Effect of Watershed (ACN) and Fertilizer Effect of Watershed (ACN) and Fertilizer Management on Soil Organic Carbon (SOC) Management on Soil Organic Carbon (SOC)

Conservation in Maize-based cropping systems in Conservation in Maize-based cropping systems in The Gambia.The Gambia.

A.K. JarjuA.K. Jarju**, M. Faye, C. Bojang, M. Suso, , M. Faye, C. Bojang, M. Suso, Y. Sanneh, B. Jobe, A. Bittaye,Y. Sanneh, B. Jobe, A. Bittaye,

F atajoF atajoNational Agriculture Research Institute National Agriculture Research Institute (NARI), PMB 526, Serekunda, The Gambia(NARI), PMB 526, Serekunda, The Gambia

andandC. Yamoah, R. Kablan, R. S.Yost*C. Yamoah, R. Kablan, R. S.Yost*

SM-CRSP Carbon Project, University of SM-CRSP Carbon Project, University of Hawaii Department of Plant and Soil Hawaii Department of Plant and Soil

Science, University of Hawaii, Honolulu, Science, University of Hawaii, Honolulu, USAUSA

RESEARCH TEAM

IntroductionIntroduction

A watershed management experiment A watershed management experiment was initiated in the Gambia from 2002 was initiated in the Gambia from 2002 to 2006 to test the hypothesis that to 2006 to test the hypothesis that ridge tillage retains rainfall and ridge tillage retains rainfall and interacts with fertilizer to produce interacts with fertilizer to produce greater maize grain and biomass yields greater maize grain and biomass yields than conventional watershed than conventional watershed management. management.

ObjectiveObjective

To evaluate existing and improved To evaluate existing and improved cropping systems for increased Carbon cropping systems for increased Carbon storage as soil Carbon and sustainable storage as soil Carbon and sustainable increased crop productionincreased crop production..

MethodologyMethodology

A split plot design with three replications A split plot design with three replications was used for the experiment. The main was used for the experiment. The main plots were ridge-tillage and conventional plots were ridge-tillage and conventional tillage watershed management. Subplots tillage watershed management. Subplots were four fertilizer rates were four fertilizer rates

MethodologyMethodology

Treatments: Treatments:

Main plotsMain plots 1.      Ridge-tillage 1.      Ridge-tillage 2. Conventional tillage2. Conventional tillage

MethodologyMethodology

Sub-plotsSub-plots 1.      check with no fertilizer1.      check with no fertilizer 2.     200 kg ha2.     200 kg ha-1 -1 NPK fertilizer + 16 kg haNPK fertilizer + 16 kg ha-1 -1 of of

urea (approximately half the national urea (approximately half the national recommended rate)recommended rate)

3.     200 kg ha3.     200 kg ha-1 -1 NPK fertilizer + 43 kg haNPK fertilizer + 43 kg ha-1 -1 of of urea (full the national recommended rate)urea (full the national recommended rate)

4.     200 kg ha4.     200 kg ha-1 -1 NPK fertilizer + 150 kg haNPK fertilizer + 150 kg ha-1 -1 of of urea (double the national recommended rate.)urea (double the national recommended rate.)

ACN Field layoutACN Field layout Ridge tillage Conv. TillageRidge tillage Conv. Tillage

F1

Determination of soil carbonDetermination of soil carbon

The widely recognized method to The widely recognized method to estimate soil carbon in cropping estimate soil carbon in cropping systems for assessment of carbon systems for assessment of carbon sequestration is the dry-combustion sequestration is the dry-combustion procedure (SM-CRSP, 2002).procedure (SM-CRSP, 2002).

Determination of soil carbonDetermination of soil carbon

For the Gambian upland soils, 5g-soil is For the Gambian upland soils, 5g-soil is pre-dried to 105 C and later to 360 C. The pre-dried to 105 C and later to 360 C. The product of percent LOI at 360 C and product of percent LOI at 360 C and 0.717 give %OM.0.717 give %OM.

Conversion of %OM to %OC is Conversion of %OM to %OC is %OM/1.724 or simply 2. %OM/1.724 or simply 2.

Effects of ridge tillage, conventional tillage systems, Effects of ridge tillage, conventional tillage systems, and fertilizer on maize yields (kg haand fertilizer on maize yields (kg ha-1-1),),

Two year pull 2005 and 2006 in Western Gambia.Two year pull 2005 and 2006 in Western Gambia.

Fertilizer Tillage systems

  2005 2006

  RT* CT RT CT

(kg ha-1) (Yield kg ha-1)

Check (no fertilizer)

431 530 632 586

200 NPK + 42 urea

1153 1052 2422 2134

200 NPK + 86 urea

1136 941 2226 1702

200 NPK + 258 urea

1105 1193 2134 1842

  Analysis of variance

Source F-value P-value F-value P-value

Tillage system (T) 0.150 >0.05 31.29 0.030

Fertilizer (F) 51.70 <0.001 280.867 <0.001

T*F 2.80 <0.05 6.588 0.007

Effects of ridge tillage, conventional tillage systems, and Effects of ridge tillage, conventional tillage systems, and fertilizer on total soil carbon (t/ha) in 2005 and % carbon fertilizer on total soil carbon (t/ha) in 2005 and % carbon

(%) in 2005, Western Gambia.(%) in 2005, Western Gambia.

Fertilizer Tillage systems  2005 2005

  RT* CT RT CT

(kg ha-1) Total soil carbon (t/ha) (%Carbon)

Check (no fertilizer)

8.73 7.91 0.72 0.63

200 NPK + 42 urea

8.90 7.83 1.26 0.95

200 NPK + 86 urea

9.96 7.70 1.12 1.02

200 NPK + 258 urea

10.05 8.61 1.10 0.98

  Analysis of variance

Source F-value P-value F-value

P-valueTillage system (T)

4.44 >0.05 43.52 0.022

Fertilizer (F) 3.34 <0.05 54.49 <0.001

T*F 1.4 >0.05 7.47 0.004

Descriptive statistics of soil carbon in ridge and Descriptive statistics of soil carbon in ridge and conventional tillage systems, 2005.conventional tillage systems, 2005.

Statistic Ridge-tillage Conventional tillage

Mean 0.87 0.73

Median 0.90 0.79

Standard deviation 0.17 0.11

Minimum 0.57 0.53

Maximum 1.09 0.88

Range 0.52 0.35

CV (%) 19.2 15.0

Returns over variable cost of fertilizer on maize in ridge Returns over variable cost of fertilizer on maize in ridge and conventional tillage systems in Western Gambia 2005 and conventional tillage systems in Western Gambia 2005

and 2006.and 2006.

Fertilizer Tillage systems

  2005 2006

  RT* CT RT CT

(kg ha-1) (Dalasis ha-1)

Check (no fertilizer)

2115 2600 2728 2508

200 NPK + 42 urea

3680 3000 9820 7312

200 NPK + 86 urea

3420 2540 7520 5234

200 NPK + 258 urea

2814 2500 5922 4646

  Statistics

Mean 2814 2638 6457 4925

Standard deviation

858 250 2979 1925

CV 0.31 0.09 0.458 0.401

Paired t-test P>0.05   P<0.057  

Plans for 2007Plans for 2007

Work with both the national extension Work with both the national extension staff and international NGOs to train staff and international NGOs to train farmers in the installation of the ADOs farmers in the installation of the ADOs and to intensify the replicate ACN on and to intensify the replicate ACN on farm program and farmer-to-farmer field farm program and farmer-to-farmer field visits.visits.

HypothesisHypothesis

e Suggests up to a 40% improvement in

crop yields can be achieved with increased carbon storage

Generic evidence to date suggest

Scaling up realized benefits of Scaling up realized benefits of ACN on farmers fieldACN on farmers field

Replicated on farm ACN technology Replicated on farm ACN technology 2007/20082007/2008

Determination post rain vegetable Determination post rain vegetable production in ACN water shed sites in production in ACN water shed sites in western and north bank region 2008 western and north bank region 2008 and beyondand beyond

Conventional Tillage

Ridge ttillage

Road from Madina sering Mass Road in middle of the Village

Fass Chaw VillageMosque

Roa

d to

Ker

r C

herin

o

Road beranch toward Kerr cherino

Conventional Tillage

The basket - Gambia experienceThe basket - Gambia experience

FARMER INNOVATION AND ACNFARMER INNOVATION AND ACN

CROSS BOARDER FACTORCROSS BOARDER FACTOR

FIVE YEARS OF EXPERIMENTATION AND FIVE YEARS OF EXPERIMENTATION AND CROP RESIDUE MANAGEMENT IMPACT CROP RESIDUE MANAGEMENT IMPACT ON CROP YIELD FERTILIZER FREE PLOTSON CROP YIELD FERTILIZER FREE PLOTS

F1: 21 days after planting F1: 21 days after planting 20032003

F1: 21 days after planting F1: 21 days after planting 20052005

F1: 21 days after planting F1: 21 days after planting 20062006

On farm discussions for adoption On farm discussions for adoption and options “ ridging vs no and options “ ridging vs no

ridging” in ACNridging” in ACN

ReflectionsReflections

Successful research is backed by Successful research is backed by a committed work force at a committed work force at

community levelcommunity level