Carbon and nitrogen dynamics in agricultural soil after application of cattle manure and eastern redcedar wood chips.

Uncontrolled proliferation of eastern redcedar tree (Juniperus virginiana) in the Midwest United States requires new alternatives for utilization of waste wood, such as mulching, that promotes efficient tree management by landowners. Similarly, efficient use of manure from animal feeding operations in cropping systems can reduce negative environmental impacts and increase cropland productivity. The objectives of this study were to quantify the nitrogen (N) and carbon (C) decomposition rates, availability, and effects on soil chemical properties of eastern redcedar wood chips (WC), cattle manure (CM), and the combination of cattle manure and wood chips (MW). A 120-day incubation and a 12-month field experiment were conducted in Nebraska. In the incubation study, CM decomposed the fastest, followed by MW and WC. At the end of the experiment, WC induced N immobilization. In the field experiment, most decomposition for all amendments occurred during the period between May and August (spring/summer). Decomposition was most rapid for CM and WC with 44% and 55% organic-C loss by mass, respectively. Approximately, 40% of the organic N in CM mineralized during the 1-year field study. Wood chips induced N immobilization after 6 months for shallow soil layers compared to control (no amendment) but did not induce N immobilization when combined with manure. Changes in soil organic matter concentration due to amendment application were not observed at any stages of the field experiment, likely due to the length of the experiment. However, consecutive applications of comingled MW may provide benefits of C contribution to the soil without inducing N limitations.