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1.
Phosphorus fractions and adsorption characteristics in grassland soils of varied soil phosphorus status 总被引:2,自引:0,他引:2
Characterization of phosphorus (P) in soils is important both agronomically and environmentally, although the outcome may
depend on the technique applied. Consequently, we evaluated fractionation and adsorption, individually and jointly, and relevant
ancillary soil attributes, to determine the dominant functional characteristics of soil P in 32 fertilized temperate grassland
Inceptisols classified by eight soil series, and by two soil-P index and parent material groups. Residual P was low (30.7%)
and organic P (Po) prominent, 42.0% vs. 17.5% for equivalent soils in unfertilized natural ecosystems. Labile fractions comprised
6.8% inorganic P (Pi) and 9.1% Po. The proportional increase in high vs. low index soils (Morgan P > 6.0 mg l−1 vs. ≤ 6.0 mg l−1) was higher for Pi, and highest for labile and moderately labile fractions. Only moderately labile Pi and Po differed significantly
between soils of limestone and non-limestone origin. Oxalate extractable Fe (Feox) and buffering (EBC) were higher in the latter. The equilibrium P concentration (EPC) was substantially higher in the high
index group, and EBC and binding energy (k) substantially lower, with no significant difference in sorption maximum (Pmax).
EBC equated with weak to strong buffering in different soil series, and conformed better than k to ancillary attributes. Pmax
correlated in order Alox > clay > OC > Feox, and more broadly reflected sorption attributes than oxalate-based sorption capacity (PSC). Principal component (PC) analysis
showed consistent differentiation of P fractions, mostly labile and moderately labile, in PC 1 vs. adsorption and ancillary
attributes in PC 2. However, scatterplots of PC scores showed that adsorption characteristics provided better functional differentiation
than P fractions for distinguishing individual soil series, which may have implications in selection and interpretation of
extractants not only for environmental but also for agronomic soil-tests. 相似文献
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The interactions between three polynuclear aromatic hydrocarbons (PAHs), namely fluorene, naphthalene and anthracene, and three fractions of a soil, namely fulvic acid (FA), humic acid (HA) and humin/inorganic fractions, were studied experimentally. Prepared PAH + soil fraction binary mixtures, with PAH concentrations ranging over 0.8–7 mass%, were tested using a differential scanning calorimeter (DSC) over a temperature range of 20?390°C. The DSC thermograms for the PAH + HA mixtures showed distinctly different characteristics compared to mixtures with the other two soil fractions, where the endothermic peak for the vaporization of the PAH was absent. With the aid of vapour-liquid flash calculations, the lack of the boiling point peak is interpreted to be due to the liquid-phase miscibility of the PAHs and the HA fraction. Implications of the DSC results on the design and performance of the thermal desorption process are discussed. 相似文献
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Smallholder farmer management impacts on particulate and labile carbon fractions of granitic sandy soils in Zimbabwe 总被引:1,自引:0,他引:1
Crop production in maize-based smallholder farming systems of Southern Africa is hampered by lack of options for efficiently
managing limited and different quality organic nutrient resources. This study examined impacts of farmers’ short- and long-term
organic resource allocation patterns on sizes and quality of soil organic matter (SOM) fractions. Farmers’ most- (rich) and
least- (poor) productive fields were studied for two seasons under low (450–650 mm yr−1) to high (>750 mm yr−1) rainfall areas in Zimbabwe, on Lixisols with ∼6% clay and 88% sand. Rich fields received 0.5–14 Mg C ha−1 compared with <4 Mg C ha−1 for poor fields, and the differences were reflected in soil particulate organic matter (POM) fractions. Organic inputs were
consistent with resource endowments, with well-endowed farmers applying at least five times the amounts used by resource-constrained
farmers. Rich fields had 100% more macro-POM (250–2,000 μm diameter) and three times more meso-POM (53–250 μm) than poor fields.
Application of high quality (>25 mg N kg−1) materials increased labile C (KMnO4 oxidizable) in top 60 cm of soil profile, with 1.6 Mg C ha−1 of Crotalaria juncea yielding labile C amounts similar to 6 Mg C ha−1 of manure. Labile C was significantly related to mineralizable N in POM fractions, and apparently to maize yields (P < 0.01). Farmers’ preferential allocation of nutrient resources to already productive fields helps to maintain critical levels
of labile SOM necessary to sustain high maize yields. 相似文献
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The distribution of phosphorus fractions and desorption characteristics of some soils in the moist savanna zone of West Africa 总被引:2,自引:0,他引:2
O.C. Nwoke B. Vanlauwe J. Diels N. Sanginga O. Osonubi 《Nutrient Cycling in Agroecosystems》2004,69(2):127-141
The fractionation of soil P into various organic and inorganic pools with differing levels of bioavailability, coupled with knowledge of the P adsorption and desorption characteristics of the soils, provides insights into management strategies that enhance P availability to crops. Sequential soil P fractionation was conducted on samples from 11 soil profiles and different experimental fields selected from the derived savanna (DS) and northern Guinea savanna (NGS) zones of the West African moist savanna to assess the influence of soil characteristics and management on soil P pools. Phosphorus adsorption and desorption studies were conducted on samples from the surface horizon of the soil profiles. The total P content varied within and among the soil profiles and tended generally to decrease as depth increased. The total P content in topsoil varied from 90 to 198 mg kg–1 of which about 30% was organically bound P. The resin P fraction was generally low (mean = 5 mg kg–1, topsoil) and decreased with depth. These low resin P levels indicate low P availability. Within the DS, where the organic resource (OM) was Senna siamea residues, the effects on soil P fractions of OM and soluble P fertilizer (PF), whether sole or in combination, were site-specific. While resin P was significantly increased by OM in some sites, no significant differences were observed in others. In the NGS fields, farmyard manure (organic resource, OM) combined with PF and PF applied alone increased the inorganic P (Pi) fractions extractable with resin, bicarbonate, and NaOH by about 400% but had no significant effect on the organic P (Po) pools and the more stable Pi forms. The P sorption capacities were low, with the adsorption maximum deduced from the Langmuir equation ranging from 36 to 230 mg kg–1. The amount of P sorbed to maintain 0.2 mg l–1 in solution ranged between 0.6 and 16 mg kg–1. Phosphorus desorption with anion exchange resin differed among the soils, with the recovery of added P ranging from 17 to 66% after 96 h. On average, more of the applied P was recovered in the DS soils than in the NGS soils. Because of the relatively low sorption capacity and the relatively high percentage recovery, small additions of P to most of the soils studied might be adequate for crop growth. In essence, quantities of P fertilizer needed in these soils might be estimated based on considerations of P uptake by crops rather than on sorption characteristics. 相似文献
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T. Németh M. Magyar P. Csathó E. Osztoics G. Baczó S. Holló I. Németh 《Nutrient Cycling in Agroecosystems》2002,63(1):81-89
The effect of two P-forms and the P fertilization system were studied in field trials set up on two moderately acidic Hungarian soils. Reactive Algerian rock phosphate and Kola superphosphate doses were based on the phosphorus equivalence. The experimental design makes it possible to compare the effect of annual 35 kg/ha P doses with initial one-time application of the 175 kg/ha P level in a five-year interval. Ammonium-lactate (AL)-, NaHCO3 (Olsen)- and DW-P contents as well as Lakanen- Erviö (LE)- soluble Cd, Cr and Sr contents were also determined. The results of the first five-year period are reported in the paper. Responses to P fertilization were related to the original P supply of the soils. There was no significant difference between the two P forms and between the P fertilization systems on both grain yield and P-uptake. While AL- method overestimated, and Olsen-method – on the other hand – underestimated the P supply of reactive Algerian rock phosphate, distilled water (DW)-soluble P contents indicated the soil P status more accurately. Phosphorus balances were positive after the fifth year of the trials in the P treated plots. The soluble Cd and Cr contents did not increase in the Algerian rock phosphate treated plots. On the other hand, Kola superphosphate application at 175 kg/ha P level resulted in higher LE-Sr contents in soils. The Algerian rock phosphate is an economic alternative P source on the moderately or strongly acidic Hungarian soils. 相似文献
6.
Effect of amending high phosphorus soils with flue-gas desulfurization gypsum on plant uptake and soil fractions of phosphorus 总被引:1,自引:0,他引:1
William L. Stout Andrew N. Sharpley Stefan R. Weaver 《Nutrient Cycling in Agroecosystems》2003,67(1):21-29
Flue gas desulfurization (FGD) gypsum, a coal combustion by-product, can be used to decrease water-extractable soil P, thereby lowering the potential for P export to surface waters. This decrease results from a conversion of loosely bound inorganic P (IP) which is readily desorbable to water, to less soluble Al- and Fe-bound IP and, to a lesser extent, calcium-bound IP pools. Although this conversion has little effect on predictors of plant-available soil P (e.g., Mehlich-3 P), little is known about the plant uptake of P over several growth cycles after high P soils are amended with FGD. In a greenhouse experiment, we measured P uptake by ryegrass (Lolium perenne) using a modified Stanford–Dement procedure (three growth cycles), and the extent to which IP was being removed from each soil IP fraction (Hedley fractionation), for three soils treated with FGD gypsum (equivalent to 22.4 Mg ha–1). Treatment with FGD decreased water extractable soil P 38 to 57%, but had little effect on Mehlich-3 soil P. During the first growth cycle, the shift from resin IP to less available Al, Fe, and Ca IP remained stable. Repeated growth cycles of ryegrass removed resin IP and thus, had a continued effect on lowering water-extractable P. After three growth cycles and harvests, ryegrass dry-matter production was not affected by FGD treatment (P > 0.05), although cumulative P uptake (20%) and P concentration of ryegrass tops (25%) were greater in FGD treated than untreated soils. Our results confirm that treatment of high P soils with FGD gypsum decreases water-extractable P by conversion to soil IP fractions that are stable with time, does not decrease plant production, and suggests that the potential for P export in surface runoff may be reduced for several years. 相似文献
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P. Loganathan M.J. Hedley M.R. Bretherton J.S. Rowarth 《Nutrient Cycling in Agroecosystems》2004,70(1):77-84
When fine particulate, slow-release fertilizers are applied to pastures, earthworm activity can physically move the particles both horizontally and vertically in the soil. This physical movement needs to be accounted for when researchers attempt to determine the rate of fertilizer dissolution by measuring the quantity of undissolved fertilizer residue remaining in the soil. A hard igneous phosphate rock (Phalaborwa PR) and an inert chromite ore were used as tracers to follow the physical movement of the reactive PR (RPR), NCPR applied to grazed pasture on a Pallic Soil (Aeric Fragiaqualf) isolated in galvanised steel cylindrical cores (150 mm diameter and 100 mm height) with or without nylon mesh sleeve (63 µm) at the bottom. The soil cores were sampled after 113, 270 and 559 days and analysed for PR and chromite residues. Results from both tracers showed that there was a significant movement of particles laterally out of the cores and vertically below 40 mm soil depth. Phalaborwa PR particle movement to 40–60 mm soil depth was 8% in 112 days and 24% in 270 days. Between 270 and 559 days no significant movement of particles was observed. Particle movement appeared to occur in discrete non-continuous events that were associated with the major end-of-autumn peaks in earthworm activity. When corrected for particle movement, the measured rate of NCPR dissolution satisfactorily fitted the rate of dissolution predicted by two models of PR dissolution. 相似文献
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硒酵母培养过程中亚硒酸钠添加量对硒酵母中硒含量分布的影响 总被引:10,自引:0,他引:10
采用在培养基中添加亚硒酸钠的方法,培养出了五种不同含硒量的硒酵母,并对硒酵母中总硒、无机硒、有机硒、硒蛋氨酸和硒胱氨酸的含量进行了测定,从所测数据中可以得出酵母同化无机硒为有机硒的基本规律,确定了在硒酵母的培养过程中最适宜的亚硒酸钠添加量为15~20μg/ml。 相似文献
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Seung Jo Kim Min Chul Choi Jong Min Park An Sik Chung 《International journal of molecular sciences》2021,22(21)
Functions of selenium are diverse as antioxidant, anti-inflammation, increased immunity, reduced cancer incidence, blocking tumor invasion and metastasis, and further clinical application as treatment with radiation and chemotherapy. These functions of selenium are mostly related to oxidation and reduction mechanisms of selenium metabolites. Hydrogen selenide from selenite, and methylselenol (MSeH) from Se-methylselenocyteine (MSeC) and methylseleninicacid (MSeA) are the most reactive metabolites produced reactive oxygen species (ROS); furthermore, these metabolites may involve in oxidizing sulfhydryl groups, including glutathione. Selenite also reacted with glutathione and produces hydrogen selenide via selenodiglutathione (SeDG), which induces cytotoxicity as cell apoptosis, ROS production, DNA damage, and adenosine-methionine methylation in the cellular nucleus. However, a more pronounced effect was shown in the subsequent treatment of sodium selenite with chemotherapy and radiation therapy. High doses of sodium selenite were effective to increase radiation therapy and chemotherapy, and further to reduce radiation side effects and drug resistance. In our study, advanced cancer patients can tolerate until 5000 μg of sodium selenite in combination with radiation and chemotherapy since the half-life of sodium selenite may be relatively short, and, further, selenium may accumulates more in cancer cells than that of normal cells, which may be toxic to the cancer cells. Further clinical studies of high amount sodium selenite are required to treat advanced cancer patients. 相似文献
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农作物、化肥、土壤的营养特性和我国农田养分平衡的估算 总被引:2,自引:0,他引:2
对农作物、化肥和我国土壤营养特性作了简要描述,并对全国和几个典型地区的农田养分平衡作了估算。从作物营养、环境保护、生态高效农业和西部开发的不同角度,展望了我国化肥产业新的发展机遇。 相似文献
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D M Hadjimarkos 《Food and cosmetics toxicology》1973,11(6):1083-1095