*Article* **Short-Term Effect of Nitrogen Fertilization on Carbon Mineralization during Corn Residue Decomposition in Soil**

**Tanjila Jesmin \*, Dakota T. Mitchell and Richard L. Mulvaney**

Department of Natural Resources and Environmental Sciences, University of Illinois, Turner Hall, 1102 S. Goodwin Avenue, Urbana, IL 61801, USA; mitchelldako@gmail.com (D.T.M.); mulvaney@illinois.edu (R.L.M.)

**\*** Correspondence: jesmin2@illinois.edu

**Abstract:** The effect of N fertilization on residue decomposition has been studied extensively; however, contrasting results reflect differences in residue quality, the form of N applied, and the type of soil studied. A 60 d laboratory incubation experiment was conducted to ascertain the effect of synthetic N addition on the decomposition of two corn (*Zea mays* L.) stover mixtures differing in C:N ratio by continuous monitoring of CO2 emissions and periodic measurement of microbial biomass and enzyme activities involved in C and N cycling. Cumulative CO2 production was greater for the high than low N residue treatment, and was significantly increased by the addition of exogenous N. The latter effect was prominent during the first month of incubation, whereas N-treated soils produced less CO2 in the second month, as would be expected due to more rapid substrate depletion from microbial C utilization previously enhanced by greater N availability. The stimulatory effect of exogenous N was verified with respect to active biomass, microbial biomass C and N, and cellulase and protease activities, all of which were significantly correlated with cumulative CO2 production. Intensive N fertilization in modern corn production increases the input of residues but is not conducive to soil C sequestration.

**Keywords:** aerobic incubation; CO2 production; microbial metabolism; enzyme activities; active biomass; gross mineralization/immobilization
