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

Authors: NIU, M. - University Of California; APPUHAMY, J.A.D.R.N. - Iowa State University; Dungan, Robert - Rob; KEBREAB, E. - University Of California; Leytem, April

Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2017
Publication Date: 12/1/2017
Publication URL: https://handle.nal.usda.gov/10113/5823469
Citation: Niu, M., Appuhamy, J., Dungan, R.S., Kebreab, E., Leytem, A.B. 2017. Effects of diet and manure storage method on carbon and nitrogen dynamics during storage and plant nitrogen uptake. Agriculture, Ecosystems and Environment. 250:51-58.

Interpretive Summary: Altering dairy cattle diets to reduce both enteric methane production and nitrogen 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, short term plant N availability, and overall system N use efficiency. Cattle were fed diets with either high or low crude protein, and high or low forage content. Manure collected from cattle fed diets with differing forage and crude protein content were stored via three methods (slurry, static pile, turned pile) for 29 weeks and sampled at week 0, 1, 2, 3, 4, 9, 14, 19, 24, and 29 with losses of nitrogen and carbon determined during storage. Mass losses of total carbon ranged from 28 to 50% and followed the trend static pile > slurry > turned pile .Total nitrogen losses ranged from 20 to 47% with the slurry and static pile treatments having larger (but similar) losses than the turned pile treatment. The soil 2-week plant available nitrogen was similar in the static pile and turned pile treatments and were 67% less than the slurry treatment. The short-term plant nitrogen use efficiency was similar for both the static pile and slurry treatments (22-24%), which were greater than that of the turned pile treatment (16%). Overall estimated system nitrogen use efficiencies were 5% greater for lower crude protein diets compared to high crude protein diets. While rapidly drying manure may conserve carbon and nitrogen, there may be a tradeoff with plant nitrogen utilization which could affect overall system efficiencies.

Technical Abstract: 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, short term plant N availability, and overall system N use efficiency. Manure collected from cattle fed diets with differing forage and crude protein (CP) content were stored via three methods (slurry, static pile, turned pile) for 29 weeks and sampled at week 0, 1, 2, 3, 4, 9, 14, 19, 24, and 29. Mass losses of total carbon (C) ranged from 28 to 50% and followed the trend static pile > slurry > turned pile (P < 0.01). Total N losses ranged from 20 to 47% with the slurry and static pile treatments having larger (but similar) losses than the turned pile treatment (P < 0.01). The soil 2-week plant available N was similar in the static pile and turned pile treatments and were 67% less than the slurry treatment. The short-term plant N use efficiency was similar for both the static pile and slurry treatments (22-24%), which were greater than that of the turned pile treatment (16%). Overall estimated system N use efficiencies were 5% greater for lower CP diets compared to high CP diets. While rapidly drying manure may conserve C and N, there may be a tradeoff with plant N utilization which could affect overall system efficiencies.