10.5424/sjar/2008062-320

The aim of this experiment was to evaluate the effects of adding DMPP (3,4-dimethylpyrazole phosphate) to urea on nitrate leaching and maize (Zea mays L.) yield over two growing seasons. Two nitrogen (N) levels (optimum and excessive) were applied to an irrigated maize crop under Mediterranean conditions. There were five treatments: optimal N (as urea) and the same dose plus DMPP; optimal N (as urea plus 40 kg N/ha) and the same N dose plus DMPP; and a control with no added N fertilizer. The maize was irrigated with an overhead mobile-line sprinkler system. EnviroSCAN probes were used to determine drainage and evapotranspiration and ceramic cups to obtain soil solution samples at a soil depth of 1.4 m. The use of DMPP with urea reduced nitrate leaching. No phytotoxic effects were observed due to the DMPP. There were no differences in grain yield between treatments with and without DMPP at the same rate of N. When DMPP was applied, sodium was displaced from the soil exchange complex due to increased NH4+ concentration, which also increased the electrical conductivity of soil in the drainage zone.