Evaluation of suitability of chemical extractants for assessing available zinc in acid and alkaline soils amended with farmyard manure and sludge

A greenhouse pot experiment was conducted to assess the suitability of DTPA, EDTA, Mehlich-3 and Ca(NO3)(2) in predicting Zn content of plant grown on acid and alkaline soils amended with organics using Indian spinach (Beta vulgaris L. var. all green) as test crop. For this purpose, the effect of four levels of Zn (0, 5, 50 and 100 mg kg(-1)) and two organics, namely FYM and sludge (3% w/w), on the extractable Zn in acid and alkaline soils was studied. Application of FYM reduced the extractable Zn in soil to a greater extent as compared to sludge. On the average, Mehlich-3 extracted the highest amount of Zn (20.9 mg kg(-1)) followed by EDTA (19.9 mg kg(-1)), DTPA (14.3 mg kg(-1)) and Ca(NO3)(2) (4.47 mg kg(-1)). The relative order of suitability of these extractants for predicting Zn content in Indian spinach could be arranged as Mehlich-3 > EDTA > DTPA > Ca(NO3)(2).