Influences on Soil Nitrogen Mineralization: Implications for Soil Resto

Influences on Soil Nitrogen Mineralization: Implications for Soil Restoration and Revegetation Introduction Nitrogen is a macronutrient essential to the growth of plants and is also one of the most deficient nutrients in most soils. Insufficient levels of available soil nitrogen limit microbial growth and decay and growth of the plants themselves. Because site disturbance adversely affects the flow of nitrogen through soil-plant-microbial systems, the re-establishment of the cycle of nitrogen flow in the soil is crucial to revegetation attempts. Mineralizable nitrogen--nitrogen in forms readily usable by plants--is dependent upon a number of factors. According to Stanford and Smith (1972), those factors include soil moisture, pH level, temperature, microbial biomass, and amounts of other nutrients. Three of the more significant and interrelated influences--microbial biomass, temperature, and moisture--are discussed here. This is certainly not an exhaustive list of factors influencing soil nitrogen mineralization, but instead, a general overview of the more significant considerations. Microbial Processes Microbial decay of organic material is the main release process of soil nitrogen. Nitrogen is released from microbial decay in the form of ammonium, but can also be immobilized by microbes which take up nitrate and ammonium to satisfy their own requirements. The mobilization or immobilization of nitrogen is dependent upon the amount of N the decomposing material itself provides; insufficient nitrogen released from decaying organic matter will result in the absorption of ammonium and nitrate by the microbes. An excess of N will satisfy the requirements of the microbes and provide a surplus to be released into the soil... ...6-100. Campbell, C.A., V.O. Biederbeck, and F.G. Warder. 1971. Influence of simulated fall and spring conditions on the soil system: Effect on soil nitrogen. Soil Sci. Soc. Am. J. 35:480-483. Cassman, K.G., and D.N. Munns. 1980. Nitrogen mineralization as affected by soil moisture, temperature, and depth. Soil Sci. Soc. Am. J. 44:1233-1237. Myrold, David D. 1987. Relationship between microbial biomass nitrogen and a nitrogen availability index. Soil Sci. Soc. Am. J. 51:1047-1049. Powers, Robert F. 1980. Mineralizable soil nitrogen as an index of nitrogen availability to forest trees. Soil Sci. Soc. Am. J. 44:1314-1320. Singer, Michael J. and Donald N. Munns, 1986, Soils: An Introduction: New Jersey, Prentice-Hall, Inc., 480 p. Stanford, George and S.J. Smith. 1972. Nitrogen mineralization potentials of soils. Soil Sci. Soc. Amer. Proc. 36:465-472.