摘要:

Soil pH is probably the most important, single, parameter characterizing its fertility. For theoretical and practical reasons the soil pH is usually measured in salt solutions of different strength. The most common solution used in Europe is 1M potassium chloride (KCl) in a soil/solution ratio of 1:2.5 (W/V). The ultimate goal of the international projectCopernicusof the European Community is to develop a uniform soil testing program based on the universal 0.01M calcium chloride (CaCl2)‐extraction procedure. In the Czech Republic, Hungary, The Netherlands, and Poland over 2,500 samples of representative soils have been collected and analyzed for soil pH in 1M KC1 and 0.01M CaCl2. Statistical analysis of these data shows a close correlation between pH values in both extracts. In very acid and acid soils, the pH in 0.01M CaCl2is higher than in 1M KCl. In neutral and alkaline soils, there is no significant difference in soil pH measured by both methods. Soil samples from all countries present the same population in respect to the relation between soil pH in KCl and CaCl2.

ISSN:0010-3624    

DOI:10.1080/00103629809370054

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The results of a joint project of institutes in the Czech Republic, Hungary, Poland, and the Netherlands on calibration of the 0.01M calcium chloride (CaCl2) soil testing procedure for magnesium (Mg) are presented. In soil samples collected in the participating countries, the analytical procedure for soil research according conventional extraction procedures are compared with data achieved with the 0.01M CaCl2procedure. Linear and quadratic regression analysis were applied to quantify the relations of Mg in the 0.01M CaCl2extract with the different conventional extractants. With the relatively weak extractant, 0.01M CaCl2somewhat lower quantities of Mg are extracted from the soil samples compared to the extraction solutions used in Poland (0.0125M CaCl2), in Hungary [1M potassium chloride (KCl)], and in the Netherlands [0.5M sodium chloride (NaCl)]. With the relatively strong extractant used in the Czech Republic (Mehlich II), more Mg is extracted. The relations of conventional extraction procedures and 0.01M CaCl2for Mg have such high correlation coefficients that direct translation of interpretation tables for the Mg status of soils is considered to be possible.

ISSN:0010-3624    

DOI:10.1080/00103629809370055

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The results of a joint project of institutes in the Czech Republic, Hungary, Poland, and the Netherlands on calibration of the universal 0.01M calcium chloride (CaCl2) soil testing procedure for potassium (K) are presented. In soil samples collected in the participating countries, the conventional extraction procedures were compared with the 0.01M CaCl2procedure. Linear and multifactorial regression analysis were applied to quantify the relations of K in the 0.01M CaCl2extract and in the different conventional extractants. With the relatively weak unbuffered extractant 0.01M CaCl2less K is extracted from the soils compared to the relatively strong conventional extraction solutions [Mehlich‐2, Egner‐Riehm, ammonium lactate, and hydrochloric acid (HCl)]. In general the relative amount of K extracted from a soil sample using 0.01M CaCl2is lower the higher the clay and organic matter content of the soil is. The explained variance (r2) between the 0.01M CaCl2procedure and conventional methods varied from 0.53 to 0.96. Relationships improved when clay content or organic matter content were taken into account.

ISSN:0010-3624    

DOI:10.1080/00103629809370056

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Numerous soil fertility studies to determine the spatial variability of crop production fields have not explored sampling intensities less than 0.04 hectares. A result of such methods has led to very sparsely populated variograms for sampling distances less than 20 meters (m). The purpose of this research is to accurately define the spatial variability within normal production fields by collecting single core soil samples at three different intensities in two fields. Main level sampling in each field was in a diamond pattern grid measuring 20 m x 20 m. Two of these grids were sub‐sampled in a 0.9 m x 0.9 m diamond pattern. Finally, three of these sub‐grids were sub‐sub‐sampled in a 0.1 m x 0.1 m diamond pattern. Descriptive statistics and semivariograms were calculated for each sampling level. Variograms exhibited many cyclic patterns over the entire sampling distance with a general upward trend. Calculations indicate that if sampling is performed at the maximum limit of spatial correlation [5–6 m for pH, 0.1–0.2 m for phosphorus (P), 20 m for potassium (K), 6–125 m for calcium (Ca) and magnesium (Mg), and 34–111 m for organic matter (OM)], then precision of the data must be reported as ±0.3–0.7 pH, ±25–36 mg P kg‐1, ±31–38 mg K kg‐1, ±276–342 mg Ca kg‐1, ±61–69 mg Mg kg‐1, and ±0.4–0.6% OM, respectively. Only for sampling distances less than these does spatial correlation exist. Therefore, complete characterization of fields at minimum variance can only be approached at sampling distances less than or equal to 1 m for pH, 0.1 m for P, 1 m for K, 1–6 m for Ca and Mg, and 10 m for OM. Sampling at 0.1 m for all nutrients can reduce estimates of variance to levels that approach the precision in laboratory determinations. A question remains, “How precise do we need to be?”;

ISSN:0010-3624    

DOI:10.1080/00103629809370057

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

To ensure that a laboratory produces credible analytical results, it is important to participate in collaborative studies utilizing check samples as a method of implementing a quality control procedure. This paper describes the following twelve check sample programs in which the Canadian Forest Service has participated during a 25‐year period to ensure that it produces high quality analytical results: Acid Rain Direct/ Delayed Response Project, Alberta Institute of Pedology, AOAC INTERNATIONAL, Canada Soil Survey Committee, Energy Resources Conservation Board, Expert Committee on Soil Survey, International Soil‐analytical Exchange, International Union of Forestry Research Organizations, Laboratory Exchange, Long Range Transport of Air Pollutants, Utah State University, and Western Enviro‐Agricultural Laboratory Association.

ISSN:0010-3624    

DOI:10.1080/00103629809370058

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A proposal for developing a unified proficiency testing program for soil and plant analysis laboratories in the North American region is presented. The proposed North American Proficiency Testing Program (NAPT) will be based on the quarterly submission to participating laboratories of six soil and/or three plant materials for chemical analysis using reference methods of analysis described in the four Regional Soil Work Group publications of NEC‐67, NCR‐13, SERA‐6, and WCC‐103 and methods outlined in Methods Manual for Forest Soil and Plant Analysis, Forestry Canada. Participating laboratories would complete sample analyses for all or any of the specified analytes and provide results to the NAPT program coordinator for statistical evaluation. Upon completion of the quarterly analysis each laboratory will be provided an evaluation of their individual performance on each of the methods listed. Annually the program will provide a report to each participant of the performance of the individual laboratory and that of the agricultural laboratory industry. An extension outreach program to aid participating laboratories in improving the quality of their analytical results will be implemented.

ISSN:0010-3624    

DOI:10.1080/00103629809370059

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The fertilizer recommendation guidelines for over 160 crops for the State of São Paulo, Brazil were updated in 1996 based on recent results of research on soil and plant analysis, and crop responses. Recommendations are based mainly on soil analysis and expected yield. Limestone rates are calculated to raise soil base saturation as a percentage of the cation exchange capacity (CEC) of the soil at pH 7.0, to levels which vary with crop species (i.e., to 50% for rice, coffee, and cassava, 60% for sugar cane and soybeans, 70% for cotton and maize, and 80% for grapes and onions). In addition, exchangeable magnesium (Mg) contents must reach a minimum level. Exchangeable subsoil aluminum (Al) and calcium (Ca), and clay content are used to determine rates of gypsum as amendment of subsoil acidity. Fairly consistent data on soil phosphorus (P) and potassium (K) calibration are available for Brazilian soils. Potassium rates are recommended based on values of soil exchangeable K and, for P fertilization, ion exchange resin‐extractable P is used. For the later the ranges of interpretation of soil analysis are different for horticultural, annual, perennial, and forestry crops. No soil test is used for nitrogen (N) advisory purposes. For many crops, especially grains, N rates depend on the class of expected response to this element, defined as a function of previous management history, crop rotation, texture etc. For some perennial crops N fertilizer rates take into account leaf N contents which were shown to correlate well with N response for citrus, mango, and coffee. Soil analysis for micronutrients, extracted with hot water [boron (B)] or DTPA‐TEA [iron (Fe), copper (Cu), manganese (Mn), and zinc (Zn)] is also used as criterion for fertilizer recommendation although for most crops only B and/or Zn are required.

ISSN:0010-3624    

DOI:10.1080/00103629809370060

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

With wheat yields below normal for two consecutive years (1995 and 1996) in most Oklahoma wheat fields due to abnormal weather conditions and disease pressure, soil nutrients probably had accumulated at a level that would allow application of lesser amounts of fertilizers to produce normal yields the following year. A free wheat soil testing and education program was initiated to promote statewide soil testing for improved fertilizer recommendations and for helping farmers to cut wheat production cost. This was offered to wheat producers from June 15 to August 15, 1996 by Oklahoma Cooperative Extension Services. Three thousand and seventy‐nine surface (0–6 inches) and 2,957 subsurface (6–24 inches) soil samples were sent to Oklahoma State University (OSU) Soil, Water and Forage Analytical Laboratory over a two‐month period. Surface soil samples were analyzed for pH, buffer index (BI) if pH was less than 6.5, nitrate‐nitrogen (NO3‐N), available phosphorus (P) index, and available potassium (K) index. Subsurface soil samples were analyzed for NO3‐N only. Twenty‐four informational meetings, with a total attendance of 980, were conducted at the end of the program to help fanners interpret soil testing results and understand fertilizer recommendations. Topics at the meeting also included fertilizer nutrient management, soil‐plant‐nutrient interactions, economics of liming low pH soils. Soil testing results showed that 39% of the wheat fields had soil pH less than 5.5. About 50% and 84% of the fields did not need any P and K, respectively. Significant amounts of NO3‐N were found in subsoil samples. By combining NO3‐N from the surface and subsurface samples, there were 54% of the fields that had NO3‐N greater than 80 lb A‐1which is enough nitrogen (N) for a yield goal of 40 bu A‐1. Farmers would save more money on fertilizer cost if the fertilizer programs had been based on recommendations from soil testing reports. This program clearly demonstrated the need for regular soil testing and the importance of taking subsoil samples for estimating residual N.

ISSN:0010-3624    

DOI:10.1080/00103629809370061

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

One hundred surface soil samples were randomly selected from actual fanner samples submitted to the North Dakota State University Soil Testing Laboratory for comparing the usefulness of the Mehlich‐III extractant with results from currently used methods for extracting phosphorus (P), potassium (K), zinc (Zn), iron (Fe), manganese (Mn), and copper (Cu) from neutral to alkaline pH soils from the northern Great Plains. Soil pH's were distributed across a range from pH 7.0 to 8.3. The Mehlich‐III extractant correlated well with P, K, and Zn values obtained by the Olsen, neutral normal ammonium acetate (1M NH4OAc, pH 7.0) or DTPA (diethylenetriamenepentaacetic acid) extraction procedures, respectively. The Mehlich‐III extractant was somewhat correlated with Cu by the DTPA method but poorly correlated with DTPA‐extractable Fe and Mn. The Mehlich‐III extractant appears to be adequate for extraction of P, K, and Zn across concentration ranges normally found in most agricultural soils in North Dakota.

ISSN:0010-3624    

DOI:10.1080/00103629809370062

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Soil nutrient availability is known to vary across landscapes. Consequently, variable rate fertilization is being studied to improve fertilizer use efficiency. The objective of this study was to examine the long term effects of variable phosphorus (P) fertilization and constant P fertilization on variably responsive sites within a field using a predictive response model. A 15.5 x 155.4 m cultivated area was divided into five transects each containing 50 3.1 x 3.1 m cells. Soil samples from the 250 cells were collected in the summer of 1996. Mehlich III soil test P (pp2m) ranged from 10 to 88, over the 250 cells. Data from P analysis was then used to determine the long‐term effects of both constant and variable rate application of P fertilizer to continuous wheat production. Projections from the data were made using a model that considers crop yield and response to fertilizer P at different soil test P levels. Soil test P values were adjusted following each annual yield projection using a relationship of one soil test P unit equal to 9 kg ha‐1input or removal of P. Annual application of 23 kg P ha‐1resulted in increased soil test P, however variability remained unchanged over a projected 50 years. Variable rates were identified as the P fertilizer level required to remove crop deficiency for winter wheat(Triticum aestiviumL.) based on an existing soil test calibration. Annual variable rate application of P fertilizer reduced variability, as measured by standard deviation, which reduced by 50% after 20 years. Seasonal marginal profit of variable rate application over a constant‐rate application increased as the field element size (resolution or area to which different rates are applied) decreased. Furthermore, as field element size decreased total P fertilizer used and yield increased for the entire area.

ISSN:0010-3624    

DOI:10.1080/00103629809370063

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor