Comparison between DTPA Extracting Methods for Available Zinc with Multinutrient Extractants in Vertisols and Inceptisols

Abstract

Aims: To evaluate relationships between some universal soil extractants and legacy methods.
 Place and Duration of Study: The study was carried out at IISS, Bhopal.
 Methodology: Samples were analyzed by different methods being related; e.g. GLOSOLAN/international method or rapid methods/universal extractant and legacy methods. Measured data was obtained under the best achievable laboratory quality control conditions, for maximal transfer function reliability with the lowest RMSE (Root Mean Square Error). Out of the 60 samples in each category, a representative set (80% of the samples) was used (e.g. by linear regression analysis) for the development of the transfer function and the rest 20% of the samples were retained for validation of transfer functions. Residuals (differences) between measured and estimated soil property values were calculated. The correlation and RMSE (Root Mean Square Error) were calculated for the validation data set.
 Results: The Zinc extractable DTPA and Mehlich-3 had a regression coefficient of R2= 0.92. while the extracted with AB DTPA had the regression coefficient of R2= 0.72 with DTPA, with extraction in the order of Mehlich3> AB DTPA> DTPA. Hence, Mehlich-3 and AB-DTPA both extractants can replace DTPA extractants for the determination of available micronutrients in soils in Vertisols.
 Conclusion: In conclusion, different regression equations are developed between the various methods of analysis that must be used to compare the results obtained from different extraction methods.