Jagadamma, Sindhu (Ohio State University, Department of Soil Science, School of Natural Resources, 210 Kottman Hall, Ohio State University, 2021 Coffey Road, Columbus, Ohio,
43210; Phone: 614-291-8902 (Res.); Fax:
614 -292-7432; Email: jagadamma.1@osu.edu)

Nitrogen fertilization and cover cropping impacts on soil carbon sequestration on a silt loam soil in West Central Illinois


Sindhu Jagadamma *, Rattan Lal, Robert G. Hoeft, Eric Adee


Soil carbon sequestration, important to enhancing soil quality and mitigating the climate change, depends on the amount of crop residue returned to the soil and the attendant soil and crop management practices. Nitrogen (N) management plays an important role in soil carbon dynamics. Thus, this study was conducted with the objective of evaluating the effect of N fertilizer application and cover cropping on soil organic carbon (SOC) pool and other properties, which affects soil quality. Replicated soil samples were collected from a long-term experiment (20 years) at the North Western Experimental Center, Monmouth, Illinois. The experimental design is split-split plot within a randomized complete block and the soil type is Mascatine silt loam. There were three main plot treatments: continuous corn (Zea mays), and two rotation plots with corn and soybean (Glycine max) grown in alternate years. These main plots were divided into two subplots: with and without oats (Avena sativa) grown as cover crops. The split-split plot treatments were five N rates (0 (N0), 70 (N1), 140 (N2), 210 (N3) and 280 (N4) kg N ha-1). Core samples were collected from each plot up to 90 cm depth and analyzed for total C, total N, bulk density, aggregate stability, soil texture and pH. Corn grain yield increased with increasing N rates. The maximum grain yield of 12.7 Mg ha-1 was obtained for N4 compared to the lowest yield of 8.3 Mg ha-1 from the unfertilized plots (N0). Soil bulk density decreased with increasing N level and ranged from 1.21-1.33 Mg m-3 in continuous corn and 1.25-1.37 Mg m-3 in rotation corn. Water stability of aggregates increased with increasing rates of N from 45.3% (N0) to 53.8% (N4). Mean weight diameter of the aggregates decreased with increasing rates of N fertilizer application, ranging from 0.75 mm for N0 to 0.51 mm for N4. There was an increasing trend in SOC pool with the addition of N fertilizers, ranging from 68 Mg ha-1 (N0) to 80 Mg ha-1 (N3) for continuous corn and from 65 kg ha-1 (N0) to 74 Mg ha-1 (N4) for rotation corn in 0-30 cm depth. The rate of soil carbon sequestration for high rate of N application is 600 kg ha-1yr-1 for continuous corn and 450 kg

 ha-1yr-1 for rotation corn. This study shows the critical role of N and crop rotation in building-up of soil organic carbon stock and mitigating global climate change