Mineralization of C and N and nitrification in Scots pine forest soil treated with nitrogen fertilizers containing different proportions of urea and its slow-releasing derivative, ureaformaldehyde

The effects of fast-release urea (U), slow-release ureaformaldehyde (Nitroform, NF) and a mixture of the two in different proportions (NF100%, NF80%, NF50%, NF25%) on soil microbial activities were studied. Urea fertilization enhances nitrification which can cause nitrogen leaching. Our aim was to find whether it is possible to avoid unwanted effects of urea by using mixtures of organic N compounds of different solubility. Net nitrification and mineralization of N and C were determined during aerobic laboratory incubation of soil samples taken 3 months after fertilization. The numbers of autotrophic nitrifiers were estimated by a Most Probable Number (MPN) method and the number of heterotrophic bacteria by plate count. Ion-exchange resin bags placed in the soil below the organic horizon were used to estimate movements of nutrients in soil. The soil pH and the number of heterotrophic bacteria increased in soils receiving high amounts of fast-release N, but CO2 production did not increase. The concentration of exchangeable NH4+ and the number of ammonium oxidizers in the soil were related to the proportion of urea in the applied mixtures; highest numbers were found in the urea and lowest numbers in the NF100-treated soils. The low amount of NO3− found in the soil and accumulated in the resins indicates low nitrification activity in this site. However, the number of ammonium oxidizers indicates that the increase in nitrifier population correlates with the release rate of NH4+. The slow-release NF did not increase nitrification activity and it had a positive effect on microbial activity even at high doses, hence it seems a possible alternative as a slow-release N fertilizer in forestry.

[1]  Alvin Alexander,et al.  Ureaform as a Slow Release Fertilizer: A Review , 1990 .

[2]  P. Martikainen,et al.  Nitrification in forest soil after refertilization with urea or urea and dicyandiamide , 1992 .

[3]  J. T. Touchton,et al.  Agronomic Evaluation of New Ureaforms for Flooded Rice , 1986 .

[4]  D. Binkley.  Ion Exchange Resin Bags: Factors Affecting Estimates of Nitrogen Availability1 , 1984 .

[5]  M. Firestone,et al.  Spatial and temporal effects on plant-microbial competition for inorganic nitrogen in a california annual grassland , 1989 .

[6]  Effect of nitrite concentration and pH on most probable number enumerations of non-growing Nitrobacter spp. , 1991 .

[7]  R. Knowles,et al.  The Ureolytic Microflora in a Black Spruce (Picea mariana Mill.) Humus1 , 1967 .

[8]  P. Martikainen,et al.  Availability and mobility of nutrients in acid forest soil treated with fast and slow-release nutrients , 1995 .

[9]  G. G. Pohlman.  Soil Science Society of America Proceedings , 1948, Soil Science Society of America Journal.

[10]  L. E. Ensminger,et al.  METHODS OF SOIL ANALYSIS , 1965 .

[11]  P. Martikainen.  Numbers of autotrophic nitrifiers and nitrification in fertilized forest soil , 1985 .

[12]  R. Sen.  Intraspecific variation in two species of Suillus from scots pine (Pinus sylvestris L.) forests based on somatic incompatibility and isozyme analyses , 1990 .

[13]  E. L. Schmidt,et al.  An Acidophilic and a Neutrophilic Nitrobacter Strain Isolated from the Numerically Predominant Nitrite-Oxidizing Population of an Acid Forest Soil , 1988, Applied and environmental microbiology.

[14]  E. Beauchamp,et al.  Reactions of 15N-labelled urea with jack pine forest-floor materials , 1985 .

[15]  W. Boer,et al.  Urea stimulated autotrophic nitrification in suspensions of fertilized, acid heath soil , 1989 .

[16]  G. Möller,et al.  Nitrogen recovery in soil and needle biomass after fertilization of a Scots pine stand, and growth responses obtained , 1981 .

[17]  M. Roberge.  Respiration rates for determining the effects of urea on the soil-surface organic horizon of a black spruce stand. , 1976, Canadian journal of microbiology.

[18]  E. Beauchamp,et al.  MICROBIAL ACTIVITY IN A PINUS BANKSIANA LAMB. FOREST FLOOR AMENDED WITH NITROGEN AND CARBON , 1980 .

[19]  P. Martikainen.  Nitrification in two coniferous forest soils after different fertilization treatments , 1984 .

[20]  G. Henderson,et al.  Nitrification Potential of Secondary-Succession Upland Oak Forests: II. Regulation of Ammonium-Oxidizing Bacteria Populations , 1990 .

[21]  H. J. Laanbroek,et al.  Competition for Ammonium between Nitrifying and Heterotrophic Bacteria in Continuously Percolated Soil Columns , 1992, Applied and environmental microbiology.

[22]  E. Bååth,et al.  Changes in carbon content, respiration rate, ATP content, and microbial biomass in nitrogen-fertilized pine forest soils in Sweden , 1989 .

[23]  A. Cajander,et al.  Theory of forest types , 1926 .

[24]  O. Lunt,et al.  Availability of various fractions of urea-formaldehyde , 1967 .

[25]  M. K. Mahendrappa,et al.  Microbial Respiration and Exchangeable Ammonium in Podzol Organic Horizon Materials Treated with Urea , 1975 .

[26]  R. Sen.  Isozymic identification of individual ectomycorrhizas synthesized between Scots pine (Pinus sylvestris L.) and isolates of two species of Suillus , 1990 .

[27]  Skogshögskolan.  Studia forestalia Suecica , 1963 .

[28]  H. J. Laanbroek,et al.  Effects of Grazing by Flagellates on Competition for Ammonium between Nitrifying and Heterotrophic Bacteria in Chemostats , 1992, Applied and environmental microbiology.

[29]  M. K. Mahendrappa,et al.  AMMONIA VOLATILIZATION FROM BLACK SPRUCE RAW HUMUS TREATED WITH NORMAL AND CONTROLLED‐RELEASE UREA , 1974 .

[30]  Z H Bhuiya,et al.  Autotrophic nitrifying bacteria in acid tea soils from Bangladesh and Sri Lanka. , 1977, The Journal of applied bacteriology.

[31]  I. Schalin.  On the effect of nitrogen fertilization on the bacteria and microfungi in humus layer. , 1967 .

[32]  B. Lundgren,et al.  Effects of nitrogen-fertilization on the activity and biomass of fungi and bacteria in a podzolic soil , 1981 .

[33]  T. Fox,et al.  Soil Nitrogen Mineralization Potential in a Fertilized Loblolly Pine Plantation , 1991 .

[34]  G. Host,et al.  Regional variability in nitrogen mineralization, nitrification, and overstory biomass in northern Lower Michigan , 1989 .

[35]  S. Gerards,et al.  Most Probable Numbers of chemolitho‐autotrophic nitrite‐oxidizing bacteria in well drained grassland soils: Stimulation by high nitrite concentrations , 1990 .