USING THIOPAQ SULFUR FOR REDUCING NH3 VOLATILIZATION FROM CALCAREOUS SOILS AND INCREASING N USE

Abstract

A laboratory and greenhouse studies were conducted to evaluate the effect of different rates (0.1, 0.5 and 1.0 ton ha-1) of THIOPAQ elemental sulfur (TES) application to the urea amended calcareous soils on NH3-N volatilization from soil surface and on N uptake efficiency by corn plants. In incubation experiment under laboratory conditions, daily ammonia loss was measured for up to 30 days after surface urea-N applied to soil (200 kg N ha-1) using closed dynamic airflow system. Results showed that daily NH3-N loss in tested soils were in the order: M. Ismail > Adam > Abu Bakr soils within the first 18 days of incubation then turned to Abu Bakr > Adam > M. Ismail soils until the end of experiment. Total NH3-N volatilization from urea-treated soils were 50.3, 49.8 and 66.6% of applied N in Abu Bakr, Adam and M. Ismail soils, respectively. Significant reductions in NH3-N volatilization were observed in urea amended with TES and this reduction increased by increasing applied TES rate. The percentage inhibition in NH3-N loss as a result of application of different TES to tested soils ranged between 14.60-37.52, 75.28 – 84.52 and 70.00 – 77.42 in Abu Bakr, Adam and M. Ismail soils, respectively. The reduction in NH3-N loss by TES was accompanied by a decrease in soil pH and increase in concentrations of water soluble SO42-. It is concluded that application of TES by rates 0.1 and 0.5 tons ha-1 had significant effect in reducing ammonia volatilization from surface applied urea. Results of greenhouse experiment showed that TES application and T. thiooxidans inoculation had significant effects on biomass production and N uptake by corn plant. Soil inoculation without addition of S increased N uptake in both shoots and roots by 22.25 and 19.5%, respectively, and reflects the promoting role for bacteria on N uptake. TES application significantly increased N uptake by plant shoots and roots and more uptake was obtained with applied TES and inoculation with T. thiooxidans.