Evaluation of soil test methods for estimating plant available micronutrient cations (Fe, Mn, Zn, Cu) in selected upland soils of Thailand
1992
Monkol Panichkul
Study on the relative predictability of DTPA extracting method (DTPA 0.005 M, CaCl2, 0.01 M, pH 7.3, extracting time 2 hours) for plant available micronutrient cations (Fe, Mn, Zn, Cu) in some upland soils of Thailand consisted of pot experiment, plant analyses and soil testing. The response of corn, soybean and cassava to added micronutrient cations varied with type of crops and soils. Calcareous Takhli soil series and acidic Banbung soil series are clearly deficient in zinc. Generally, DTPA soil test method is fairly promising for estimating plant available micronutrient cations in Takhli soil series particularly zinc whereas its validity for some other acid soils was not consistent. Concerning the evaluation of 15 modified DTPA methods, the original DTPA method could economically be modified with comparable reliability. Particularly for light textured-acid soils by using the extractant's pH at 7.3, DTPA concentration at 0.0025 M and 1 hour extracting time.
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