Changes in the Rhizosphere Due to NH4+ and NO3‐ Fertilization and Phosphorus Uptake by Corn Seedlings (Zea mays L.)

Abstract

Corn (Zea mays L.) seedlings were grown for 11 days on 3 soils of pH 7.1, 5.5, and 4.3, and fertilized with monocalcium phosphate, and either (NH₄)₂SO₄, Ca(NO₃)₂, or CaCl₂.Rhizocylinder (roots plus adhering soil) and bulk soil solutions were isolated by centrifugal filtration and analyzed for pH and phosphate.The pH of the rhizocylinder solution was lowered by the absorption of NH₄⁺ and increased slightly by NO₃^‐ absorption. Reduced rhizocylinder pH was associated with increased rhizocylinder solution phosphate concentration and P uptake by corn seedlings. The difference in P absorption between NH₄⁺‐fertilized and NO₃^‐‐fertilized corn can be explained by induced changes in the H₂PO₄‐concentration associated with rhizocylinder pH. But, in addition, NH₄⁺ and NO₃^‐ enhanced P absorption probably as a result of increased physiological capacity to absorb P and/or increased root growth.