Reducing losses but failing to sequester carbon in soils – the case of Conservation Agriculture and Integrated Soil Fertility Management in the humid tropical agro-ecosystem of Western Kenya

The impacts of integrated soil fertility management (ISFM) in conservation agriculture need short-term evaluation before continuation of its long-term practice. A split-split plot experiment with tillage (minimum tillage, MT vs. conventional tillage, CT) as the main plot, residue (20% residue, R vs. no residue as a control, NR) as the sub-plot, and compost (Trichocompost, LC; bio-slurry, BS; and recommended fertilization, RD) as the sub-sub plot treatment was conducted for two consecutive years. Composite soils were collected after harvesting the sixth crop of an annual mustard-rice-rice rotation to analyze for nutrient distribution and soil structural stability. The LC increased rice equivalent yield by 2% over RD and 4% over BS, and nitrogen (N) uptake by 11% over RD and 10% over BS. Likewise, LC had higher soil organic carbon (SOC), N, and available sulphur (S) than BS and RD. Conversion of CT to MT reduced rice equivalent yield by 11%, N uptake by 26%, and N-use efficiency by 28%. Conversely, soil structural stability and elemental quality was greater in MT than in CT, indicating the potential of MT to sequester C, N, P, and S in soil aggregates. Residue management increased rice yield in the second year by 4% and corresponding N uptake by 8%. While MT reduced the yield, our results suggest that ISFM with Trichocompost and residue retention under MT improves soil fertility and physical stability to sustain crop productivity.

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Understanding system innovation adoption: A comparative analysis of integrated soil fertility management uptake in Tamale (Ghana) and Kakamega (Kenya)

Renewable Agriculture and Food Systems ◽

10.1017/s1742170517000485 ◽

2017 ◽

Vol 34 (04) ◽

pp. 313-325 ◽

Cited By ~ 2

Author(s):

Ivan Solomon Adolwa ◽

Stefan Schwarze ◽

Boaz Waswa ◽

Andreas Buerkert

Keyword(s):

Soil Fertility ◽

Farming Systems ◽

Conservation Agriculture ◽

Northern Ghana ◽

Development Programs ◽

Soil Fertility Management ◽

Integrated Soil Fertility Management ◽

Fertility Management ◽

Plot Area ◽

Key Policy

AbstractSustainable intensification of African farming systems has been high on the agenda of research and development programs for decades. System innovations such as integrated soil fertility management (ISFM) and conservation agriculture have been proposed to tackle the complex challenges farmers face. In this study, we assess how different factors at the plot, farm and institutional level can influence the adoption of ISFM. We employed a stratified sampling approach to randomly select 285 and 300 farmers in Tamale, northern Ghana and Kakamega County, western Kenya, respectively. These two locations were selected to understand the underlying reasons for their divergent adoption levels. Ordinal regression models were used to identify determinants of adoption. In Tamale, adoption rates of ISFM are much lower than in Kakamega. Only 3% of the farmers fully adopted the recommended practices compared with 36% in Kakamega. The low availability of improved seeds is a major reason for the lower uptake of the complete ISFM paradigm in Tamale. The econometric analysis revealed that plot level variables such as soil carbon, soil texture, slope and plot area had a significant effect on the number of adopted ISFM components at both locations. Moreover, family labor availability is also an important factor. Other farm and household characteristics, such as off-farm occupation, livestock ownership, and membership in associations, matter for Kakamega only. Key policy recommendations include promotion of locally available organic resources and improved access to improved seeds in Tamale.

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