Effects of Mapogoro phillipsite on availability of phosphorus in phosphate rocks

The effectiveness of Mapogoro phillipsite (a zeolitic cation exchanger) to enhance chemical breakdown of apatite in two phosphate rocks (PR) of igneous and sedimentary origin from Tanzania was evaluated in a greenhouse study using an acidic P-deficient soil from Mbimba, Mbeya region. The treatments tested were 40 mg P kg -1 of triple superphosphate (TSP), Panda PR (igneous), and Minjingu PR (sedimentary) applied singly and in combination with Mapogoro phillipsite at ratios of 1 :1, 1 :10, and 1 :100. The TSP increased dry matter (DM) yield of maize fivefold indicating that the soil used required supplemental P. Application of the igneous Panda PR alone had no significant effect on yield due to low solubility and reactivity. However, the yield increases due to sedimentary Minjingu PR was almost fourfold the yield of the control indicating that it was relatively more reactive than Panda PR. Mapogoro phillipsite had no effect on the solubilization of Panda PR. However, it enhanced the breakdown of Minjingu PR substantially, especially at the PR :zeolite ratio of 1 :100. This was reflected in significantly higher available P in the soil, P uptake, and DM yield.