Influence of foliar and soil applications of iron and manganese on soybean dry matter yield and iron-manganese relationship in a Calcareous soil

Iron (Fe) and manganese (Mn) are essential nutrients for plants. Application of high levels of either Fe or Mn is often accompanied by relatively low levels of uptake for the other nutrient. The antagonistic relationship of these nutrient elements may occur either during absorption by roots or during translocation from roots to shoot. A greenhouse study was carried out to study the effect of soil and foliar applications of Fe and Mn on yield and Fe-Mn status of soybean plant. Results showed that soil or foliar application of Fe or Mn did not influence soybean root or shoot dry matter yield (SDMY). Both soil and foliar applications of Fe significantly increased shoot Fe concentration and uptake; however, foliar application was more effective. Foliar spray of 1 % Fe sulfate improved plant Fe content and had no effect on SDMY or on shoot Mn concentration. Soil addition of Fe decreased root Mn concentration/uptake probably due to the well-known antagonistic effect of Fe on Mn absorption; whereas, foliar Fe application had no negative effect on shoot Mn status . Shoot Mn uptake was more negatively affected by soil Fe application than root Mn uptakes. Hence, reduction of root Mn absorption and translocation to shoot were the main reasons for suppressing effect of Fe on Mn nutrition. Also, high level of soil applied Mn (i.e., 30 mg Mn kg) decreased Fe translocation from root to shoot. In conclusion, foliar Fe/ Mn applications are appropriate methods of applying these nutients for preventing yield reduction and nutrient imbalance in soybean grown on such calcareous soils.