ABSTRACT
We propose an approach for assessing the efficiency of coating materials on controlling nitrogen (N) availability to plants. It is based on the use of coated and soluble urea (UR) applied to corn over 3 growing cycles, as follows: coated UR with longevity of 2 (UR-2m) or 4 months (UR-4m) with application of 900 mg N∙pot−1 at the beginning of the experiment, soluble UR with a split application of 900 mg N∙pot−1 (300 mg N∙pot−1 per growing cycle, UR-3x), soluble UR with a sole application of 900 mg N∙pot−1 at the beginning of the experiment (UR-1x), and a control treatment. At the end of each growing cycle, shoots were harvested to estimate N provision by the UR by quantifying dry matter (DM) and N uptake. In the first cycle, UR-2m and UR-4m promoted lower plant growth and N accumulation in shoots than UR-1x. However, in the third cycle, higher shoot N uptake and DM production was recorded in UR-4m than in UR-1x. Furthermore, fertilizer contribution for shoot N uptake in UR-4m plants was higher than those in UR-1x and UR-2m at the end of the experiment. Accordingly, consecutive growing cycles combined with forms of soluble UR application were able to characterize the pattern of N release from coated fertilizers, being, thus, a suitable method to evaluate the efficiency of such products. We argue that our practical approach could be used by the industry in fertilizer quality programs and to register fertilizer coating materials by regulatory agencies.
Key words
coating; fertilizer efficiency; nitrogen fertilizer; nutrient uptake
