Green manure and inorganic fertiliser as management strategies for witchweed and upland rice

Weed infestation, especially the Witchweed (Striga asiatica) is a serious problem in fertility-depleted soils of Tanzania. The use of urea fertiliser is known to control weed but resource-poor farmers cannot afford thistechnology due to high costs involved. To alleviate the problem of Striga and soil fertility, green-manure applications could be an alternative strategy. Ths study was conducted to (a) evaluate the potential of green manure against Striga, and (b) determine the potential of inducing Striga suicidal germination by selected green manures. For the first part of the study, treatments included three green manure species, Crotolaria ochlroleuca G. (sunhemp), Mimosa invisa L.(Colla) and Cassia obtusifolia L.(Sicklepod) superimposed with three fertiliserrates 0, 25 and 50 kg N ha-1. The treatments were laid out in a randomised complete block design (RCBD). In the second study part, the 3 green manure species were evaluated for their potential to stimulate Striga seed germination in the laboratory and the field. Results showed that green manure applications significantly reduceStriga infestation, resulting in significant rice yield increases. Green manure exhibited potential to induce suicidal germination of Striga. Based on these findings, green manure  applications should be promoted especially among smallholder resource-poor farmers as a strategy for control of Striga infestation in rice fields. Additionally, croprotation using rice and C. ochlroleuca is the best option since it reduces Striga infestation and increases yield of rice

Green Manure and inorganic Fertiliser as Management Strategies for Witchweed and Upland Rice

Weed infestation, especially the Witchweed ( Striga asiatica ) is a serious problem in fertility-depleted soils of Tanzania. The use of urea fertiliser is known to control weed but resource-poor farmers cannot afford this technology due to high costs involved. To alleviate the problem of Striga and soil fertility, green-manure applications could be an alternative strategy. Ths study was conducted to (a) evaluate the potential of green manure against Striga, and (b) determine the potential of inducing Striga suicidal germination by selected green manures. For the first part of the study, treatments included three green manure species, Crotolaria ochlroleuca G. (sunhemp), Mimosa invisa L.(Colla) and Cassia obtusifolia L.(Sicklepod) superimposed with three fertiliser rates 0, 25 and 50 kg N ha-1. The treatments were laid out in a randomised complete block design (RCBD). In the second study part, the 3 green manure species were evaluated for their potential to stimulate Striga seed germination in the laboratory and the field. Results showed that green manure applications significantly reduce Striga infestation, resulting in significant rice yield increases. Green manure exhibited potential to induce suicidal germination of Striga. Based on these findings, green manure applications should be promoted especially among smallholder resource-poor farmers as a strategy for control of Striga infestation in rice fields. Additionally, crop rotation using rice and C. ochlroleuca is the best option since it reduces Striga infestation and increases yield of rice.Désherber l'infestation surtout de witchweed ( Striga asiatica ) est un problème sérieux dans les sols de fertilité réduite de Tanzanien. L'usage de l'urée est connu pour contrôler les mauvaises herbes mais les agriculteurs avec les ressources pauvres ne peuvent pas se permettre ces technologies en raison des hauts coûts impliqués. Pour alléger le problème de de Striga , les applications de fumier vert pourraient être une stratégie alternative. Cette étude a été dirigée pour (a) évaluer le potentiel de fumier vert contre Striga, et ( b) déterminer le potentiel d'induire la germination suicidaire de Striga pour des fumiers verts choisis. Pour la première partie de l'étude, les traitements ont inclus trois espèces de fumier verte, Crotolaria ochlroleuca G. (Sunhemp), le Mimosa invisa L. (Colla) et Cassia obtusifolia L. (Sicklepod) a superposé avec trois taux d'engrais 0, 25 et 50 kg N ha-1. Les traitements ont été faits dans une conception des blocs complètement aléatoire (RCBD). Dans la deuxième partie d'étude, la 3 espèce de fumier verte a été évaluée pour son potentiel de stimuler la germination de semence de Striga dans le laboratoire et le champ. Les résultats ont montré que l'application de fumier vert réduit significativement l'infestation de Striga, avec comme résultat des augmentations de rendement de riz significatives. Le fumier vert a exposé le potentiel pour induire la germination suicidaire de Striga. A la lumière de ces résultats l'application de fumier vert devrait être surtout promues parmi le petit exploitant agriculteurs pauvre comme une stratégie de contrôle d'infestation de Striga dans les champs de riz. En plus, la rotation de récolte utilisant du riz et C. ochlroleuca est la meilleure option puisque il réduit l'infestation de Striga et augmente le rendement de riz

Pedological and soil fertility characteristics of striga infested soils under maize in Chunya and Iringa districts of Tanzania

Enhancing Dissemination of Soil and Water Research Outputs of SADC UniversitiesMaize yields in both Iringa and Chunya districts have been reported to be low due to infestation with Striga. A study was therefore conducted to characterize Striga infested soils and assess their fertility status under maize production in 6 villages of Chunya and Iringa districts. The soils of Iringa were classified as Cambisols and those of Chunya as Arenosols. The results further showed that, the majority of the soils were of sand to loamy sand texture. Such soils are well drained with low water holding capacity, conditions that favour Striga germination. The fertility status was established through physical and chemical analyses of the soils. One hundred and four composite soil samples were collected from the two districts. Laboratory analysis showed that most of the soils were acidic with pH ranging from 4.13 to 7.74 and low to medium cation exchange capacity (CEC). Organic carbon was low with a range of 0.01 to 0.07% while total N values were also low ranging from 0.028 to 0.86%. Phosphorus was low with few samples indicating medium values. Exchangeable bases were generally low with most soils having saturation values of < 50%. Overall, the soils are of low fertility status. The low fertility status and the sandy texture are possibly the cause of high Striga infestation and low maize yields in the two districts. The soils are of low productivity requiring improvement of their organic matter content and application of inorganic fertilizers if improved maize yields are to be realized. It is further recommended that tillage practices that improve the soil physical conditions be adopted, not only for greater maize yields but also as one of the strategies to control the Striga weed. Key words: fertility, maize, soil, strig

Participatory appraisal of institutional and political constraints and opportunities for innovation to address parasitic weeds in rice

Parasitic weeds in smallholder rice production systems, of which Striga asiatica, Striga hermonthica and hamphicarpa fistulosa are the main representatives, form an increasing problem for food and income security in sub-Saharan Africa (SSA). The objective of this paper is to identify institutional and political constraints and opportunities for innovation to address parasitic weed problems in rice. Constraints and opportunities for innovation were studied across three nested systems: the parasitic weed control system, the crop protection system, and the agricultural system. Multi-stakeholder workshops, interviews and surveys were held to gather data on key constraints faced by different stakeholder groups across three parasitic weed infested study sites in both Tanzania and Benin. The results demonstrate that in both countries, the majority of institutional and political constraints relate to the functioning of the broader crop protection and agricultural systems and not specifically to parasitic weeds. Although differences were observed between the two countries and the different stakeholder groups, the majority of constraints perceived by the stakeholders were caused by a lack of capabilities and resources and a limited access to credit. Awareness raising of parasitic weed problems among farmers, extension and crop protection officers at the local level, combined with improved input and service supply and enhanced agricultural education and training curricula at the national level, were identified as important elements for improvement. More structural collaboration between key stakeholder groups is expected to contribute to a better recognition of agricultural problems, like that of parasitic weeds in rice, and a more timely identification of feasible solutions

Rapid Appraisal of Agricultural Innovation Systems (RAAIS): constraints and opportunities for innovation in controlling parasitic weeds in rainfed rice production in Tanzania

Agricultural Innovation Systems (AIS) approaches have been advocated as a framework for integrated and holistic analyses of complex agricultural problems. The potential of AIS approaches to address complex agricultural problems remains largely unexplored. One of the reasons is the lack of a coherent set of conceptual and methodological building blocks that can provide insights into the (added) value of the AIS approach. This paper presents RAAIS, an ex-ante diagnostic tool that can support the analysis of AIS. RAAIS provides a first characterisation of complex agricultural problems, and the agricultural system in which the problem is embedded. RAAIS offers insight into the most relevant system dimensions, multilevel interactions, and the constraints, needs and interests of multiple stakeholders. In this study, we reflect on the application of RAAIS in the analysis of parasitic weed problems in rainfed rice production in Tanzania. Semistructured interviews, farmer and extensionist surveys and multistakeholder workshops were held in three districts in Tanzania where parasitic weeds are prevalent. The results show that, in Tanzania, the national crop protection system focuses on the control of (insect) pests and diseases, and not on weed prevention, which is essential for addressing parasitic weed problems effectively. Constraints along the rice value chain concentrate around the limited use of clean (certified) rice seed, which facilitates the spread of parasitic weed seeds through the informal rice seed system. Weeds, and parasitic weeds in particular, receive little attention in the agricultural research and training system in Tanzania. Consequently, extension and crop-protection officers have limited knowledge of parasitic weeds and how to effectively prevent and control them. More general challenges relate to the lack of policy coherence and coordinated action between public and private stakeholders in the agricultural system. We conclude that RAAIS can facilitate the delineation of AIS boundaries and the effective selection and action-oriented use of other, more in-depth, systems tools to enhance innovative capacity in agricultural systems

Pedological and soil fertility characteristics of striga infested soils under maize in Chunya and Iringa districts of Tanzania

Enhancing Dissemination of Soil and Water Research Outputs of SADC UniversitiesMaize yields in both Iringa and Chunya districts have been reported to be low due to infestation with Striga. A study was therefore conducted to characterize Striga infested soils and assess their fertility status under maize production in 6 villages of Chunya and Iringa districts. The soils of Iringa were classified as Cambisols and those of Chunya as Arenosols. The results further showed that, the majority of the soils were of sand to loamy sand texture. Such soils are well drained with low water holding capacity, conditions that favour Striga germination. The fertility status was established through physical and chemical analyses of the soils. One hundred and four composite soil samples were collected from the two districts. Laboratory analysis showed that most of the soils were acidic with pH ranging from 4.13 to 7.74 and low to medium cation exchange capacity (CEC). Organic carbon was low with a range of 0.01 to 0.07% while total N values were also low ranging from 0.028 to 0.86%. Phosphorus was low with few samples indicating medium values. Exchangeable bases were generally low with most soils having saturation values of < 50%. Overall, the soils are of low fertility status. The low fertility status and the sandy texture are possibly the cause of high Striga infestation and low maize yields in the two districts. The soils are of low productivity requiring improvement of their organic matter content and application of inorganic fertilizers if improved maize yields are to be realized. It is further recommended that tillage practices that improve the soil physical conditions be adopted, not only for greater maize yields but also as one of the strategies to control the Striga weed. Key words: fertility, maize, soil, strig