Effect of Different Levels of Phosphorus on Availability of Micronutrients in Soils and Their Uptake by Rice Under Submerged and Aerobic Conditions

The effect of added Phosphorus on the availability of micronutrients (Zn, Mn, Cu and Fe) in soils and their uptake by rice were studied under submerged and aerobic water regimes as main factors, and five levels of phosphorus (0, 20, 40, 60 and 80 kg P2O5 ha-1) as sub-factors in a factorial RCBD with three replications. Submerged conditions increased soil Fe and Mn availabilities significantly (P=0.05) up to a considerable period of plant growth while Cu was only at the early stage. The aerobic conditions reported higher Zn availability at 40 days after Phosphorus application. P application affected only Fe availability at the early stage of the crop. Concentrations of Mn, Fe and Zn in grain and Mn and Fe in straw was increased significantly (P<0.05) in submerged conditions. Levels of P application did not significantly (P>0.05) influence the micronutrient concentrations in grain or straw except Fe in grain. Submerged condition increased uptake of all micronutrients while the rate of P level over 40 kg P2O5 ha-1 did not significantly (P>0.05) increase the micronutrient uptake by grain and straw. Growing rice under the submerged conditions with 40 kg P2O5 ha-1 can be recommended to ascertain sufficient levels of availability and optimum uptake of micronutrients by rice plants growing in the studied soil.