Effect of soil pH on iron uptake and its specific activity by two cultivars of soybeans differing in ability to accumulate iron and by oleander

Abstract

PI54619–5–1 and Hawkeye soybeans (Glycine max L.) were grown in Yolo loam soil with different amendments to alter the soil pH (5, 6, 7.4, and 8.2). High specific activity ⁵⁹Fe had been equilibrated with the soil before transplanting. The numbers of plants per pot varied to create competition (8 or 2 for each variety plus 4 of each variety together). The PI54619–5–1 soybeans were Fe deficient at pH 7.2 and both Varieties were deficient at pH 8.5. The Hawkeye accumulated the most Fe except at pH 8.5. Iron accumulation and specific activity were both decreased at this pH value. Specific activity otherwise increased with soil pH, but varietal difference was most pronounced at pH 8.5. No stress effects were noted for growing the two soybean varieties together in these same pots. A high level of hydroquinone (10^‐3 M) in the nutrient solution increased both Fe level and specific activity of ⁵⁹ Fe in PI54619–5–1 soybeans. The DTPA (diethylene triamine pentaacetic acid) did not always extract the same specific activity of ⁵⁹Fe as was present in soybeans and oleander (Nerium oleander).

Key words:

• Iron chlorosis
• iron‐efficient plants
• iron‐inefficient plants
• lime
• DTPA extracfable Fe