Effect of a Chemical Modified Urea Fertilizer on Soil Quality: Soil Microbial Populations Around Corn Roots

Slow-release nitrogen (N) fertilizers are used to increase N-use efficiency and extend N availability over a plant-growing season. One formula of this fertilizer commonly used in turf and horticultural crops is methylene -urea triazone. After this compound is applied in the soil, it is subject to bacterial degradation and becomes available for uptake by plants. The objective of this work is to elucidate the application of methylene-urea-triazone in the soil microbial population as well as effects on soil quality. Zea mays was planted in a silty loam soil. Urea and methylene-urea-triazone were incorporated into the soil. Two weeks and 6 weeks after inoculation, soil samples were collected and used to inoculate agar plates and for DNA extraction. Bacterial colony morphology was examined. Denaturing gradient gel electrophoresis (DGGE) was performed with the polymerase chain reaction (PCR) amplicons from the internal transcribed spacer (ITS) of the rRNA gene cluster. The Shannon Wiener index was determined for colony morphology and DGGE bands. There was a difference between urea and the slow-release fertilizer on both plant responses and bacterial diversity. Although for the first 2 weeks DGGE did not show any difference in bacterial diversity, after 6 weeks, differences in the composition of the bacterial community were observed. There were concomitant effects on plant growth and microorganism population and diversity, probably reflecting changes in the richness and in the eveness of the bacterial population in the rhizosphere caused by the fertilizers. Therefore, both soil microorganisms and plant growth respond to environmental changes over time.