Effects of Conventional and Stabilized Urea Fertilizers on Soil Biological Status

Abstract

Effects of stabilized urea fertilizers [Alzon 46 (A) and UREAstabil (US)] on soil microbiological and chemical parameters and also on grain yield, 1000-grain weight, and oil content were tested in a precise field study on Luvisol in 2010–2012. Winter rapeseed (Brassica napus L. cv. Californium) was fertilized both in autumn [45 kg nitrogen (N) ha⁻¹] and in spring (155 kg N ha⁻¹) with A [urea with DCD (dicyandiamide) plus pyrrodiazole (1,2,4-1H-triazole)], US {urea with NBPT [N-(n-butyl)-thiophosphoric acid triamide]}, and conventional N fertilizers (pure urea, calcium ammonium nitrate). Eleven parameters were used to evaluate the soil status: microbial biomass carbon (C; microwave method [MW]), dehydrogenase activity, arylsulfatase activity, available organic carbon, electroconductivity, C_org (MW method), and pH (in water, H₂O). None of the 11 parameters demonstrated significant difference between control, conventional N fertilizers, and stabilized urea fertilizers. The greatest yield significantly different from the control (zero kg N ha⁻¹; 2598 ± 881 kg ha⁻¹) was found for both stabilized urea fertilizers: A (200 kg N ha⁻¹; 3772 ± 759 kg ha⁻¹) and US (200 kg N ha⁻¹; 3764 ± 625 kg ha⁻¹). The control achieved the greatest oil content (46.0 ± 1.2%), which was significantly different from all N-fertilized variants, and also the greatest 1000-grain weight (5.62 ± 0.62 g).

Keywords:

• Arylsulfatase
• DCD plus 1,2,4-1H-triazole
• dehydrogenase
• NBPT
• microbial biomass
• urease and nitrification inhibitors
• winter rapeseed