Soil Inorganic Nitrogen with Incubation of Rye Cover Crop Biomass

A soil incubation study was conducted to evaluate the effect of winter cereal rye (Secale cereale L.) cover crop (CC) biomass and fertilizer nitrogen (N) addition on soil inorganic-N. Rye aboveground biomass was collected following corn (Zea mays L.) and soybean Glycine max (L.) Merr.], and incubated at equivalent field temperatures for 105 d at rates of 1120, 2240, and 3360 kg dry matter (DM) ha^?1. Despite N addition from the rye biomass at any rate, there was no real effect on ammonium (NH₄)-N, and only from 63 d to 105 d a limited net increase in nitrate (NO₃)-N and inorganic-N was observed compared to no-rye. Nitrate-N and inorganic-N concentrations change per heat unit (HU) accumulation was negative with rye addition through 7 d, but was positive consistently across the remaining incubation period with or without rye. Overall, the rye CC biomass had only a neutral to small positive effect on soil inorganic-N.