Assessment of the Impact of Biodegradable Coated Fertilizers on Corn Yield

The aim of the study was to assess the impact of fertilizer type (urea, compound fertilizer), biodegradable coating type (linseed oil or hemp oil based) and nitrogen dose (135 and 180 kg N·ha−1) on the yield of corn intended for silage. A three-year field experiment was conducted using a randomized block design with three replicates. The test plant was corn intended for silage. The field experiment was conducted in a factorial design comprising three experimental factors: fertilizer type (two levels), coating type (two levels), and fertilizer dose (two levels). Controlled-release fertilizers (CRF) based on biodegradable coatings are an emerging solution in sustainable nitrogen management, yet their field-scale performance remains insufficiently validated. This study investigated how biodegradable coatings based on linseed and hemp oils affect nutrient release dynamics and maize yield under three-year field conditions. The study represents the first field validation phase translating laboratory coating characteristics into agricultural performance metrics. Statistical analysis (ANOVA, Tukey’s test) showed that in the first year of the study, the greatest impact on plant height and corn yield was observed in the case of type of fertilizer used (η2p up to 17.83%), type of coating (η2p up to 63.15%) and their interaction (η2p up to 11.92%). The symbol η2p (partial eta squared) represents a measure of effect size in analysis of variance (ANOVA). The largest plant size (average 307–310 cm) and the highest yield (107.33 t·ha−1) were obtained in the case of yields in which compound fertilizer or urea with coatings were used in relation to the series in which fertilizers without coatings were applied (differences up to 11 t·ha−1). Statistical analysis using repeated measures ANOVA confirmed a significant time effect, with fertilizer effectiveness declining in subsequent years of the experiment (p < 0.05). In the experiment, no effect of the tested factors on the number of corn cobs was found (η2p < 2.27%). The highest fresh matter yield for silage production was obtained with coated NPK compound fertilizer (98.80 t·ha−1), representing a 48% increase compared to the unfertilized control (66.90 t·ha−1). The results of the study indicate that the use of coated compound fertilizers—NPK has the most beneficial effect on yield and biometric parameters of plants in the first growing season after their soil application. The enhanced nutrient release from biodegradable coatings provided greatest benefits in the first growing season, with diminishing effects in subsequent years due to coating degradation and residual soil nutrient accumulation.