Nitrogen mineralization in chernozemic soils amended with manure from cattle fed dried distillers grains with solubles

Inclusion of dried distillers grain with solubles (DDGS) in cattle diets, coupled with the increasing use of construction and demolition waste (CDW), particularly the wood and drywall fractions as bedding in beef cattle feedlots, may affect nitrogen (N) dynamics when the resulting manure is applied to soil. This laboratory incubation study was conducted to evaluate the mineralization of N in contrasting Chernozemic soils amended with regular manure (RM) from cattle fed a grain-based diet versus manure from cattle fed a diet containing DDGS (DGM). The effect of adding CDW to DGM (DGMCDW) was also assessed. The soils (a Black Chernozem and a Brown Chernozem) were amended with manure (40 g kg soil-1, dry wt.) and incubated at 15 and 25°C. Nitrogen mineralization in the manure-amended Brown Chernozem exhibited negative net mineralization. In the Black Chernozem, the first-order mineralization rate constant varied among manure treatments and decreased in the order DGMCDW > DGM > RM. The rate constants were not significantly affected by temperature, but the temperature sensitivity (Q10) of N mineralization was significantly greater for RM (1.0) and DGM (1.3) than DGMCDW (0.3). The percentages of total organic N mineralized from RM and DGM were greater than that for DGMCDW, with RM producing the greatest mineralization. This suggests that adding CDW to manure will affect N dynamics by lowering the amount of N mineralized, which may necessitate either applying higher manure rates (and risking excess phosphorus build-up) or supplementing with inorganic fertilizers to minimize N deficiency in receiving crops.