Development of Visual Extension Material for a Striga Control Programme in Northern Ghana through Action Research.
Abstract In the last two decades, research has developed techniques to control the parasitic weed Striga sp. (Scrophulariaceae), one of the worst pests in the West African Sahel. Yet, some of the control measures are economically not viable, at least not in the short-run, others cure part of the problem only, while some require changes of the entire farming system. The complexity of the problem demands an integrated control approach with solutions that are flexible enough to match the diversity and variability of the farming systems. A better understanding of the parasite's biology by farmers will encourage them to appreciate the current complex and time-consuming Striga control measures. Such an approach calls for close collaboration between researchers, extensionists and farmers. Through action research, a picture supported group extension programme was developed, which was characterised by a shift from a teaching-centred to a learner-centred extension approach in Northern Ghana. The cost for developing...
Putting it into practise
Emphasis has been made on various control options and their combination in an integrated approach in the previous chapter. In this section, the aspect of how to make use of research findings and on how to assist farmers in reducing the threat by parasitic weeds on their livelihood will be the main emphasis.
Influence of Microvariability in Sandy Sahelian Soils on Millet Growth
Microvariability is assumed to be a constraint on crop production in the Sahel zone. Causes and development of microvariability were studied for millet (Pennisetum glaucum [L.]) on sandy soils. A descriptive model for the development of soil and millet growth microvariability is presented. The investigations (Ct, Nt, Pt, NO3-, PBray 1, soil respiration, crop-growth parameters) on two differently managed fields (fallow/crop rotation, continous cropping) at the ICRISAT Sahelian Centre, Sadore, Niger, show that mainly biological factors (pre-clearing vegetation, termites) lead to soil microvariability. The organic matter cycle, especially the mineralized nitrate at the beginning of the rainy season, is decisive for the development of crop microvariability in an early stage. Water balance simulation demonstrates that the grain yield can be influenced later, especially during flowering, by water stress. 
 
 
 
Der Einflus der Mikrovariabilitat sandiger Boden auf das Hirsewachstum im Sahel 
 
 
 
Mikrovariabilitat ist ein begrenzender Faktor fur den Pflanzenbau in der Sahelzone. Ursachen und Entwicklung der Mikrovariabilitat wurden fur Perlhirse (Pennisetum glaucum [L.]) auf sandigen Boden untersucht. Ein deskriptives Modell fur die Entwicklung der Mikrovariabilitat der Boden und des Pflanzenwachstums wird vorgestellt. Die Untersuchungen (Ct, Nt, Pt, NO3-, PBray 1, Bodenatmung, Ertragsparameter) auf zwei unterschiedlich bewirtschafteten Feldern des ICRISAT Sahelian Centre, Sadore, Niger, ergaben, das hauptsachlich biogene Faktoren (Brachevegetation, Termiten) die Boden-Mikrovariabilitat verursachen. Der Kreislauf der organischen Substanz, speziell der Nitratgehalt am Anfang der Regenzeit, ist entscheidend fur die Entstehung der Mikrovariabilitat des Pflanzenwachstums in der fruhen vegetativen Phase. Wasserhaushaltssimulationen zeigen, das in einem Jahr der Kornertrag starker durch Wassermangel wahrend der Blute beeinflust wurde.