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Although evaluations of the availability of cadmium (Cd) contaminants in phosphate fertilizers have been made, few have examined the transfer efficiency of Cd from fertilizers to plants, especially under field conditions. This 2-year field study determined the transfer of added Cd to lettuce (Lactuca sativa L.) (Royal Green) from a western phosphate rock (PR) and a triple superphosphate (TSP) as affected by liming and rate of fertilizer (or Cd) input. A readily soluble Cd salt, CdCl2, was included in the study for comparison. The cumulative amounts of Cd added from the fertilizers and CdCl2 over the 2-year period ranged from 0 to 1440 g ha–1. Lettuce yield increased with increasing TSP rates, but was unaffected by PR. Significant (P < 0.01) effects of Cd source and rate, lime, and year were found on Cd accumulation by lettuce. The transfer of the added Cd was consistently higher for CdCl2 than for the fertilizers regardless of lime rate. A contrasting year effect was also found between the two P fertilizers. In the second year of application, the Cd transfer efficiency increased in the soil treated with the PR, but decreased in the soil treated with the TSP. The Cd transfer efficiency for the plant was better measured with DTPA–Cd (r
2= 0.78 – 0.80) or CaCl2–Cd (r
2= 0.57 – 0.76) than with soil total Cd (r
2= 0.39 to 0.54) across all Cd sources and lime rates. This is because DTPA–Cd or CaCl2–Cd reflected the influences of the amount of Cd added, Cd source, and lime rate on Cd accumulation by the plant better than did the soil total Cd. Of the amount of Cd added from the fertilizers an average of 1.0% or less was accumulated in the harvested lettuce tissue. Applications of the fertilizers at high rates could result in increased Cd accumulation in the soil over time. 相似文献
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Effects of long-term phosphorus fertilization and winter cover cropping on soil phosphorus transformations in less weathered soil 总被引：3，自引：0，他引：3
Information concerning sources and sinks of available P in soil is needed to improve soil P management and protect water quality. This study, conducted from 1989 to 1998 on a Sultan silt loam soil (Aquantic Xerochrept), determined the annual P removal rate by corn (Zea mays L.) and P transformation as affected by P rate and winter cover cropping. Treatments included two P rates (0 and 44 kg P ha–1) applied to corn at planting each year. All cover crops received 19.6 kg P ha–1 at seeding each fall. Also included was a control without any cover crop and with no P addition. Corn yield and P uptake were affected by P fertilizer additions, but not by cover crops. A fairly constant amount of P was supplied from indigenous soil P when no external P was added. When the amount of P added exceeded that removed by corn, the excess P was converted mainly to NaOH-extractable inorganic P (NaOH-Pi). When the amount of P applied was below that removed by corn, indigenous soil NaOH-Pi acted as a source of available P for the plant. With no reduction of organic P (Po) extractable by NaOH or NaHCO3, the contribution from Po to the available P pool appeared limited. The role of NaOH-Pi in P availability in the soil was substantiated by its significant correlation with labile NH4Cl-extractable P (NH4Cl-P; r2 =0.60, P <0.001) or NaHCO3-Pi (r2 =0.81, P <0.001) pools. The NaOH-Pi for the soil reflected the changes in soil P resulting from past fertilizer P input and P removal by the crops.Scientific Paper Number 0005-34 相似文献
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LI Jian ZHAN Wen-hua HUANG Mei-jin CAI Shi-rong reas Bembenek Peter M.Schlag 《园艺学报》2006,22(6):1196-1198
AIM:To investigate the density of mature d endritic cells (DC) in sentinel lymph nodes (SLN) and non-SLN in patients with d ifferent levels of metastatic involvement .METHODS:The female breast cancer patients were divided into 3 groups:group A,all lymph nodes without evidence for tumor cells;group B,sma ll tumor deposits in SLN defined as:B1,isolated tumor cells in SLN,non-SLN wi thout evidence of tumor cells;B2,micrometastases in SLN,non-SLN without evide nce of tumor cells;group C,macrometastases in SLN,involved or un-involved non -SLN one section of all SLN and non-SLN of these patients was underwent immunohi stochemical examination by using the DC-LAMP-antibody for identification of matu re dendritic cells.The density of the DC-LAMP+-cells of each slide was quanti fied by a Zeiss imaging system enregistering the percentage of the area occupied by DC-LAMP+-cells.The Wicoxon-test and Mann-Whitney-test were used to compar e the mean density of DC-LAMP+-cells of SLN and non-SLN individually in each g roup and interindividually between the different groups,respectively.RESULTS:The DC-LAMP+-cell density increased significantly in the SLN compared to non-SLN patients with tumor free lymph nodes and patients wi th micrometastases in the SLN (P＜0.05,P＜0.01).No significant increase in DC-LAMP+-cell density between the SLN of the three groups,but a significan tly reduced DC-density in non-SLN of patients with micrometastases and isolated tumor cells was observed,compared to the other two groups (P＜0.05，P＜0.01). CONCLUSION:The results further underlined the prominent role o f the SLN for tumor-lymph node interactions,revealing significant differences b etween SLN and non-SLN in regard to the density of DC-LAMP+-cells. 相似文献
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Some waste-derived trace element fertilizers may contain elevated amounts of arsenic (As) and/or lead (Pb), and the impact of their use on As and Pb accumulation in soil and uptake by plants should be investigated. This greenhouse study examined how increasing rates of an iron (IR) fertilizer, containing 4806 mg kg?1 of As, and a zinc fertilizer (G-Zn), containing 18080 mg kg?1 of Pb, and liming affected As and Pb availability and uptake by lettuce (Lactuca sativa L.) in a silt loam soil. Additions of As as As2O3 and Pb as PbCl2 to the soil were included for comparison. Soil total and NaHCO3-extractable As increased with increasing inputs of As regardless of As source. This was true also for soil total and DTPA-extractable Pb. Sufficient oxidation of arsenopyrite (FeAsS) in the IR could have occurred, resulting in 36.4% of total As in IR being extractable by NaHCO3. Only extremely small fractions of the added As from IR (5×10?3%) and of the added Pb from G-Zn (7×10?3%) were accumulated in the plant. Source had an effect on As, but not Pb, accumulation by lettuce. The lower accumulation of As by the plant from IR than from As2O3 could be attributed to a high molar ratio of Fe to As (419) in the readily labile As fraction to render As in IR less available than As in As2O3. The molar ratio of Fe to Pb in the readily labile fraction of Pb in G-Zn was zero, which limited the influence of Fe on the accumulation of Pb from G-Zn despite its extremely high total Fe (18.3%) content. The transfer coefficients of the added As (0.013) and Pb (0.014) over all sources and lime rates were very low. Since nearly all of As and Pb added from the fertilizers remained in the soil, effects of long-term use of the products on As and Pb accumulation in the soil and uptake by the plant remain to be studied. 相似文献
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Some phosphorus and trace element fertilizers may contain elevatedamounts of toxic metals such as cadmium (Cd) and repeated uses of the fertilizers at high rates over time may increase Cd uptake by plants. This greenhouse study investigated the availability to leaf lettuce (Lactuca sativa L.) (Royal Green) of Cd in a western phosphate rock (PR), and a zinc (G-Zn) and an iron (IR) fertilizers that are by products of industrial wastes. The water-soluble CdCl2 was included in the study for comparison. Applications of Cd from the fertilizers orCdCl2 up to 16 times the Canadian Standards for maximum annual Cd loading limit increased soil total Cd. This was true also for the labileCd extractable by DTPA (diethylenetriaminepentaacetic acid) or 0.05 M CaCl2 for all Cd sources except IR. Lime and Cd source and rate allaffected Cd availability in the soil and accumulation by the plant. Theadded Cd from CdCl2 was more labile and readily available to the plant than the added Cd from the PR or G-Zn. Lettuce-Cd was best describedby CaCl2-Cd (r2 = 0.782), followed by DTPA-Cd (r2 = 0.686), with soil total Cd being least effective in predicting lettuce-Cd (r2 = 0.186). If soil total Cd has to be used in describing Cd accumulation bythe plant, it should be included with pH in a stepwise multiple regression. The Cd transfer coefficient for the fertilizers should be measured based on labile Cd extractable by CaCl2 or DPTA, instead of soil total Cd. The labile-based Cd transfer coefficient could improve the assessment ofthe risk of human exposure to the metal in the fertilizers through consumption of the food crop. 相似文献
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