摘要:

Modern agricultural management practices for phosphorus (P), including soil testing, can no longer focus exclusively on soil fertility and agricultural productivity but must also address the role of agricultural P in nonpoint source pollution of surface waters. The eutrophication of streams, rivers, lakes, and bays as a result of P loss from soil to water points to the need for advances in soil testing that can contribute to water quality protection. A concerted research effort to modify, refine, and advance soil testing for P to achieve environmental as well as agronomic objectives has been underway for the past decade; unfortunately, little of this research has been adopted by soil testing programs in the United States. The intent of this paper is two‐fold. First, to briefly review some of this research, illustrating its potential value in soil P management programs that, by necessity, must today have both agronomic and environmental components. And second, to provide recommendations as to how soil testing laboratories can be more proactive at integrating advances in research on the environmental uses of soil P testing into their programs and, by doing so, in re‐shaping their roles in sustaining a productive, environmentally sound agriculture

ISSN:0010-3624    

DOI:10.1080/00103629809370044

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In nature, trace element toxicities occur in all living organisms. The consequences of these toxicities have been described in crops, livestock and humans. In some instances, the toxicities are a direct consequence of the organism's position in the food chain and their environment, while in others, they are based upon genetic abnormalities resulting in physiological impairment.Nutrient toxicities in crops are more frequent for manganese (Mn) and boron (B) than for other nutrients. Manganese toxicity is found on acid soils in many parts of the world. Boron toxicities occur in irrigated regions where the well or irrigation waters are exceptionally high in B. Most other nutrient toxicities occur when large amounts of nutrients in question have been added in waste, e.g., sewage sludge. Crops grown near mines and smelters are prone to nutrient toxicities. Generally, the symptoms of toxicity in crops occur as burning, chlorosis and yellowing of leaves. Toxicities can result in decreased yield and/or impaired crop quality. Toxicity levels of trace elements range from 20 to 50μg g‐1for copper (Cu) and B to several hundredμgg‐1for Mn, molybdenum (Mo) and zinc (Zn). With the exception of Mo, toxicity of other nutrients can be reduced by liming. Following recommended rates of fertilizers and the safe and controlled use of waste materials, such as sewage sludge and coal fly ash, should reduce metal loading and nutrient toxicity in crops. Use of crop species and genotypes less susceptible to toxicity are recommended where toxicity is suspected. Toxicities of trace elements in animals are caused by the consumption of either feeds or grazing on pastures with high contents of the element in question. Accidental excess applications of minerals in grain mixes or oral ingestions of elements have been described as causing toxicity. Some toxicities, e.g., of Mo result in deficiency of other elements such as Cu. Some of the most toxic elements for livestock include Cu, lead (Pb), mercury (Hg), Mo, and selenium (Se). Under certain conditions, toxicities of arsenic (As), cobalt (Co), fluoride (Fl), iodine (I), iron (Fe), Mn, and Zn have also been reported. Symptoms of toxicity have been described in detail in the animal section. Trace elements, when in excess quantities, accumulate chiefly in the blood, liver, and kidneys. Measures of control for various trace element toxicities include removal of animals from affected areas or removal of the source of toxicity; gastric lavage and the specific use of oral doses of salts and chelates depending upon the element in question. Trace element/metal toxicities in humans are not common under normal conditions. Most toxicities are caused by environmental and/or genetic abnormalities, from excessive intake, by deliberate or accidental overdose, or from induced deficiencies (e.g. excess Zn causing Fe deficiency). Among the elements causing relatively frequent cases of toxicity are Pb, cadmium (Cd), Hg, Cu, Zn, and Fe. Selenium toxicity is generally limited to those areas/regions of the world, e.g. in certain parts of China, where soils with abnormally high Se content produce food crops containing highly toxic Se concentrations. Effective measures to control metal toxicities include gastric lavage, resuscitation, and the use of chelating agents in the acute phase. Protective legislation against the use of metal alloy utensils used for cooking is the long‐term control strategy.

ISSN:0010-3624    

DOI:10.1080/00103629809370045

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Procedural approaches used for sample preparation have remained relatively unchanged in recent years except for a trend toward extracting or digesting larger numbers of samples and the possible use of microwave digestion. The use of sequential extraction schemes for metals and metalloids has increased as a result of a growing interest inin sutiremediation of contaminated soils. Here questions focus on how soil amendments or treatments have rendered metals or metalloids less reactive or bioavallable. The use of computers for control of instruments, sample presentation, and interference correction represent significant advancements for many of the routine analytical instruments in use today. The development of inductively coupled plasma‐mass spectrometry (ICP‐MS) allows for much lower detection limits for certain elements and the possibility of performing isotope ratio analysis. Synchrotron radiation‐based techniques have become more common in recent years and offer nondestructive methods for examining metal and metalloid speciation in environmental media. Applications for the complex mixtures found in natural samples are developing. Bioavailability measurements are also becoming more important in light of trends in soil remediation. Feeding studies andinvitrobioaccessibility studies can be used to estimate bioavailability or bioaccessibility for elements such as arsenic (As) and lead (Pb) and the results can be used for determining remediation strategies for sites with contaminated soils.

ISSN:0010-3624    

DOI:10.1080/00103629809370046

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Site specific management (SSM) (precision agriculture) holds both promises and pitfalls. Ignoring the pitfalls while only focusing on the promises can distort research activities and limit positive impacts for end users. Particular attention is given to how SSM differs from other modem production technologies that attempt to suppress or nullify ecological variation rather than respond to it. It is argued that the “homogenizing”; mind‐set associated with other production technologies is distorting the analytical rigor applied to developing and promoting SSM systems. A true SSM system should allow the producer to respond to ecological variation in a rational and pro‐active fashion. Other promises of SSM are associated with emerging information markets, using SSM to develop risk reduction management strategies, biotechnology, and environmental protection.

ISSN:0010-3624    

DOI:10.1080/00103629809370047

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A review of methods for soil extraction used in the United States is given starting from the early 1940s to today. With the use of multielement analyzers, primarily the inductively coupled plasma emission spectrometer (ICP‐AES), extraction procedures being adopted today are those with multielement capabilities, such as Mehlich No. 3 and ammonium bicarbonate‐DTPA (AB‐DTPA).

ISSN:0010-3624    

DOI:10.1080/00103629809370048

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Due to the complexity of the soil plant system and in spite of the enormous amount of information available, the search for better methods to determine the bioavailability of nutrients to plants continues to be important. The large number of methods of soil analysis available worldwide in routine soil testing is an unquestionable demonstration of the lack of agreement on best alternatives. The question discussed in this paper, based on a literature review, is if those methods, considered here as the “standard methods”; of soil analysis, are the best possible alternatives for the evaluation of bioavailability of elements in soil. As alternative non‐standard methods, electroultrafiltration (EUF), the extraction with 0.01 mol calcium chloride (CaCl2L‐1solution, the extraction with ion‐exchange resin and the adsorption of phosphorus (P) on iron oxide treated paper filter (Pi), were considered. These four methods were compared with the standard methods Olsen, Mehlich 1, Bray 1, Mehlich 3, AB‐DTPA, Egnér, water, ammonium acetate (NH4OAc), and DTPA. The criterion used to compare the different methods was the percent variation (100 r2) associated with the correlations of plant indexes of bioavailability, in most cases uptake by plants, and soil contents of the elements. For P, the extraction with ion‐exchange resin presented considerable higher values of the percent variation, in comparison with the standard methods, EUF, and CaCl2. The resin extraction is adaptable to all types of soils, including acid and alkaline, which is not the case for the standard methods. Comparisons for other elements was impaired by the limited amount of data available, but better alternatives to the standard methods are not yet available. The extraction with resin seems to be feasible for other elements, including potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), nitrogen (N), molybdenum (Mo), copper (Cu), manganese (Mn), zinc (Zn), cadmium (Cd), and lead (Pb), but there is a need for a practical laboratory technique to determine all those elements and the biological validation with plant experiments. Thus only for P is there a more accurate alternative to evaluate bioavalilabity of nutrients in soils.

ISSN:0010-3624    

DOI:10.1080/00103629809370049

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Indirect, non‐destructive sensor‐based methods of plant and soil analyses could replace many of the wet chemistry testing methods that are in place today. Over 140 years have past since Justus von Liebig first employed soil testing in 1850. Today, simultaneous analyses of moisture, organic carbon (C), and total nitrogen (N) in plants and soils using non‐destructive near infrared reflectance spectrophotometry are possible. Recent work has targeted indirect measurements of the nutrient status in soils using spectral radiance data collected from growing crop canopies. The use of spectral measurements from plant canopies has heen driven, in part, by newer variable rate technologies which apply nutrients to prescribed areas. More recent work has documented significant soil variabiliry on a 1 m2scale. Because of this, indirect measures are necessary to avoid the cost of chemical analyses (10,000 samples requiredper hectare) and to avoid on‐the‐go chemistry. Also, in order for application technologies to be environmentally sensitive, they must treat the resolution where real differences, exist in the field. Present state‐of‐the‐art methods can sense N deficiencies in winter wheat (December ‐ February) on a 1 m2scale and apply variable foliar N on‐the‐go at 15 kph. These indirect methods rely on indices developed using the sufficiency concept that originally applied only to immobile nutrients. Plant canopy sensing methods allow for sufficiency to be used for both immobile and mobile nutrients since intensity and capacity can be integrated into one component, total nutrient uptake.

ISSN:0010-3624    

DOI:10.1080/00103629809370050

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Four different running capillary zone electrophoresis (CZE) buffers suitable for an indirect photometric detection were studied. The influence of several variables (buffer pH, concentration of electrophoretic flow modifiers, capillary diameter and applied voltage) on determination of chloride, sulphate, nitrate, fluoride, and phosphate was tested for each buffer. All the tested buffers proved to be suitable for the determination. PMA‐TEMED running buffer (pyromellitic acid‐tetramethylethylendiamine) was finally adopted for further investigation. The optimized PMA‐TEMED method was tested on several hundred samples of atmospheric deposition taken in the Czech Soil Monitoring Programme and lyzimetric waters from experimental stations. For analysis of water soil extracts six different soils from international and national soil proficiency tests were analyzed. Analysis of the water soil extracts was more complicated than analysis of atmospheric deposition because more unknown peaks were detected. Concentration of phosphorus in the water soil extracts was usually lower than the detection limit of the method. The proposed method proved to be suitable for determination of chloride, sulphate, nitrate, and fluoride in atmospheric deposition, lyzimetric waters, and soil water extracts.

ISSN:0010-3624    

DOI:10.1080/00103629809370051

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Precision Fanning addresses the small‐scale variability of soil fertility parameters in the field and consequently transforms them into variable fertilizer applications. Geocoded information about spatially variable soil characteristics is required in a close enough distance of 30 to 50 meters to meet the spatial correlation which is a prerequisite for the interpolation of data in order to obtain Digital Agro Resource Maps (DARMs). The self surveying approach efficiently provides geocoded information of time constant soil parameters, such as geomorphology, and organic matter and clay contents in optional density. It combines Gobal Positioning System (GPS) navigation and positioning with human sensory capabilities.

ISSN:0010-3624    

DOI:10.1080/00103629809370052

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The economical and operational aspects of multinutrient extractants make them attractive for soil testing programs. However, the value of a multi element extractant is primarily determined by the relationship between the amount of nutrient extracted and crop response. To determine the perspectives of the 0.01M calcium chloride (CaCl2) extraction procedure as a multinutrient extractant, this paper reviews literature on the soil chemical, analytical and plant nutritional aspects of CaCl2solutions as a soil extractant. Recent decades, CaCl2solutions were common single nutrient extractants in plant nutritional and soil chemical research but the amount of nutrient extracted was sensitive for differences in sample treatment and extraction procedure. Therefore, a 0.01M CaCl2procedure should be standarized to obtain a robust procedure. Calibration studies between conventional soil extraction procedure and the 0.01M CaCl2procedure show fairly good relationships. A first step to develop a multielement 0.01M CaCl2soil testing program is to convert conventional soil testing programs into 0.01M CaCl2programs based on these relationships. Validation of these programs with pot and field experiments remains necessary. Further research is suggested to test if the ‘labile’ pool of plant nutrients in a soil can be estimated based on the pH. The composition of the supernatant and soil characteristics. It is concluded that the 0.01M CaCl2procedure is a promising tool in near future farm nutrient management.

ISSN:0010-3624    

DOI:10.1080/00103629809370053

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor