Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    ‘Force of Nature’ : climate shocks, food crises and conflict in Colonial Africa and Asia, 1880-1960
    Papaioannou, Kostadis J. - \ 2017
    Wageningen University. Promotor(en): E.H.P. Frankema; E.H. Bulte. - Wageningen : Wageningen University - ISBN 9789463431668 - 238
    climatic change - environmental degradation - environmental impact - agricultural development - agriculture - agriculture and environment - historical ecology - history - colonialism - colonization - africa - asia - nigeria - rainfed agriculture - rain - klimaatverandering - milieuafbraak - milieueffect - landbouwontwikkeling - landbouw - landbouw en milieu - historische ecologie - geschiedenis - kolonialisme - kolonisatie - afrika - azië - nigeria - regenafhankelijke landbouw - regen

    “Global climate change poses one of the most urgent challenges of our age. The increasing frequency and intensity of weather shocks, such as heat waves, droughts, floods, and hurricanes, are all anticipated to adversely affect conditions of agricultural production, and jeopardize efforts to achieve global food security. In recent years, there has been a rapidly growing body of literature across multiple disciplines aiming to quantify and assess the adverse consequences of climate on relatively poor rural societies. Building entirely on original primary sources, this dissertation provides evidence that weather shocks raised property crime, triggered civil conflict and shaped patterns of human settlement in British colonial Africa and Asia during the first half of the twentieth century (~1880-1960). By merging the theoretical and empirical insights of several strands of literature (e.g. economics, history, geography), this dissertation has both academic and social merit. Its academic merit lies in its promise to disentangle the net effect of climate on societies from the many other contextual factors that may affect them. And its social merit lies in its capacity to reveal key factors that can mitigate the adverse consequences of weather shocks, enabling tailor-made policy interventions. In sum, the present dissertation contributes to a better understanding of long-term agrarian development in tropical Africa and Asia, offering fresh input to academic debates on how to mitigate the effects of weather extremes”

    Sustainable use of land and water under rainfed and deficit irrigation conditions in Ogun-Osun River Basin, Nigeria
    Adeboye, O.B. - \ 2015
    Wageningen University. Promotor(en): E. Schultz, co-promotor(en): K.O. Adekalu; K. Prasad. - Leiden : CRC Press/Balkema - ISBN 9789462572782 - 237
    landgebruik - watergebruik - duurzaamheid (sustainability) - irrigatie - regenafhankelijke landbouw - watertekort - modellen - bodemwaterbalans - gewasopbrengst - nigeria - land use - water use - sustainability - irrigation - rainfed agriculture - water deficit - models - soil water balance - crop yield - nigeria
    Summary

    Human population is increasing faster than ever in the history. There is an urgent need to scale up food production in order to meet up with food demands, especially in Sub-Saharan Africa. In Ogun-Osun River Basin, Nigeria, more than 95% of the crop production is done under rainfed conditions. Fluctuation in rainfall as a result of climate change is a major challenge in the recent times in the basin. Land productivity can be greatly improved by using affordable water conservation practices by peasant farmers who produce crops in the basin. Similarly, water saving measures would have to be adopted by using drip irrigation and application of water at critical stages of growth of crops. Fertility of the soil needs to be maintained by cultivating crops that naturally replenish soil nutrients. Such measures will go a long way in ensuring sustainable use of land and water in Ogun-Osun River Basin.

    An indeterminate cultivar of Soybeans TGX 1448 2E was cultivated at the Teaching and Research Farms of Obafemi Awolowo University, Ile-Ife, Nigeria during the rainy seasons from May to September, 2011 and June to October, 2012. Similarly, the crop was drip irrigated for two dry seasons from February to May in 2013 and from November, 2013 to February, 2014. The purpose of conducting the experiments in the rainy and dry seasons was to compare the yields and their components and to evaluate the performances of the crop in terms of water use and productivity. The experimental field during the dry season was located at about 1 km from the field used during the rainy season due to the nearness to the source of water. During the experiments in the four seasons, key biometric data of the crop were taken from emergence to physiological maturity. The crop cycle during the rainfed experiment lasted for 117 and 119 days in 2011 and 2012 respectively, while in the dry season it lasted for 112 days in the first season and 105 days in the second season. The lengths of the crop cycles in the four seasons differed a little bit. This is attributed to environmental factors such as weather conditions, nutrient availability in the soil and period of cultivation. During the rainy seasons, six water conservation treatments were used namely Tied ridge, Mulch, Soil bund, Tied ridge plus Soil bund, Tied ridge plus Mulch, Mulch plus Soil bund and Direct sowing without water conservation measure (conventional practice), which was the control treatment. The treatments were placed in a randomised complete block design with four replicates in an area of 31 by 52 m (1,612 m2) and standard agronomic measures were taken. Soil water balance approach was used in determining evapotranspiration during the rainfed and irrigation seasons. Seasonal evapotranspiration was partitioned into the productive transpiration from the plants and non-productive evaporation from the soil.

    Seasonal average canopy extinction coefficients were 0.46 and 0.51 respectively in the rainy seasons of 2011 and 2012, while in the dry seasons of 2013 and 2013/2014 they were 0.43 and 0.49. The plant height ranged from 51.3 cm for Soil bund to 67.8 cm for the conventional practice in 2011 while in 2012, it ranged from 60.3 cm for Tied ridge plus Soil bund to 80.3 cm for Mulch plus Soil bund. The minimum fraction of Intercepted Photosynthetically Active Radiation was 0.13 during establishment for Tied ridge plus Soil bund while the peak fraction was 0.97 during seed filling for Soil bund during the rainy seasons. Similarly, the minimum and peak leaf area indices were 0.13 m2 m-2 for Tied ridge plus Soil bund during establishment in 2011 and 6.61 m2 m-2 for Soil bund during seed filling in 2012. There were strong and significant correlations between the fraction of Intercepted Photosynthetically Active Radiation and the leaf area indices (LAI) (0.70 ≤ r2 ≤ 0.99) in 2011 and (0.93 ≤ r2 ≥ 0.99) in 2012 by using an exponential model. Seasonal rainfall in 2011 and 2012 was 539 and 761 mm respectively. Seasonal water storages in the soil in 2011 ranged from 407 mm for the conventional practice to 476 mm for Tied ridge plus Mulch, while in 2012 it ranged from 543 mm for Tied ridge to 578 mm for Tied ridge plus Soil bund.

    Radiation Use efficiency was determined by plotting dry above ground biomass measured at intervals of seven days against the Daily Photosynthetically Active Radiation from Solar radiation and the Instantaneous Photosynthetically Active Radiation measured near solar noon for all the treatments. For the Photosynthetically Active Radiation obtained from solar radiation, Radiation Use Efficiency of the crop ranged from 1.18 g MJ-1 for Tied ridge to 1.98 g MJ-1 of Intercepted Photosynthetically Active Radiation for Tied ridge plus Soil bund in 2011, while in 2012 it ranged from 1.45 g MJ-1 for Tied ridge to 1.92 g MJ-1 for Mulch. There was no significant difference in the average seasonal Radiation Use Efficiency in the two seasons. By using instantaneous measurement of the Photosynthetically Active Radiation, Radiation Use Efficiency ranged from 0.80 g MJ-1 of Intercepted Photosynthetically Active Radiation for Tied ridge to 1.65 g MJ-1 for Tied ridge plus Soil bund in 2011, while in 2012 it ranged from 0.94 g MJ-1 for Tied ridge to 1.24 g MJ-1 for Soil bund. The two approaches gave relatively similar values of Radiation Use Efficiency. Positive -correlation coefficients (0.50 ≤ r2 ≤ 0.89) were found among the treatments between the dry above ground biomass simulated by using a light model and those measured in the field in the two seasons.

    The seasonal crop water use ranged from 311 mm for Mulch plus Soil bund to 406 mm for Tied ridge plus Soil bund in 2011, while in 2012 it ranged from 533 mm for Mulch plots to 589 mm for Soil bund. Seasonal transpiration ranged from 190 mm for Tied ridge plus Mulch to 204 mm for Soil bund in 2011 while in 2012 it ranged from 164 mm for Tied ridge plus Mulch to 195 mm for Mulch plot. Seasonal evaporation was higher in 2012 ranging from 338 mm for Mulch plots to 408 mm for Soil bund while in 2011 it ranged from 311 mm for Mulch plus Soil bund to 406 mm for Tied ridge plus Soil bund. Water storage in the soil and seasonal crop water use are significantly related. Similarly, the seasonal crop water use, Intercepted Photosynthetically Active Radiation and Radiation Use efficiency were highly related for the crop over the two seasons.

    Marketable seed yield ranged from 1.68±0.50 t ha-1 for Tied ridge to 2.95±0.30 t ha-1 for Tied ridge plus Soil bund in 2011, while in 2012 the yield ranged from 1.64±0.50 t ha-1 for the conventional practice to 3.25±0.52 t ha-1 for Mulch plus Soil bund. In 2011, seed yield for Tied ridge plus Soil bund was 15.6, 15.9, 25.4, 28.5, 43.1 and 47.1% higher than seed yield for Mulch plus Soil bund, Soil bund, Mulch, Tied ridge plus Mulch, Tied ridge and conventional practice respectively. In 2012, seed yield for Mulch plus Soil bund was 7.4, 21.8, 32.0, 32.3, 43.7 and 49.5% higher than the seed yields for Soil bund, Tied ridge, Mulch, Tied ridge plus Mulch, Tied ridge plus Soil bunds and Direct sowing respectively. Average seasonal seed yield of the crop was significantly related to the Total Intercepted Photosynthetically Active Radiation but not to the Radiation Use Efficiency. Harvest indices ranged from 47.4±4.5% for Tied ridge to 57.6±1.1% for Tied ridge plus Soil bund in 2011 and 53.1±3.0% for Soil bund to 58.1±2.3% for Tied ridge 2012. The highest harvest indices were obtained in Tied ridge plus Soil bund and Tied ridge in 2011 and 2012 respectively. Harvest index was not significantly related to both Intercepted Photosynthetically Active Radiation and Radiation Use Efficiency of the crop.

    Average seasonal transpiration efficiencies - the ratio of the dry above ground biomass at harvest to the seasonal transpiration - for all the treatments were 7.0 kg ha-1 mm-1 in 2011 and 14.9 kg ha-1 mm-1 in 2012. Transpiration efficiency of the crop was strongly related to Intercepted Photosynthetically Active Radiation but not to Radiation Use Efficiency under field conditions in the rainy seasons. The peak water productivity for seed was 7.99 kg-1 ha-1 mm-1 in 2011 and 5.76 kg-1 ha-1 mm-1 for Mulch plus Soil bund in 2012. Water productivity for seed was strongly and significantly related to Intercepted Photosynthetically Active Radiation. However, it was not significantly related to Radiation Use Efficiency. These findings will provide information to the crop yield modellers during the simulation of yields of Soybeans under water conservation practices.

    The construction of ridges and Soil bund especially for Tied ridge, Mulch plus Soil bund and Tied ridge plus Soil bund increased the average seasonal cost of production by 28.9% compared with Mulch and conventional practice and by 10.1% compared with Soil bund. In addition, economic water productivity was 3.90 US$ ha-1 mm-1 for Mulch plus Soil bund while for Soil bund and conventional practice, it was 3.30 and 2.27 US$ ha-1 mm-1 respectively.

    Due to increase in demand for food, there is the need to produce more crop per drop of water under rainfed conditions and to manage water for agriculture at basin scale. The key priority in the study area was to increase the seed yields, water and economic productivity and the financial benefits at the end of a cropping season. The results show that the use of Mulch plus Soil bund had the average maximum transpiration efficiency, seed yield, water and economic productivity, and revenue of 1,630 US$ per ha. By comparing the average seasonal transpiration efficiency, crop water use, yield, water productivity and costs of production for the six conservation practices with those of the conventional practice in the two rainy seasons, Mulch plus Soil bund had the maximum average seed yield, water and economic productivity. Mulch plus Soil bund is hereby recommended for the cultivation of the crop in the study area. Other conservation practices, such as Soil bund, also performed satisfactorily in terms of seed yield and water productivity, although with a slight reduction in revenue. The use of these water conservation practices will not only increase the yields of the crop, but reduce depletion of water in the soil, which could initiate or increase land degradation in the study area to the barest minimum. Hence, sustainability of land and water in Ogun-Osun River Basin can be ensured. These findings demonstrate that land and water productivity of Soybean under rainfed conditions can be significantly improved with water conservation practices under the current fluctuations of rainfall and competition for land resources between agriculture and urban land use in Ogun-Osun River Basin.

    Field trials were also conducted for two irrigation seasons from February to May, 2013 and November, 2013 to February, 2014. The crop was planted in a Randomized Complete Block Design with three replicates and in-line drip irrigation was applied to supply water to the crops. Five treatments were selected and these are: (i) full irrigation, skipping of irrigation every other week during (ii) flowering; (iii) pod initiation; (iv) seed filling and (v) commencement of maturity. Biometric data, which are number of leaves, plant height, leaf area indices and dry above ground biomass, were taken and recorded every week from sowing until maturity in the two irrigation seasons. Soil moisture contents were taken at the root zone of the plants prior to irrigation in order to determine the net irrigation water requirements at each stage of growth. Harvest indices were determined for each treatment. Number of pods per plant, number of seeds per pod and yields under each treatment were determined after physiological maturity in each season. Regression equations were generated for: (i) yield; (ii) number of pods per plant; (iii) number of seeds per pod; (iv) number of leaves; (v) seasonal transpiration and leaf area indices. Similarly, regression equations were generated for: (i) plant heights; (ii) seasonal transpiration; (iii) number of pods per plant; (iv) number of seeds per pod; (v) dry above ground biomass. Linear regressions were also fitted to the yield, dry above ground biomass and seasonal crop water use. The crop response factor was determined. Water productivity and Irrigation water productivity were computed and compared for each treatment. Linear models were fitted to the water productivity, irrigation water productivity and harvest index.

    Rainfall contribution to the crop water use was 262 and 50 mm for 2013 and 2013/2014 irrigation seasons respectively. Maximum Leaf Area Index in the 2013 irrigation season was 7.10 m2 m-2 for full irrigation during seed filling, while in the 2013/2014 irrigation season, it was 3.44 m2 m-2 for full irrigation during flowering. The dry above ground biomass after maturity ranged from 359 g m-2 where irrigation was skipped every other week at the commencement of maturity to 578 g m-2 for full irrigation. The seed yields ranged from 1.81 t ha-1 when irrigation was skipped every other week during seed filling to 3.11 t ha-1 for full irrigation. Average seasonal seed yield for full irrigation was 18.8, 21.8, 24.4 and 47.9% higher than yields for treatments where irrigation was skipped every other week during flowering, pod initiation, commencement of maturity and seed filling respectively. Seasonal transpiration ranged from 217 mm when irrigation was skipped every other week during seed filling to 409 mm for full irrigation in the 2013 irrigation season, while in the 2013/2014 irrigation season it ranged from 28 mm for the treatment where irrigation was skipped every other week during seed filling to 223 mm for full irrigation. Seasonal crop water use ranged from 463 mm when irrigation was skipped every other week during flowering to 523 mm for full irrigation in the 2013 irrigation season, while in the 2013/2014 irrigation season it ranged from 364 mm when irrigation was skipped every other week during seed filling to 507 mm for full irrigation. Harvest indices ranged from 56.0% when irrigation was skipped during seed filling to 65.9% when irrigation was skipped during flowering in the 2013 irrigation season, while in the 2013/2014 irrigation season, it ranged from 43.2% when irrigation was skipped during seed filling to 63.9% for full irrigation. Water productivity for seed production ranged from 3.89 kg ha mm-1 when irrigation was skipped during seed filling to 5.95 kg ha-1 mm-1 for full irrigation in the 2013 irrigation season while in the 2013/2014 irrigation season, it ranged from 1.93 kg ha mm-1 when irrigation was skipped during seed filling to 3.00 kg ha-1 mm-1 for full irrigation. Irrigation water productivity ranged from 8.90 kg ha mm-1 when irrigation was skipped during seed filling to 14.0 kg ha-1 mm-1 when irrigation was skipped during flowering in 2013, while in the 2013/2014 irrigation season, it ranged from 2.24 kg ha-1 mm-1 when irrigation was skipped during seed filling to 3.32 kg ha-1 mm-1 for full irrigation. Leaf area indices and yield, number of leaves, number of pods per plant, number of seeds per pod and seasonal transpiration were significantly correlated. Similarly, dry above ground biomass and seasonal transpiration, number of pods per plant, number of seeds per pod were significantly correlated. The crop response factor (Ky), a measure of the relative decrease in seed yield due to relative decrease in evapotranspiration, was 2.24. It indicates that the deficit irrigation imposed on the crop was high and that relative decrease in yields due to deficit irrigation was higher than relative decrease in evapotranspiration.

    Results show that skipping of irrigation at any growth stage of the crop led to reduction in the leaf area indices, dry above ground biomass and seasonal crop water use. Deficit irrigation had significant effects on both the dry matter and yields. The effect of deficit irrigation was more pronounced on seed yields than on dry matter. Severity of the effects of deficit irrigation depended on the stage of growth and its duration. Deficit irrigation reduced significantly dry matter at flowering and pod initiation. However, deficit irrigation did not affect the plant height. Number of seeds per plant at flowering and commencement of maturity were reduced significantly by deficit irrigation. The number of seeds per pod was significantly reduced when irrigation was skipped at pod initiation only. Seed yields were significantly reduced when irrigation was skipped during seed filling. In the 2013 irrigation season water productivity when irrigation was skipped during flowering was 2.3, 16.1, 23.5, and 36.1% higher than water productivity for full irrigation, when irrigation was skipped during pod initiation, commencement of maturity and seed filling respectively. In the same season, irrigation water productivity when irrigation was skipped during flowering was 15, 20, 29.3 and 36.4% higher than for full irrigation, when irrigation was skipped during pod initiation, commencement of maturity and seed filling respectively. In the 2013/2014 irrigation season, however, water productivity for full irrigation was 8.7, 16.3, 24.7 and 35.7% higher than when irrigation was skipped during pod initiation, commencement of maturity, flowering and seed filling respectively. Similarly, irrigation water productivity was 7.2, 15.4, 24.1 and 32.5% higher than when irrigation was skipped during pod initiation, commencement of maturity, flowering and seed filling respectively. In addition, irrigation water productivity for full irrigation was 24.1 and 32.5% higher than when irrigation was skipped during flowering and seed filling respectively. Stage of growth, its duration, water requirements and seasonal environmental conditions influenced the seasonal water use, water productivity and irrigation water productivity of Soybean. Maximum water productivity and irrigation water productivity were obtained when irrigation was skipped every other week during flowering only in the first season, whereas in the second season full irrigation gave the peak water and irrigation water productivity. This suggests that irrigation water productivity of Soybean can be improved upon by skipping irrigation during flowering and pod initiation.

    In this study, the costs of production for all the irrigation scenarios were high. This is due to the high cost of water, which constituted between 54 to 59% of the production cost if water is purchased and cost of drip irrigation equipment, which constituted between 75.6 to 76.7% of the total cost of production if water would be given without financial implication. Under the prevailing price and economic conditions after harvest, the use of in-line drip irrigation does not offer economic benefit to peasant farmers, who are the predominant growers of the crop in the study area. Economic benefit may be achieved after long periods of usage with proper maintenance of the irrigation facilities and elimination of the fixed cost from the total cost of production.

    The water driven crop model AquaCrop was calibrated and validated to predict canopy cover, dry above ground biomass, seed yield, evapotranspiration, soil moisture content and water productivity of the crop. The simulated and measured data compare adequately except for water productivity that was over predicted in the validation data set. The AquaCrop model predicted canopy cover with error statistics of 0.93 ≤ E ≤ 0.98 for both full and deficit irrigation and the degree of agreement d = 0.99 with 4.3 ≤ RMSE ≤ 5.9 (root mean square error) for full irrigation while for deficit irrigation, 0.96 ≤ d ≤ 0.99 with 5.3 ≤ RMSE ≤ 5.8. Dry above ground biomass was predicted with error statistics of 0.08 ≤ RMSE ≤ 0.14 t ha-1 with 0.98 ≤ d ≤ 0.99 for full irrigation, while for deficit irrigation it was 0.06 ≤ RMSE ≤ 1.09 t ha-1 with 0.85 ≤ d ≤ 0.99. One in every five predictions of the above ground biomass was outside 20% deviation from the measured values.

    The seed yields were predicted with error statistics of RMSE = 0.10 t ha-1 and d = 0.99 and one in five predictions was outside 15% deviation from the measured data. The prediction error statistics for seasonal crop water use for both full and deficit irrigation treatments was 15.4 ≤ RMSE ≤ 58.3 in the two seasons. The AquaCrop model over predicted percolation also in the validation data set. These observations suggest that the percolation components of the model need to be adjusted to ensure better performance. The performance of the AquaCrop model in predicting canopy cover, seed yield and other quantities in this study are commendable and satisfactory.

    Specific and distinct features, such as the use of canopy cover rather than leaf area index, make the model suitable for developing countries like Nigeria, where researchers may not have access to state-of-the-art equipment for measuring the leaf area index. Similarly, water productivity that is normalized for atmospheric demand and carbon dioxide concentration and its focus on water makes it suitable for diverse locations. Over the years, it has been observed that no model is universal in its ability to take into consideration all differences in cultivar, environment, weather and management conditions. Other cultivars of Soybeans in Nigeria and other agro-climatic environments need to be tested and fine-tuned in the model, in order to ascertain the accuracy of the model. generally, the model predicted the stated parameters with reasonable degree of accuracy and is hereby recommended for use in Ile-Ife and other parts of Ogun-Osun River Basin and Nigeria.

    Although land, water, and economic productivity of the crop were higher where water was conserved under rainfed conditions, treatment of the soil to conserve water and regular maintenance increased the average seasonal cost of production compared with the conventional practice. High cost of production may reduce the benefits obtained by the crop growers, except when there is improvement in the market price. Therefore, sustainable practice of the water conservation measures must be accompanied with lower cost of production. Under irrigation conditions, the land and water productivity are lower compared with rainfed cultivation. The productivity in the dry season reduces with the severity of the water stress. Average crop water productivity and economic water productivity of all the six water conservation measures in the rainy season were higher than with full irrigation in the dry season. The costs of production of the crop in the dry season were significantly above the cost during the rainfed conditions. Higher water productivity under rainfed conditions in this study is in agreement with the finding that in a significant part of the least developed and emerging countries there is larger opportunity for improving water productivity under rainfed conditions compared to irrigated agriculture.

    Expansion of arable land may not be feasible in Ile-Ife because of the huge investments involved. Thus, the focus of efforts to expand food production in the area would have to be on raising land productivity on the existing arable lands and improving production efficiencies, outcomes that can only be achieved by using improved cultivars together with improved agronomic practices. Agronomic practices, especially under rainfed conditions, would have to be designed to improve water productivity. Improving water productivity requires vapour shift (transfer) whereby soil physical conditions, soil fertility, crop varieties and agronomy are applied in tandem and managed to shift the evaporation into useful transpiration by plants. During the dry season, the crop would have to be irrigated in order to achieve maximum land and water productivity. Skipping of irrigation during seed filling would have to be avoided in order to prevent significant reduction in yield. Irrigation at the commencement of maturity after the pods have been completely filled with seeds can be skipped. Under water limiting conditions, the amount of water saved by skipping irrigation during flowering, pod initiation, seed filling and maturity can be used for cultivating other crops and thereby increasing the opportunity cost. Incidental rainfall during the dry season would have to be used in order to increase irrigation water productivity of the crop.

    Mission report carrying capacity cage farming Nigeria
    Wijsman, J.W.M. - \ 2015
    Yerseke : IMARES (Rapport / IMARES ) - 8
    aquacultuur - technieken - kennis - monitoring - nigeria - aquaculture - techniques - knowledge - monitoring - nigeria
    Short- to mid-term impact of conservation agriculture on yield variability of upland rice: evidence from farmer's fields in Madagascar
    Bruelle, G. ; Naudin, K. ; Scopel, E. ; Domas, R. ; Rabeharisoa, L. ; Tittonell, P.A. - \ 2015
    Experimental Agriculture 51 (2015)1. - ISSN 0014-4797 - p. 66 - 84.
    cropping systems - tillage systems - maize productivity - soil - erosion - africa - degradation - nigeria - surface - runoff
    Family farming in the tropics suffers from low crop productivity mainly due to a combination of poor soil fertility, low investment capacity, and a variable climate. The Lake Alaotra region of Madagascar is no exception and rainfed production is particularly hard hit. To evaluate the agronomic benefits of conservation agriculture (CA) in a region of erratic rainfall, we analysed four years of yield, management and climatic data from 3803 upland rice fields cultivated by farmers and monitored by researchers. Fields located on rainfed lowlands and hillsides were cultivated with sole rice using conventional tillage (Cv) or rice sown with no-tillage on dead organic mulch and rotated with other cereal/legume combinations (CA) from 2006 to 2011. A first global comparison across seasons, locations and years of adoption showed significantly higher average yields under CA, with no change in variance (on lowland: 2.6 ± 0.9 t ha–1 Cv, 2.8 ± 0.9 t ha–1 CA; on hillside: 2.1 ± 0.8 t ha–1 Cv, 2.4 ± 0.8 t ha–1 CA). Grouping fields according to the number of years under CA (first to fourth) revealed that CA gradually increased average yields and reduced the coefficient of variation in the short and mid-term (on lowland: +0.2 t ha–1 and –6% coefficient of variation; on hillside: +0.7 t ha–1 and –13% coefficient of variation, over four to six years of successive CA cropping). The average yield increase under CA was not associated with an increase in mineral fertiliser use, as farmers used the same amounts of fertilisers (or none) under Cv and CA. The comparison Cv versus CA also highlighted a major benefit of CA regarding climate: it widened the window of possible sowing dates. A classification and regression tree analysis of the entire dataset revealed that rice yield was more affected by agro-environmental factors than management factors (fertilisation, Cv or CA), and extreme climate variability such as the severe drought of 2007–2008 could not be offset by CA. The hypothesis of yield penalties during the first years of implementation of CA cannot be verified with the evidence presented in this study.
    Aid and trade for livestock development and food security in West Africa
    Lee, J. van der; Schiere, J.B. ; Bosma, R.H. ; Olde, E. de; Bol, S. ; Cornelissen, J.M.R. - \ 2014
    Lelystad : Wageningen UR Livestock Research (Rapport / Wageningen UR Livestock Research 745) - 101
    vee - veehouderij - economische ontwikkeling - ontwikkelingshulp - internationale handel - nigeria - ghana - benin - burkina faso - mali - livestock - livestock farming - economic development - development aid - international trade - nigeria - ghana - benin - burkina faso - mali
    Livestock keeping traditionally is very important in West Africa, occurring in many forms and fulfilling roles that change over time and from north to south. This report presents the results of a quickscan done by Wageningen UR Livestock Research and La Ventana consulting, mainly for policy discussions, but also giving suggestions for action by the private sector. The report is written for the Dutch Ministries of Economic Affairs (Department of European Agricultural Policy and Food Security, Directorate-General Agro) and Foreign Affairs (Directorate-General of International Cooperation). The central issue in this study is the search for opportunities for livestock development to enhance food security in West Africa through aid and trade. The report discusses win-win and trade-offs between aid and trade, reflecting a rather traditional divide between development aid and economic development. Nowadays the notion public and private might replace that of aid and trade.
    Unique characteristics of Pb in soil contaminated by red lead anti-corrosion paint
    Brokbartold, M. ; Temminghoff, E.J.M. ; Weng, L. ; Marschner, B. - \ 2013
    Soil and Sediment Contamination 22 (2013)8. - ISSN 1532-0383 - p. 839 - 855.
    donnan membrane technique - chemical speciation - southern thailand - trace-metals - solubility - cd - exposure - cadmium - nigeria - copper
    Red lead (Pb3O4) has been extensively used in the past in anti-corrosion paints for the protection of steel constructions such as electricity pylons or bridges. Until recently, little has been known about the behavior of these Pb compounds in soils. Therefore, three pylon soils and six red lead anti-corrosion paints were characterized in terms of solubility, Pb mineral composition, extractability, sorption and desorption, and the chemical speciation of Pb in soil extracts. The pylon soils were characterized by moderate total Pb concentrations (˜700 mg kg-1), while NH4NO3 extractable Pb was exceptionally high (up to 15% of total Pb). In soil extracts, the free Pb2+ fraction ranged from 33 to 81% of total soluble Pb. The equilibrium concentration of Pb derived from Pb3O4 in ultra-pure water reached 68.5 mg L-1. This high solubility explains the observed high extractability in soils and contradicts earlier reports of much lower water solubilities of the compound.
    Morphological Characterization of African Bush Mango trees (Irvingia species) in the Dahomey Gap (West Africa)
    Vihotogbe, R. ; Berg, R.G. van den; Sosef, M.S.M. - \ 2013
    Genetic Resources and Crop Evolution 60 (2013)4. - ISSN 0925-9864 - p. 1597 - 1614.
    phenotypic variation - indigenous fruits - domestication - gabonensis - cameroon - selection - nigeria - accessions - kernels - farmers
    The variation of the morphological characters of bitter and sweet African bush mango trees (Irvingia species) was investigated in the Dahomey Gap which is the West African savannah woodland area separating the Upper and the Lower Guinean rain forest blocks. African bush mangoes have been rated as the highest priority multi-purpose food trees species that need improvement research in West and Central Africa. A total of 128 trees from seven populations were characterized for their bark, fruits, mesocarp and seeds to assess the morphological differences between bitter and sweet trees and among populations. Multivariate analysis revealed that none of the variables: type of bark, mature fruit exocarp colour, fruit roughness and fresh mesocarp colour, could consistently distinguish bitter from sweet trees in the field. The analysis of the measurements of fruits, mesocarps and seeds demonstrated that bitter fruits have the heaviest seeds and this consistently distinguishes them from sweet fruits. However, the measurements of the fruit, mesocarp and seed did not have a joint effect in grouping types and populations of ABMTs. This indicates high diversity with a potential for selection existing across all phytogeographical regions investigated. The sweet trees of Couffo and those of Dassa in Benin are clearly different from all other populations. This can be attributed to traditional domestication (bringing into cultivation) and climate, respectively. The large fruits and the heavy seeds of the cultivated populations are evidence of successful on-going traditional selection of sweet trees in the Dahomey Gap.
    Schmallenberg virus outbreak in the Netherlands: Routine diagnostics and test results
    Bouwstra, R.J. ; Kooi, E.A. ; Kluijver, E.P. de; Verstraten, E.R.A.M. ; Bongers, J.H. ; Maanen, C. van; Wellenberg, G.J. ; Spek, A.N. van der; Poel, W.H.M. van der - \ 2013
    Veterinary Microbiology 165 (2013)1-2. - ISSN 0378-1135 - p. 102 - 108.
    akabane virus - antibodies - cattle - orthobunyavirus - shamonda - nigeria - bovine
    In 2006 and 2007 pig farming in the region of Lombardy, in the north of Italy, was struck by an epidemic of Swine Vesicular Disease virus (SVDV). In fact this epidemic could be viewed as consisting of two sub-epidemics, as the reported outbreaks occurred in two separate time periods. These periods differed in terms of the provinces or municipalities that were affected and also in terms of the timing of implementation of movement restrictions. Here we use a simple mathematical model to analyse the epidemic data, quantifying between-farm transmission probability as a function of between-farm distance. The results show that the distance dependence of between-farm transmission differs between the two periods. In the first period transmission over relatively long distances occurred with higher probability than in the second period, reflecting the effect of movement restrictions in the second period. In the second period however, more intensive transmission occurred over relatively short distances. Our model analysis explains this in terms of the relatively high density of pig farms in the area most affected in this period, which exceeds a critical farm density for between-farm transmission. This latter result supports the rationale for the additional control measure taken in 2007 of pre-emptively culling farms in that area.
    Seed quality in informal seed systems
    Biemond, P.C. - \ 2013
    Wageningen University. Promotor(en): Paul Struik, co-promotor(en): Tjeerd-Jan Stomph. - S.l. : s.n. - ISBN 9789461736420 - 120
    zaadkwaliteit - zaadfysiologie - vigna unguiculata - vignabonen - zaadkieming - zaadpathologie - mycotoxinen - zea mays - nigeria - seed quality - seed physiology - vigna unguiculata - cowpeas - seed germination - seed pathology - mycotoxins - zea mays - nigeria

    Keywords: informal seed systems, seed recycling, seed quality, germination, seed pathology, seed health, seed-borne diseases, mycotoxigenic fungi, Fusarium verticillioides, mycotoxins, Vigna unguiculata, Zea mays, Nigeria.

    Seed is a crucial input for agricultural production. Approximately 80% of the smallholder farmers in Africa depend for their seed on the informal seed system, consisting of farmers involved in selection, production and dissemination of seed. The lack of overhead, distribution and seed testing costs enables seed-producing farmers to offer seed for low prices, but seed quality is not always good. Seed-producing farmers multiply their seed on-farm without frequent seed renewal, referred to as seed recycling, which may lead to low seed quality. This research analysed the effect of seed recycling on physiological quality and seed health of cowpea and maize, and compared seed quality of the formal and informal seed system.

    We tested the physical and physiological quality of cowpea seeds produced by the formal and informal seed system. Five out of six foundation seed samples, 79 out of 81 samples of farmers’ seed, and six out of six seed company samples failed to meet standards for foundation and certified seeds of the National Agriculture Seed Council (NASC), the seed industry regulatory agency in Nigeria. No evidence was found for a negative effect of seed recycling on physiological quality of cowpea seeds. We analysed 45,500 cowpea seeds for seed-borne bacteria and fungi to compare the performance of formal and informal seed systems. All samples were heavily infected with seed-borne pathogens, including Fusarium oxysporum (69% of the samples) and Macrophomina phaseolina (76%). No evidence was found that seed recycling in the informal seed system did lead to increased levels of seed-borne pathogens. We also analysed seed quality of farmer-produced maize seed to compare it with the formal seed system. The seed company samples had significantly higher germination (99.3%) than farmer-produced seed (97.7%), but not a single sample passed the requirements for certified seed of the NASC. Twelve seed-borne pathogens were identified including Bipolaris maydis (found in 45% of the farmer-produced samples), Botryodiplodia theobromae (97%) and Fusarium verticillioides (100%). Seed recycling had no negative effect on the physiological quality or seed health of maize seed. We analysed formal and informal seed systems to assess the opportunities to prevent mycotoxigenic fungi infection in maize seeds. A range of control methods to avoid fungal infection and mycotoxin production is discussed in relation to three criteria for sustainable implementation in developing countries. An integrated approach is recommended, with special attention towards the local seed system. As an overall conclusion of the work it can be stated that the informal seed system did not underperform compared to the formal seed system for cowpea, but did underperform in relation to seed company samples of maize. There was no evidence that seed recycling reduces seed quality of cowpea and maize seed samples, so frequent seed renewal will not improve seed quality of the informal seed system. We recommend a new quality assurance system for the informal seed system based on seed quality testing by farmers themselves, without interference by government or external laboratories. Farmers publish their seed testing results on the bag, while buyers can retest the seed to verify the quality. Further research is required to develop and implement this system in different countries, agro-ecologies and crops, and to develop methods that enable farmers to test seed health quality themselves.

    Does the informal seed system threaten cowpea seed health?
    Biemond, P.C. ; Oguntade, O. ; Lava Kumar, P. ; Stomph, T.J. ; Termorshuizen, A.J. ; Struik, P.C. - \ 2013
    Crop Protection 43 (2013). - ISSN 0261-2194 - p. 166 - 174.
    nigeria
    Most smallholder farmers in developing countries depend on an informal Seed System (SS) for their seed. The informal SS is often criticized because farmer-produced seed samples are not tested for seed health, thus accepting the risk of planting infected seeds. Here we aimed at assessing the quality of seeds acquired from the informal SS, and compared this with the quality of seeds obtained from the formal SS. Cowpea seed production in northern Nigeria was used as a case study to evaluate the seed health of samples from farmers, seed companies, and foundation seed producers. In two years, a total of 45,500 seeds from 91 seed samples from 43 sources (farmers, seed companies and research) were tested for seed-borne bacteria and fungi by plating disinfested seed onto an agar medium. The most commonly isolated plant pathogens were Fusarium oxysporum (69% of the samples), Macrophomina phaseolina (76%) and Pseudomonas syringae pv. phaseolicola (48%). The infection incidence, the percentage of seeds infected per sample, varied from 0.2 to 75.6%. F. oxysporum had a median infection incidence of 9% in 2009 and 25% in 2010, while M. phaseolina had a median infection between 4 and 10%. On average, 8.8 species per sample were isolated from foundation seed, 9.2 from farmer-produced seed and 9.8 from seed companies' seed. No evidence was found that seed recycling in the informal SS did lead to increased levels of seed-borne pathogens. In contrast to farmers, seed companies distribute seed over large distances, and therefore form a potential threat for spreading diseases at relatively large scale. Responsible authorities are recommended to make seed dressing mandatory for all seeds sold by seed companies.
    Farmers' knowledge and perception of agricutural wetland management in Rwanda
    Nabahungu, N.L. ; Visser, S.M. - \ 2013
    Land Degradation and Development 24 (2013)4. - ISSN 1085-3278 - p. 363 - 374.
    soil fertility - tanzania - adoption - nigeria - water - sustainability - conservation - challenges - ethiopia - impacts
    Most of Rwanda's wetlands are being reclaimed under government schemes with the aim of growing rice as the main crop. In the present study, information on farmers' knowledge and perceptions of agricultural wetland management was collected in Cyabayaga and Rugeramigozi wetlands. The two wetlands were selected as representatives for typical reclaimed wetland agriculture in Rwanda. They provide contrasts in both environmental and social terms. Three tools were used to investigate farmers' knowledge and perception of agricultural wetland management: (i) household survey; (ii) focus group discussions; and (iii) transect walk. The major constraints identified by farmers in the two wetlands were water shortage and lack of availability of improved seeds and high prices of fertilisers. The primary benefits from wetlands for farmers are income generation in Cyabayaga and food security in Rugeramigozi. The most commonly reported concern about the wetlands in the Cyabayaga and Rugerameragozi was that they are a source of malaria. Rice is an important crop in both wetlands, whereas farmers in Cyabahaga wish to continue cultivating rice, Rugeramigozi farmers prefer to grow rice only after it has been tested for its adaptability. Farmers have sufficient knowledge on the causes and the potential solutions to overcome most constraints. They know that soil suitability is closely related to relief. They classify soils by a number of criteria and choose crops accordingly. Any programme designed to address wetland management in the region will have to take account of farmers' knowledge and adopt a holistic view of wetland management
    Characterization of urban and peri-urban agroecosystems in three West African cities
    Abdulkadir, A. ; Dossa, L.H. ; Lompo, D.J.P. ; Abdu, N. ; Keulen, H. van - \ 2012
    International Journal of Agricultural Sustainability 10 (2012)4. - ISSN 1473-5903 - p. 289 - 314.
    farming systems - nigeria - agriculture - water - kano - opportunities - management - scale - land - contamination
    Systems of urban and peri-urban agriculture (UPA) take many forms in terms of integration of different activities, production intensities and production orientations. The present study is aimed at a refined characterization of the diversity in terms of production orientation, resource endowments and production strategies of the different types of farm households involved in urban and peri-urban agriculture in three West African cities. A total of 318 UPA households were surveyed using a standardized semi-structured questionnaire in the West African cities Kano (Nigeria), Bobo Dioulasso (Burkina Faso) and Sikasso (Mali). Through categorical principal component analysis and two-step cluster analysis, six distinct household clusters were identified based on resource endowments and the degree of integration of vegetable, field crop and animal production. Three clusters appeared in all three cities; the remaining three were specific for one of the cities each and comprised (i) commercial gardening plus field crop-livestock (cGCL) keeping, (ii) commercial livestock plus subsistence field cropping (cLsC), (iii) commercial gardening plus semi-commercial field cropping (cGscC), (iv) commercial gardening plus semi-commercial livestock (cGscL) keeping, (v) commercial field cropping (cC) and (vi) commercial gardening (cG). Production constraints were similar across the cities, that is, high costs of inputs, water shortages and lack of fertilizers in the garden and field crop production systems, while feeding constraints and animal diseases were the main constraints in livestock production. UPA remains an important economic activity to livelihood strategy for urban and peri-urban farmers. Appropriate policies should be formulated that efficiently target the site-specific constraints for improving the quality and sustainability of UPA production systems.
    Wood waste minimization in the timber sector of Ghana: a systems approach to reduce environmental impact.
    Eshun, J.F. ; Potting, J. ; Leemans, R. - \ 2012
    Journal of Cleaner Production 26 (2012)May. - ISSN 0959-6526 - p. 67 - 78.
    industrial sector - sustainability - management - challenges - scenarios - forestry - nigeria
    This paper explores the potential of minimizing wood waste to reduce the environmental impact in the timber sector i.e. forestry and timber industry subsystem of Ghana. This study is a follow up of 3 earlier studies on the timber sector. These studies consistently identified minimizing wood waste as a major point of departure for reducing the environmental impact of timber sector of Ghana. When wood waste generated by the 5 wood products were further compared for 3 different functional units (m3, kg or €). The chosen functional unit was sensitive to the wood waste impact results. The results of our study show that combining technological changes, good operational practices and recycling measures could reduce wood waste by approximately 50%. We therefore conclude that the reduction of wood waste in the timber sector may also reduce the other environmental impacts in the timber sector. Since our earlier studies established that wood wastes may function as a reasonable single indicator for land use as proxy for biodiversity loss and the other impact categories.
    Failing to Yield? Ploughs, conservation agriculture and the problem of agricultural intensification: An example from the Zambezi Valley, Zimbabwe
    Baudron, F. ; Andersson, J.A. ; Corbeels, M. ; Giller, K.E. - \ 2012
    Journal of Development Studies 48 (2012)3. - ISSN 0022-0388 - p. 393 - 412.
    resource-poor farmers - land husbandry act - communal area - africa - management - discourse - nigeria
    Agricultural intensification, or increasing yield, has been a persistent theme in policy interventions in African smallholder agriculture. This article focuses on two hegemonic policy models of such intensification: (1) the ‘Alvord model’ of plough-based, integrated crop-livestock farming promoted in colonial Zimbabwe; and (2) minimum-tillage mulch-based, Conservation Agriculture, as currently preached by a wide range of international agricultural research and development agencies. An analysis of smallholder farming practices in Zimbabwe's Zambezi Valley, reveals the limited inherent understanding of farmer practices in these models. It shows why many smallholder farmers in southern Africa are predisposed towards extensification rather than intensification, and suggests that widespread Conservation Agriculture adoption is unlikely.
    Development of a virus neutralisation test to detect antibodies against Schmallenberg virus and serological results in suspect and infected herds
    Loeffen, W.L.A. ; Quak, J. ; Boer-Luijtze, E.A. de; Hulst, M.M. ; Poel, W.H.M. van der; Bouwstra, R.J. ; Maas, H.A. - \ 2012
    Acta Veterinaria Scandinavica 54 (2012). - ISSN 0044-605X
    akabane virus - orthobunyavirus - shamonda - nigeria - cattle - japan
    Background: At the end of 2011, a new orthobunyavirus, tentatively named Schmallenberg virus (SBV), was discovered in Germany. This virus has since been associated with clinical signs of decreased milk production, watery diarrhoea and fever in dairy cows, and subsequently also with congenital malformations in calves, lambs and goat kids. In affected countries, initial surveillance for the infection was based on examination of malformed progeny. These suspicions were followed up by real-time reverse transcription polymerase chain reaction (RT-PCR) on brain tissue. For epidemiological purposes, a serological assay was, however, needed. Results: A virus neutralisation test (VNT) was developed and optimized, and subsequently evaluated. This VNT has a specificity of >99% and the sensitivity is likely also very close to 100%. The assay is highly repeatable and reproducible. The final assay was used to test for antibodies in cows, ewes and does from herds known to be infected or suspected to be so. Targets for sampling in these herds were the mothers of malformed offspring. In herds with an RT-PCR confirmed SBV infection, more than 94% (190 out of 201) of the ewes and 99% (145 out of 146) of the cows were seropositive. In herds with suspicion of SBV infection based on birth of malformed offspring only (no or negative RT-PCR), more than 90% (231 out of 255) of the ewes and 95% (795 out of 834) of the cows were seropositive. In goats, on the other hand, only a low number of seropositives was found: overall 36.4%, being 16 out of 44 goats tested. Conclusions: Given the characteristics of this VNT, it can be used at a relative high throughput for testing of animals for export, surveillance, screening and research purposes, but can also be used as a confirmation test for commercially available enzyme-linked immunosorbent assays (ELISA's) and for (relative) quantification of antibodies. Suspicions of SBV infections that were confirmed by RT-PCR were almost always confirmed by serology in cows. Due to individual registration and identification of cows and calves, affected offspring could almost always be traced back to the mother. Ewes on the other hand were not always the mothers of affected lambs, but were in many cases herd mates with unaffected lambs. This indicated a high within-herd seroprevalence of antibodies against SBV.
    Seroprevalence of Schmallenberg Virus Antibodies among Dairy Cattle, the Netherlands, Winter 2011-2012
    Elbers, A.R. ; Loeffen, W.L.A. ; Quak, J. ; Boer-Luijtze, E.A. de; Spek, A.N. van der; Bouwstra, R.J. ; Maas, H.A. ; Spierenburg, M.A.H. ; Kluijver, E.P. de; Schaik, G. van; Poel, W.H.M. van der - \ 2012
    Emerging Infectious Diseases 18 (2012)7. - ISSN 1080-6040 - p. 1065 - 1071.
    akabane virus - orthobunyavirus - arthrogryposis - infections - australia - shamonda - nigeria - japan
    Infections with Schmallenberg virus (SBV) are associated with congenital malformations in ruminants. Because reporting of suspected cases only could underestimate the true rate of infection, we conducted a seroprevalence study in the Netherlands to detect past exposure to SBV among dairy cattle. A total of 1,123 serum samples collected from cattle during November 2011–January 2012 were tested for antibodies against SBV by using a virus neutralization test; seroprevalence was 72.5%. Seroprevalence was significantly higher in the central-eastern part of the Netherlands than in the northern and southern regions (p
    The quest for sustainable livelihoods : women fish traders in Ibaka, Niger Delta, Nigeria
    Udong, E.E. - \ 2011
    Wageningen University. Promotor(en): Anke Niehof, co-promotor(en): Aad van Tilburg. - [S.l.] : S.n. - ISBN 9789085859345 - 317
    vrouwen - geslacht (gender) - vis - markthandelaars - handel - strategieën voor levensonderhoud - duurzaamheid (sustainability) - duurzame ontwikkeling - visverwerking - marketing - sociologie - hiv-infecties - acquired immune deficiency syndrome - nigeria - afrika - women - gender - fish - market traders - trade - livelihood strategies - sustainability - sustainable development - fish processing - marketing - sociology - hiv infections - acquired immune deficiency syndrome - nigeria - africa

    The contribution of fisheries to food security in Africa cannot be underestimated. It provides

    over 30 percent of the protein consumed by the Nigerian population. However, Nigeria

    produces only about 45 percent of the fish requirement locally while the shortfall of about 55

    percent is imported. Over 80 percent of the local production is from the artisanal, small scale

    sector. While several studies have been conducted on the productivity of many water bodies,

    endemic fish species, different fisheries, boats mechanization and the role of the fishermen,

    socio-economic and gender issues in fisheries have received scant attention. Such research has

    therefore become necessary for the development of relevant policies and intervention

    programmes. The sustainable livelihood approach was used in facilitating the understanding of

    how the women fish traders’ livelihoods are created, sustained and constrained by a set of

    complex factors and processes including institutions and culture. The main objectives of this

    study were to:

    1. Contribute towards the livelihood and gender theory by focusing on the performance of

    women fish traders in the economic and domestic domains in a coastal fishing

    community, given the institutional and cultural constraints, their vulnerability and

    susceptibility to HIV and AIDS;

    2. Identify the implications for household food and livelihood security and the critical

    factors needed to be considered in the development of relevant policies that would

    ensure sustainable livelihoods and lower vulnerability levels for the women fish traders

    and their households.

    Specifically, the study aimed at highlighting the complexity of sustaining rural

    livelihoods by women fish traders in a coastal fishing community in Nigeria and the flexibility

    and variation, which give the fish trading system its continuing ability to link other commercial

    and non-commercial sectors, characterised by constantly shifting relationships. A gender

    perspective was applied throughout the study. The study was carried out in Ibaka, a dynamic

    commercial centre and the largest coastal fishing community in Akwa Ibom State in the Niger

    Delta of Nigeria, which is largely undeveloped but has over 70 percent of the population

    depending on the fisheries for their livelihood. A cross-sectional study design was used, in

    combination with qualitative and quantitative research methods. Apart from being descriptive

    in nature, an analytical approach was also used by arranging and processing the collected data

    in different ways and through testing different hypotheses.

    Due to the large variation in the range and scale of enterprises obtained, the fish traders

    comprise some of the largest wholesalers on the Nigerian coastline and some of the poorest

    strolling hawkers, living from hand-to-mouth. This is a characteristic feature of a major

    market, and the study seeks to identify the key social, economic and institutional forces, which

    generate, maintain and continue to reshape this diversity. The forces originate from the market,

    its links with the household, community, and national level processes, which create conflicting

    interests and pressures on the individual fish traders as they struggle for survival and the

    accumulation of wealth. These contradictions renew and transform the trading relations,

    including their constraints.

    The main household resources available and accessible were the labour of the women

    fish traders themselves and the female members of their families. Through family ties,

    churches, professional associations, social clubs and osusu groups trade networks and social

    churches, professional associations, social clubs and osusu groups trade networks and social

    capital, on which depended success in the fish trade were developed. The economic resource

    was the different species of fish provided by the sea. The physical resources included equipments such as boats, nets, outboard engines, landed properties, houses, and mobile

    phones. The women also used their own trading and language skills, and years of experience in

    the trade to their advantage. Those with sufficient years of education also deployed their

    educational skills to their advantage. The gendered nature of the fish trade and the fact that it

    requires professional skills ensures that labour is expensive to hire. Only very few women fish

    traders, operating on a large scale and earning higher incomes possessed tangible assets, and

    were able to acquire equipments such as outboard engines, fishing and transport boats, and

    other assets such as land, houses, generators, deep freezers, market stalls as well as fish trade

    titles

    Processing and trading in either bonga, big fish or crayfish, and providing labour for

    fish processing remain the main livelihood strategies and the main source of livelihood for

    most women fish traders in Ibaka. Most of the incomes used for the maintenance of their

    children and households are derived from these. Diversification into other economic activities

    including fashion designing, subsistence farming, food processing, money lending, food

    vending and petty trading is also adopted by most women, while the better-off are involved in

    water transportation, equipment leasing, money lending, bukka business. The strategies

    adopted are affected by factors such as age, skills acquired, years of experience, working

    capital available for the trade, educational status, and number and ages of children. Younger

    traders try to acquire other skills and formal education to enable them diversify while the older

    women concentrate on earning higher incomes through developing their social capital,

    expanding their networks, and making better business connections, to enable them diversify,

    educate their children and secure their livelihoods

    The study identifies three groups of women fish traders in Ibaka: the bonga, big fish

    and crayfish traders, who all operate as small, medium and large scale traders, depending on

    the amount of working capital used. Many similarities were observed in the lack of access to

    resources, lack of infrastructural facilities, the mode of recruitment into the trade, the

    involvement of family members, the use of social capital, and the use of incomes for the

    livelihood sustenance of their households. However, significant differences by age, educational

    status, years of experience, working capital and wealth status were observed between the three

    fish trade groups. Big fish traders with older members had more experience, higher working

    capital and incomes, and consequently more assets than bonga and crayfish traders. In

    addition, limited access to resources for most of the poor fish traders, especially from the

    bonga group, forced them into activities that yielded low returns, such as casual labour and

    subsistence farming, re-enforcing their poor performance in the economic and domestic

    domains.

    The study shows that the fish trade is a gendered activity, and the most profitable

    livelihood strategy undertaken for the sustenance of households in Ibaka, providing the women

    with incomes used for the maintenance and upkeep of their households, and the payment of

    their children’s school fees, healthcare bills and other needs.

    However, in spite of their different circumstances, interests and opportunities, the

    women fish traders all face similar risks, shocks and stress, associated with their location and

    environment. These include seasonality, conflicts, and HIV and AIDS, as well as institutional

    and cultural constraints, which make them vulnerable. The institutional constraints identified

    include lack of physical and marketing infrastructure, financial services, and access to

    resources, information asymmetries, high transaction and labour costs, while the cultural

    constraints include the beliefs, taboos, ethnicity, norms, values and family life. The adaptation

    strategies used for the institutional constraints included buying and selling on credit, use of

    social capital and networking, membership of osusu groups, patronising local money-lenders,

    use of family labour, including under-aged children, sourcing for water from shallow wells and

    commercial boreholes for washing and drinking respectively, patronising traditional health

    practitioners and patent medicine stores, and the churches over their health problems. On the

    other hand, the adaptation strategies for the cultural constraints included intermarriage with the

    indigenes, joining associations and clubs, working from home on days of cultural festivals,

    non-pooling of incomes and striving for independence and autonomy.

    Apart from the cultural and institutional constraints the study shows that the fish trade

    is affected by seasonality which is a major cause of vulnerability. During the lean season which

    covers about six months of the year, fishing activities and incomes are reduced to a minimum

    for all the fish species due to high fish prices at the beach and insufficient working capital. The

    traders then experience periods of food shortage and hunger in the household, making them

    highly vulnerable and susceptible to poverty and HIV and AIDS. Fire incidents and conflicts

    also contribute to their vulnerability.

    The study shows that participation in the fish trade is through kinship and marriage, and

    only women who possess specific skills, working capital, available networks and social capital,

    and belong in a certain culture, location and ethnicity can participate. It is also determined by

    household structures, gender division of labour, marriage, residence and inheritance patterns.

    However, in the absence of functional institutions, and with several cultural barriers to contend

    with, the fish trade, which is often regarded as an extension of household tasks embarked upon

    to ensure the livelihood sustenance of the household, is carried out by the women fish traders

    using social networking and social capital, to facilitate their trading profession. Sources of

    social capital include kin, neighbours, friends, matron-client relationships, mutual trust, osusu

    groups, social clubs and associations, norms and values, and churches.

    The study shows that the Ibaka fish market, like most rural food markets in West

    Africa, operates without any supporting structures. It lacks infrastructural facilities and access

    to information, with a non-existent line of communication between the women fish traders and

    the consumers. The provision of an improved communication system, infrastructural facilities,

    credit systems and adequate information would therefore reduce the transaction costs and make

    for a better coordination mechanism in the market. The study also shows that the fish market in

    Ibaka operates through incomplete contract transactions, where it is impossible to reach an

    agreement in advance about all possible events that could affect the exchange. Even though it

    is a rural market dealing with a single commodity, and does not quite fit into the modern urban

    market category, it possesses many attributes of an imperfect market. These include nonhomogenous

    products, fewer buyers and sellers, no market transparency and barriers to entry

    and exit. The various types and degrees of market imperfection characterise Ibaka market as a

    missing market and a thin, incomplete and interlocked market.

    The study shows that performance in the economic domain is mainly determined by the

    women fish traders’ ability to mobilize sufficient working capital from different sources and

    arrange for regular supply of fish, social capital and networking ability, the years of

    experience, skills acquired, the ability to pay for labour, the profitability of the enterprise, level

    of income, the ability to save, their assets base and wealth status, among others. Performance in

    the domestic domain is determined by the ability to educate children, the type of housing, the

    energy type used for lighting and cooking, the health status of the household, and the number

    of hours spent in the household.

    The study shows that performance in both domains is influenced by age, years of

    experience, skills acquired, amount of working capital used, educational status, status of

    mother in the trade, social capital and the number of children. The women fish traders also

    derive potential benefits associated with their location if they successfully adapt to the

    conditions and adopt sustainable livelihood strategies. All these together, affect their

    performance in the economic and domestic domains, and their success at maintaining the

    livelihoods of their households. The big fish and crayfish traders seemed to perform better than

    the bonga traders generally, both in the economic and domestic domains.

    The study also shows that good performance in the economic domain engenders good

    performance in the domestic domain because the possession of sufficient incomes enables the

    women to feed and educate their children, maintain a healthy household and take care of

    themselves. Sufficient incomes also engender the ability to own or live in permanent structures

    in the community and the use of generating sets for lighting and kerosene stoves for cooking in

    the households. However, the lack of basic information and documentation on HIV and AIDS

    in Ibaka has made it impossible to determine how susceptible and vulnerable the women fish

    traders and their families are to the disease even though evidence from fishing communities in

    other countries has shown fisherfolk to be more vulnerable than rural upland populations.

    In conclusion, the resilience of the women fish traders and their survival in the fisheries

    sector can be explained through the rigid and gendered division of labour. This is backed by

    the determination of the women to become independent economically and overcome the

    cultural biases imposed through patriarchy, polygamy and discriminatory inheritance laws.

    Also, there is the incentive of being able to take care of themselves and their children, gain

    some power, agency and autonomy. The realization that men depend on the women to dispose

    of their fish catches, giving the fish economic value, further strengthens the position of the fish

    traders in the fishery economy of Ibaka. The women fish traders’ conversion of profits made

    from the fish trade into ownership of fishing and transportation boats is true entrepreneurship.

    Using new and innovative ways of finding new or acquiring more customers and accumulating

    capital is also entrepreneurial. However, there is far less risk, both socially and economically,

    in expanding the scope in the trade and climbing in the female market hierarchy than in

    investing in a male domain.

    The fact that the women fish traders live in the same community and locality, and are

    exposed to similar institutional and cultural constraints does not mean that there are no

    differences between the three fish trade groups. The constraints impact differentially both

    within and between the groups and the strategic responses depend on the category the fish

    trader belongs to within the group and her wealth status in the trade and the community.

    Environmental factors and processes such as climate change and oil pollution, and the general

    economic crisis, also make fisherfolk vulnerable and susceptible to HIV and AIDS. While the

    government is trying to extend development to the rural areas, it is pertinent that remote

    communities like Ibaka should be specially targeted. Gender mainstreaming should also be

    incorporated in the development process in order to reduce glaring inequalities, with certain

    social groups being marginalized while others are privileged. This will reduce the women

    traders’ level of vulnerability to constraints, stresses, risks, and shocks in our rural

    communities.

    Understanding the diverse roles of soil organic matter in the cereal - Striga hermontica interaction
    Ayongwa, G.C. - \ 2011
    Wageningen University. Promotor(en): Thomas Kuijper, co-promotor(en): Tjeerd-Jan Stomph. - S.l. : s.n. - ISBN 9789085858430 - 131
    striga hermonthica - sorghum bicolor - parasitaire onkruiden - organisch bodemmateriaal - bodemvruchtbaarheid - experimenteel veldonderzoek - stikstof - mineralisatie - beperkingen - gewasproductie - kameroen - nigeria - striga hermonthica - sorghum bicolor - parasitic weeds - soil organic matter - soil fertility - field experimentation - nitrogen - mineralization - constraints - crop production - cameroon - nigeria

    Keywords: Striga hermonthica, Sorghum bicolor, soil fertility, organic matter, N-mineralisation, farmers’ priority, production constraints, intensification.


    The problem of the parasitic weed striga (Striga hermonthica (Del.) Benth.) has worsened for African farmers, in conjunction with degrading soil fertility. An analysis of the striga problem showed that scientists, policy makers and farmers conceptualise striga differently. Whether striga is viewed as a weed or a symptom of degraded soils raises two questions: Should farmers control striga, even when the impact on yields would be negligible? Or should fertility enhancement, leading to higher yields, be their focus, even when not accompanied by an immediate reduction in striga? This study seeks to understand how organic matter inputs affect nutrient dynamics, sorghum (Sorghum bicolor [L.] Moench) production and striga abundance.
    Surveys in northern Cameroon showed that striga infestation increased over the past two decades. Increased land pressure led to reduced fallow periods and enhanced cereal (mono-) cropping. Reduced access to fertiliser and manure hampered options to improve soil fertility. Yields from farmers’ fields did not correlate with striga incidence, confirming farmers’ prioritisation of soil fertility, weeds, and labour as production constraints, rather than striga. The entry point to tackle low yields and the worsening of the striga situation should follow farmers’ priority of alleviating low soil fertility.
    Whether and how soil fertility improvement, through organic matter, enhances agricultural productivity and reduces striga, was investigated in field experiments. Organic matter amendments significantly depressed striga seed survival, with the strongest effect achieved at higher quality; presumably due to higher microbial activity. Organic matter enhanced soil water retention and soil temperature but without effects on striga seed survival. Organic matter did not affect soil ethylene concentrations. The effect of organic matter amendments was directly related to N mineralisation, both for better cereal growth and reduced striga survival. The organic matter amendments and use of fallow, as applied here, however, may not be practicable for the resource-poor farmer.
    Increasing N-fertilisation increased sorghum root N mass concentration, which resulted in a lower striga seed germination. That relationship was linear up to a root N mass concentration of 19.5 mg g-1 where seed germination was close to but always still above 0%.
    In a broader framework of the research findings, the ultimate solution for farm productivity for Africa is in sustainable farm intensification by investing in soil fertility. However, the prevailing land tenure system and limited access to fertiliser and organic matter need to be overcome. A new conceptual model is proposed, indicating how changes in both cereal yield and striga infestation over time co-vary with changes in soil fertility. The implication of this model is that recovery of soil fertility should be the priority. The challenge to agronomists remains to consider how to make farm intensification rewarding and attainable for resource-poor farmers. In areas where striga is an obstacle, an integrated scheme for the intensification of cereal cropping should start with integrated soil fertility management. Crop rotation and intercropping with selected non-host leguminous crops are essential ingredients.

    Striga infestation in northern Cameroon: Magnitude, dynamics and implications for managament
    Ayongwa, G.C. ; Stomph, T.J. ; Hoevers, R. ; Ngoumou, T.N. ; Kuyper, T.W. - \ 2010
    NJAS Wageningen Journal of Life Sciences 57 (2010)2. - ISSN 1573-5214 - p. 159 - 165.
    soil fertility management - sub-saharan africa - hermonthica control - savanna zone - nigeria - land - sahel - productivity - cultivation - challenges
    Surveys of Striga (S. hermonthica (Del.) Benth.) infestation in northern Cameroon over the period 1987–2005 assessed Striga dynamics and evaluated its control strategies. In that period the percentage of Striga-infested fields increased in North and Far-North Provinces. Striga incidence increased more in maize fields than in the already heavily infested sorghum fields, where it remained almost constant. During the study period increased land pressure led to a reduction in the use of fallow and a higher frequency of cereal (mono-) cropping. Yields from farmers’ fields did not correlate with Striga incidence, confirming farmers’ prioritization of soil fertility, weeds, and labour for weeding as production constraints, rather than Striga. We discuss how conceptualization of Striga as a weed in the research arena may have led to a misunderstanding of farmers’ constraints. The decline of the cotton industry reduced farmers’ access to fertilizers, while access to organic manure remained limited, increasing the soil fertility constraint. We conclude that two decades of emphasis on Striga were unsuccessful. Enhanced crop yield through soil fertility management should be the entry point to tackle low yields and further worsening of the Striga situation
    Decision-making for heterogeneity : diversity in resources, farmers' objectives and livelihood strategies in northern Nigeria
    Berkhout, E.D. - \ 2009
    Wageningen : Wageningen UR (Tropical resource management papers 94) - ISBN 9789085856702 - 231
    besluitvorming - natuurlijke hulpbronnen - boeren - bodemvruchtbaarheid - teeltsystemen - gemengde landbouw - rotatie - braaksystemen - landbouwhuishoudens - doelstellingen - bedrijfssystemen - west-afrika - nigeria - ontwikkelingseconomie - strategieën voor levensonderhoud - modelleren - decision making - natural resources - farmers - soil fertility - cropping systems - mixed farming - rotation - fallow systems - agricultural households - objectives - farming systems - west africa - nigeria - development economics - livelihood strategies - modeling
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