Variability in analyses from WANA soil laboratories
1997
Ryan, J. | Garabet, S. (ICARDA, Aleppo (Syria))
In dryland farming of the Mediterranean zone, which has rain in winter with long dry summers, inadequate soil moisture is generally the dominant factor limiting crop growth. Nitrogen (N) and phosphorus (P) can significantly and economically increase yields in most circumstances when both elements are deficient. Soil testing can serve as a basis for identifying nutrient deficiencies and, with field calibration, can provide a basis for fertilizer recommendation. Fundamental to such endeavors is the use of appropriate tests and consistency of test results. Thus, a standard soil sample (Calcixerollic Xerochrept), along with a questionnaire, was sent to 50 laboratories in the region which are involved with soil analysis. Of the 36 respondents, most ran tests for available nutrients, pH and EC, but few did tests for total P, boron or sulfur. Most laboratories made some recommendations for clients. Few laboratories were involved with 15N or 32P analysis, while a small number performed clay mineral analysis. Units of measurement varied among laboratories. While most laboratories were close to the normal values for the test sample, others showed wide variation, especially for Olsen P and organic matter. By communicating these findings to survey participants in this workshop, we hope that the sources of such variation can be identified. Analyses can be improved by use of reference samples of known composition. The survey can help broaden and improve communication among soil scientists in ICARDA's Soil Fertility Network and improve the effectiveness of soil and fertilizer use research
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