@article{fdi:010071040,
  title = {{F}arm-scale greenhouse gas balances, hotspots and uncertainties in smallholder crop-livestock systems in {C}entral {K}enya},
  author = {{O}rtiz-{G}onzalo, {D}. and {V}aast, {P}. and {O}elofse, {M}. and de {N}eergaard, {A}. and {A}lbrecht, {A}lain and {R}osenstock, {T}. {S}.},
  editor = {},
  language = {{ENG}},
  abstract = {{C}limate-smart approaches have gained momentum in tropical, agricultural development. {H}owever, to date, few studies have examined whole-farm greenhouse gas({GHG}) balances in smallholder crop-livestock systems. {T}his study aimed to quantify {GHG} balances at farm-scale, identify {GHG} hotspots and assess mitigation options in coffee-dairy farms undergoing agricultural intensification in {C}entral {K}enya. {I}n recent decades, decreasing farm size has forced the shift from extensive practices to zero-grazing systems and higher nitrogen ({N}) inputs. {W}e hypothesised that different farm strategies and intensification levels determine the farm's {GHG} balance. {A} farm typology was constructed through principal component analysis ({PCA}) and hierarchical clustering from 125 farms surveyed. {F}our farm types were identified ranging relatively from small to large farms, low to high livestock intensities, and low to high {N} input rates. {W}hole-farm {GHG} balances were estimated using an adapted version of the {C}ool {F}arm {T}ool ({CFT}). {F}arms were found to be net sources of {GHG}, averaging from 4.5 t {CO}2 eq ha(-1) yr(-1) in less intensive farms to 12.5 t {CO}2 eq ha(-1) yr(-1) in high intensive farms. {W}ithin the farm {GHG} hotspots identified, methane ({CH}4) from enteric fermentation processes accounted for 26-39% of total farm {GHG} emissions; nitrous oxide ({N}2{O}) and {CH}4 from manure management systems ({MMS}) for 26-38%; soil background and fertilizer induced {N}2{O} emissions for 24-29%; off-farm production of feeds and agrochemicals for 10-22%; and crop residue management ({CRM}) for the remaining 1-3%. {W}ithin the mitigation practices assessed, zero-grazing stalls already lowered the livestock maintenance energy requirements, reducing enteric fermentation emissions. {S}tall-feeding, however, brings the necessity-opportunity to manage the manure and our results showed that {MMS} can be a determining factor in the {GHG} balance. {I}ncreasing the frequency of manure collection from stalls in favour of solid storage systems can reduce {N}2{O} emissions by up to 75%. {F}urthermore, dry manure storage reduced the {CH}4 emissions of liquid slurry systems by more than 70%. {F}urther benefits in terms of carbon ({C}) sequestration were identified along farm types from manure and crop residues applications in soils (with averages of -1.3 to -2.3 t {CO}2 eq ha(-1) yr(-1)) and biomass growth in agroforestry systems (-1.2 to -2 t {CO}2 eq ha(-1) yr(-1)). {T}ogether, soils and woody biomass offset 25-36% of farm emissions. {W}e conclude that reduced farm size and increased livestock density lead to higher emissions per unit area, though this increase is smoothed by larger negative fluxes in soils (by higher {C} inputs) and woody biomass (by higher tree densities) until a steady state is reached. {A}verage yield-scaled emissions, or product carbon footprints ({CF}s), resulted in 1.08 kg {CO}2 eq kg coffee berry(-1), 0.64 kg {CO}2 eq kg maize(-1) and 1.05 kg {CO}2 eq kg milk(-1) on average. {CF}s did not always differ between farm types and intensification levels, meaning that increases in productivity were not higher than increases in {GHG} fluxes from intensification. {T}his may be due to: 1) increases in productivity are the result of more processes other than {N} inputs; and/or 2) emissions from {N} inputs are overestimated by {EF}s and {GHG} calculators. {S}mallholders may benefit in the near future from climate initiatives and further field characterisation, models calibration and monitoring are required to overcome critical levels of uncertainty and provide more accurate estimations of {GHG} balances at farm-scale.},
  keywords = {{A}groforestry ; {C}arbon footprint ; {C} sequestration ; {C}offee ; {C}limate-smart ; {D}airy ; {S}ustainable intensification ; {W}hole-farm {GHG} balance ; {Z}ero-grazing ; {KENYA}},
  booktitle = {},
  journal = {{A}griculture {E}cosystems and {E}nvironment},
  volume = {248},
  numero = {},
  pages = {58--70},
  ISSN = {0167-8809},
  year = {2017},
  DOI = {10.1016/j.agee.2017.06.002},
  URL = {https://www.documentation.ird.fr/hor/fdi:010071040},
}