Nitrogen release from different polymer-coated urea fertilizers in soil is affected by soil properties

The use of urea as nitrogen (N) fertilizer in agriculture needs to consider envi-ronmental, economic and resource conservation aspects because of low N- use efficiency (NUE). Polymer-coated urea (PCU) offers an effective way to improve the NUE of urea and to reduce its environmental trade- offs. However, we lack information on the impact of climate and soil properties on N release from PCU. Therefore, this study was performed to quantify the effects of soil texture, mois-ture and temperature on the release kinetics of N from PCU. We designed a test system for soil incubation experiments and investigated three fertilizers with different release patterns, five topsoils, three moisture levels and two tempera-tures over 48 days. We analysed the concentrations of inorganic N (NH4+ - N and NO3- - N) in the soil and estimated N release rates using the unified Richards model. Soil texture did not change the N release patterns, but release rates varied significantly among the investigated soils. Changes in soil moisture for a given soil had no effect on N release from PCU and urea when fertilizers were incor-porated into the soil at conditions supportive of crop growth. Lowering soil tem-peratures, however, decreased N release rates from PCU by 16%- 49% but only in silt loam and not in sandy loam. We conclude that PCU improves the N residence time in soil, but predictions on N release from PCU must be adapted to the pre-vailing environmental conditions and cannot be generalized across differently textured soils.