Greenhouse gas emissions from rice production
in two soils under two water management
regimes in Central Kenya
Jane Gitonga, Lutz Merbold, David Pelster, Hunja Murage
CLIFF Network Workshop 2017- Cologne, Germany

Background
§ Rice is the most important cereal crop for more than half of the world’s
population(GRiSP,2013);
§ An important staple crop throughout Africa (FAO, 2013); third after maize
and wheat;
§ Critical for global food security (McLean, 2002);
§ 90% harvested rice globallyis grown in flooded conditions;
§ Water scarcity increasinglychallenge global rice production;
§ Rice emits approximately four times the GHG emissions per ton of product
than maize or wheat (Linquist,2012)

Background
§ CH4 is the dominantGHG produced and emitted;
§ Alternate wetting and drying (AWD): reduce CH4, irrigation water,
maintaining/improvingyields
§ Inadequate research on how rice cultivation in Kenya as well as in other
SSA countries contribute to GHG emissions;
§ Neither it is clear, whether AWD is a feasible method that can be used to
not onlyconserve water but also mitigate GHG emissions;
§ Studies are needed to overcome this knowledge gap.

Research Objectives
§ Quantify GHG emissions from rice production in vertisols and nitosols under two
water management regimes (alternate wetting and drying- AWD and continuous
flooding-CF) in Mwea irrigation scheme (MIS), Kenya.
§ Assess the effect of rice production in vertisols and nitosols on GHG emissions;
§ Assess the effect of rice production under AWD& CF on GHG emissions;
§ Test whether there is an interaction between the two water management regimes
and soil type on GHG emissions;
§ Assess yield from the two water management regimes and soil type;
Specific Objectives
Main Objective

Hypotheses
§ Under rigorous and careful management of the AWD, GHG emissions (CH4
and N2O) and water use will be lower than under continuous flooding, while
maintainingyields irrespective ofthe soil type

Site Description
Base map of the Mwea Irrigation scheme,
Kenya.
§ MIS is the largest scheme in Kenya (5
sections)
§ 86% of rice produced is from MIS
§ Soils:
ü Vertisols (impervious heavy - black
cotton)
ü Humic Nitosols (free draining -
reddish brown lateritic clay loamy
soils) KALRO - Mwea Kirogo Research
Farm- (000 38’S; 37022E;
elevation 1159m.a.s.l - Tebere
section)

Methods
§ Split plots in completely randomized design, four replicates in
each plot;
§ Observation will cover one growing season (June 2017-Dec2017)
§ Variety-Basmati 370;
§ Gas sampling:
ü Before seedlingtransplanting(1 month)
ü After transplanting- every week during the entire growing
season & twice a week after fertilizer application
ü Once after harvest
ü Between 0900h to 0100h;

Methods

Methods
§ Using 60 ml plastic syringes at four equal
time intervals of ten minutes (T0, T10, T20
and T30);
§ Samples were immediately transferred into
20 ml pre-evacuated glass vials - analyzed
within 2days from dayof sampling;
§ GHG concentrations (CH4, N2O and CO2)
were derived by gas chromatography
§ Within the Mazingira Centre at the
International Livestock and Research Institute
(ILRI);

Methods
𝐹 =
𝑏 × 𝑀𝑤 × 𝑉 × 60 × 106
𝐴 × 𝑉𝑚 × 109
(Butterbach-Bahl et al., 2011)
§ GHG fluxes were calculated from rate of
concentrationin headspace over time
§ Irrigation Water Management:
ü Field water tubes were used to monitor the
water level at AWD plots;
ü Irrigation water was supplied when water level
was 15cm below soil surface;
ü Plots were re-flooded up-to 10cm in AWD plots;
ü Approximately 10cm in the continuously flooded
plots;

Methods
§ Soil analyses
Soil parameters to be measured include:
i. Total soil extractable N (NH4+ - N and NO3 – N
ii. Soil PH
iii. Soil Texture Analysis
iv. CN Analysis

Preliminary Results
i. CH4 emissions are higher in Vertisols as compared to Nitosols in both water
management regimes;
ii. CH4 emissions are higher under CF plots as compared to the AWD;
iii. CH4 emissions increase with the increase in number of tillers;

Preliminary Results
i. N2O emissions are higher in Nitosols as compared to Vertisols
in both water management regimes
ii. N2O emissions are higher in the AWD water management
regime than CF

Preliminary Results
i. Negative CO2 fluxes were observed due to photosynthesis
process since chambers were allowing light to go through
ii. Patterns of CO2 emissions were similar between the two soils

Conclusions, Future work & Research
application
i. CH4 emissions are higher in Vertisols while N2O emissions are higher in Nitosols,
hence soil texture affects GHG emissions;
ii. Inverse relationship between CH4 and N2O, such that during draining cycle, CH4
emissions are reduced while on the other hand N2O emissions increase
iii. N2O emissions increase with fertilizer application
v Future Work – More research is required to quantify GHG emissions from rice
production in Kenya. This study was carried out for one cropping season hence it is
important to collect data over more than one season and also quantify GHG under
different fertilizer application
v Research application – The study will give an estimate of GHG emissions from rice
production in Kenya

Acknowledgements
The CGIAR research program on
Climate Change, Agriculture and
Food Security (CCAFS), through
SAMPLES program and CLIFF
Network, and Mazingira Centre-
ILRI Kenya, contributed to this
research