Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/5/2007
Publication Date: 11/1/2007
Citation: Cahill, S., Osmond, D., Crozier, C., Israel, D.W., Weisz, R. 2007. Winter Wheat and Maize Response to Urea Ammonium Nitrate and a New Urea Formaldehyde Polymer Fertilizer. Agron. J. 99:1645-1653. Interpretive Summary: New slow release N fertilizer sources hold promise for increasing the efficiency of N use by crops as a result of releasing N at the time the crop has the highest N requirement. The urea formaldehyde product that was thought to have slow release properties did produced yields similar to urea ammonium nitrate. In lab incubation tests with a mineral organic and sandy soil the urea formaldehyde product release 100% of its nitrogen as NH4 and NO3 within 2 weeks This work demonstrates that these products need to be carefully tested in multiple locations and with a range of soils to demonstrate that they indeed possess the slow release characteristics before being marketed to producers.
Technical Abstract: Slow release nitrogen (N) fertilizers have potential to improve yield and nitrogen use efficiency (NUE) in winter wheat (Triticum aestivum L.) and maize (Zea mays L.). A slow release urea formaldehyde polymer (UFP) was compared with conventional aqueous urea-ammonium nitrate (UAN) [(NH2)2CO, NH4NO3] during a two-year field experiment in North Carolina (NC). Crops were grown on three soils: Candor (sandy, siliceous, thermic Grossarenic Kandiudult), Portsmouth (fine-loamy over sandy or sandy-skeletal, mixed, semiactive, thermic Typic Umbraquult) and Cape Fear (fine, mixed, semiactive, thermic Typic Umbraquult). Treatments were N source (UAN and UFP) and N rate (0, 50, 78, 106, 134, 162, and 190 kg N ha-1 for wheat and 0, 39, 78, 118, 157, 196, and 235 kg N ha-1 for maize). Both sources were band applied as a split application for wheat, while maize received UFP at planting and split application of UAN. Throughout NC, less than half of UAN is applied at planting and the remainder prior to the end of tillering or at V4-6. Harvest biomass and grain were sampled to assess N availability. For both crops and both sites, grain yield and NUE with UAN were statistically similar to or better than UFP. Laboratory incubations suggested UFP release of urea and urea hydrolysis were complete in less than 2 weeks. Hence, UFP release was limited to a time scale of days, considered insignificant for summer crop (corn) growth conditions. Since the UFP did not significantly improve yield, UFP may only be economical if priced similar to UAN.