Ridge Tillage for Carbon Sequestration in the Gambian Cropping Systems

1
Ridge Tillage for Carbon Sequestration in the
Gambian Cropping Systems

• Jarju A. K., B. Jobe, F. Fatajo, M. Faye, A.
  Bittaye, C. Yamoah, R. A . Kablan, R.S. Yost and
  K. Brannan

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Objective

• To determine the potential of ridge-tillage in
  combination with modest fertilizer application on
  maize yields and soil C storage in Gambia where
  animal traction is an important component of
  cropping systems

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Materials and Methods

• Design was a split-plot with two main plots and
  four sub-plots with three replications
• Main plots were
• 1) Ridge Tillage
• 2) Conventional Tillage.

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Materials and Methods

• NPK Sub-plots treatments consisted of
• check (with no fertilizer)
• 200 kg ha-1 fertilizer 16 kg ha-1 of urea, i.e.
  half the national recommended rate,
• 200 kg ha-1 NPK fertilizer 43 kg ha-1 of urea
  i.e. full the national recommended rate
• 200 kg ha-1 NPK fertilizer 150 kg ha-1 of urea
  i.e. double the national recommended rate.

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Materials and Methods
Calculation of soil and plant carbon

• Measurement of C is by Loss on Ignition (105 oC
  followed by 360 oC in the Gambian lab). The
  weight of sample at 360 oC 0.717 OM.
• Then, OC OM/1.724.
• Calculation of soil carbon is based on soil
  carbon content, bulk density, soil depth and
  area.
• Crop carbon is measured using yield, harvest
  index, and root-to-shoot ratio

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Materials and Methods
Input/Outputs costs

• NPK fertilizer 400 Dalasis per 50 kg bag
• Urea 350 Dalasis per 50 kg bag
• Maize 440 Dalasis per 100 kg bag

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RESULTS
Effect of ridge tillage, conventional tillage
systems, and fertilizer on soil carbon content (t
ha-1)
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RESULTS
Effect of ridge tillage, conventional tillage
systems, and fertilizer on maize yields (kg ha-1)
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RESULTS
Effect of ridge tillage, conventional tillage
systems, and fertilizer on maize carbon content
(t C ha-1)
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RESULTS
Returns over variable costs of fertilizer on
maize yields (mean4)
130 Dalasis
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Collaborating Farmers Perspectives
Perspectives of approximately 150 farmers
involved in the farmer-to-farmer activities
1-Cost effectiveness of the low rate compared
to the full or double rate 2-Big cob size 3-Few
lodging
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Collaborating Farmers Perspectives
Perspectives of approximately 150 farmers
involved in the farmer-to-farmer activities
4-Few diseases 5-Stay green (sign of
healthiness) 6-Good soil fertility (this is
seen in the cob size, stay green etc.) 7-High
yield potential
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Collaborating Farmers Perspectives
Perspectives of approximately 150 farmers
involved in the farmer-to-farmer activities
8-Moderate crops density 9-Ideal spacing between
stand 10-Free from striga
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Collaborating Farmers Perspectives
Outlook of 2004 and beyond

• Over 150 farmers who were affiliated to the
  project will be grouped roughly into 12 clusters
  based on their locations.
• Each cluster consisting of 5 to 10 farmers will
  appoint their own leaders.
• Research team will assist in setting up on-farm
  trials on leaders of each cluster.

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Collaborating Farmers Perspectives
Outlook of 2004 and beyond

• The on-farm trial will compare ridge-tillage
  with conventional tillage in various
  agro-ecological zones of Gambia.
• Both tillage will receive the lowest fertilizer
  rate (200 NPK 42 urea kg ha-1) as expressed by
  farmers in the farmer-to-farmer dialogue.
• Clusters serve as replicates

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Collaborating Farmers Perspectives
Outlook of 2004 and beyond

• Analysis will cover a wider geographical area and
  emphasis will be placed on grain and stover
  yields, soil organic carbon economic evaluation
  and risk analysis.
• This approach will have a multiplying effect by
  ensuring that the project reaches its target goal
  early in terms of increased soil C storage and
  sustained high yields.

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Acknowledgements
The carbon community project is funded by SM-CRSP
and the workshop was jointly supported by NASA
(the US National Aeronautics and Space
Administration) and USAID