Evaluation of National Proficiency Testing (PT) Provision in the Scheme of Soil Analysis on PH, Organic Carbon, Total Nitrogen and Available Phosphorus Based On the Same Soil Sample Exchange in Ethiopia

Introduction

Soil and agronomic studies have been conducted in Ethiopia since the 1950s. A great deal of work has been conducted related to crop response to fertilizer applications and soil survey and mapping. However, the data collected from the studies are scattered across different individuals and organizations and exist in diverse formats. As a result, most of the data are difficult to access and lack standards or are incomplete, which diminishes their utility. This resulted in duplication of effort and wasting of resources to collect redundant data. Those research technologies were released based on data collected from field and laboratory experiments. The soil laboratories is fundamental to such agricultural research endeavors, involving: analysis of soils as a basis for soil characterization and classification, identifying plant nutrient constraints, and establishing criteria for fertilizer application and efficient nutrient use, along with water, plant, and fertilizer analysis. Decision- making by policymakers, farmers, and researchers depends on reliable data on soils, water, and crops. However, a study conducted in 2016 on the status of Ethiopian soil laboratory infrastructure indicated that the data collected (in the chain of soil sampling to laboratory output) are not reliable enough for decision-making purposes [1]. Accordingly, the study emphasized the need to improve the output of Ethiopian soil, plant, and water laboratories and suggested strategies for them to fully reach their potential.

The findings of the study cast a shadow over the quality of the legacy data and data being collected and/or analyzed by the Ethiopian public and private laboratory infrastructure. Therefore, besides collating legacy soil and agronomic data, the implementation of a careful standardization and harmonization mission for legacy data is indispensable for national synthesis. It is advisable to follow global and national soil data standardization and harmonization guidelines such as the World Soil Information Service (WoSIS)- Towards the standardization and harmonization of world soil data [2].

Various institutions have made efforts since 1963 to generate soil information for Ethiopia for assessing the agricultural development potential of each soil. These studies varied widely in scope, scale, and approach as well as in the quality of outputs [3]. The first attempt to map the soils of Ethiopia was made by Schantz and Marbut in 1923 as part of the mission of mapping the soils of Africa at a scale of 1:25 million. Among early efforts was the soil fertility survey conducted by Murphy HF [4], who also studied the general fertility status of soils in Ethiopia by collecting some 2,600 samples along the main roads across the country. Proficiency testing (PT) is a significant component in the laboratories competency process as it allows laboratories to monitor the quality of their analytical results as stipulated in ISO/IEC 17025. There are a number of benefits to participating in PT, including improving quality of analytical results measurements, demonstrating analytical competence, developing and training analysts, and the validation of methods and instruments. In this regard, Holeta Agricultural Research Center Soil laboratory takes an initiative to coordinate soil PT provision for interested soil laboratories (Fifteen soil laboratories of EIAR and regional centers) of Ethiopia. Currently, there are 68 soil laboratories distributed over 35 cities in different parts of Ethiopia [1].

PT evaluation is to monitor the quality of their analytical results, demonstrating analytical competence, developing and training analysts, and the validation of methods and instruments as stipulated in ISO/IEC 17025 in Ethiopia. Among few accredited soil laboratories, Holeta Agricultural Research Center (HARC) soil laboratory has been accredited since 2014.

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**Data Analysis**

Description of the statistical analysis was used, including the determination of assigned values and any outlier detection techniques Microsoft Excel software or self-programmed software for the data processing was used after the functionality according to the intended purposes proved on the basis of a sufficient number of test sets of data. All data were back-up to eliminate potential loss of electronic data. Assigned values are based on consensus values, obtained from the results of the participants using their routine methods. The robust standard deviation is used as standard deviation for proficiency assessment.

Participant’s performance was evaluated by calculating Z scores: $z_i = \left( x_i - xpt \right) / \sigma - pt$

The following criteria were used for the performance assessment.

• $Iz$-score $\leq 2.0$: Satisfactory Performance,
• $2.0 < Iz$-score $\leq 3.0$: Questionable Performance,
• $Iz$-score $\geq 3.0$: Unsatisfactory Performance

The uncertainty in the assigned value is calculated as:

$$ ux = 1.25 * s / \sqrt{N} $$

Where:

• $s$ = robust standard deviation
• $N$ = number of results

The uncertainty in the assigned value may influence the evaluation of the results (calculated Z-scores).

**Result and Discussion**

Participants in the soil proficiency testing scheme were listed below

From 15 different soil laboratories were participated in the proficiencies tests

• EIAR: - Holeta, Melkasa, kulumsa, Pawe, Jimma, Assosa, and DebreZeit Agricultural Research Centers soil laboratories
• OIAR: - Batu, Bedele Agricultural Research Centers
• AIAR: - Adet, Debribihan Agricultural Research Centers
• SolAR: - Jinka, Areka, Hawasa Agricultural Research Centers
• Netherland: - WEPAL

All laboratories submitted the analysis result based on the instruction though some laboratories lately submitted the results. Most of the laboratories tested and submitted results for about six parameters as indicated in the Table 1.

Conclusion

From the above result the laboratories should take serious measures (analyzing the root cause, implement and document appropriate corrective action) to improve the OC, TN and Available P testing result. However, the data generated from the Ethiopian soil laboratories are not reliable enough and need to improve their analytical services quality. Reliable and acceptable data was generated when laboratories fulfill ISO/ IES 17025 standard, gets an accreditation certificate and participate in Proficiencies tests.