摘要:

Most digestion procedures for the preparation for plant tissue for elemental analysis are often very laborious. Elemental contents of plant tissue prepared by microwave digestion were compared to those obtained by conventional dry ashing and sulfuric acid‐hydrogen peroxide wet digestion. All three digestion methods produced comparable quantitative values for the elements P, K, Ca, Mg, Fe, Mn, Zn, and Cu for all plant materials used. Thus, the microwave digestion technique was shown to be a viable rapid method for digesting relatively small numbers of samples prior to elemental analysis.

ISSN:0010-3624    

DOI:10.1080/00103629009368373

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Soil nitrate test reports are being used more widely for making nitrogen fertilizer recommendations. Seldom does the literature refer to the ammonium concentration in the soil. Seemingly, an assumption is made that the level is insignificant or a constant. Selected soils upon which both NO3‐N and NH4‐Nwere analyzed were surveyed to determine the degree of variation that is found in routine soil samples from different situations. Our 134 sets of data were divided into groups by area (state) and date (month sampled). Group means and standard deviations, medians, coefficient of variations (C.V.), and ranges were determined for soil nitrate nitrogen (NO3‐N), ammonium‐nitrogen (NH4‐N), sum of NO3‐N + NH4‐N (Sum N), % of N found as NO3‐N, and ratio of NH4‐N/ NO3‐N.

ISSN:0010-3624    

DOI:10.1080/00103629009368374

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A method for washing charcoal to remove phosphorus contamination prior to decolorisation of soil extracts is reported. Washing with 6M HCl in a column was more effective than washing with the extractant solution. Leaching of the charcoal in a column allowed a more uniform washing and was less demanding of operator time than shaking and leaching through a Buchner funnel.

ISSN:0010-3624    

DOI:10.1080/00103629009368375

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The use of acetylene (C2H2) in the inhibition of N2O to N2is widely used for measuring denitrification. The objective of this study was to determine the effectiveness of acetylene inhibition of N2O reduction for short‐term and prolonged incubation studies in soils of varying water saturation, and to find out the possible reasons for lower N2O recovery in continuously sealed incubations. Two experiments carried out in the laboratory reconfirmed that acetylene was very effective in inhibiting the reduction of N2O in denitrification even for the prolonged incubation period (up to 96 h) under moist to saturated soil water contents. With 90 and 120% water‐filled pore space (WFPS), the accumulated N2O in containers kept sealed throughout the study period, was 28 to 41% less than total headspace N2O produced in containers that were opened, flushed and fresh C2H2added every 24 h. Interpretation of our results suggest the lower N2O amount recovered from continuously sealed containers at high WFPS, as compared to short‐term incubations (flushed containers), resulted primarily from delayed N2O release from soil and not greater N2O dissolved in soil solution, lower rates of denitrification, or decomposition/loss of C2H2during prolonged incubation. Reduction of N2O diffusion from soil cores showed direct relationship with head space concentration‐of N2O and soil WFPS. From these results it is concluded that to obtain quantitative recovery of N2O produced via denitrification, especially from soil with high WFPS soil cores should be vigorously shaken before head‐space N2O analysis.

ISSN:0010-3624    

DOI:10.1080/00103629009368376

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Farmers are increasingly aware of the need for correct fertilizer management, and have developed a keen interest in the rapid and accurate assessment of soil nutrient status. A simple field‐based soil test for phosphorus (P), adapted from commonly used laboratory tests would allow the farmer to assess quickly fertilizer requirements. We have adapted themalachite green method forthe determination of P in water to a single‐solution technique for the determination of inorganic P in Olsen and Bray No. 1 extracts of soil. The method was modified for use in the field. The proposed method is at least four times as sensitive as the commonly‐used ascorbic acid method, simpler in application and the reagent is much more stable.

ISSN:0010-3624    

DOI:10.1080/00103629009368377

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Ammonium oxalate extractable phosphorus represents a potentially useful measure of the P associated with the amorphous iron and aluminum oxides in soils. However, because oxalate complexes molybdate, the colorimetric determination of phosphorus in ammonium oxalate extracts by the traditional molybdenum‐blue procedure is not possible. In this study, a method was developed whereby excessive molybdate was added to the extracts to complex the oxalate and eliminate the interference of oxalate with the formation of the phospho‐moblydate complexes necessary for color development. The method development and recommended procedure for colorimetrically measuring phosphorus in ammonium oxalate soil extracts are described.

ISSN:0010-3624    

DOI:10.1080/00103629009368378

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Hot water, water and 2M DTPA (room temperature), all at 1:1.5 volume ratio, and saturation extracts with and without added DTPA, were compared for their ability to assess the availability of B in pottting media. In three experiments, B concentrations in the extractants were highly linearly correlated with one another, although medium components and pH affected the slopes of the relationships. Hot water extracted between 38 and 77% of the B inPinus radiata‐based media and 58 to 97% of that in peat. The proportion was little affected by the pH of the medium. The solutions at room temperature extracted considerably less B than did hot water and the proportion extracted decreased with increasing pH. B in extracts at room temperature was more highly correlated ( r2= 0.90–0.97) with B uptake by a range of plants with widely differing tolerance of high concentrations of B than was hot water soluble B (r2= 0.79–0.94). No symptoms typical of B deficiency were observed at the lowest concentrations of extractable B attained in these experiments, which were 0.08 and 0.27 mg/L B in 2 mM DTPA (1:1.5 by volume) and saturation extracts containing DTPA respectively. Other evidence suggests that concentrations at the detection limit (about 0.03 mg/L) of the analytical technique used are adequate for normal flowering ofChrysanthemum morifoliumcv. Yellow Mandalay. For absence of foliar toxicity symptoms in horticultural plants sensitive to B, 2 mM DTPA (1:1.5 by volume) and saturation extracts containing DTPA should not contain more than about 0.6 and 1 mg B/L, respectively. Tolerant species can remain symptom‐free in media giving up to about 5 and 8.3 mg B/L in the two extracts, respectively. These results will be particularly useful for checking for potential B toxicity in potting media containing composted waste materials.

ISSN:0010-3624    

DOI:10.1080/00103629009368379

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The applicability of 0.01 M CaCl2solution as a single extraction agent for soils as a basis for fertilizer recommendation was tested on a variety of soils both from the Netherlands and from some tropical countries. Air‐dry soil samples were subjected to extraction with 0.01 M CaCl2and to several conventional extraction procedures, and the results were compared. In the soil suspensions pH was measured, whereas in the extracts Na, K, Mg, P, different extractable N‐forms and Zn were measured. The values found in CaCl2extracts are discussed in relation to results of other extraction procedures and as to their potential value in soil quality assessment. It is concluded that a single extraction procedure with 0.01 M CaCl2can be applied for fertilizer recommendation purposes. The possibility of determining different extractable N‐forms (NH4, NO3, soluble organic N) significantly enhances the value of the method in predicting the N‐fertilizer needs. Furthermore it was found that the concentration of Zn in 0.01 M CaCl2extracts was a good indicator of phytotoxicity in a polluted area. Additional advantages of this extraction are low costs, simplicity and repro‐ducibility.

ISSN:0010-3624    

DOI:10.1080/00103629009368380

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Precipitation of Al(OH)3and aluminum phosphate may occur in nutrient solution if a large amount of Al and P have been added to a relatively high pH. The objective of this study was to develop and test a supernatant‐solution method for Al phytotoxicity studies with large and/or old plant seedlings. Effects of pH and additions of Al and P on ionic strength and concentrations of Al and P in supernatant nutrient solutions were investigated. Two sets of supernatant nutrient solutions at two pH levels were prepared. The pH 4.0 set and 4.5 set contained seven levels of Al (maximum Al concentration of 6355 and 378 μM) and similar P concentration about 32 and 6 μM P, respectively. The Al concentrations in supernatant solutions were dependent on preparation procedure. The pH 4.0 set was tested in the greenhouse study with 6‐month‐old citrus seedlings and found to be successful as culture solutions for Al phytotoxicity studies. These two sets are suitable for growth of large (about 0.3 m) and/or old (about 6 mon.) seedlings. This supernatant‐solution method makes it possible to study Al phytotoxicity of large and/or old seedlings, to avoid the confounding effects of P on Al with respect to plant growth, and to report the actual concentrations of Al and P in growth solutions.

ISSN:0010-3624    

DOI:10.1080/00103629009368381

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A pot experiment was conducted in the greenhouse to determine the influence of vesicular‐arbuscular mycorrhizal (VAM) inoculation on growth of pineapple (Ananas comosus,cv.’Smooth Cayenne') and its interaction with fosetyl‐Al in a Wahiawa soil (Tropeptic Eutrustox) at soil solution P levels of 0.003, 0.02 and 0.2 mg/L. Pineapple crowns were dipped in a solution of fosetyl‐Al before planting. Inoculation of soil with the fungusGlomus aggregatum(Schenck & Smith emend. Koske) significantly increased VAM colonization of pineapple roots at soil solution P levels of 0.003 and 0.02 mg/L. VAM inoculation also increased mycorrhizal effectiveness measured six weeks after planting. At harvest, pineapple grown in the inoculated soil at the lowest P level had significantly higher D‐leaf P concentration and plant fresh weight than that grown in the uninoculated soil. Fosetyl‐Al appears to have no significant effect on VAM‐pineapple interaction.

ISSN:0010-3624    

DOI:10.1080/00103629009368382

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor