Effects of diet and manure storage method on carbon and nitrogen dynamics during storage and plant nitrogen uptake

Altering dairy cattle diets to reduce both enteric methane (CH4) production and nitrogen (N) excretion are valuable tools for mitigating the environmental impact of dairy production. We examined the impact of altering diets on changes in physicochemical properties of manure during storage and short term plant N availability. Manure collected from cattle fed diets with differing forage and crude protein (CP) content were stored via two methods (slurry and static pile) for 29 weeks and sampled at week 0, 1, 2, 3, 4, 9, 14, 19, 24, and 29. There was no effect of diet on C and N dynamics during storage for either storage treatment. Mass losses of total carbon (C) were 10% greater for the static pile manure treatment than the slurry (P < 0.01). Total N losses ranged from were approximately 46% with no treatment differences. The soil 2-week plant available N was 67% less in the static pile than the slurry treatment, while the short-term plant N use efficiency was similar for both the static pile and slurry treatments (22-24%). Due to the high inorganic N content of slurry following storage, greater care may be needed to ensure that environmental losses do not occur.