Release of formaldehyde and other organic compounds from nitrogen fertilizers

In addition to nitrogen, carbonyl compounds such as formaldehyde, acetaldehyde, isobutyraldehyde and crotonaldehyde can be released from slow release fertilizers based on urea-aldehyde by hydrolytic or biotic processes. A possible relevance of such releases in the practical application of corresponding products was investigated in laboratory experiments. In the first part, emissions of organic compounds from the pure products were determined in desiccators under static conditions in dry and water-saturated air as well as during direct contact with water. Significant emissions of isobutyraldehyde were found for products containing isobutylidene diurea. Several formulations emitted acetaldehyde and formaldehyde, especially in the case of higher air humidity and when solved in water. However, crotonaldehyde was not detected in the desiccator air. Other organic components such as herbicides or their degradation products and nitrification inhibitors were released from fertilizers containing these compounds. In further experiments, sticks and granules were applied into potting soil and the release of organic compounds in emission chambers was examined under dynamic conditions. No substances that could be directly attributed to the fertilizers were detected in these experiments. However, relevant emission rates of formaldehyde were observed for the spray fertilizers containing urea-formaldehyde after application to tomato plants. The possible contribution of these emissions to atmospheric formaldehyde concentrations is discussed. Finally, the formaldehyde concentrations in a greenhouse for private use are estimated. It is likely that immediately after spray application of a urea-formaldehyde fertilizer increased formaldehyde concentrations in the breathing air of the greenhouse occur.