Evaluation of different methods for estimating available zinc in soils of Egypt

Four methods for estimating soil available Zn in Egyptian soils were evaluated. These methods were EDTA (NH4)2CO3, DTPA E-value and A-value. The four methods were compared and checked with the uptake of zinc by barley plant from the unfertilized soils. The data revealed that the average amounts of soil-Zn extracted by DTPA and EDTA (NH4)2CO3 were 5.4 and 4.96 ppm, respectively, while the average of A- and E-values were 29.03 and 12.62 ppm Zn, respectively. The relationship between plant -Zn uptake and soil available Zn for all methods were highly significant. However, the different methods could be arranged in the following order, according to the values of correlation coefficient: DTPA > EDTA (NH4)2CO3 > A-value > E-value. The present study suggests that isotopic exchange and dilution of radioactive zinc can provide a reliable procedure for measurement of available soil zinc. (author)