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Spearheading Imperata control

Large areas of land are often abandoned due to Imperata infestation (Jim Ellis-Jones, Silsoe Research Institute)
Large areas of land are often abandoned due to Imperata infestation
Jim Ellis-Jones, Silsoe Research Institute

The battle against weeds is never an easy one. In the humid savannah of West Africa, farmers are finding the fight daunting and even dangerous as one particular weed, commonly known as speargrass, causes damage above and below ground. Chemical control is an option but is it a practical alternative for smallholder farmers? The results of trials with over one thousand farmer groups in Nigeria seem to indicate that it is.

Traditionally Imperata cylindrica was controlled under long fallow systems. But, as fallow periods have decreased and soils have become less fertile, this invasive weed has taken over large tracts of land with farmers often resorting to burning, even when aware that this practice is actually stimulating the growth of the weed rather than suppressing it. In addition, the weed grows tall and sharp causing injuries to people as they walk through fields, and cuts to their hands, upper body and eyes when weeding. And with rhizomes often thicker than a finger, which can pierce through the tubers of yam and cassava, yields can be seriously affected. Finally, as the weed takes hold, land is abandoned. Cultivation continues but only at the expense of further deforestation and land degradation.

Effective extension

Promising methods for control of Imperata have been developed in recent years by the International Institute of Tropical Agriculture (IITA) in partnership with National Agricultural Research Agencies. These include use of leguminous cover crops, improved crop agronomy as well as application of herbicides. However, despite the potential of these approaches, adoption has been slow and researchers have had to reconsider the links between research, extension and farmers. The way forward has been to collaborate with a broader base of interested parties, including the national agricultural research and extension services, NGOs, CBOs, farmer organisations and the private sector.

Lead farmers representing between 15 to 30 households have become the focal point within each community for testing and demonstrating the options for improved weed management. Training in leadership, communication, weed biology and control has promoted farmer to farmer dissemination, and extension agents and regional scientists have improved their communication of good weed management. The outcome has been trials for testing the use of glyphosate, the planting of Mucuna puriens as a leguminous cover crop and a combination of the two. Other methods have included the use of improved cassava cultivars that shade the Imperata. Farmer evaluation of the weed management techniques so far has ranked the use of the glyphosate as the most effective approach to controlling Imperata, particularly in maize and cassava. Interestingly, a number of women's groups have favoured the use of Mucuna, when used in conjunction with glyphosate.

Results to dye for

Farmer research group comparing cassava yields (right - herbicide only left - herbicide and mucuna) (Jim Ellis-Jones, Silsoe Research Institute)
Farmer research group comparing cassava yields (right - herbicide only left - herbicide and mucuna)
Jim Ellis-Jones, Silsoe Research Institute

But although glyphosate can be effective - how affordable is it for farmers? Jim Ellis-Jones, Participatory Extension and Farming Systems Specialist at the Silsoe Research Institute, explains that use of herbicides has to be put into perspective. "On talking to farmers, you realise the huge amount of labour that goes into weed control - not only the households' own labour but often hired labour. And we realise that they are spending considerable time, up to 70 per cent in controlling Imperata, time which is lost for doing more productive activities." But spray equipment is often inefficient and farmers have little knowledge of dilution rates, calibration and safe application. Jim Ellis-Jones agrees that these were certainly issues that had to be addressed so a key part of the project has been to work with local chemical companies in training farmers and spray contractors. Training has involved mixing a blue food colourant with the herbicide to demonstrate inefficient application and leakage onto clothes and skin - a good visual lesson not just for herbicide use but for application of insecticides, which tend to be more toxic.

Research is continuing to make glyphosate application cheaper and more effective through the use of additives that allow the active ingredient within the chemical to be reduced. The chemical companies are now realising that if the herbicide is made cheaper, easier and safer to use then demand for the product will continue to increase. Interestingly, it has been observed that in order to eradicate the weed, many farmers are prepared to pay more money than previously supposed in higher than recommended applications.

So far the collaborative project for sustainable weed management for Imperata has worked with over one thousand farmer groups in Benue, Cross River and Kogi States of Nigeria. Results have been encouraging but ultimately success will only be assured if local government, extension services and the chemical companies continue to use the participatory approaches that have been developed during the course of this project, and farmers continue to benefit once research funding comes to an end in 2004.

*Collaborative partners: International Institute for Tropical Agriculture; Federal University of Agriculture, Makurdi; Silsoe Research Institute; Local Government and State Extension services (Benue, Cross-River and Kogi); Diocese Development Services of the Catholic Church

Date published: January 2004


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