Research In Brief

The Relationship Between Tenure and Non-Tenure Track Status of Extension Faculty and Job Satisfaction

Patrick I. Nestor
Extension Agent, Associate Professor
4-H Youth, Family and Adult Development
West Virginia University
Dunbar, West Virginia
Internet address: pnestor2@wvu.edu

Paul Leary
Professor
Educational Leadership
Marshall University
South Charleston, West Virginia
Internet address: pleary@marshall.edu

Introduction

Extension and Public Service has completed 10 years in the promotion and tenure system at West Virginia University (WVU). During this period, three different Extension directors have revised the guidelines used to determine the requirements for granting tenure (WVU Extension Guidelines for Promotion and Tenure, 1985, 1989, & 1996). Additionally, three academic provosts have reviewed Extension files, which has caused unclear expectation by faculty. Also, not all Extension faculty are included in the tenure track status. Approximately 10% of Extension faculty are non-tenure track faculty (WVU Extension Faculty Directory, 1997). The dual tenure status has caused tenure and non-tenure employees to question the validity of tenure for Extension faculty.

In a study of job satisfaction of the Center for Extension and Continuing Education faculty, Manthe (1976) recommended the adoption of rank and tenure to give staff recognition and professional advancement. He also recommended further study of job satisfaction and dissatisfaction toward Extension faculty as it relates to tenure status (Manthe, 1976).

As a land-grant institution, WVU's mission is to provide integrated, coordinated educational programs to meet citizen needs (WVU Faculty Handbook, 1996). The successful implementation of educational programs requires sharing of resources among county faculty and the institution (Manthe, 1976). County Extension faculty provide the network for the dissemination of educational programs from WVU to meet local needs. Additionally, county Extension faculty provide linkages between citizens and the university to help solve problems by utilizing the resources and expertise of the university (Manthe, 1976; Shriver, 1968).

In order to accomplish the university's mission of educational outreach and to serve the needs of the citizens through the Extension and Public Service unit, a positive relationship must exist among and between the Extension faculty of the unit. This positive relationship can be achieved when Extension faculties display a high level of job satisfaction (Mallilo, 1990; Manthe, 1976; McAlister, 1990; Shriver, 1968).

Given these factors, a study of the job satisfaction level of Extension tenure track and non-tenure track faculty could be helpful in increasing the effective use of resources and implementing program design to meet institutional mission and citizen needs. Increasing job satisfaction could also increase productivity of all faculty members (Asbury, 1996; Manthe, 1976). This study was based upon the recommendations from previous studies of the topic by Asbury (1996), Manthe (1976), and Shriver (1968).

Promotion and Tenure

Initially, field agents were not part of the campus-based faculty and, thus, were evaluated under different criteria from campus-based faculty (McAlister, 1990). Over time, land-grant institutions began reviewing the criteria and processes involved in tenure, promotion, salary structure, and degree requirements relative to field agents, with the result that some institutions adopted the practice of giving field agents the same rank, promotion, and tenure as their campus-based faculty (McAlister, 1990).

Promotion and tenure evaluation criteria of faculty in higher education have been reviewed over the years (Diamond, 1993; Leigh & Anderson, 1992; McAlister, 1990). The criteria used for evaluating and granting promotion and tenure in land-grant institutions have created an anomaly in the evaluation process and procedures (Leigh & Anderson, 1992). Manthe (1976) proposed that tenure status could be a key to increasing the effectiveness of Extension field faculty by enhancing their job satisfaction.

Job Satisfaction

The concept of job satisfaction has been typically defined as an individual's attitude about work roles and the relationship to worker motivation (Vroom, 1967). The job satisfaction/job dissatisfaction theory is the basis of Herzberg's job satisfaction study of accountants and engineers (Herzberg, Mausner, & Snyderman, 1959).

Herzberg's (1959) concept of job satisfaction distinguished two separate groups of factors influencing individual job satisfaction and dissatisfaction. The first group, called "motivators," leads to job satisfaction; the second group, called "hygienes," leads to job dissatisfaction (Herzberg, 1969; Herzberg, Mausner, & Snyderman, 1959). Motivator factors of job satisfaction include achievement, recognition, the work itself, and the intrinsic interest of the job (Herzberg, 1969). Hygiene factors of the job include pay, job security, working conditions, policy and administration, and relationships with peers and supervisors (Herzberg, 1969; Herzberg, Mausner, & Snyderman, 1959). Herzberg (1969) referred to motivators as "intrinsic factors" and hygienes as "extrinsic factors."

Job Satisfaction and Selected Demographic Characteristics

Job satisfaction literature provides additional support for personal characteristics influencing work and job satisfaction (Bedeian, Farris, & Kacmar 1992; Gibson & Klein, 1970; Kasperson, 1982). Research has supported personal characteristics as predictors of job satisfaction.

1. Age (Bedeian, 1992; Bowen, Radhakrishna & Keyser, 1994; Gibson & Klien, 1970; Glenn, Taylor & Weaver, 1977; Janson & Martin, 1982; Manthe, 1976).

2. Gender (Bowen, Radhakrishna, & Keyser, 1994; Hudson, 1989; Hulin & Smith, 1964; Rosen, 1991; Sachs, Chisler, & Devlin 1992; Thoreson, Kardash, Leuthold, & Morrow, 1990).

3. Years of experience (Bedeian et al., 1992; Bowen, Radhakrishna, & Keyser, 1994; Manthe, 1976).

The literature supporting job satisfaction and age has indicated that overall job satisfaction increases as faculty members mature (Gibson & Klien, 1970; Janson & Martin, 1982). The research done on Extension faculty by Bowen et al. (1994) and Bedeian et al. (1992) has indicated that Extension faculty members' job satisfaction increased as they matured.

The literature supporting job satisfaction and gender is divergent. Freisen et al. (1983), Mwange and McCaslin (1994), and Varca et al. (1983) found that male faculty member were more satisfied with their jobs than female faulty. Conversely, Hodson (1989) and Kelly (1989) found that female employees have increased job satisfaction over males.

The literature supporting job satisfaction and years of experience has indicated that no relationship was found between job satisfaction and years of experience (Bedeian et al., 1992; O'Rielly & Roberts, 1975). However, research done by Bowen et al. (1994), Mwange and McCaslin (1994), Manthe (1976), Boltes et al. (1995), and Bertz and Judge (1994) found that overall job satisfaction increased as the years of experience increased.

Job Satisfaction and Extension Faculty

Research literature referring to the relationship of tenure track and non-tenured track Extension faculty and job satisfaction is currently limited in scope. Nonetheless, factors related to job satisfaction are relevant in the prevention of employee frustration and low job satisfaction, because employees work harder and perform better if satisfied with their jobs (Asbury, 1996; Boltes, Lippke, & Gregory, 1995; Bowen, Radhakrishna, & Keyser, 1994; Mallilo, 1990; Manthe, 1976; McCaslin & Mwangi, 1994; Riggs & Beus, 1993; Shriver, 1968).

Job Satisfaction and Tenure Status

In a study dealing with job satisfaction of tenure and non-tenure track Extension faculty in Texas, Boltes, Lippke, and Gregory (1995) conducted research to investigate the relationship between dimensions of organizational contribution and employee job satisfaction. They used faculty involvement, positive balance between work and home, vision, diversity, and professional development as predictors of job satisfaction and organizational commitment. Overall, 75% to 80% of tenured Extension faculty expressed concern or dissatisfaction in all seven dimensions of the survey.

The six predictors used by Riggs and Beus (1993) to evaluate job satisfaction among Extension field faculty in eight western states represented both motivators and hygiene factors. Findings from the Extension faculty surveyed indicated overall job satisfaction was moderately high.

Purpose of Study

This study attempted to analyze the roles of tenure and non-tenured track status of Extension faculty of West Virginia University and their relationship to job satisfaction. Additionally, this study analyzed selected demographic characteristics of Extension faculty of West Virginia University and their relationship to job satisfaction.

Research Questions

1. Is there a significant relationship between tenure track status of Extension faculty and their job satisfaction?

2. Is there a significant relationship between tenure track status of non-tenured Extension faculty and their job satisfaction?

3. Is there a significant relationship between non-tenure track status of Extension faculty and their job satisfaction?

4. Is there a significant relationship between age of Extension faculty and their job satisfaction?

5. Is there a significant relationship between gender of Extension faculty and their job satisfaction?

6. Is there a significant relationship between years of experience of Extension faculty and their job satisfaction?

Population/Sample

The population of Extension faculty consisted of all tenure track and non-tenure track faculty (N=190) employed in the West Virginia University Extension and Public Service unit as listed by the WVU Department of Human Resources and Office of Management Services at WVU Extension during the current year. The entire population of 190 Extension faculty was surveyed. The findings allowed for generalizability to the West Virginia Cooperative Extension Service.

Instrumentation

This study used an instrument divided into two parts to collect the data. Part I included a demographic response section, and Part II included a job satisfaction response section.

The Mohrman-Cooke-Mohrman Job Satisfaction Scale (MCMJSS) was used to evaluate the job satisfaction of tenure and non-tenure track Extension faculty of West Virginia (Mohrman, Cooke, Mohrman, Duncan, & Zaltman, 1977). The instrument was designed to measure self-perception of job satisfaction using an 8-item scale subdivided into two sections. Each of the two sections contained four questions, each using a 6-point Likert-type scale. The 6-point Likert-type scale allows for the highest responses to be indicated as 6 and the lowest response to be indicated as 1.

Demographic data were collected using a version of the questionnaire designed by Manthe (1976). The demographics selected for use in this study included: current tenure status, gender, age, and years of experience.

Methods

This study was a one-shot case study (Campbell & Stanley, 1963). The study used self-reported questionnaire survey methods to gather data. Each Extension faculty member was mailed copies of the survey instrument with response instructions, along with a letter of introduction and an assurance of respondent confidentiality. The population was asked to complete and return the instrument within 10 working days in an enclosed self-addressed, stamped envelope. Within the 10 working days, a second survey was mailed to Extension faculty. Responses were numbered by date of collection. A return rate of 50% plus one was the goal of the study to allow data analyses to provide relevant findings (Kerlinger, 1986). Telephone contacts were made to increase the number of responses prior to analysis of the data.

Analysis of Data

Data were analyzed using the General Linear Models included in the Statistical Analysis System (SAS). Additionally, the variables were compared using regression, analysis of variance, frequency distributions, and descriptive analyses to examine for significance factors. The MCMJSS instrument was reviewed to establish an internal, an external, and an overall score for each individual. An Alpha level of 0.05 was used as the level of significance for this study. The data were configured in a 3X3 paradigm: three independent variables were analyzed with three dependent variables. The remaining independent variables were analyzed with the three dependent variables. Post hoc analyses were conducted as needed.

Descriptive Data

The first demographic item asked respondents about their tenure status, and 124 indicated they were in a tenure track position. Forty-two of the respondents reported they were not in a tenure track position. In the surveys returned, 91 respondents were tenured, and 33 respondents were not tenured in the tenure track position.

The respondents were to choose one of seven categories listed on the survey sheet that best described their job category. The seven choices were:

1. 4-H/Youth Program
2. Agriculture Programs
3. State Program Specialist
4. Family & Consumer Science Program
5. Community & Economic Development Program
6. Administrative/Leadership Team
7. Other

The responses indicated that 47 (29%) were 4-H/Youth, 27 (16.7%) were in agriculture, 23 (14.27%) were state specialists, 19 (11.7%) were in Family and Consumer Science, 11 (6.8%) were in Community and Economic Development, 12 (7.4%) were administrators, and 23 (14.2%) indicated other. The other category included respondents indicating they had responsibilities for more than one program area.

One hundred sixty (98.7%) of the 162 respondents indicated their gender. Eighty (50%) were female, and 80 (50%) were male.

All 162 respondents indicated their age, and the mean age reported was 44 years. From an array of respondent ages, the range was divided into four groups of equal frequency. These four quartile ranges were ages 23-33, 34-45, 46-50, and more than 51 years. The age range 23-33 had a 35 (22%) response level. The age range 34-45 had a 52 (32%) response level (the largest number of surveys returned). The age range 46-50 had a 33 (20%) response level. The age range more than 51 years had a 42 (26%) response level.

The 162 respondents indicated their years of experience as an Extension faculty member at West Virginia University. The four quartile ranges were 1-5, 6-9, 10-19, and more than 20 years of experience. In the first quartile, 43 (27%) indicated they had 1-5 years of experience at WVU. In the second quartile, 42 (26%) indicated they had 6-9 years of experience at WVU. In the third quartile, 38 (23%) respondents indicated they had 10-19 years of experience at WVU. In the fourth quartile, 39 (24%) respondents indicated they had more than 20 years of experience at WVU. The mean was 12.62 years.

Respondents' total years of experience in Extension indicated the mean score for the 162 (85%) respondents was 13 years of total experience in Extension. The ranges were 1-5, 6-13, 14-19, and more than 20 total years of experience in Extension. Of the faculty returning surveys, 48 (30%) indicated 1-5 years of experience in Extension, 41 (25%) indicated 6-12 years of experience in Extension, 37 (22%) reported 14-20 years of experience, and 37 (23%) respondents reported more than 20 total years of experience in Extension.

The respondents were also asked the highest academic degree acquired. Thirteen (8.0%) indicated holding a bachelor's degree; 114 (70.4%) indicated holding a master's degree; and 35 (21.6%) indicated holding a doctoral degree.

In addition to demographic descriptive data, respondents were asked their perception of the importance of tenure, and two-thirds (66%) of respondents indicated tenure was important to them. Respondents were recorded on a f5-point Lickert-type scale.

Major Findings

Research Questions 1 and 2: Is there a significant relationship between tenure track status of tenured and non-tenured Extension faculty and their job satisfaction?

The research questions were tested, and it was determined that no significant relationships existed between the variables. Table 1 presents the analysis of variance summary for Research Questions 1 and 2.

Table 1.

Analysis of Variance Summary for Tenure Status and Non-Tenure Status of Intrinsic, Extrinsic, and Overall Job Satisfaction

Research Question 3: Is there a significant relationship between non-tenure track status of an Extension faculty and their job satisfaction?

The analysis showed a statistically significant relationship between non-tenure track status and intrinsic job satisfaction. The F value for the relationship between intrinsic job satisfaction and tenure status was 5.97. This F value was statistically significant at 0.0161. Therefore, it was determined that there was a statistically significant relationship between intrinsic job satisfaction and non-tenure track status Extension faculty. Those respondents that were non-tenure track status had more intrinsic job satisfaction than tenure track status respondents. The F value for the relationship between extrinsic job satisfaction and non-tenure status was 1.39, which is not statistically significant. The F value for the relationship between non-tenure track status and overall job satisfaction was 3.75, which was not statistically significant. Table 2 presents the analysis of variance summary for research question three.

Table 2.

Analysis of Variance Summary for Non-Tenure Status of Extension Faculty and Their Job Satisfaction

Research Question 4: Is there a significant relationship between age of Extension faculty and their job satisfaction?

The relationship between age of an Extension faculty and his or her job satisfaction was tested, and it indicated that a significant relationship existed between age and intrinsic job satisfaction of Extension faculty. The F value for the relationship between age and intrinsic job satisfaction was 2.69, which was statistically significant at the 0.0481 alpha level.

Further analysis of the data through the use of Duncan's Multiple Range Test revealed that comparisons of intrinsic means for the age ranges 23-33 and 46-50 indicated significant differences between those means. This analysis revealed that Extension faculty in age group 23-33 and 46-50 were more intrinsically satisfied with their jobs than Extension faculty in age groups 34-45 and more than 51 years of age.

Research Questions 5: Is there a significant relationship between gender of Extension faculty and their job satisfaction?

The relationship between gender of Extension faculty and their intrinsic, extrinsic, and overall job satisfaction was tested, and the analysis of variance revealed no statistically significant relationship between these variables.

Research Question 6: Is there a significant relationship between years of experience of Extension faculty and their job satisfaction?

As for the relationship between years of experience of Extension faculty and job satisfaction, it was determined that no statistically significant relationship existed between these variables. The relationship between years of experience and intrinsic job satisfaction was not statistically significant.

Further analysis of the data, however, indicated that years of experience at West Virginia University was statistically significant as related to intrinsic and overall job satisfaction.

Additional analysis of the data through the use of the Tukey's Studentized Range (HSD) Test reaffirmed the statistical significance that existed between intrinsic and overall job satisfaction and years of experience of Extension faculty at WVU. This analysis revealed that Extension faculty were intrinsically and overall significantly more satisfied with their job the longer they were employed with WVU.

Conclusions

The findings generated by the analyses of data resulted in the following conclusions. The literature has indicated that there is a relationship between tenure status and job satisfaction (Bretz & Judge, 1994; Horenstein, 1993; Leigh & Anderson, 1992; Riggs & Beus, 1993). In this study, there was no statistically significant relationship between tenure status and extrinsic and overall job satisfaction. However, in this study a statistically significant relationship was found between non-tenure track status and intrinsic job satisfaction. This finding does not substantiate the assertion that tenure status improves job satisfaction. This study indicates that non-tenure track status faculty have higher job satisfaction among Extension faculty in West Virginia.

Additionally, the literature has indicated that there is a positive relationship between gender and job satisfaction, with female respondents having higher job satisfaction (Friesen, Holdaway, & Rice, 1983; Glenn, Taylor, & Weaver, 1977; Hodson, 1989; Loscocco & Roschell, 1991), years of experience, (Gruneberg, 1979; O'Reilly & Roberts, 1975; Bedeian, Ferris, & Kacmar, 1992). However, in this study, no statistically significant relationship existed between these variables.

Further analyses of the data revealed that a relationship exists between the respondents' years of experience at WVU and their increased intrinsic and overall job satisfaction. These findings support the research done by Bedeian, Ferris, and Kacmar (1992) and Bowen, Radhakrishina, and Keyser (1994) that Extension faculty have increased job satisfaction the longer they are employed at an institution.

Additionally, the literature contains numerous references to the relationship between age and job satisfaction (Bedeian, Ferris, & Kacmar, 1992; Gibson & Klein, 1970; Glenn, Taylor, & Weaver, 1977; Gruneberg, 1979; Janson & Martin, 1982; McCaslin & Mwangi, 1994). The Extension faculty in this study indicated higher intrinsic job satisfaction in ages of 23-33 and 46-50 when compared to ages of 34-46 and more than 51 years. These findings support the findings by Janson and Martin (1983) and McCaslin and Mwangi (1994), which indicated that the older an employee, the higher his or her job satisfaction.

Implications

The results of this study provided information related to the significant relationship between non-tenure track status and intrinsic job satisfaction. One implication is that the more support provided in the work place, the more highly satisfied the faculty member is likely to be. These data supporting the relationship between non-tenure track status and job satisfaction could be most important when new faculty are recruited. Also, new faculty, when considering a position, could review the data on tenure status in formulating their career plans (Bretz & Judy, 1994; Horenstein, 1993).

Given the foregoing, it is reasonable to assume that land-grant institution administrators and faculty should work together to provide greater levels of achievement, recognition, and work task satisfaction among tenured and non-tenured faculty. This could be accomplished by providing mentoring of new faculty by mature faculty or by emphasizing teamwork and collaboration on job tasks.

Institutions that train faculty could, based on the results of this study, use job satisfaction as a method for identifying, recruiting, and selecting potential faculty members. Administrators could also develop job satisfaction as a program goal for in-service and professional development courses.

Additionally, Extension organizations and institutions that recognize the relationship between age and job satisfaction could provide mentoring programs for the 34-45 and more than 51 age groups. This mentoring could reinforce the support structure for the 23-33 and 46-50 age groups (Bediean, Ferris, & Kacmar, 1992; Glenn, Taylor, & Weaver, 1977; Gibson & Klein, 1970). Given the need to support the 34-45 and more than 51 age groups, this added mentoring could increase their job satisfaction, while the other age groups would gain recognition for the new relationship and support for them. Consequently, the entire organization would benefit from the increased job satisfaction of the faculty.

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Practical Considerations When Selecting a Soil Testing Laboratory for an Educational Program

Jerry Neufeld
Extension Educator-Crops
University of Idaho Cooperative Extension System
Caldwell, Idaho
Internet address: jerryn@uidaho.edu

Jay Davison
Area Specialist
Nevada Cooperative Extension
Fallon, Nevada
University of Nevada, Reno

Introduction

Cooperative Extension professionals and program collaborators commonly use laboratory analysis of soil samples in educational programs to assist in quantifying the nutrient status of soils. When done properly, soil testing is a highly effective tool in producing high crop yields for the lowest possible costs. However, inaccurate analysis can result in additional costs, lowered production, or environmental damage from excessive fertilizer applications. The accuracy of soil testing is dependent upon proper field sampling techniques and laboratory analysis.

This article discusses variability of results associated with soil testing laboratories and suggests practical actions that Extension professionals and program collaborators can take to select a laboratory that provides accurate and precise soil testing information.

Reasons for Soil Testing

In areas under intense cultivation for many years, current crop production practices remove nutrients from the soil faster than they can be replaced by natural soil formation processes. Therefore, periodic soil testing is necessary and the only tool available to quantitatively determine current soil nutrient levels. It is widely accepted in production agriculture that soil testing is a practice that helps producers obtain high yields while enabling them to use best management practices that benefit the environment (Hawkes et al., 1985). If, however, a producer is using inaccurate soil fertility data, he or she may apply fertilizer when there is no likelihood that the application will increase yield or profits. Conversely, if the soil fertility analysis data does not indicate a need for fertilizer when it is needed, maximum economic yields may be foregone and income lost.

Agricultural producers in Idaho, Nevada, and many other areas of the U.S. are experiencing pressure from various environmental groups and government agencies to reduce non-point sources of pollution. Nitrogen and phosphorous fertilizers applied to agricultural lands are sources of environmental degradation, and their detrimental effects have been well documented (Ongley, 1996).

Principal problems related to agricultural runoff are contamination of surface and ground water; loss of ecosystem diversity; ecosystem dysfunction; and increases in water-borne diseases (Ongley, 1996). Agricultural crops require large amounts of macronutrients; therefore, frequent applications are necessary for optimum crop production. Accurate and precise soil analysis enables producers to apply only the amount of fertilizers needed by the crop, thereby reducing the potential for offsite movement.

Definition of the Problem

Hundreds of laboratories in North America analyze agricultural soil samples. Consequently, there are varying levels of quality in the analytical results being provided to the customer. Also contributing to soil testing variability are the different extraction methods used to quantify the same soil constituents. Certain extraction methods have been shown through research to be more accurate and precise than other methods (Miller & Kotuby-Amacher, 1996), while other extraction methods are applicable to only certain types of soil and climates (Ankerman & Large). There are no certified reference standards across the soil testing industry for quantitatively evaluating the fertility status of agricultural soil samples. All of these factors can contribute to a high degree of reporting variability.

Analytical results from soil testing laboratories can be highly variable within individual laboratories as well as between laboratories. There are methods that can be used to deal with variability when submitting large quantities of samples. For example, soil samples with known properties (reference samples) can easily be submitted as a set of blind samples within a larger set of soil samples. The results on the reference sample can then be evaluated for deviations from its known properties.

However, the authors and most producers are more likely to submit small numbers of samples. When small numbers of samples are submitted, it is harder to check on the accuracy and precision of the laboratories' results. The authors' experience indicates that it is often difficult to determine when analytical results obtained from soil testing laboratories are accurate and that excessive variability between and within laboratories is the norm rather than the exception. Therefore, a project to evaluate the variability between and within several laboratories likely to conduct soil analysis work for northern Nevada producers was undertaken. A set of recommendations to assist Cooperative Extension professionals and clientele in selecting an accurate and precise soil testing laboratory was also developed.

Materials and Methods

In 1995 and 1996, the authors conducted a project to document and evaluate soil testing variability problems encountered when using commercial soil testing laboratories. In the fall of 1995, two 5-gallon samples of Creemon silt loam soil were collected from the upper 12 inches of soil from two locations in an alfalfa field south of Battle Mountain, Nevada. Each sample was air dried, crushed, and passed through an eighteen-mesh screen to remove large particles and debris. The samples were then thoroughly mixed to make a uniform composite sample. Each composite sample was used to fill 20 soil bags, for a total of 40 samples.

Two samples from each composite sample were sent to five different soil testing laboratories (each laboratory received four samples). Two weeks later, the remaining two samples from each composite sample were sent to the same five laboratories. This procedure was repeated in the fall of 1996, except a Sonoma silt loam from Lovelock, Nevada, was used. In summary, each laboratory evaluated four replications of four different soil samples over a period of 2 years (80 samples total).

Soil laboratories commonly use different extraction methods to analyze for the same soil constituents. Nine different soil constituents were analyzed for precision in this project. They were selected because the five laboratories use the same extraction method for these constituents, thus making direct comparisons possible. Table 1 lists the constituents, the extraction methods, and units used for this project.

Table 1.

Constituents Analyzed, Extraction Methods, and Units Used

The analytical results received from the laboratories were summarized and then compared to the North American Proficiency Testing Program (NAPT, formerly called the Western States Proficiency Testing Program) values for the same years. The NAPT objectives are: 1) to provide an external measure of individual laboratory accuracy, 2) to develop a framework for improving the long-term quality of agricultural analyses, and 3) to identify levels of accuracy and precision for specific analytical methods (Miller & Kotuby-Amacher, 1996).

The NAPT's objectives are met through an intensive program whereby soil samples with known properties are submitted to voluntarily participating laboratories on a quarterly basis. Each laboratory analyzes the soil samples for nutrient status using established analytical procedures. (Miller & Kotuby-Amacher, 1998) Laboratories provide their results to the NAPT, where they are compiled and analyzed statistically. The statistical results provided by the NAPT to each laboratory show how they performed on the quarterly sample analysis compared to all other participating laboratories.

A statistical procedure called the "relative standard deviation" (RSD) is the main procedure used to evaluate laboratory results for precision. RSD is also known as "coefficient of variation" (CV). The RSD is a measure of the relative dispersion of the values in a data set (Little & Hills, 1978). RSD is calculated by dividing the standard deviation by the mean from a data set and then multiplying the dividend by 100. The lower the RSD value, the higher the level of precision. In 1995, the NAPT calculated an RSD value for 35 soil constituents submitted from 102 laboratories. In 1996, the NAPT calculated RSD values for 35 soil constituents submitted from 104 participating laboratories.

Laboratories participating in the NAPT can use the statistical data to compare their analytical results to industry-wide values and ultimately improve their analytical procedures. The NAPT does not provide data to the public about specific laboratories. Interested people must inquire from their individual laboratories as to whether or not they participate in this or any other proficiency program and whether they will share their proficiency testing data with you. However, the NAPT program does provide an annual report to the public with a summary of the data collected.

Following is an example of how proficiency testing program data can be used in a Cooperative Extension crops program. Anyone can request the annual report summarizing soil testing accuracy and precision results from the NAPT. You can also ask your laboratory to provide results from their participation in the NAPT. A review of the data will show how your laboratory compares to all other participating laboratories. As a rule of thumb, the NAPT suggests that accuracy data should be no greater than 10% of industry-wide values. Precision values (RSD) for individual laboratories should be no greater than 15% of industry-wide values and are analysis dependent (R. O. Miller, personal communication, April 1, 1998).

Results and Discussion

There is a wide range of variability between and within the results received from the five laboratories conducting the soil analyses for this project. Table 2 shows median RSD values obtained from the NAPT for 1995. This table also shows RSD values from the laboratories participating in this study in 1995. Table 3 shows the same data for 1996. RSD values exceeding the median NAPT values plus 15% are shown in bold type. Any RSD value exceeding the median NAPT value plus 15% indicates a lack of precision.

Table 2.

1995 NAPT RSD Values and Sampled Laboratory RSD Values