Habitat management strategies for the control of cereal stemborders and striga in maize in Kenya

Maize is the principal food and cash crop for millions of people in the predominantly mixed crop-livestock farming systems in Kenya. Stemborers and striga (Striga hermonthica) are major constraints to increased maize production in eastern Africa. An intercropping and trap crop system has been developed, using a 'push-pull' strategy, for the control of stemborers in small scale maize farming systems. The 'push-pull' strategy involves trapping stemborers on highly susceptible trap plants (pull) and driving them away from the crop using repellent intercrops (push). Napier grass (Pennisetum purpureum Schumach) and Sudan grass (Sorghum vulgare sudanense Stapf.) are used as trap plants, whereas molasses grass (Melinis minutiflora Beauv.) and two species of desmodium (Desmodium uncinatum Jacq. and Desmodium intortum Urb.) repel ovipositing stemborers. The integrated 'push-pull' strategies were shown to increase parasitism of stemborers through attraction of parasitoids to one of the intercrops, molasses grass. The leguminous intercrop, silver leaf desmodium, drastically reduced damage to maize by the parasitic weed, striga. This aspect was further investigated and developed for integration with stemborer control. On-farm trials with farmers in Kenya have shown significant yield increases in maize farming. RÉSUMÉ Le maïs est la principale nourriture et culture commerciale pour des millions de personnes pratiquant le système agricole prédominant au Kenya, associant la culture et l'élevage. Les foreurs des tiges et le striga (Striga hermonthica) sont les contraintes majeures de l'accroissement de la production de maïs en Afrique de l'Est. Un système de cultures associées et pièges, utilisant une stratégie de répulsion-attraction, à été développé pour contrôler les foreurs des tiges dans les petites exploitations agricoles. La stratégie de répulsion-attraction consiste à piéger les foreurs de tiges sur des plantes pièges fortement attractives (attraction) et à les éloigner de la culture en utilisant des cultures associées répulsives (répulsion). On utilise l'herbe à éléphants (Pennisetum purpureum Schumach) et l'herbe du Soudan (Sorghum vulgare sudanense Stapf) comme plantes pièges tandis que l'herbe à mélasse (Melinis minutiflora Beauv) et deux espèces de desmodium (Desmodium uncinatum Jacq. et Desmodium intortum Urb.) repoussent les foreurs de tiges prêts à pondre. La stratégie de répulsion-attraction permet d'augmenter le parasitisme des foreurs des tiges en attirant les parasitoïdes vers l'une des cultures associées, l'herbe à mélasse. L'association du desmodium à feuilles argentées (Légumineuse), réduit de façon drastique les dégâts causés au maïs par l'herbe parasite striga. Ce résultat a été approfondi et développé pour être associé avec la lutte contre les foreurs des tiges. Des essais au champ réalisés avec des fermiers au Kenya ont montré des augmentations de rendements significatives dans la culture du maïs

Management of Napier stunting disease

A poster prepared on stunt disease management in Keny

ARPN Journal of Agricultural and Biological Science INFLUENCE OF PHOSPHORUS ON SELECTED DESMODIUM GROWTH AND NODULATION PARAMETERS

ABSTRACT Phosphorus is known to affect growth and formation of nodules although its role in the process is less understood. Several workers have, however, related phosphorus nutrition with rhizabial activities in leguminous plants. In other studies, it has been shown that nodules are stronger sinks for phosphorus-compared roots, shoots and even young mature leaves. We initiated this study to determine the effect of phosphorus on selected desmodium species growth and nodulation parameters in a pot experiment. A 2 by 8 factorial experiment was laid in a complete randomized design (CRD) at KARI-CYMMIT Research Station located in western Kenya. Pots were each filled with 7.5 kg 2 mm sieved dry soil. The treatments consisted of two desmodium species (D. intortum and D. uncinatum) and 8 levels of phosphorus applied at 0, 10.3, 20.6, 30.9, 41.2, 51.5, 61.8 and 72.1 mg P kg -1 soil. The experiment was replicated 3 times. Plants were top dressed with urea (at 85.5 mg N pot -1 ) at 21 days after emergence (DAE). Shoots were harvested twice during the growth period (at 15 and 28 weeks after planting) while dry root weight and nodulation parameters were determined at 34 wap. Results showed that shoot biomass produced in the second harvest was 21% and 42% higher than production in the first harvest for D. uncinatum and D. intortum, respectively. Root biomasses was significantly (p = 0.045) increased at 41.2 mg P kg -1 soil compared to the control treatment in the D. uncinatum plant while D. intortum had significant increase in root weight at ≥ 30.9 mg P kg -1 soil. Addition of phosphorus in excess of these rates did not translate into gain in biomass except at 72.1 mg P kg -1 soil. Application of phosphorus at ≥ 20.6 mg P kg -1 soil significantly (p = 0.039) increased the number of nodules produced by D. intortum species from an average of 37 (control) to 86.8 nodules -1 pot at 51.5 mg P kg -1 soil. The number of active nodules obtained in the control treatment was significantly (p = 0.041) low compared to that obtained at 30.9 mg P kg -1 soil in the D. uncinatum species. Whereas D. uncinatum produced few but heavy nodules, D. intortum had relatively large number and light nodules, phosphorus rates not withstanding. Relationships between nodule number and root biomass are also discussed

Assessing Crop-Livestock Interaction in Mixed Farming Systems of North Western Kenya

A study was conducted in the four counties the maize- wheat-teapotato and sugarcane-based farming system in North western Kenya to explore the variability among household characteristics and farm productivity. The aim of this work was to establish homogenous groups of crop-livestock mixed farming systems of Kenya. A two step approach was adopted for the study. The first was a rapid rural appraisal followed by a formal survey aimed at establishing farm types to facilitate detailed analysis of synergistic crop-livestock interaction systems. A random sample of 423 farmers was interviewed using a semi structured questionnaire. Descriptive and multinomial techniques were used in the analysis. Two classifications were utilized, the first step was establishing the criteria for classification and the second based on resource accessibility by farmers. The criteria used were the proportions of various crop and livestock enterprises and resource endowment. The process came up with eight farm types based mainly on the farm enterprise orientation, farm size, land productivity, cattle breeding, and farm by-products. Based on the formal survey three farm types were identified as intensive, semi intensive and extensive systems. The resource groups in all the counties were identified by: crop-livestock management, soil fertility management, food security and farm and off-farm income as important indicators of variability. However, all households were net food buyers, implying food insecurity. In addition, off-farm activities and off farm income were important livelihood survival strategies. Development planners and policy makers need to develop unique interventions targeting each specific group, since blanket policies are not appropriate in such a situation. Options such as optimizing livestock numbers to match available feed resources and improving feed availability through breeding and adoption of dual-purpose crop varieties with better digestibility coefficient, improving the cost-effectiveness of existing nutrition technologies (e.g. crop-by-products’), and bringing more land under fodder crops need to be explored. Since the farm sizes within the region had continued to decline, limiting the availability of on-farm livestock feed, there is need for policy instruments that can discourage land fragmentatio

Problem Formulation and Options Assessment (PFOA) for genetically modified organisms: the Kenya case study

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