Browsing by Subject "Sahel"

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Effects of water management on microclimate and yield physiology in irrigated rice in semi-arid environments
(2014) Stürz, Sabine; Asch, Folkard
Growth and grain yield reductions have been widely observed when traditionally flooded rice fields were subjected to water-saving irrigation measures, where a continuous floodwater layer is avoided. These observations led to the perception of rice being a plant extremely sensitive to soil water deficits even when grown in soils close to their water holding capacity. Since the rice plant’s meristem is below the water surface until the early reproductive stage in flooded fields, the difference in heat capacity between water and air can lead to changes in meristem temperature, when a ponded water layer is omitted. Therefore, the objectives of this study were to quantify the effects of water-saving irrigation on the field’s microclimate and its influence on gas-exchange parameters and to investigate growth and yield parameters under flooded and non-flooded conditions in response to microclimate and varying climatic conditions. On two sites in Senegal, field experiments were conducted, where rice was sown on bi-monthly staggered dates and grown under flooded and non-flooded conditions. In the flooded treatment, a ponded water layer was maintained in the field throughout the growing season, whereas in the non-flooded treatment, irrigation water was applied until soil saturation on a frequent basis, in order to avoid standing water and soil water deficits at the same time. Microclimatic parameters and phenology were observed and leaf gas-exchange and plant growth parameters, yield and yield components were determined. Minimum soil temperature and temperature at meristem level were usually lower without standing water, whereupon temperature differences between irrigation treatments increased with decreasing air temperature. Stomatal conductance depended mainly on minimum soil and meristem temperature and minimum relative humidity inside the canopy. Assimilation rate was positively correlated with solar radiation and soil and meristem temperature, but depended mainly on stomatal conductance. Without standing water, stomatal conductance and assimilation rate were significantly lower, but the results could be explained with differences in microclimate. In most cases, leaf area was reduced under non-flooded conditions. Leaf area expansion rate was correlated with meristem temperature during the night. With minimum meristem temperature being lower under non-flooded conditions, lower leaf area expansion rates under non-flooded conditions could be attributed to lower meristem temperature. Yield reductions under non-flooded conditions were mainly observed in the cold-dry-season, whereas slight yield increases were found in the hot-wet-season. Among the yield components, reduced number of spikelets per panicle and decreased spikelet fertility accounted for the largest share of the yield gap. Leaf area per tiller was positively correlated with meristem temperature in the observed temperature range, and a positive relationship was found between leaf area per tiller and the number of spikelets per panicle. Furthermore, spikelet fertility increased with meristem temperature between panicle initiation and booting stage. Therefore, lower meristem temperature led to smaller leaf area per tiller, less spikelets per panicle and decreased spikelet fertility under non-flooded conditions. We concluded that water-saving irrigation in lowland rice production can lead to growth and yield reductions in comparison to traditional lowland irrigation even in the absence of soil water deficits, due to changes in soil and meristem temperature when a ponded water layer is omitted. Differences in assimilation rate, leaf growth and yield between irrigation treatments increased with decreasing air temperature and a clear seasonal pattern was observed, with large growth and yield reductions in the cold-dry-season, whereas in the hot-wet-season, growth and yield were less affected by irrigation treatment. When water-saving irrigation measures are applied in areas where night temperatures below 20°C occur, the effect of changes in meristem temperature should be considered. To mitigate impairment of growth under water-saving irrigation, a floodwater layer could be used to bridge cool periods, or a less temperature-responsive variety should be chosen. Nevertheless, the physiological mechanisms of the differential effects of day and night temperature remain unknown und need further investigation. Possibly, there is a combined effect of low night temperature and high evaporative demand during the day, which could lead to growth limitations due to restrictions of the plant’s water status. Furthermore, we want to highlight the need for a robust model of water temperature in paddy fields, which should be incorporated in rice growth models, since even tough existing models simulate growth and grain yield under upland and lowland conditions, the effects of changes in microclimate due to irrigation method are inadequately considered so far.
Seedball technology development for subsistence-oriented pearl millet production systems in Sahelian West Africa
(2019) Nwankwo, Charles Ikenna; Herrmann, Ludger
The objectives of this study were to review the potential of the local material-based innovation – i.e. the seedball technology, at enhancing pearl millet seedlings establishment under Sahelian conditions, identify its potential constraints as well as applicability, chemically and mechanically optimize the seedball, and validate its performance under Sahelian field conditions. Seedball is a local seed pelleting techniques that aims at improving seedlings performance and to stabilize yield. First, the potential local materials such as sand, loam, wood ash, gum arabic, termite soil, charcoal as well as animal dung as the seedball components were identified and reviewed. These materials were selected based on their affordability to the local farmers. Potential constraints to seedball applicability as well as adoption in the Sahel were evaluated, and options for adaptation were discussed with the farmers. Afterwards, mechanical and chemical optimization of the seedball technology in several greenhouse experiments were conducted, followed by a germination test of the optimized seedball in the Sahelian field. Lastly, the mechanism of pearl millet seedlings root and shoot enhancement was investigated using micro-suction cup and computer tomography. Our evaluation showed that the materials needed for seedball production are locally available at affordable costs. The seedball technology totally conforms to the agronomic management practices in the African Sahel. In addition, the socio-economic status as well as cultural practices seemed not to reduce the chances of seedball technology adoption in this region. Our greenhouse studies showed that the seedball base dough, from which about ten 2 cm diameter-sized seedballs can be produced, is derived from the combination of 80 g sand + 50 g loam + 25 ml water. Either 1 g mineral fertilizer or 3 g wood ash can be added as nutrient additive to enhance early biomass of pearl millet seedlings. With respect to nutrient additives, ammonium fertilizers and urea hampered seedlings emergence. Wood ash amended (Sball+3gAsh) and mineral fertilizer-amended seedballs (Sball+1gNPK)enhanced shoot biomass by 60 % and 75-160 %, root biomass by 36 % and 94 %, and root length density of pearl millet by 14 % and 28 %, respectively, relative to the control. Again, the mineral fertilizer amended seedball in particular enhanced root dry matter by 227 %, compared to the control. Although the shoot nutrient content was not clearly enhanced by the seedball, nutrient extraction, calculated as the product of biomass yield and nutrient content, was higher in the nutrient-amended seedballs, compared to the conventional sowing. In Senegal, optimized seedballs showed over 95 % emergence in an on-station trial, indicating its viability in the Sahel region. With respect to seedball enhancement mechanism, the mineral fertilizer-amended seedball in particular promoted root growth within the vicinity of the seedball as early as 7 days after planting. The analysis of the sampled soil solution revealed that P as well as other cations and anions, observed through EC measurement, were released by the seedball in direct proximity of the seedball. Most likely, the nutrient release by the seedball triggered the observed fine root growth and overall higher root biomass of pearl millet seedlings. However, due to nutrient depletion in the root zone, nutrient supplementation was needed after three weeks after sowing to further promote growth of the well-established seedlings. At the Sahelian field, where seedlings enhancement is decisive for higher panicle yield in pearl millet, nutrient amended seedballs can potentially increase panicle yield under subsistence production. The seedball technology is cheap, and seems to have favorable conditions for adoption in the Sahel, coupled with its minimal seed usage and simple sowing on the sandy soil. A recommendation will be to conduct long-term, on-farm as well as on-station field trials, testing the seedball technology under different seasonal weather conditions. Pearl millet and sorghum are the major Sahelian staple crops. Fonio (Digitaria spp) is often neglected despite its high nutritional values. It is, therefore, recommended to test the seedball technology on the other fine-grained cereal crops.
Sozio-ökonomische Beurteilung von Innovationen: Untersuchungen über die Innovationenakzeptanz auf Betriebs-Haushaltsebene in Niger
(2004) Haigis, Jörg; Heidhues, Franz
The presented research study deals with the question, which socio- economic and personal characteristics of the heads of household as the main decision persons within the nigerian farm-household-systems influence significantly their adoption behaviour. Simultaneous innovation adoption of thirteen selected different new technologies were in the focus of the study. The study emphasizes especially the time of the adoption state, which could be observed for all considered innovations by all investigated heads of household at a certain reference point of time. The reference point of time is the year 1995. The analysis of the selected farm-household-systems produced an erratic use for most of the thirteen considered innovations over time until first adoption. Simultaneously the adoption behaviour of the household chiefs show a distinct regional emphasis in terms of the adopted technology type. These emphasis merely reflect rudimentary the climatical site conditions in the republic of Niger. They correspond only apparently the climate gradient of the research sites. At drier sites there the households favour particularly resource saving innovations, for which an internal input availability exist. In contrast the farmers put their emphasis on the adoption of labour-saving technologies at the climatical favourable sites. With a closer look there are less the climatical conditions which influence this behaviour than local particularities, especially within the farm-household-systems. Above all this particularities are the limited access of agricultural active women to use the household labour force for the work on their fields. Exclusively women cultivate groundnuts in this region. Thereby the groundnut cultivation is the main activity within the crop production. Groundnut production is predominantly for the women a profitable business through processing. Because of these circumstances in this region exist a well funded demand for wage labour to prepare groundnut fields with animal-drawn implements. The temporal discontinuity of an adopted innovation is found especially for external and yearly obtainable inputs. Accordingly the cumulative behaviour of each household chief show a variable mixture of actual, former and never occurred adoption. Five adopter groups can be found within this complex appearing behaviour situation with the help of cluster analysis methods. The group-specific adoption behaviour rises in an order from low until especially innovative. Except of the low innovative household chiefs, each adopter group show a significant technological emphasis in terms of the type of adopted technologies. This emphasis coincide with the regional one. The order of the adoption behaviour does not correspond with the climate gradient. Neither a comparison of the identified adopter groups with variance analysis nor the econometric analysis using a multi-nomial logit-model resulted in a clear finding that personal or socio-economic characteristics of the household chief influence significantly their adoption behaviour. In fact the results of the logistic regression confirm a high dependency from the location for the observable adoption behaviour. The distinct regional division between high and special innovative household heads on the one side opposite to all others indicates a significant influence on the individual adoption behaviour by local and regional factors. But the question could not be resolved in the context of this farm-household-system based study, wherein these factors are in detail. The adoption of technological innovations shows not only a distinct regional emphasis and a partly temporal discontinuity but also it is characterised by an adaptation in terms of the spatial use of adopted technologies. The farmers cultivate their fields not homogeneously over the whole field area. Rather they apply a kind of site-specific cul¬tivation. In doing so they adapt each cropping measure to the site conditions changing on a small-scale within in a field. This spatial adaptation includes also the adopted innovations. The observable adoption behaviour of the household chiefs points up the basic willingness to use new technologies and with it the change of the previous traditional cropping methods. The identified particularities of the innovation adoption confirm on the one hand the significant adaptation ability of the farmers to the particular local and temporal conditions. On the other hand these particularities are an indication of the inadequate adaptation of the recommended innovations. As a result the success of further efforts to modernise the nigerian agricultural farms depends greatly from the stronger consideration of these particularities in the future development and diffusion of new technologies.