to maximize growth of rudbeckia.
7
Huang, Xiaolong, e Dunjiu Cai. "Systematics of Isomeric Cross-Section Ratios for (n,2n), (n, p), (n, α) Reactions at 14.5 MeV". Nuclear Science and Engineering 125, n. 3 (marzo 1997): 371–75. http://dx.doi.org/10.13182/nse97-a24282.
8
Zhang, Lin, Lijuan Liu, Kaiwen Pan, Wei Li, Yanjie Wang, Mingrui Deng, Jiguo Xia e Xu Yang. "Post-wildfire soil and plant foliar nutrient ratios and soil fungi : bacterial ratios in alpine meadows on the southeastern Qinghai-Tibet Plateau". International Journal of Wildland Fire 24, n. 7 (2015): 933. http://dx.doi.org/10.1071/wf14147.
Abstract (sommario):
Wildfire is increasingly considered as a common ecological phenomenon in grassland. However, little is known about its effects on soil and plant nutrient ratios, especially in alpine ecosystems where wildfires are common. In the present study, nutrient ratios of the post-wildfire surface soil (0–5 cm) and nine dominant plant species leaves, in addition to soil fungi : bacterial ratios (F : B ratios), were investigated in the alpine meadows on the south-eastern Qinghai-Tibet Plateau, approximately 20 months after a high-severity wildfire. The results indicated that the burned sites had lower soil nitrogen : phosphorus (N : P) and nitrogen : potassium (N : K) ratios compared with unburned sites. Moreover, foliar N concentrations were lower on burned than unburned sites, but foliar N : P ratios were not different. Compared with the unburned sites, greater foliar K concentrations and lower N : K ratios were observed in burned sites. The idiosyncratic responses of foliar nutrient ratios to wildfire varied greatly, especially N and related nutrient ratios with plant species. Soil F : B ratios were positively correlated with soil C : N and C : P ratios, whereas they were negatively correlated with soil N : P and N : K ratios. The results of the present study suggest that there is reduced supply capacity of soil N for plants relative to soil P and K in the post-fire alpine meadow, which could have potential ecological implications in this region.
9
Buseva, Zh F., Sh G. Farahani, V. I. Razlutskij, E. A. Sysova, N. N. Maisak, K. V. Myagkova e P. C. Frost. "Stoichiometry and planktonic communities structure in littoral and pelagic zones of two lakes with different trophic types in Belarus". Doklady of the National Academy of Sciences of Belarus 66, n. 6 (3 gennaio 2023): 595–604. http://dx.doi.org/10.29235/1561-8323-2022-66-6-595-604.
Abstract (sommario):
Stoichiometric C : N : P ratios were compared between primary producers in littoral and pelagic ecosystems of mesotrophic relatively shallow lake Obsterno and shallow macrophyte covered low trophic lake Nobisto from May to October over the next two years. Elemental seston ratios of lake Obsterno revealed smaller differences between littoral and pelagic zones in comparison with lake Nobisto in 2017. During the studied period, in the both lakes, the seston C : N and C : P ratios were higher than the Redfield ratio (106 : 16 : 1 C : N : P) on most dates and N : P was always more than 16. Pelagic C : P and N : P ratios in lake Obsterno were the highest in May in 2017, July and September in 2018 with significant differences between littoral and pelagic zones. N : P ratios decreased in October but there were no significant differences among habitats. In lake Nobisto in 2018, seston C : P and N : P ratios increased from May to July in littoral and pelagic zones but then decreased in September to October. Our research shows differences in stoichiometric ratios in littoral and pelagic zones of these two lakes, which indicates food quality (seston C : N : P ratios) differences for zooplankton species depending on season and location.
10
Hawke, David J. "Soil P in a forested seabird colony: inventories, parent material contributions, and N : P stoichiometry". Soil Research 43, n. 8 (2005): 957. http://dx.doi.org/10.1071/sr05075.
Abstract (sommario):
Guano from breeding seabirds provides a large external source of nutrients to the soils of breeding colonies. However, little is known of guano P retention relative to N or the relative importance of guano and soil parent material as P sources. Soil profile N and P inventories (0–0.60 m, n = 4; 0–0.36 m, n = 1) and guano N and P concentrations were measured at a Westland petrel colony, and the parent material contributions of P were calculated using Ca, Al, Fe, Ti, and Zr as reference elements. Median inventories (0–0.60 m) were 1.49 kg N/m2 and 332 × 10–3 kg P/m2, the N result being similar to that from a seabird colony on peat soil where N retention was very low. Calculated parent material contributions were smallest (32–66% of soil P) when based on Ca and largest (47–102% of soil P) when based on Zr. Contributions were similar for Al, Fe, and Ti; Al (41–87% soil P) was selected for subsequent calculations. Regardless of the reference element, parent material therefore contributed a large part of soil P. Phosphorus in excess of parent material supply (Pexcess) was significantly correlated with soil C, implying that guano P is held primarily in organic form. The median soil N : P molar ratios were 9.6 : 1 based on total P and 11.2 : 1 based on Pexcess, compared with ratios for Westland petrel guano of 4.1 : 1 (when birds were consuming fisheries waste) and 16.4 : 1 (when fisheries waste was replaced by fish). The similarity between soil and guano N : P ratios implies that both N and P are lost from soil at similar rates, although volatilisation of N would enrich soil drainage water in P. Calculations using guano deposition rates from the literature yielded P residence times of 4–15 years (Pexcess) and 11–41 years (total P), consistent with a highly dynamic soil system.
11
Smagula, John M., Walter Litten e Scott Dunham. "623 Lowbush Blueberry Response to Phosphorus Fertilizers with Different P: N Ratios". HortScience 35, n. 3 (giugno 2000): 504E—504. http://dx.doi.org/10.21273/hortsci.35.3.504e.
Abstract (sommario):
In three commercial fields with a history of low leaf P concentrations, triple super phosphate (TSP) (1 P: 0 N), monoammonium phosphate (MAP) (2.1 P: 1 N), and diammonium phosphate (DAP) (1.11 P: 1 N) with P at 67.2 kg·ha-1 were compared to a control in a randomized complete-block design with 12 blocks. In 1995, all fertilizer treatments were comparable in raising soil P concentrations, but MAP and DAP resulted in higher P leaf concentrations compared to the control. DAP was more effective than MAP in raising N leaf concentrations. Leaf concentrations of Mg, B, and Cu were lowered by MAP and DAP but not TSP. Stem density, stem length, flower buds per stem, flower bud density, and yield were raised by DAP. The same treatments were applied in May 1997 and in May 1999 to the same plots in the same fields. In 1997, by the time of tip dieback in the prune year of that cycle, foliar concentration of P and N averaged higher than in the previous cycle, but still were not up to the standard for N. Fruit yield for the second cycle averaged substantially higher for the controls and for all three treatments, most dramatically for the DAP. In 1999, with only two fields available, response to treatments depended on soil N availability. At the field where leaf N was lower in control plots, MAP and DAP were more effective than TSP in raising leaf P.
12
Suttle, C. A., e P. J. Harrison. "Ammonium and phosphate uptake rates, N: P supply ratios, and evidence for N and P limitation in some oligotrophic lakes1". Limnology and Oceanography 33, n. 2 (marzo 1988): 186–202. http://dx.doi.org/10.4319/lo.1988.33.2.0186.
13
Singh, A., S. E. Baer, U. Riebesell, A. C. Martiny e M. W. Lomas. "C : N : P stoichiometry at the Bermuda Atlantic Time-series Study station in the North Atlantic Ocean". Biogeosciences 12, n. 21 (9 novembre 2015): 6389–403. http://dx.doi.org/10.5194/bg-12-6389-2015.
Abstract (sommario):
Abstract. Nitrogen (N) and phosphorus (P) availability, in addition to other macro- and micronutrients, determine the strength of the ocean's carbon (C) uptake, and variation in the N : P ratio of inorganic nutrient pools is key to phytoplankton growth. A similarity between C : N : P ratios in the plankton biomass and deep-water nutrients was observed by Alfred C. Redfield around 80 years ago and suggested that biological processes in the surface ocean controlled deep-ocean chemistry. Recent studies have emphasized the role of inorganic N : P ratios in governing biogeochemical processes, particularly the C : N : P ratio in suspended particulate organic matter (POM), with somewhat less attention given to exported POM and dissolved organic matter (DOM). Herein, we extend the discussion on ecosystem C : N : P stoichiometry but also examine temporal variation in stoichiometric relationships. We have analyzed elemental stoichiometry in the suspended POM and total (POM + DOM) organic-matter (TOM) pools in the upper 100 m and in the exported POM and subeuphotic zone (100–500 m) inorganic nutrient pools from the monthly data collected at the Bermuda Atlantic Time-series Study (BATS) site located in the western part of the North Atlantic Ocean. C : N and N : P ratios in TOM were at least twice those in the POM, while C : P ratios were up to 5 times higher in TOM compared to those in the POM. Observed C : N ratios in suspended POM were approximately equal to the canonical Redfield ratio (C : N : P = 106 : 16 : 1), while N : P and C : P ratios in the same pool were more than twice the Redfield ratio. Average N : P ratios in the subsurface inorganic nutrient pool were ~ 26 : 1, squarely between the suspended POM ratio and the Redfield ratio. We have further linked variation in elemental stoichiometry to that of phytoplankton cell abundance observed at the BATS site. Findings from this study suggest that elemental ratios vary with depth in the euphotic zone, mainly due to different growth rates of cyanobacterial cells. We have also examined the role of the Arctic Oscillation on temporal patterns in C : N : P stoichiometry. This study strengthens our understanding of the variability in elemental stoichiometry in different organic-matter pools and should improve biogeochemical models by constraining the range of non-Redfield stoichiometry and the net relative flow of elements between pools.
14
Singh, A., S. E. Baer, U. Riebesell, A. C. Martiny e M. W. Lomas. "C : N : P stoichiometry at the Bermuda Atlantic Time-series Study station in the North Atlantic Ocean". Biogeosciences Discussions 12, n. 12 (19 giugno 2015): 9275–305. http://dx.doi.org/10.5194/bgd-12-9275-2015.
Abstract (sommario):
Abstract. Nitrogen (N) and phosphorus (P) availability determine the strength of the ocean's carbon (C) uptake, and variation in the N : P ratio in inorganic nutrients is key to phytoplankton growth. A similarity between C : N : P ratios in the plankton biomass and deep-water nutrients was observed by Alfred C. Redfield around 80 years ago and suggested that biological processes in the surface ocean controlled deep ocean chemistry. Recent studies have emphasized the role of inorganic N : P ratios in governing biogeochemical processes, particularly the C : N : P ratio in suspended particulate organic matter (POM), with somewhat less attention given to exported POM and dissolved organic matter (DOM). Herein, we extend the discussion on ecosystem C : N : P stoichiometry but also examine temporal variation of stoichiometric relationships. We have analysed elemental stoichiometry in the suspended POM and total (POM + DOM) organic matter (TOM) pools in the upper 100 m, and in the exported POM and sub-euphotic zone (100–500 m) inorganic nutrient pools from the monthly data collected at the Bermuda Atlantic Time-series Study (BATS) site located in the western part of the North Atlantic Ocean. C : N : P ratios in the TOM pool were more than twice that in the POM pool. Observed C : N ratios in suspended POM were approximately equal to the canonical Redfield Ratio (C : N : P = 106 : 16 : 1), while N : P and C : P ratios in the same pool were more than twice the Redfield Ratio. Average N : P ratios in the subsurface inorganic nutrient pool were ~ 26 : 1, squarely between the suspended POM ratio and the Redfield ratio. We have further linked variation in elemental stoichiometry with that of phytoplankton cell abundance observed at the BATS site. Findings from this study suggest that the variation elemental ratios with depth in the euphotic zone was mainly due to different growth rates of cyanobacterial cells. These time-series data have also allowed us to examine the potential role of climate variability on C : N : P stoichiometry. This study strengthens our understanding of elemental stoichiometry in different organic matter pools and should improve biogeochemical models by constraining the range of non-Redfield stoichiometry.
15
Smagula, J. M., W. Litten e S. Dunham. "Lowbush Blueberry Response to Different Phosphorus/Nitrogen Ratios". HortScience 33, n. 3 (giugno 1998): 529d—529. http://dx.doi.org/10.21273/hortsci.33.3.529d.
Abstract (sommario):
Lowbush blueberries (Vaccinium angustifolium Ait.) in three commercial fields were treated with 67.2 kg P/ha from triple super phosphate (TSP), monoammonium phosphate (MAP), or diammonium phosphate (DAP) and compared to a control in a randomized complete-block design with 12 blocks. Correction of P deficiency by fertilizers with different ratios of P to N was assessed by leaf nutrient concentrations. Samples of stems collected in July from three 0.03-m2 quadrats per treatment plot indicated MAP and DAP had no effect on dry weight of stem tissue, but increased average dry weight of leaf tissue. P and N Leaf concentrations were raised to higher levels by MAP and DAP than by TSP. TSP had no effect on leaf N concentrations but raised leaf P concentrations compared to controls. Stem length, flower buds per stem and flower bud density were increased by both MAP and DAP, but not TSP. MAP and DAP increased fruit yield by about 340 kg/ha compared to the control.
16
Bo, Fujing, Yunxiang Zhang, Han Y. H. Chen, Pingan Wang, Xuming Ren e Jinping Guo. "The C:N:P Stoichiometry of Planted and Natural Larix principis-rupprechtii Stands along Altitudinal Gradients on the Loess Plateau, China". Forests 11, n. 4 (25 marzo 2020): 363. http://dx.doi.org/10.3390/f11040363.
Abstract (sommario):
Carbon:nitrogen:phosphorus (C:N:P) stoichiometry plays a critical role in nutrient cycling, biodiversity, and ecosystem functionality. However, our understanding of the responses of C:N:P stoichiometry to elevation and forest management remains elusive. Here we sampled 18 Larix principis-rupprechtii sites along altitudinal gradients (1700-2300 m) on Guandishan Mountain in the Loess Plateau, China. We determined the leaf, litter, and soil C N P contents and C:N:P stoichiometric ratios, as well as nutrient resorption efficiency (NuRE), and diameter at breast height (DBH) increments in both planted and natural stands, and then tested the impacts of elevation and stand origin on these parameters’ management. We found different C:N:P stoichiometry between natural and planted forests. The results revealed that: soil C, N, and N:P ratios, litter C:P and N:P ratios, leaf C:N and N:P ratios increased significantly; however, soil C:N ratios, litter P, leaf N and P, nitrogen resorption efficiency (NRE), and DBH increments decreased significantly with elevation in the planted forests. Soil C,N and N:P ratios, litter C, as well as C:N and C:P ratios increased significantly with elevation in natural forests. The soil N, P and N:P ratios, litter C:P and N:P ratios, leaf C, C:P and N:P ratios, nitrogen resorption efficiency (NRE), phosphorus resorption efficiency (PRE), and DBH increments were, on average, higher in the planted, rather than natural forests. Our results indicated that there was an enhancing P-limitation in both the planted and natural forests, and the plantations were more restricted by P. Moreover, compared to natural forests, plantations converged toward a higher conservative N- and P-use strategy by enhancing resorption efficiencies of internal nutrient cycling and a higher annual growth rate.
17
Flohr, A., A. K. van der Plas, K. C. Emeis, V. Mohrholz e T. Rixen. "Spatio-temporal patterns of C : N : P ratios in the northern Benguela upwelling system". Biogeosciences 11, n. 3 (14 febbraio 2014): 885–97. http://dx.doi.org/10.5194/bg-11-885-2014.
Abstract (sommario):
Abstract. On a global scale the ratio of fixed nitrogen (N) and phosphate (P) is characterized by a deficit of N with regard to the classical Redfield ratio of N : P = 16 : 1 reflecting the impact of N loss occurring in the oceanic oxygen minimum zones. The northern Benguela upwelling system (NBUS) is known for losses of N and the accumulation of P in sub- and anoxic bottom waters and sediments of the Namibian shelf resulting in low N : P ratios in the water column. To study the impact of the N : P anomalies on the regional carbon cycle and their consequences for the export of nutrients from the NBUS into the oligotrophic subtropical gyre of the South Atlantic, we measured dissolved inorganic carbon (CT), total alkalinity (AT), oxygen (O2) and nutrient concentrations in February 2011. The results indicate increased P concentrations over the Namibian shelf due to P efflux from sediments resulting in a C : N : P : -O2 ratio of 106 : 16 : 1.6 : 138. N reduction further increase C : N and reduce N : P ratios in those regions where O2 concentrations in bottom waters are < 20 μmol kg−1. However, off the shelf along the continental margin, the mean C : N : P : -O2 ratio is again close to the Redfield stoichiometry. Additional nutrient data measured during two cruises in 2008 and 2009 imply that the amount of excess P, which is created in the bottom waters on the shelf, and its export into the subtropical gyre after upwelling varies through time. The results further reveal an inter-annual variability of excess N within the South Atlantic Central Water (SACW) that flows from the north into the NBUS, with highest N values observed in 2008. It is postulated that the N excess in SACW occurred due to the impact of remineralized organic matter produced by N2 fixation and that the magnitude of excess P formation and its export is governed by inputs of excess N along with SACW flowing into the NBUS. Factors controlling N2 fixation north of the BUS need to be addressed in future studies to better understand the role of the NBUS as a P source and N sink in the coupled C : N : P cycles.
18
Xie, Junyi, Haifu Fang, Qiang Zhang, Mengyun Chen, Xintong Xu, Jun Pan, Yu Gao, Xiangmin Fang, Xiaomin Guo e Ling Zhang. "Understory Plant Functional Types Alter Stoichiometry Correlations between Litter and Soil in Chinese Fir Plantations with N and P Addition". Forests 10, n. 9 (28 agosto 2019): 742. http://dx.doi.org/10.3390/f10090742.
Abstract (sommario):
Research Highlights: This study identifies the effect of nitrogen (N) and phosphorus (P) addition on stoichiometry correlations between understory plants and soil in subtropical Chinese fir plantations. Background and Objectives: Nitrogen and P are two nutrients limiting forest ecosystem production. To obtain more wood production, N and P are usually applied in plantation management. Changes in soil N and P will generally alter the stoichiometric characteristics of understory plants, which control carbon (C) and nutrient cycles between plants and soil. However, different correlations between plant and soil stoichiometry among functional groups of understory plants have not been investigated, which also impacted element cycling between plants and soil. Materials and Methods: Subtropical Chinese fir plantations were selected for N (100 kg ha−1 year−1) and P (50 kg ha−1 year−1) addition study. We collected fresh litter and the corresponding soil of four understory plants (Lophatherum gracile Brongn., Woodwardia japonica (L.f.) Sm., Dryopteris atrata (Kunze) Ching and Dicranopteris dichotoma (Thunb.) Berhn.) for study of C, N, and P stoichiometric ratios. Results: Nitrogen and P addition affected C, N, and P concentrations and stoichiometric ratios in litter and soil as well as correlations between litter and soil stoichiometric ratios. Understory plant species with different functional types impacted the correlations between plants and soil in C, N, and P stoichiometric ratios, especially correlations between litter C and soil C and N. Conclusions: Changes in soil N and P affect the stoichiometric ratios of understory plants. Functional groups impacted the correlation in C, N, and P stoichiometric ratios between plants and soil, indicating functional groups varied in their impacts on element cycling between plants and soil in plantations with exogenous nutrient addition, which should be considered in future management of plantations with intensive fertilization practice.
19
Liu, Jing, Feng Lu e Yan Zhao Yang. "A Study on the Characteristics of Nitrogen and Phosphorus Runoff from Farmland under Wheat-Rice Rotation in Nansi Lake Basin". Advanced Materials Research 518-523 (maggio 2012): 1426–29. http://dx.doi.org/10.4028/www.scientific.net/amr.518-523.1426.
Abstract (sommario):
Field runoff pools were used to collect the surface runoff samples of wheat-rice rotation in Nansi Lake region, and different forms of nitrogen (N) and phosphorus (P) data were analyzed. The average runoff concentrations, losses, and characteristic ratios of N and P were studied. The average runoff concentrations of TN and TP in wheat–rice rotation were 0.87–7.94 and 0.08–0.81, respectively. The characteristic ratios of N and P were also observed. And the characteristic ratios of NO3--N, NH4+-N, DP, and PO43--P were 45.03%, 17.55%, 71.43%, and 54.01% in wheat–rice rotation, respectively.
20
Tanioka, Tatsuro, e Katsumi Matsumoto. "A meta-analysis on environmental drivers of marine phytoplankton C : N : P". Biogeosciences 17, n. 11 (9 giugno 2020): 2939–54. http://dx.doi.org/10.5194/bg-17-2939-2020.
Abstract (sommario):
Abstract. The elemental stoichiometry of marine phytoplankton plays a critical role in global biogeochemical cycles through its impact on nutrient cycling, secondary production, and carbon export. Although extensive laboratory experiments have been carried out over the years to assess the influence of different environmental drivers on the elemental composition of phytoplankton, a comprehensive quantitative assessment of the processes is still lacking. Here, we synthesized the responses of P:C and N:C ratios of marine phytoplankton to five major drivers (inorganic phosphorus, inorganic nitrogen, inorganic iron, irradiance, and temperature) by a meta-analysis of experimental data across 366 experiments from 104 journal articles. Our results show that the response of these ratios to changes in macronutrients is consistent across all the studies, where the increase in nutrient availability is positively related to changes in P:C and N:C ratios. We found that eukaryotic phytoplankton are more sensitive to the changes in macronutrients compared to prokaryotes, possibly due to their larger cell size and their abilities to regulate their gene expression patterns quickly. The effect of irradiance was significant and constant across all studies, where an increase in irradiance decreased both P:C and N:C. The P:C ratio decreased significantly with warming, but the response to temperature changes was mixed depending on the culture growth mode and the growth phase at the time of harvest. Along with other oceanographic conditions of the subtropical gyres (e.g., low macronutrient availability), the elevated temperature may explain why P:C is consistently low in subtropical oceans. Iron addition did not systematically change either P:C or N:C. Overall, our findings highlight the high stoichiometric plasticity of eukaryotes and the importance of macronutrients in determining P:C and N:C ratios, which both provide us insights on how to understand and model plankton diversity and productivity.
21
Yang, Shuang, Zhaoyong Shi, Yichun Sun, Xiaohui Wang, Wenya Yang, Jiakai Gao e Xugang Wang. "Stoichiometric Ratios of Carbon, Nitrogen and Phosphorus of Shrub Organs Vary with Mycorrhizal Type". Agriculture 12, n. 7 (20 luglio 2022): 1061. http://dx.doi.org/10.3390/agriculture12071061.
Abstract (sommario):
Mycorrhizal types are a predictive framework for nutrient cycling within and across ecosystems, and their types represent different nutrient-acquisition strategies for plants. Carbon (C), nitrogen (N) and phosphorus (P) stoichiometric ratios are essential for understanding biogeochemical processes. The purpose of this study was to reflect the balance in the process of plant resource acquisition by exploring the C, N and P stoichiometric ratios (C/N, N/P, and C/P) in shrub organs in different mycorrhizal types. In this study, the C, N, and P stoichiometric ratios in leaves, stems and roots were analyzed in the types of arbuscular mycorrhizal (AM), ectomycorrhizal (ECM) and AM + ECM of shrubs in Northern China. The results showed that C/N in the stems and roots of AM plants (95.75 and 81.42) was significantly lower than in AM + ECM plants (109.89 and 102.37) and ECM plants (107.67 and 96.93), while both N/P and C/P in the leaves, stems and roots of AM shrubs (38.67, 36.17, 40.69; 1028.14, 2989.13, and 2659.18) were significantly higher than in ECM shrubs (30.52, 22.31, 20.47; 796.51, 2208.28, and 1714.95). Moreover, different elements among the same plant organs were closely correlated, and the same pattern was found among the same element ratios among different plant organs. This suggests that mycorrhizal type can influence C, N and P ratios among different organs.
22
Goldman, Joel C. "On phytoplankton growth rates and particulate C: N: P ratios at low light1". Limnology and Oceanography 31, n. 6 (novembre 1986): 1358–63. http://dx.doi.org/10.4319/lo.1986.31.6.1358.
23
Rodriguez, Ian R., Grady L. Miller e L. B. McCarty. "Bermudagrass Establishment on High Sand-content Soils Using Various N-P-K Ratios". HortScience 37, n. 1 (febbraio 2002): 208–9. http://dx.doi.org/10.21273/hortsci.37.1.208.
Abstract (sommario):
For drainage, turfgrass is often established on sand-based soils, which are typically nutrient-deficient and require supplemental fertilization. The objective of this study was to determine the optimum N-P-K fertilizer ratio for establishing bermudagrass from sprigs in sand. `FloraDwarf' and `Tifdwarf' bermudagrasses [Cynodon dactylon (L.) Pers. × C. transvaalensis Burt-Davy] were sprigged on a United States Golf Association (USGA) green [85 sand: 15 peat (v/v)] in Aug. 1996 at the Univ. of Florida's Envirogreen in Gainesville, Fla. `TifEagle' bermudagrass was sprigged on a USGA green [85 sand: 15 peat (v/v)] and `Tifway' bermudagrass [C. dactylon (L.) Pers.] was sprigged on native soil at Clemson Univ. in Clemson, S.C. in May 1999. Treatments consisted of fertilizer ratios of 1N-0P-0.8K, 1N-0P-1.7K, 1N-0.4P-0.8K, 1N-0.9P-0.8K, and 1N-1.3P-0.8K applied based on a N rate of 49 kg·ha-1/week for 7 weeks. Growth differences were apparent among cultivars. A 1N-0P-0.8K or 1N-0P-1.7K ratio is insufficient for optimum growth of bermudagrass during establishment, even when planted on a soil high in P. Increased coverage rate with additional P was optimized at a ratio of 1N-0.4P at all four sites. Increased coverage with P was greatest on the sand-based greens, probably due to the very low initial P levels of the soils. On two of the sand-based greens, P in excess of a 1N-0.4P ratio decreased coverage rate.
24
Gjyli, Laura, Ariola Bacu, Jerina Kolitari, Silvana Gjyli e Anisa Trifoni. "Estimation of N/P Ratios Levels in a Coastal Bay, Southern Adriatic Sea". Journal of Agriculture and Ecology Research International 8, n. 1 (10 gennaio 2016): 1–9. http://dx.doi.org/10.9734/jaeri/2016/25052.
25
Pulfrey, D. L., J. J. Kuek, M. P. Leslie, B. D. Nener, G. Parish, U. K. Mishra, P. Kozodoy e E. J. Tarsa. "High UV/solar rejection ratios in GaN/AlGaN/GaN p-i-n photodiodes". IEEE Transactions on Electron Devices 48, n. 3 (marzo 2001): 486–89. http://dx.doi.org/10.1109/16.906440.
26
Thirumoolan, D., K. Anver Basha, Tapan Kanai, S. Mohammed Safiullah, K. Vetrivel, K. Abdul Wasi e B. Ranjithkumar. "Synthesis, characterization and reactivity ratios of poly N-(p-bromophenyl)-2-methacrylamide-Co-N-vinyl-2-pyrrolidone". Journal of Saudi Chemical Society 20, n. 2 (marzo 2016): 195–200. http://dx.doi.org/10.1016/j.jscs.2013.09.003.
27
Arcila, Juan S., Daniela Céspedes e Germán Buitrón. "Influence of wavelength photoperiods and N/P ratio on wastewater treatment with microalgae–bacteria". Water Science and Technology 84, n. 3 (1 luglio 2021): 712–24. http://dx.doi.org/10.2166/wst.2021.257.
Abstract (sommario):
Abstract This research investigates the effect of mixing wavelength light photoperiods (12 h blue, 8 h blue: 4 h green, 4 h blue: 8 h green, and 12 h green) and N/P ratios (1.3 to 8.3) on the growth microalgae–bacteria systems, organic matter, and nutrient removals. The highest microalgae–bacteria growth performance (μ = 0.2 d−1, 481.1 ± 15.3 mg DW L−1) was observed when a 8 h blue: 4 h green mixed wavelength and a low N/P ratio were used. For both N/P ratios, biomass productivity was favored when using the blue light dominated at longer time periods. Mechanisms for nitrogen removal by assimilation depend on the N/P ratio, achieving assimilation between 49 and 65% at a low N/P ratio. High nitrogen removal (>50%) showed a strong relation with alkalinity culture conditions (pH > 8.5). The mixing of wavelength photoperiods seems to be a promising strategy to achieve high biomass productivity and nutrient removal. However, for optimal conditions, N/P ratios in the wastewater should be considered.
28
Alamrousi, Ahmed, Eduardo Casais, Érika García-Cardesín, Ingrid Masaló, José Pintado e Javier Cremades. "Influence of pH, N, P, N: P Ratio, and Dissolved Inorganic Carbon on Ulva ohnoi Growth and Biomass Quality: Potential Implications in IMTA-RAS". Aquaculture Journal 2, n. 4 (3 novembre 2022): 285–301. http://dx.doi.org/10.3390/aquacj2040017.
Abstract (sommario):
Ulva ohnoi has a big potential in IMTA-RAS fish–seaweed systems. In order to design the best production strategy in these systems, the effect of the main environmental factors, such as pH, nutrient concentration (N, P, and N: P ratios) and dissolved inorganic carbon (DIC), on the productivity, bio filtration capacity, and quality of the biomass obtained was studied. It is concluded that in closed systems, strong pH variations (7.9–10.1) do not influence the growth of U. ohnoi and growth is slowed down due to the depletion of DIC. This fact would not be a problem in IMTA-RAS fish–macroalgae systems, due to the physiological activity of the fish contributing CO2 to the medium and replenishing it. The results obtained in the wide range of N: P ratios tested (2–410), allow us to conclude that this ratio should not be a limiting factor for the cultivation of Ulva ohnoi in IMTA-RAS systems. Based on those results, the best strategy to follow in an IMTA-RAS sole–sea lettuce would be to maintain the algae with highest level of nitrogen. This procedure implies a high rate of water renewal, which would also guarantee the maintenance of an adequate DIC and the best commercial quality of seaweed.
29
Flohr, A., A. K. van der Plas, K. C. Emeis, V. Mohrholz e T. Rixen. "Spatio-temporal patterns of C : N : P ratios in the northern Benguela upwelling regime". Biogeosciences Discussions 10, n. 6 (27 giugno 2013): 10459–89. http://dx.doi.org/10.5194/bgd-10-10459-2013.
Abstract (sommario):
Abstract. Dissolved carbon to nutrient ratios in the oceans' interior are remarkably consistent with the classical C : N : P : O2 Redfield ratio of 106 : 16 : 1 : 138 reflecting the mean composition of organic matter photosynthesized in the sunlit surface ocean. Deviations from the Redfield ratio indicate changes in the functioning of the biological carbon pump, which is driven and limited by the availability of nutrients. The northern Benguela coastal upwelling system (NBUS) is known for losses of fixed nitrogen (N = NO3–, NO2– and NH4+) and the accumulation of phosphate (P) in sub- and anoxic bottom waters and sediments of the Namibian shelf. To study the impact on the regional carbon cycle and consequences for the nutrient export from the BUS into the oligotrophic subtropical gyre of the South Atlantic Ocean we measured dissolved inorganic carbon (CT), oxygen (O2), and nutrient concentrations as well as the total alkalinity (AT) in February 2011. Our results indicate that over the Namibian shelf the C : N : P : O2 ratio decreases to 106 : 16 : 1.6 : 138 because of phosphate efflux from sediments. N reduction further increase C : N and reduce N : P ratios in those regions where O2 concentrations in bottom waters are < 20 µmol kg–1. However, off the shelf along the continental margin the mean C : N : P : O2 ratio is again close to the Redfield stoichiometry. Comparing the situation of 2011 with nutrient concentration data measured during 2 cruises in 2008 and 2009 implies that the amount of excess P that is created in the bottom waters on the shelf and its export into the subtropical gyre after upwelling varies through time. The magnitude of excess P formation and export is governed by inputs of excess N along with the South Atlantic Central Water (SACW) flowing into the NBUS from the north as a poleward compensation current. Since excess N is produced by the remineralization of N-enriched biomass built up by N2-fixing organisms, factors controlling N2 fixation north of the BUS need to be addressed in future studies to better understand the NBUS' role as P source and N sink in the coupled C : N : P cycles.
30
Neatrour, Matthew A., Robert H. Jones e Stephen W. Golladay. "Assessment of Nutrient Limitation in Floodplain Forests with Two Different Techniques". Research Letters in Ecology 2008 (2008): 1–4. http://dx.doi.org/10.1155/2008/260754.
Abstract (sommario):
We assessed nitrogen and phosphorus limitation in a floodplain forest in southern Georgia in USA using two commonly used methods: nitrogen to phosphorus (N:P) ratios in litterfall and fertilized ingrowth cores. We measured nitrogen (N) and phosphorus (P) concentrations in litterfall to determine N:P mass ratios. We also installed ingrowth cores within each site containing native soil amended with nitrogen (N), phosphorus (P), or nitrogen and phosphorus (N + P) fertilizers or without added fertilizer (C). Litter N:P ratios ranged from 16 to 22, suggesting P limitation. However, fertilized ingrowth cores indicated N limitation because fine-root length density was greater in cores fertilized with N or N + P than in those fertilized with P or without added fertilizer. We feel that these two methods of assessing nutrient limitation should be corroborated with fertilization trials prior to use on a wider basis.
31
Duan, Yehui, Fengna Li, Lili Li, Juexin Fan, Xiaoming Sun e Yulong Yin. "n-6:n-3 PUFA ratio is involved in regulating lipid metabolism and inflammation in pigs". British Journal of Nutrition 111, n. 3 (15 agosto 2013): 445–51. http://dx.doi.org/10.1017/s0007114513002584.
Abstract (sommario):
The objective of the present study was to investigate the optimal dietary n-6:n-3 PUFA ratios that regulate lipid metabolism and inflammation in pigs. A total of ninety-six cross-bred (Large White × Landrace) growing-finishing pigs (73·8 (sem 1·6) kg) were chosen and fed one of the four isoenergetic diets with n-6:n-3 PUFA ratios of 1:1, 2·5:1, 5:1 and 10:1. The growth performance of pigs fed the diet with an n-6:n-3 PUFA ratio of 5:1 was the best, but the group fed the diet with an n-6:n-3 PUFA ratio of 1:1 had the highest muscle mass and the lowest adipose tissue mass (P< 0·05). The concentrations of IL-6 and IL-1β of pigs fed the diet with an n-6:n-3 PUFA ratio of 1:1 were decreased compared with those of the other groups (P< 0·05). The concentration of adiponectin of pigs fed the diet with an n-6:n-3 PUFA ratio of 1:1 was also markedly decreased, but the concentration of leptin was increased compared with that of the groups fed the diets with n-6:n-3 PUFA ratios of 5:1 and 10:1 (P< 0·05). Additionally, the optimal dietary ratios of n-6:n-3 PUFA of 1:1 and 5:1 markedly suppressed the expression levels of lipid metabolism-related genes and proteins such as phosphoinositide-3-kinase-α, fatty acid transport protein-1 and PPARγ. They also significantly suppressed the expression levels of the inflammatory cytokines IL-1β, TNF-α and IL-6. The results indicated that the optimal n-6:n-3 PUFA ratios of 1:1 and 5:1 exerted beneficial effects on lipid metabolism and inflammatory system, leading to the availability of more energy and nutrients for high performance and homeostatic pathways.
32
Vrede, Katarina, Mikal Heldal, Svein Norland e Gunnar Bratbak. "Elemental Composition (C, N, P) and Cell Volume of Exponentially Growing and Nutrient-Limited Bacterioplankton". Applied and Environmental Microbiology 68, n. 6 (giugno 2002): 2965–71. http://dx.doi.org/10.1128/aem.68.6.2965-2971.2002.
Abstract (sommario):
ABSTRACT Marine bacterioplankton were isolated and grown in batch cultures until their growth became limited by organic carbon (C), nitrogen (N), or phosphorus (P). Samples were taken from the cultures at both the exponential and stationary phases. The elemental composition of individual bacterial cells was analyzed by X-ray microanalysis with an electron microscope. The cell size was also measured. The elemental content was highest in exponentially growing cells (149 ± 8 fg of C cell−1, 35 ± 2 fg of N cell−1, and 12 ± 1 fg of P cell−1; average of all isolates ± standard error). The lowest C content was found in C-limited cells (39 ± 3 fg of C cell−1), the lowest N content in C- and P-limited cells (12 ± 1 and 12 ± 2 fg of N cell−1, respectively), and the lowest P content in P-limited cells (2.3 ± 0.6 fg of P cell−1). The atomic C:N ratios varied among treatments between 3.8 ± 0.1 and 9.5 ± 1.0 (average ± standard error), the C:P ratios between 35 ± 2 and 178 ± 28, and the N:P ratios between 6.7 ± 0.3 and 18 ± 3. The carbon-volume ratios showed large variation among isolates due to different types of nutrient limitation (from 51± 4 to 241 ± 38 fg of C μm−1; average of individual isolates and treatments ± standard error). The results show that different growth conditions and differences in the bacterial community may explain some of the variability of previously reported elemental and carbon-volume ratios.
33
Wan, Z., H. Bi, J. She, M. Maar e L. Jonasson. "Model study on horizontal variability of nutrient N/P ratio in the Baltic Sea and its impacts on primary production, nitrogen fixation and nutrient limitation". Ocean Science Discussions 9, n. 1 (31 gennaio 2012): 385–419. http://dx.doi.org/10.5194/osd-9-385-2012.
Abstract (sommario):
Abstract. The analysis of measured nutrient concentrations suggests that the ratio of dissolved inorganic nitrogen (DIN) alteration before and after spring blooms relative to the alteration of dissolved inorganic phosphorus (DIP) remains quite constant over the years (2000~2009). This ratio differs from the Redfield ratio and varies from 6.6 : 1 to 41.5 : 1 across basins within the Baltic Sea. If the found N/P ratios are indicators of phytoplankton stoichiometry, this would affect nutrient cycles in ecosystem models. We therefore tested the effects of using horizontally variable N/P ratio instead of fixed ratio (N/P = 10 : 1 or 16 : 1) on phytoplankton uptake and remineralization in a 3-D physical-biogeochemical coupled model ERGOM. The model results using the variable N/P ratio show systematical improvements in model performance in comparison with the fixed ratios. In addition, variable N/P ratios greatly affected the model estimated primary production, nitrogen fixation and nutrient limitation, which highlights the importance of using an accurate N/P ratio.
34
Li, Fengna, Yehui Duan, Yinghui Li, Yulong Tang, Meimei Geng, Oso Abimbola Oladele, Sung Woo Kim e Yulong Yin. "Effects of dietary n-6:n-3 PUFA ratio on fatty acid composition, free amino acid profile and gene expression of transporters in finishing pigs". British Journal of Nutrition 113, n. 5 (23 febbraio 2015): 739–48. http://dx.doi.org/10.1017/s0007114514004346.
Abstract (sommario):
Revealing the expression patterns of fatty acid and amino acid transporters as affected by dietary n-6:n-3 PUFA ratio would be useful for further clarifying the importance of the balance between n-6 and n-3 PUFA. A total of ninety-six finishing pigs were fed one of four diets with the ratio of 1:1, 2·5:1, 5:1 and 10:1. Pigs fed the dietary n-6:n-3 PUFA ratio of 5:1 had the highest (P< 0·05) daily weight gain, and those fed the dietary n-6:n-3 PUFA ratio of 1:1 had the largest loin muscle area (P< 0·01). The concentration of n-3 PUFA was raised as the ratio declined (P< 0·05) in the longissimus dorsi and subcutaneous adipose tissue. The contents of tryptophan, tasty amino acids and branched-chain amino acids in the longissimus dorsi were enhanced in pigs fed the dietary n-6:n-3 PUFA ratios of 1:1–5:1. The mRNA expression level of the fatty acid transporter fatty acid transport protein-1 (FATP-1) was declined (P< 0·05) in the longissimus dorsi of pigs fed the dietary n-6:n-3 PUFA ratios of 1:1–5:1, and increased (P< 0·05) in the subcutaneous adipose tissue of pigs fed the dietary n-6:n-3 PUFA ratios of 5:1 and 10:1. The expression profile of FATP-4 was similar to those of FATP-1 in the adipose tissue. The mRNA expression level of the amino acid transceptors LAT1 and SNAT2 was up-regulated (P< 0·05) in the longissimus dorsi of pigs fed the dietary n-6:n-3 PUFA ratios of 1:1 and 2·5:1. In conclusion, maintaining the dietary n-6:n-3 PUFA ratios of 1:1–5:1 would facilitate the absorption and utilisation of fatty acids and free amino acids, and result in improved muscle and adipose composition.
35
Güsewell, Sabine, e Mark O. Gessner. "N : P ratios influence litter decomposition and colonization by fungi and bacteria in microcosms". Functional Ecology 23, n. 1 (febbraio 2009): 211–19. http://dx.doi.org/10.1111/j.1365-2435.2008.01478.x.
36
Patel, Dinesh, Martina Marzano, Chieh-I. Liu, Heather M. Hill, Mattias Kruskopf, Hanbyul Jin, Jiuning Hu et al. "Accessing ratios of quantized resistances in graphene p–n junction devices using multiple terminals". AIP Advances 10, n. 2 (1 febbraio 2020): 025112. http://dx.doi.org/10.1063/1.5138901.
37
Bitao, Hu, P. P. Zarubin e U. U. Juravlev. "Isomeric cross-section ratios resulted from reaction (p,n) on targets 100Ru and 104,106,110Pd". European Physical Journal A 2, n. 2 (giugno 1998): 143–47. http://dx.doi.org/10.1007/s100500050102.
38
Davydova, N. K., O. V. Sinitsyna, V. N. Sergeev, I. Perevyazko e E. E. Laukhina. "Towards DNA sensing polymers: interaction between acrylamide/3-(N,N-dimethylaminopropyl)-acrylamide and DNA phage λ at various N/P ratios". RSC Advances 6, n. 63 (2016): 58212–17. http://dx.doi.org/10.1039/c6ra11231e.
Abstract (sommario):
The present study relates to the development of cationic polymers that are of great interest due to their enormous potential for biomedical applications, especially as non-viral vectors for gene therapy, active components in DNA sensing devices, etc.
39
Frossard, Emmanuel, Nina Buchmann, Else K. Bünemann, Delwende I. Kiba, François Lompo, Astrid Oberson, Federica Tamburini e Ouakoltio Y. A. Traoré. "Soil properties and not inputs control carbon : nitrogen : phosphorus ratios in cropped soils in the long term". SOIL 2, n. 1 (29 febbraio 2016): 83–99. http://dx.doi.org/10.5194/soil-2-83-2016.
Abstract (sommario):
Abstract. Stoichiometric approaches have been applied to understand the relationship between soil organic matter dynamics and biological nutrient transformations. However, very few studies have explicitly considered the effects of agricultural management practices on the soil C : N : P ratio. The aim of this study was to assess how different input types and rates would affect the C : N : P molar ratios of bulk soil, organic matter and microbial biomass in cropped soils in the long term. Thus, we analysed the C, N, and P inputs and budgets as well as soil properties in three long-term experiments established on different soil types: the Saria soil fertility trial (Burkina Faso), the Wagga Wagga rotation/stubble management/soil preparation trial (Australia), and the DOK (bio-Dynamic, bio-Organic, and “Konventionell”) cropping system trial (Switzerland). In each of these trials, there was a large range of C, N, and P inputs which had a strong impact on element concentrations in soils. However, although C : N : P ratios of the inputs were highly variable, they had only weak effects on soil C : N : P ratios. At Saria, a positive correlation was found between the N : P ratio of inputs and microbial biomass, while no relation was observed between the nutrient ratios of inputs and soil organic matter. At Wagga Wagga, the C : P ratio of inputs was significantly correlated to total soil C : P, N : P, and C : N ratios, but had no impact on the elemental composition of microbial biomass. In the DOK trial, a positive correlation was found between the C budget and the C to organic P ratio in soils, while the nutrient ratios of inputs were not related to those in the microbial biomass. We argue that these responses are due to differences in soil properties among sites. At Saria, the soil is dominated by quartz and some kaolinite, has a coarse texture, a fragile structure, and a low nutrient content. Thus, microorganisms feed on inputs (plant residues, manure). In contrast, the soil at Wagga Wagga contains illite and haematite, is richer in clay and nutrients, and has a stable structure. Thus, organic matter is protected from mineralization and can therefore accumulate, allowing microorganisms to feed on soil nutrients and to keep a constant C : N : P ratio. The DOK soil represents an intermediate situation, with high nutrient concentrations, but a rather fragile soil structure, where organic matter does not accumulate. We conclude that the study of C, N, and P ratios is important to understand the functioning of cropped soils in the long term, but that it must be coupled with a precise assessment of element inputs and budgets in the system and a good understanding of the ability of soils to stabilize C, N, and P compounds.
40
Frossard, E., N. Buchmann, E. K. Bünemann, D. I. Kiba, F. Lompo, A. Oberson, F. Tamburini e O. Y. A. Traoré. "Soil properties and not inputs control carbon, nitrogen, phosphorus ratios in cropped soils in the long-term". SOIL Discussions 2, n. 2 (21 settembre 2015): 995–1038. http://dx.doi.org/10.5194/soild-2-995-2015.
Abstract (sommario):
Abstract. Stoichiometric approaches have been applied to understand the relationship between soil organic matter dynamics and biological nutrient transformations. However, very few studies explicitly considered the effects of agricultural management practices on soil C : N : P ratio. The aim of this study was to assess how different input types and rates would affect the C : N : P molar ratios of bulk soil, organic matter and microbial biomass in cropped soils in the long-term. Thus, we analysed the C, N and P inputs and budgets as well as soil properties in three long-term experiments established on different soil types: the Saria soil fertility trial (Burkina Faso), the Wagga Wagga rotation/stubble management/soil preparation trial (Australia), and the DOK cropping system trial (Switzerland). In each of these trials, there was a large range of C, N and P inputs which had a strong impact on element concentrations in soils. However, although C : N : P ratios of the inputs were highly variable, they had only weak effects on soil C : N : P ratios. At Saria, a positive correlation was found between the N : P ratio of inputs and microbial biomass, while no relation was observed between the nutrient ratios of inputs and soil organic matter. At Wagga Wagga, the C : P ratio of inputs was significantly correlated to total soil C : P, N : P and C : N ratios, but had no impact on the elemental composition of microbial biomass. In the DOK trial, a positive correlation was found between the C budget and the C to organic P ratio in soils, while the nutrient ratios of inputs were not related to those in the microbial biomass. We argue that these responses are due to differences in soil properties among sites. At Saria, the soil is dominated by quartz and some kaolinite, has a coarse texture, a fragile structure and a low nutrient content. Thus, microorganisms feed on inputs (plant residues, manure). In contrast, the soil at Wagga Wagga contains illite and haematite, is richer in clay and nutrients and has a stable structure. Thus, organic matter is protected from mineralization and can therefore accumulate, allowing microorganisms to feed on soil nutrients and to keep a constant C : N : P ratio. The DOK soil represents an intermediate situation, with high nutrient concentrations, but a rather fragile soil structure, where organic matter does not accumulate. We conclude that the study of C, N, and P ratios is important to understand the functioning of cropped soils in the long-term, but that it must be coupled with a precise assessment of element inputs and budgets in the system and a good understanding of the ability of soils to stabilize C, N and P compounds.
41
Wang, Yao, Yi Zheng, Yan Liu, Jian Huang e Ali Mamtimin. "Spatial Prediction Models for Soil Stoichiometry in Complex Terrains: A Case Study of Schrenk’s Spruce Forest in the Tianshan Mountains". Forests 13, n. 9 (1 settembre 2022): 1407. http://dx.doi.org/10.3390/f13091407.
Abstract (sommario):
Spatial patterns of soil carbon (C), nitrogen (N) and phosphorus (P) and their stoichiometric characteristics (C:N:P) play an important role in nutrient limitations, community dynamics, nutrient use efficiency and biogeochemical cycles, etc. To date, the spatial distributions of soil organic C at various spatial scales have been extensively studied, whereas little is known about the spatial patterns of N and P and C:N:P ratios in various landscapes, especially across complex terrains. To fill this gap, we estimated the spatial patterns of concentrations of soil C, N and P and C:N:P ratios in Schrenk’s spruce (Picea schrenkiana Fisch. & C. A. Mey.) forest in the Tianshan Mountains based on data from soil cores collected from 2012 to 2017, and using the following four regression models: multiple linear regression, stepwise regression, ridge regression and lasso regression. We found the following: (1) elevation and climatic variables jointly contributed to concentrations of C, N and P and C:N:P ratios, (2) soil C, N and P concentrations, and their stoichiometric ratios, demonstrated continual spatial patterns in Schrenk’s spruce forest, (3) Multiple linear regression could be reliably used to estimate the spatial patterns of soil elemental concentrations and stoichiometric ratios in mountainous terrain. We suggest that more independent variables (including biotic, abiotic and anthropogenic factors) should be considered in future works. Additionally, adjustment of multiple linear regression and other models should be used for a better delineation of spatial patterns in the concentrations of soil elements and stoichiometric ratios.
42
Nong, Qiuyun, Liyi Wang, Yanbing Zhou, Ye Sun, Wentao Chen, Jintang Xie, Xiaodong Zhu e Tizhong Shan. "Low Dietary n-6/n-3 PUFA Ratio Regulates Meat Quality, Reduces Triglyceride Content, and Improves Fatty Acid Composition of Meat in Heigai Pigs". Animals 10, n. 9 (1 settembre 2020): 1543. http://dx.doi.org/10.3390/ani10091543.
Abstract (sommario):
The objective of this study was to investigate the effects of dietary supplementation with different n-6/n-3 polyunsaturated fatty acid (PUFA) ratios on growth performance, meat quality, and fatty acid profile in Heigai pigs. A total of 54 Heigai finishing pigs (body weight: 71.59 ± 2.16 kg) were randomly divided into three treatments with six replications (three pigs per replication) and fed diets containing different n-6/n-3 PUFA ratios: 8:1, 5:1, and 3:1. Pigs fed the dietary n-6/n-3 PUFA ratio of 8:1 had the highest feed to gain ratio (p < 0.01), carcass weight (p < 0.05), redness a* (p < 0.01), and yellowness b* (p < 0.01). Fatty acid compositions in longissimus dorsi muscle (LDM) and subcutaneous adipose tissue (SAT) were significantly changed (p < 0.01). Notably, the meat from the pigs fed with the low dietary n-6/n-3 PUFA ratio had higher n-3 PUFA contents (p < 0.01) and lower n-6/n-3 PUFA ratio (p < 0.01). The triglyceride and total cholesterol contents were significantly decreased in SAT from the pigs fed with dietary n-6/n-3 PUFA ratios of 5:1 (p < 0.05) and 3:1 (p < 0.01). Reducing n-6/n-3 PUFA ratio upregulated the expression of HSL (p < 0.05), CPT1 (p < 0.01), and FABP4 (p < 0.01) but downregulated ATGL (p < 0.01) expression. These results demonstrate that the lower n-6/n-3 PUFA ratio regulates meat quality and enhances the deposition of n-3 PUFA in Heigai pigs.
43
Zhao, Xiaojie, Guihong Bi, Richard L. Harkess e Eugene K. Blythe. "Effects of Different NH4:NO3 Ratios on Growth and Nutrition Uptake in Iris germanica ‘Immortality’". HortScience 51, n. 8 (agosto 2016): 1045–49. http://dx.doi.org/10.21273/hortsci.51.8.1045.
Abstract (sommario):
The form of nitrogen (N) in fertilizer can influence plant growth, nutrient uptake, and physiological processes in the plant. However, few studies have been conducted on the effects of N form on tall bearded (TB) iris (Iris germanica L.). In this study, five NH4:NO3 ratios (0:100, 25:75, 50:50, 75:25, and 100:0) were applied to investigate the response of TB iris to different N form ratios. NH4:NO3 ratios in fertilizer did not affect the leaf, root, and rhizome dry weight, or total plant dry weight. Plant height and SPAD reading were affected by NH4:NO3 ratios in some months, but not over the whole growing season. Neither spring nor fall flowering was influenced by NH4:NO3 ratios. Across the whole growing season, leachate pH was increased by higher NH4:NO3 ratios. At the end of the growing season, concentrations of phosphorous (P), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu) in leaf; calcium (Ca), magnesium (Mg), Mn, boron (B) in root; and N, P, Mg, Fe, Mn, and Zn in rhizome tissues were affected by NH4:NO3 ratios. Greater NH4:NO3 ratios increased the uptake of Fe, Mn, and Zn. The net uptake of N was unaffected by NH4:NO3 ratios, which indicates TB iris may not have a preference for either ammonium or nitrate N.
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Mao, Qinggong, Hao Chen, Cong Wang, Zongqing Pang, Jiangming Mo e Xiankai Lu. "Effect of Long-Term Nitrogen and Phosphorus Additions on Understory Plant Nutrients in a Primary Tropical Forest". Forests 12, n. 6 (18 giugno 2021): 803. http://dx.doi.org/10.3390/f12060803.
Abstract (sommario):
Humid tropical forests are commonly characterized as N-rich but P-deficient. Increased N deposition may drive N saturation and aggravate P limitation in tropical forests. Thus, P addition is proposed to mitigate the negative effects of N deposition by stimulating N cycling. However, little is known regarding the effect of altered N and P supply on the nutrient status of understory plants in tropical forests, which is critical for predicting the consequences of disturbed nutrient cycles. We assessed the responses of N concentration, P concentration, and N:P ratios of seven understory species to N and P addition in an 8-year fertilization experiment in a primary forest in south China. The results showed that N addition had no effect on plant N concentration, P concentration, and N:P ratios for most species. In contrast, P addition significantly increased P concentration, and decreased N:P ratios but had no effect on plant N concentration. The magnitude of P concentration responses to P addition largely depended on the types of organs and species. The increased P was more concentrated in the fine roots and branches than in the leaves. The gymnospermous liana Gnetum montanum Markgr. had particularly lower foliar N: P (~9.8) and was much more responsive to P addition than the other species studied. These results indicate that most plants are saturated in N but have great potential to restore P in primary tropical forests. N deposition does not necessarily aggravate plant P deficiency, and P addition does not increase the retention of deposited N by increasing the N concentration. In the long term, P inputs may alter the community composition in tropical forests owing to species-specific responses.
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Cheng, Cong, Jiaxiang Yu, Lidong Wang, Haiyan Liang, Yanru Wang e Xiaoli Yan. "Effects of the Cultivation Substrate pH and Ammonium-to-Nitrate Nitrogen Ratio on the C:N:P Stoichiometry in Leaves of Cunninghamia lanceolata and Schima superba". Forests 15, n. 6 (30 maggio 2024): 958. http://dx.doi.org/10.3390/f15060958.
Abstract (sommario):
We aimed to clarify the nutrient allocation strategies of Cunninghamia lanceolata (CL) and Schima superba (SS) and their differences in N uptake and utilization under acidic stress and heterogeneous allocation of N. One-year-old seedlings of CL and SS were cultured in sands with three pH levels (pH rate 4.5, 5.5, and 6.5) and five different N form ratios (NH4+-N to NO3−-N ratios 10:0, 7:3, 5:5, 3:7, and 0:10) in the greenhouse. The C, N, and P contents and C:N:P stoichiometry in leaves, total biomass, and NH4+-N and NO3−-N contents in the cultivation substrate were analyzed after 160 days. At the pH rate of 4.5, the N contents of CL and SS significantly decreased. However, the N contents of SS increased at the pH rate of 5.5. At the pH rate of 5.5, the N content of CL and SS increased under the cultivation substrate, with ratios of 10:0 and 7:3, and 3:7 and 0:10, respectively. The N content of CL was significantly positively correlated with its P content. The C:P ratios of CL and SS were significantly positively correlated with their C:N ratios and N:P ratios. Under the same treatment, the differences in C:N:P stoichiometry were more significant between CL and SS at the pH rate of 5.5. The NH4+-N content of the cultivation substrate in CL and SS was higher than the NO3−-N content. At the ratio of 7:3, the C:N stoichiometric ratio of CL and C:N:P stoichiometric ratio of SS were negatively correlated with total biomass. At the pH rate of 5.5, cultivation environments with high NH4+-N and NO3−-N amount respectively increased the N content of CL and SS. The CL is susceptible to N limitation, and SS is susceptible to N and P limitation.
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Tanner, Danny K., John C. Brazner e Valerie J. Brady. "Factors influencing carbon, nitrogen, and phosphorus content of fish from a Lake Superior coastal wetland". Canadian Journal of Fisheries and Aquatic Sciences 57, n. 6 (1 giugno 2000): 1243–51. http://dx.doi.org/10.1139/f00-062.
Abstract (sommario):
The narrow fish nutrient ranges (C, 42.8-48.4%; N, 9.6-12.7%; P, 1.91-2.74%) in this study suggest that overall mean values are adequate for quantifying movement of C, N, or P as part of fish-mediated nutrient transport. We measured C, N, and P in 20 species of Lake Superior coastal wetland fish to better understand variability in fish elemental content caused by differences in species, habitat, season, life stage, or size. Fish were sampled within Bark Bay slough and at its inlet/outlet to Bark Bay, Lake Superior, from May to November 1995. Elemental content averaged across all fish (n = 192) was 45.1% for C, 11.3% for N, and 2.45% for P. We did find significant differences (p [Formula: see text] 0.05) among nine tested species. However, less than one third of the analyses were significant for effects of location or date of capture or fish length on fish nutrient content and nutrient ratios. Regressions of N:P ratios against growth rate indices and, separately, fineness ratios were significant, suggesting that growth rate and body shape are important factors driving N:P ratios in fish.
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Gong, Zhang e Guo. "Warming and Nitrogen Addition Change the Soil and Soil Microbial Biomass C:N:P Stoichiometry of a Meadow Steppe". International Journal of Environmental Research and Public Health 16, n. 15 (29 luglio 2019): 2705. http://dx.doi.org/10.3390/ijerph16152705.
Abstract (sommario):
: Soil and soil microbial biomass (SMB) carbon: nitrogen: phosphorus (C:N:P) stoichiometry are important parameters to determine soil balance of nutrients and circulation of materials, but how soil and SMB C:N:P stoichiometry is affected by climate change remains unclear. Field experiments with warming and N addition had been implemented since April 2007. Infrared radiators were used to manipulate temperature, and aqueous ammonium nitrate (10 g m-2 yr-1) was added to simulate nitrogen deposition. We found that molar nutrient ratios in the soil averaged 60:11:1, warming and warming plus N addition reduced soil C:N by 14.1% and 20% (P < 0.01), and reduced soil C:P ratios by 14.5% and 14.8% (P < 0.01). N addition reduced soil C:N significantly by 17.6% (P < 0.001) (Figs. 2B, 2D). N addition and warming plus N addition increased soil N:P significantly by 24.6% and 7.7% (P < 0.01). The SMB C:N, C:P and N:P ratios increased significantly with warming, N addition and warming plus N addition. Warming and N addition increased the correlations between SOC and soil microbial biomass C (SMBC), soil total P and soil microbial biomass P (SMBP), warming increased the correlation between the soil total N and soil microbial biomass N (SMBN). After four years’ treatment, our results demonstrated that the combined effects of warming and N fertilization could change the C, N, P cycling by affecting soil and SMB C:N:P ratios significantly and differently. At the same time, our results suggested SMB might have weak homeostasis in Sonnen Grassland and warming and N addition would ease N-limitation but aggravate P-limitation in northeastern China. Furthermore, these results further the current demonstration of the relationships between the soil and SMB C:N:P stoichiometry in response to global change in temperate grassland ecosystems.
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Awoonor, Johnny Kofi, Bright Fafali Dogbey e Ibrahim Salis. "Human-induced land use changes and phosphorus limitation affect soil microbial biomass and ecosystem stoichiometry". PLOS ONE 18, n. 8 (30 agosto 2023): e0290687. http://dx.doi.org/10.1371/journal.pone.0290687.
Abstract (sommario):
Soil and microbial biomass carbon (C), nitrogen (N), and phosphorus (P) play an important role in soil nutrient dynamics in biogeochemical cycles of terrestrial ecosystems. However, increased human activities as a result of agricultural intensification on soil nutrients and microbial C:N:P stoichiometry are poorly understood in this fragile forest-savanna transition agroecosystem. This study aimed to (i) assess soil and microbial C, N, and P stoichiometry in different land use systems, and (ii) examine the effect of soil and microbial C, N, and P stoichiometry on soils susceptible to human-induced land use changes. A total of 82 composite soil samples at a depth of 0–20 cm were sampled from forest, savanna, grassland, fallow and cropland for laboratory analysis. The results revealed that the concentrations of C, N, and P were low in Fallow and Cropland compared to other land use systems. Analysis of variance in microbial C, N, and P stoichiometric ratios revealed a significant decreasing tendency compared to soil C:N, C:P and N:P ratios with no statistical significance (p < 0.05). The C:P and N:P ratios were low compared to the C:N ratio in land uses. A significant positive correlation was observed between MBC and MBN (0.95; p < 0.01), and with C and N (0.69; p < 0.01). There were significant interactive effects of land use on soil and microbial variables. The estimated microbial C:N:P stoichiometric ratios (21:2:1) were well constrained in the study area. The transition from Forest to Cropland resulted in 64%, 52%, and 71% reduction in C, N, and P, respectively. This implies that phosphorus is the main factor limiting productivity. The low availability of phosphorus in these tropical soils may have resulted in low C:P and N:P ratios. Therefore, we conclude that our results highlight the importance of phosphorus limitation on ratios of microbial C:P and N:P in landuse systems. Nutrient inputs such as fertilizers, manure and crop residues should be applied to croplands to improve soil and microbial C, N and P levels. Further, effects of land use on soil nutrient status and stoichiometry at 1-meter depth will be considered in our future work.
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Liu, Wen Chao, e In Ho Kim. "Effects of different dietary n-6:n-3 PUFA ratios on growth performance, blood lipid profiles, fatty acid composition of pork, carcass traits and meat quality in finishing pigs". Annals of Animal Science 18, n. 1 (1 gennaio 2018): 143–54. http://dx.doi.org/10.1515/aoas-2017-0026.
Abstract (sommario):
Abstract A total of 72 crossbred pigs [(Landrace × Yorkshire) × Duroc] with an average initial BW of 51.59±1.59 kg were used in this 10-wk feeding trial to investigate the effects of different dietary n-6:n-3 polyunsaturated fatty acids (PUFA) ratios in finishing pigs. Pigs were randomly allotted to 3 dietary treatments (each n=24) with 6 replications and 4 pigs per pen (2 barrows and 2 gilts). Pigs were fed a corn-soybean meal-based diets formulated by replacing soybean oil with linseed oil to achieve n-6:n-3 close to 5:1, 10:1 and 15:1, respectively. The growth performance, carcass traits and meat quality parameters (meat color, sensory evaluation, cooking loss, drip loss, pH, longissimus muscle area and water holding capacity) were not influenced (P>0.10) by various dietary n-6:n-3 ratios. Pigs fed dietary n-6:n-3 PUFA ratios of 5:1 had a lower (P<0.05) serum total cholesterol, LDL cholesterol and triglyceride levels. The concentrations of n-3 PUFA , including C18:3n-3, C22:5n-3 and C22:6n-3 were improved (P<0.05) in the longissimus dorsi muscles of pigs fed dietary n-6:n-3 PUFA ratios of 5:1. Furthermore, pigs fed dietary n-6:n-3 PUFA ratio of 5:1 decreased (P<0.05) the n-6 concentrations (C18:2n-6 and C20:4n-6) of longissimus dorsi muscles. In conclusion, lowering the dietary n-6:n-3 ratios to 5:1 could be beneficial for the blood lipid profiles, and improve the nutritional value of pork, without adverse effect on growth performance and meat quality parameters that are related to the consumer acceptance.
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Pondaven, P., P. Pivière, C. Ridame e C. Guien. "C, N and P stoichiometric mismatch between resources and consumers influence the dynamics of a marine microbial food web model and its response to atmospheric N and P inputs". Biogeosciences Discussions 11, n. 2 (20 febbraio 2014): 2933–71. http://dx.doi.org/10.5194/bgd-11-2933-2014.
Abstract (sommario):
Abstract. Results from the DUNE experiments reported in this issue have shown that nutrient input from dust deposition in large mesocosms deployed in the western Mediterranean induced a response of the microbial food web, with an increase of primary production rates (PP), bacterial respiration rates (BR), as well as autotrophic and heterotrophic biomasses. Additionally, it was found that nutrient inputs strengthened the net heterotrophy of the system, with NPP : BR ratios < 1. In this study we used a simple microbial food web model, inspired from previous modelling studies, to explore how C, N and P stoichiometric mismatch between producers and consumers along the food chain can influence the dynamics and the trophic status of the ecosystem. Attention was paid to the mechanisms involved in the balance between net autotrophy vs. net heterotrophy. Although the model was kept simple, predicted changes in biomass and PP were qualitatively consistent with observations from DUNE experiments. Additionally, the model shed light on how ecological stoichiometric mismatch between producers and consumers can control food web dynamics and drive the system toward net heterotrophy. In the model, net heterotrophy was notably driven by the parameterisation of the production and excretion of extra DOC from phytoplankton under nutrient-limited conditions. This mechanism yielded to high C : P and C : N ratios of the DOM pool, and subsequent postabsorptive respiration of C by bacteria. The model also predicted that nutrient inputs from dust strengthened the net heterotrophy of the system; a pattern also observed during two of the three DUNE experiments (P and Q). However, the model was not able to account for the low NPP : BR ratios (down to 0.1) recorded during the DUNE experiments. Possible mechanisms involved in this discrepancy were discussed.