Greenhouse Gas Emissions from U.S. Agriculture and Forestry: A ...

Table of Contents
I. Introduction ..................................................................................................................................................................... 1
II. Sources and controlling factors of GHG emissions .......................................................................................... 4
II.a. CO2 emissions ........................................................................................................................................................ 4
II.a.1. Soil organic carbon .................................................................................................................................... 4
II.a.2. Inorganic carbon ......................................................................................................................................... 8
II.a.3. Tree biomass C ............................................................................................................................................. 9
II.b. N2O emissions ...................................................................................................................................................... 10
II.b.1. Soil management ...................................................................................................................................... 10
II.b.2. Manure management .............................................................................................................................. 11
II.b.3. Grazing .......................................................................................................................................................... 12
II.b.4. Indirect fluxes ............................................................................................................................................ 12
II.c. CH4 emissions ...................................................................................................................................................... 13
II.c.1. Rice cultivation .......................................................................................................................................... 13
II.c.2. Enteric fermentation ............................................................................................................................... 13
II.c.3. Manure management .............................................................................................................................. 14
II.c.4. Grazed pastures ......................................................................................................................................... 15
III. Mitigation of GHG emissions in U.S. agriculture ......................................................................................... 15
III.a. Agricultural land management ................................................................................................................ 15
III.a.1. Soil C sequestration ................................................................................................................................. 16
III.a.2. Soil N2O emissions .................................................................................................................................... 27
III.a.3. Soil CH4 emissions .................................................................................................................................... 32
III.b. Manure management ................................................................................................................................... 33
III.c. Enteric fermentation ......................................................................................................................................... 35
III.d. Forests and Forest Management ............................................................................................................. 39
III.d.1. Afforestation/reforestation ................................................................................................................. 39
III.d.2. Reducing/Avoiding deforestation ..................................................................................................... 40
III.d.3. Forest management ................................................................................................................................. 40
IV. Current research gaps ........................................................................................................................................... 42
V. References....................................................................................................................................................................... 43
Contract # GS‐23F‐8182H, Project Technical Report