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 105d at rates of 1120, 2240, and 3360kg 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 63d to 105d 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 7d, 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.