Evaluation of Different Plant Active Iron Extractants under Conditions of Egypt

 
 
IRON status in sixty one soils of Egypt cultivated with corn was studied by determining their total and available (DTPA), iron content, and active iron in plant using different methods by determination of Fe in leaf below and opposites the ear collected at silking stage.
 
The amount of soil available iron extracted by the DTPA method ranged from 1.48 to 14.80 mg/kg Fe. According to the critical level of available iron in soil (4.5 mg Fe/kg), the data showed that 57% of the tested soils contain adequate quantities, while 23% are within the margin range, and only 20% are deficient.
         
As regards the concentration of Fe in the dry leaves collected during silking stage from corn plants ranged from 208 to 625 mg/kg Fe. The average values of active iron in leaves extracted by EDTA, DTPA, O-Ph., 2,2’ Bip. and HCl  were 33.78, 46.95, 65.07, 100.43, and 140.74 mg/kg Fe, respectively.
 
A highly significant positive correlation coefficient was obtained between the values of plant active iron extracted by any of the five extractants and DTPA-soil available Fe. These results clearly demonstrate that active iron extracted by the five solutions is favorable to be used for separating iron-deficient from non-deficient plants.
 
 The critical values of active iron extracted by EDTA, DTPA, O-Ph., 2, 2’Bip. and HCl were  40.0, 55.00, 80.00, 120.00 and 180.00 mg/kg Fe, respectively. According to these values, 59, 65, 57, 46 and 62% of the soils studied are classified as deficient, respectively. Moreover applying the critical value of Fe soil-DTPA, less than 4.5 mg/kg proved that 43% of the studied soils are in the deficiency range, In this respect, it is obvious that such value coincides well with that obtained by the 2,2’Bip plant active iron (46%). On the other hand, the price of 2,2’Bip is so high (one Kg= 15000 L.E) that makes, from the economical point of view, the use of 2,2’ Bip is excluded. Moreover, since the other extractants gave reliable results the EDTA is very suitable according to its low price(one Kg= 40 L.E).