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Kumasi, Ghana

Giller K.E.,Wageningen University | Tittonell P.,CIRAD - Agricultural Research for Development | Rufino M.C.,Wageningen University | van Wijk M.T.,Wageningen University | And 23 more authors.
Agricultural Systems | Year: 2011

African farming systems are highly heterogeneous: between agroecological and socioeconomic environments, in the wide variability in farmers' resource endowments and in farm management. This means that single solutions (or 'silver bullets') for improving farm productivity do not exist. Yet to date few approaches to understand constraints and explore options for change have tackled the bewildering complexity of African farming systems. In this paper we describe the Nutrient Use in Animal and Cropping systems - Efficiencies and Scales (NUANCES) framework. NUANCES offers a structured approach to unravel and understand the complexity of African farming to identify what we term 'best-fit' technologies - technologies targeted to specific types of farmers and to specific niches within their farms. The NUANCES framework is not 'just another computer model'! We combine the tools of systems analysis and experimentation, detailed field observations and surveys, incorporate expert knowledge (local knowledge and results of research), generate databases, and apply simulation models to analyse performance of farms, and the impacts of introducing new technologies. We have analysed and described complexity of farming systems, their external drivers and some of the mechanisms that result in (in)efficient use of scarce resources. Studying sites across sub-Saharan Africa has provided insights in the trajectories of change in farming systems in response to population growth, economic conditions and climate variability (cycles of drier and wetter years) and climate change. In regions where human population is dense and land scarce, farm typologies have proven useful to target technologies between farmers of different production objectives and resource endowment (notably in terms of land, labour and capacity for investment). In such regions we could categorise types of fields on the basis of their responsiveness to soil improving technologies along soil fertility gradients, relying on local indicators to differentiate those that may be managed through 'maintenance fertilization' from fields that are highly-responsive to fertilizers and fields that require rehabilitation before yields can improved. Where human population pressure on the land is less intense, farm and field types are harder to discern, without clear patterns. Nutrient cycling through livestock is in principle not efficient for increasing food production due to increased nutrient losses, but is attractive for farmers due to the multiple functions of livestock. We identified trade-offs between income generation, soil conservation and community agreements through optimising concurrent objectives at farm and village levels. These examples show that future analyses must focus at farm and farming system level and not at the level of individual fields to achieve appropriate targeting of technologies - both between locations and between farms at any given location. The approach for integrated assessment described here can be used ex ante to explore the potential of best-fit technologies and the ways they can be best combined at farm level. The dynamic and integrated nature of the framework allows the impact of changes in external drivers such as climate change or development policy to be analysed. Fundamental questions for integrated analysis relate to the site-specific knowledge and the simplification of processes required to integrate and move from one level to the next. © 2010 Elsevier Ltd.

Obalum S.E.,University of Nigeria | Obalum S.E.,Kinki University | Oppong J.,Academy Post Office | Igwe C.A.,University of Nigeria | Wakatsuki T.,Kinki University
Paddy and Water Environment | Year: 2011

Although the West African inland valleys are characteristically wet all-year-round, their hydrological conditions are known to be site-specific and may differ markedly between the rainy and the dry seasons. Information on their physical properties would be useful for proper water management under the sawah rice culture and for planning dry season cropping. Representative inland valleys at four locations (Gadza, Nasarafu, Shaba-Maliki and Ejeti) around Bida in the Guinea savanna zone of Nigeria were selected for the study. Apart from Ejeti where the soil is clay loam, the predominant texture is sandy loam. The total and classified water-stable aggregates (WSA) were lowest at Ejeti, followed by Nasarafu. On the average, over 82% of the WSA were below 1.0 mm. Variations among the locations progressively decreased from the largest to the smallest aggregate-size class. Aggregate stability, as evaluated by both sand-corrected WSA and the mean weight diameter (MWD), followed similar trend as the WSA. Values were generally low for soil organic matter (SOM) (0.8-2.2%), but moderate for bulk density (0.98-1.55 Mg m-3) and total porosity (40.6-62.6%). Overall, Ejeti maintained the most favourable values of these three parameters, followed by Shaba-Maliki, Nasarafu and Gadza in the order listed. Micropores constituted over 87% of the soils' pore system. Saturated hydraulic conductivities were, however, highly variable; indicating lowest rates at Ejeti. Clay fraction correlated positively with the unstable (<0.25 mm) aggregates and porosity parameters, but negatively with other structural indices. The SOM correlated negatively and positively with MWD and total porosity, respectively. Soil-water management implications of these results are discussed. © 2010 Springer-Verlag.

Obalum S.E.,Kinki University | Obalum S.E.,University of Nigeria | Buri M.M.,Academy Post Office | Nwite J.C.,P.A. College | And 5 more authors.
Applied and Environmental Soil Science | Year: 2012

The paper provides an insight into the problem of land degradation in Sub-Saharan Africa, with emphasis on soil erosion and its effect on soil quality and productivity, and proposes a lowland-based rice-production technology for coping with the situation. Crop yields are, in addition to the degree of past and current erosion, determined by a number of interacting variables. This, coupled with the generally weak database on erosion-induced losses in crop yield in spite of the region's high vulnerability to erosion, makes it difficult to attain a reliable inference on the cause-effect relationship between soil loss and productivity. Available data suggest, however, that the region is at risk of not meeting up with the challenges of agriculture in this 21st century. Based on the few studies reviewed, methodology appears to have an overwhelming influence on the erosion-productivity response, whereas issues bordering on physical environment and soil affect the shape of the response curve. We argue that the sawah ecotechnology has the potential of countering the negative agronomic and environmental impacts of land degradation in Sub-Saharan Africa. This is a farmer-oriented, low-cost system of managing soil, water, and nutrient resources for enhancing lowland rice productivity and realizing Green Revolution in the region. © 2012 Sunday E. Obalum et al.

Amoakwah E.,Academy Post Office | Frimpong K.A.,University Of Cape Coast
ARPN Journal of Engineering and Applied Sciences | Year: 2013

A study was conducted to determine the distribution of forms of K (water soluble K, exchangeable K, non exchangeable K, and total K) of potassium in some Ghanaian soils occurring along toposequence using standard laboratory procedures. The soils were the Edina, Atabadzi, Benya, Udu and Kakum series (Acrisols), which form the Edina catena. The concentrations of total K in the soils ranged from 0.64 to 2.37 (cmol (+) kg-1) with Kakum series showing the lowest (P < 0.05) value. Water soluble K and exchangeable K concentrations in the soils ranged from 0.05 to 0.25 c mol (+) kg-1, and 0.26 to 0.89 cmol (+) kg-1, respectively, with the Kakum series again showing the lowest values (P < 0.05) for both K forms. The Edina series, occurring at the summit of the catena, showed the highest concentrations of both water soluble and exchangeable K. In the study non-exchangeable K concentrations measured in the soils varied between 0.20 and 1.25 cmol (+) kg-1. The study showed that exchangeable K constituted the highest proportion of the total K measured in the soils, while the proportion of water soluble K in the total K measured was the lowest. Pooling all the data obtained in the study, water soluble K and exchangeable K concentrations positively correlated with organic matter, cation exchange capacity and percentage bas saturation. © 2006-2013 Asian Research Publishing Network (ARPN).

Obalum S.E.,Kinki University | Oppong J.,Academy Post Office | Igwe C.A.,University of Nigeria | Watanabe Y.,Kinki University | Obi M.E.,University of Nigeria
International Agrophysics | Year: 2013

The spatial variability of some physicochemical properties of topsoils/subsoils under secondary forest, grassland fallow, and bare-soil fallow of three locations was evaluated. The data were analyzed and described using classical statistical parameters. Based on the coefficient of variation, bulk density, total porosity, 60-cm-tension moisture content, and soil pH were of low variability. Coarse and fine sand were of moderate variability. Highly variable soil properties included silt, clay, macroporosity, saturated hydraulic conductivity, organic matter concentration, and cation exchange capacity. Overall, soil pH and silt varied the least and the most, respectively. Relative weighting showed that location dominantly influenced the soil variability, except for soil porosity and organic matter concentration influenced mostly by land use. Most of the soil data were normally distributed; others were positively skewed and/or kurtotic. The minimum number of samples (at 25 samples ha-1) required to estimate mean values of soil properties was highly soil property-specific, ranging from 1 (topsoil pH-H2O) to 246 (topsoil silt). Cation exchange capacity of subsoils related fairly strongly with cation exchange capacity of topsoils (R2 = 0.63). Spatial variability data can be used to extrapolate dynamic soil properties across a derived-savanna landscape. © 2013 Institute of Agrophysics.

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