DTPA (diethylenetriaminepentaacetic acid)‐extractable Fe, Mn, Cu, and Zn were determined on several neutral and calcareous soils dried at various temperatures. Extractable Fe increased linearly over the drying temperature range 22 to 100°C, whereas Mn increased in an irregular manner. Values for Cu and Zn changed only slightly over this temperature range. Extractability of all four elements increased when field‐moist samples were air dried; Fe by a factor of 2 to 3, and Mn, Cu, and Zn by a factor of about 1.3 to 1.5. The increases in extractable Fe and Mn appear to result from separate temperature and dehydration effects and are only partially reversible with rehydration and moist incubation. The results of this study indicate that sample handling be standardized for calibration and routine tests before DTPA‐extractable Fe and Mn can be used as reliable diagnostic tests for these elements. Close control of drying conditions for Zn and Cu analysis may be desirable but is not as critical as for Fe and Mn.

Reply to "Comments on The DTPA-Extractabale Iron, Manganese, Copper, and Zinc from Neutral and Calcareous Soils Dried Under Different Conditions." Dr. Benians' letter prompts the following concerning his comments on the paper by Leggett and Argyle (1983). Our report dealt only with neutral and calcareous soils, as explicitly stated in the title. It was not intended for acid or highly weathered soils without further testing, although our experience indicates that some of these soils are affected by drying and heating in the same way as calcareous soils. Benians indicates that we "berated" Standard Works for their lack of sample drying information. We did not intend to berate anything (see Webster, 1965-berate is to chide vehemently; to scold). We stated the facts as we saw them. Quite likely the main reason the subject was not covered more extensively in the Standard Works is the lack of specific information in the literature. We were well aware of the consequences of drying or heating some samples as indicated by our list of references cited. Thus, we are happy that we arrived at the same "inevitable conclusion" as did Benians that drying or heating affects the results of many analyses of soils. The field conditions of soils at sampling time is an important problem as indicated by Benians. Shuman's (1980) comprehensive study adequately points out differences that can be encountered when sampling soil in the field at different times and under different moisture conditions. We did not attempt studies of this kind. The opening sentence of the third paragraph in Benians' letter introduces the subject of changes occurring for diethylenetriaminepentraacetic acid (DTPA) extractable Fe and Mn on storing dried samples. In the discussion following this opening sentence we are not sure whether he refers to changes in already dried samples or changes encountered upon drying. In our view the fact that DTPA-extractable Fe and Mn change markedly after drying i.e., while stored dry in waterproof containers, is unusual and a serious limitation that needs to be recognized. Such changes preclude the use of quality control samples over long periods of time that are necessary in laboratory operation. We recognize, however, that this problem may not be unique for Fe and Mn determined by DTPA-extraction. Bartlett and James (1980) showed similar changes for Mn extracted by 1.2 A/NH^OAc, pH 4.8 on samples stored dry for various lengths of time. Benians asks "Why dry samples?" We did not try to settle this issue with publication of our paper. Our purpose was to point out some of the changes that occur during drying or drying and heating so that others should be aware of the consequences associated with arbitrarily selecting sample drying conditions. Our experiences indicate that many people testing soil are not aware of changes that can take place during drying, nor what effects it will have on the analytical results. In addition, many of our commonly used analytical pro-most calibration samples are air-dried before a great many routine s...

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