摘要:

Saudi Arabian soil samples from different locations have been collected and analyzed for traces of barium (Ba), cobalt (Co), nickel (Ni), titanium (Ti), vanadium (V), silver (Ag), gold (Au), copper (Cu), lithium (Li), and lead (Pb). Inductively coupled plasma mass spectrometry (ICP/MS) has been found to be useful for soil analysis. Two commonly used digestion methods, one employing nitric acid and the otheraqua regia,are employed for sample pretreatment. Percentage recovery of added element quantities are found to be within the 97.4 to 101.2% range for Ba, Co, Ni, Ti, and V usingaqua regiadigestion and within the 95.0 to 05.0% range for Ag, Au, Cu, Li, and Pb when using the nitric acid digestion method. The percentage relative standard deviation (% RSD) for five replicate samples for the two digestion procedures is less than 5% for the analyzed elements.

ISSN:0010-3624    

DOI:10.1080/00103629409369053

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Suitable plant diagnostic procedures for nitrogen (N) management in high input crops such as potato(Solanum tuberosum)and peppermint(Piper mentha)should be derivative [measuring instantaneous nitrogen (N) uptake] rather than integrative (total accumulation) and should reflect concurrent soil N availability. Analyses for dry matter or sap nitrate (NO3) in potato petioles or peppermint stems are proposed as derivative procedures, but the plant‐soil NO3relations of these analyses are not well understood. Our objectives were to test the validity of these derivative plant diagnoses as measures of concurrent uptake against the Michaelis‐Menten model of saturation kinetics. Periodic measures of dry matter and sap NO3in potato petioles and peppermint stems were taken from field experiments with various rates and timings of N fertilizer, and regressed against concurrent soil NO3(0–30 cm) by nonlinear least squares fit to the model:V = (Vmax · SN)/(Ks + SN)where: V = potato petiole or peppermint stem NO3in the dry plant tissue or fresh sap, SN = extractable soil NO3, and Vmaxand Ks are constants. Sap NO3adhered to the model well for both species (R2values of 0.74 for potato and 0.61 for peppermint), with similar values for Vmax(2314 mg NO3‐N/kg for potato and 2187 mg NO3‐N/kg for peppermint). Peppermint exhibited a greater value for Ks than potato, indicating a lesser affinity for available soil N. Dry matter NO3also fit the model well for potato (R2= 0.79) but not peppermint (R2= 0.22). Values for SNopt, the level of soil NO3required to maintain critical levels of plant NO3, were calculated from the regressions using previously established plant criteria. Under continuous N fertilization, values for SNoptranged from 5.5 to 8.5 kg NO3/kg, were similar between species and were sensitive to variances in plant criteria. The kinetic model provides a mechanistic basis for derivative plant diagnosis methods. Sap analysis has several advantages to recommend it as a derivative procedure: sap‐soil nitrate relations adhere well to a kinetic model, kinetic parameters are consistent between species, and data can be readily collected on site.

ISSN:0010-3624    

DOI:10.1080/00103629409369054

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Our purpose was to determine the influence of the textural fraction and its mineralogical characteristics on the contents of the exchangeable (Ki) and nonexchangeable (Knoi) forms of soil potassium (K). Contributions of each textural fraction on Ki were as follows: 73–80% for clay, 8–18% for silt, and 2–10% for sand. The clay fraction relative to the contribution to Ki was not the same for all the soils studied. Thus, not only the quantity of clay must be taken into account, but also the cation exchange capacity (CEC) of the involved minerals. For Knoi, the total contribution showed a greater dispersion, the corresponding figures being as follows: clay 35–68%, silt 25–52%, and sand, 4–25%. Therefore, clay was not always the main contributor. In some soils, silt was the most important fraction due to the presence of muscovite.

ISSN:0010-3624    

DOI:10.1080/00103629409369055

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The residual value of phosphorus (P) applied at 0 to 320 kg P/ha as superphosphate 9 to 12 months earlier was measured using yields of carrots(Daucus carotaL. cv. Western Red). The effectiveness of the previously‐ applied P was determined relative to the effectiveness of freshly‐applied P on an acutely P‐deficient, newly cleared Karrakatta sand in experiments over three years. Yield response was significantly (P < 0.01) higher to freshly‐applied P than residual P at all rates except 320 kg/ha. The relative effectiveness of residual P increased from 46% of freshly‐applied P at 20 kg/ha to 95% at 320 kg/ha. Bicarbonate‐soluble P extracted from the soil was determined on the residual P site in each experiment. These soil test P values were related to yield. The critical soil test values required for 95% or 99% of maximum yield were 45 and 60 μg/g, respectively. The rate of freshly‐applied P required for 95% or 99% of maximum yield decreased from 118 and 183 kg P/ha at ≤ 5 μg/g soil test to 0 at the critical values. High levels of residual P (320 kg P/ha) resulted in high soil test values (≥ 60 μg/g) and were as effective as freshly‐applied P. Results of this work showed soil testing could be used as part of the P management of carrots on sandy soils. This has twin benefits of reducing fertiliser costs to the growers and reducing the leaching of fertiliser P into waterways thereby reducing eutrophication.

ISSN:0010-3624    

DOI:10.1080/00103629409369056

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Vegetative and reproductive growth were studied in five tomato(Lycopersicon esculentumMill) cultivars under saline conditions imposed at the five‐leaf stage by addition of 50 mM NaCl to half strength Hoagland nutrient solution. The plants were raised in pots filled with washed quartz sand kept in a greenhouse. Stem height and number of leaves in tomato plants were significantly reduced when irrigated with saline regimes in contrast with control plants that received only the Hoagland solution. The highest number of flowers were obtained in the cultivar Pearson and the least in cultivar Strain B. Fruit set and yield were little affected by varietal differences and were not related to vegetative growth. Fruit weight was suppressed with NaCl stress, but improvement in weight was achieved when potassium (K) and calcium (Ca) were added to the saline water. The most detrimental effect of NaCl stress was the reduction of biomass yield in tomatoes. However, the relative dry weights of Pearson and Monte Carlo were increased to 60% and 54%, respectively, when NaCl was supplemented with Ca. Large varietal differences in biomass occurred among the NaCl‐treated and control plants. Tomato fruit quality (TSS) was improved by salinization.

ISSN:0010-3624    

DOI:10.1080/00103629409369057

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A procedure for extraction and measurement of nitrate‐nitrogen (NO3‐N) in soil is described. Extracting solution [0.025M Al2(SO4)3] and field‐moist soil are measured volumetrically, with NO3‐N concentration measured by nitrate‐sensitive colorometric test strips or nitrate‐selective electrode. Across a range of soil texture, moisture content, and NO3‐N concentration, the procedure was well correlated with conventional laboratory analysis of 2N KC1 soil extracts (r2= 0.94). This quick test procedure is proposed as an on‐farm monitoring technique to improve N management.

ISSN:0010-3624    

DOI:10.1080/00103629409369058

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Factors such as small plot size, restricted access, and remote sites can often limit adequate sampling of belowground components in field research. Thus, the objective of this study was to design and construct a simple, inexpensive, portable soil coring system for rapid deployment under field conditions which eliminated some or all of the above mentioned limitations. Components of the system included a manual driver of adjustable weight, a manual core extractor, and steel core tubes with clear plastic (butyrate) liners which encase the soil core for retrieval and transport. This system proved to be reliable and efficient in repeated field trials, causing minimal plot disturbance. The use of Styrofoam plugs to separate multiple core samples within the plastic liner drastically reduced the time spent on handling individual samples. Continuous soil cores measuring up to 1 m long can also be collected with this system. The use of plastic liners also greatly facilitated the transport and storage of samples. This low cost system was convenient to operate and assemble or disassemble in a field setting. The unit proved to be effective in cases where mechanized approaches were prohibited or unavailable.

ISSN:0010-3624    

DOI:10.1080/00103629409369059

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A variety of extractants has been used to assess the availability of molybdenum (Mo) in soils. Most of the extractants have been studied from a deficiency aspect rather than for soils with Mo toxicity, and none of them have been used to extract available Mo from mine spoils. The purpose of this study was to examine the potential of different chemical extractants for assessing the availability of Mo in mine spoils and soils. One mine spoil and three soils were treated with sodium molybdate and then subjected to wetting and drying cycles for two months. These spoil/soils were extracted with ammonium bicarbonate DTPA (AB‐DTPA), ammonium carbonate, and ammonium oxalate solution for available Mo. Crested wheatgrass (Agropyron cristatum) and alfalfa (Medicago sativa) were grown in the spoil/soils in a greenhouse to determine plant uptake of Mo. Additionally, four mine spoils and six soils were extracted and analyzed for available Mo as mentioned above. The results obtained by these three extractants were highly correlated. It was found that ammonium oxalate extracts the greatest amount of Mo among the three extractants from spoil/soils since it dissolves some adsorbed Mo from Fe‐oxide and Al‐oxide. The changes in pH of spoil/soils did not have a significant effect on the amount of Mo extracted by any of these methods. The relationships between Mo uptake and Mo extracted by each method were all significant at 1% level. None of the extractants were clearly better or worse than the others. All three methods can be used to assess Mo availability, and potential toxicity from plant uptake of Mo from reclaimed spoils.

ISSN:0010-3624    

DOI:10.1080/00103629409369060

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The effects of soluble silicon (Si) on the toxicity of aluminium (Al) to soybean roots were investigated in solution culture. A weak nutrient solution which included a low concentration of phosphorus (P) was shown to be necessary to allow the full expression of Al toxicity. As solution pH decreased below 6, reductions in root growth in the presence of Al became increasingly severe. Silicon alleviated the symptoms of Al toxicity, but the effective rate was dependent on pH. Greater concentrations of Si were required at lower pH where Al was more toxic. These results support the hypothesis that the pH‐dependent affinity of Si for Al in dilute solutions, and the consequent formation of sub‐colloidal inert hydroxyaluminosilicate species, is the basis for the alleviation of Al toxicity by Si.

ISSN:0010-3624    

DOI:10.1080/00103629409369061

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

While much research has been done with nitrification inhibitors, little information exists on their effects on total inorganic soil nitrogen (N) (TISN) (NH4+‐N + NO3‐‐N). The objective of this study was to compare the effects of 2‐chloro‐6‐(trichloromethyl)‐pyridine (nitrapyrin) and dicyandiamide (DCD) on TISN concentrations and to compare the effects of the nitrification inhibitors with those of IBDU, a slow release N source. Effects of the three N‐amendments were compared in soil planted to potato (Solanum tuberosumL. cv. Atlantic). Treatments were combinations of N at 67, 134, and 202 kg/ha; and five N‐amendments, nitrapyrin at 0.56 and 1.12 kg/ha, DCD at 5.6 and 11.2 kg/ha, and isobutylidene diurea (IBDU) applied as one‐third of fertilizer N. Studies were conducted on an Arenic ochraqualf, a Grossarenic Paleudult, and a Grossarenic Paleaquult. Concentrations of TISN were influenced by nitrapyrin rate in five of sixteen year‐ location‐sampling date combinations. Of the five, all involved interactions with N rate effects. With two of these five, TISN concentration was increased by an increase in nitrapyrin rate with 67 kg N/ha, with one other, TISN concentration was decreased with an increase in nitrapyrin rate with 67 kg N/ha. Differences between nitrapyrin and DCD in their effects on TISN were few. Thus, at the rates applied in this study, the two inhibitors had similar effects on soil N. IBDU was more effective than the nitrification inhibitors, for maintaining plant available N in the rooting zone during the middle and latter portions of the growing season.

ISSN:0010-3624    

DOI:10.1080/00103629409369062

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor