The Impact of Nitrogen Management and Winter Wheat as A Double Crop on Nitrous Oxide Emissions in A Wheat-Soybean Crop Rotation.

Optimizing nitrogen (N) management in agricultural cropping systems is important for reducing nitrous oxide (N₂O) emissions. This study examined the effect of managing N application in a winter wheat (Triticum aestivum L.) double-cropped with soybean (Glycine max L.) on biomass, grain yield, and N₂O emissions. The experiment was conducted at the Agronomy Research Center (ARC), Carbondale in Southern Illinois University, IL using a Randomized Complete Block Design (RCBD). The treatments include N timing and rate, creating three N management intensities of low, medium, and high. Low-intensity treatment received 120 kg N ha^-1 in fall and spring, medium-intensity treatment received 186 kg N ha^-1 all in spring and high intensity treatment received 186 kg N ha^-1 in fall and spring. Results revealed that the treatment with medium-intensity input of N application did not have a significant effect on winter wheat biomass, grain yield, and N₂O cumulative fluxes in comparison to the high-intensity N management treatment. The results for average soybean grain yield under the various fertilizer inputs (3,087 kg ha^-1) were significantly different when compared to the no-cover crop (NOCC) (3,527 kg ha^-1) The cumulative N₂O fluxes were similar under all treatments for soybean and winter wheat. The summed cumulative N₂O fluxes were similar in both the medium and high N-intensity treatments during the soybean and winter wheat phases but higher than those of low intensity. Since the wheat yield was similar among all treatments, reduction in N₂O during wheat-soybean rotation suggests that low-intensity treatment ensures farm profit while reducing N₂O emissions.