Two pairs of substrate treatments were used to examine the effects of simple and complex organics on fungal and bacterial N2O production, including glucose versus cellulose and winter pea (C:N ¼ 13) versus switchgrass (C:N ¼ 65). Plant materials were oven dried at 65 C for 72 h and then ground to pass through a 2-mm sieve. Soil without the addition of any organics was used as a control to help evaluate substrate-induced microbial growth. Soils
(20 g dry weight equivalent) were mixed with individual substrates (equivalent to 2 mg C g1 soil), placed in 120-ml amber jars (5.5 cm inner diameter 6.5 cm height), and packed to a bulk density of 1.1 g cm3 , assuming that soil particle density was 2.65 g cm. Following the addition of 2 mL distilled water, microcosms were incubated at room temperature
(23 ± 2C). The soil water content
was regularly checked and maintained at 60% water-filled pore
space (WFPS) by adding distilled water if necessary.