Mineralization of carbon and nitrogen, and nitrification in Scots pine forest soil treated with fast- and slow-release nitrogen fertilizers

• Published in: Biology and fertility of soils Vol. 22; no. 3; pp. 214 - 220
• Main Authors: Aarnio, T, Martikainen, P.J
• Format: Journal Article
• Language: English
• Published: 1996
• Subjects: acid soils; autotrophic nitrifiers; biological activity in soil; carbon; dicyandiamide; forest soils; leaching; mineralization; nitrates; nitrification; nitroform; nitrogen; nitrogen fertilizers; nutrient availability; Pinus sylvestris; slow-release fertilizers; soil microorganisms; urea; Finland
• ISSN: 0178-2762; 1432-0789
• DOI: 10.1007/BF00382515

We studied the effects of fast- and slow-release organic N fertilizers (urea and urea-formaldehyde, Nitroform) on mineralization, nitrification, and N leaching in an acid, poor forest soil. We also studied the effects of a nitrification inhibitor (dicyandiamide) applied together with urea. Net nitrification, mineralization of N and C were determined by aerobic laboratory incubation of soil samples taken one and three growing seasons after N application. Numbers of autotrophic nitrifiers were estimated by a most probable number method three growing seasons after the treatment. Urea increased the CO2 production immediately after application, but after three growing seasons, CO2 production was the lowest in the urea-treated soils. In the nitroform-treated soils, the concentration of exchangeable NH: after the first and third growing seasons was of the same magnitude, in contrast to the urea-treated soils, where hydrolysis took place immediately. Three growing seasons after application, the highest amount of NH: accumulated during the laboratory incubation was in the nitroform-treated soils. Unlike urea, nitroform did not increase the production of NO3(-) or the number of NH: oxidizers. In the urea+dicyandiamide-treated soils there was less NO3(-) and a lower number of nitrifiers than in the urea-treated soils. The results showed that a slow-release N fertilizer, such as nitroform, increases the availability of mineral N in acid forest soils without increasing nitrification and hence the risk of NO3(-) leaching.