ABSTRACT
Cassava (Manihot esculenta Crantz) is the third most important food crop in Southeast Asia, where it is usually grown by smallholders in marginal areas of sloping or undulating land. Farmers grow cassava because the crop will tolerate long dry periods and poor soils and will produce reasonable yields with minimum inputs. Most farmers realize, however, that cassava production on slopes can cause severe erosion, while production without fertilizer or manure inputs will lead to a gradual decline in soil productivity. Current production practices may thus not be sustainable.
436Research has shown that cassava yields can be maintained for many years with adequate application of fertilizers or manures, and that there are various ways to reduce erosion. Adoption of erosion control practices, however, has been minimal as farmers generally see little short-term benefits, while initial costs of establishing these practices may be substantial.
In order to enhance the adoption of soil conserving practices and improve the sustainability of cassava production under a wide range of socioeconomic and biophysical conditions, a farmer participatory research (FPR) approach was used not only to develop the most suitable soil conservation practices, but also to test new cassava varieties, fertilization practices and cropping systems that tend to produce greater short-term benefits. The FPR methodology was initially developed in two or three sites each in China, Indonesia, Thailand and Vietnam. The methodology includes the conducting of rapid rural appraisals in each site, farmer evaluation of a wide range of practices shown in demonstration plots, trials with farmer-selected treatments on their own fields, field days with discussions to select the best among the tested practices, scaling up of selected practices to larger fields, and farmer participatory dissemination to neighbours and neighbouring communities. Based on the results of these trials, farmers in the pilot sites have readily adopted better varieties, fertilization and intercropping practices, and many farmers have planted contour hedgerows to control erosion.
In the second phase of this project, supported by the Nippon Foundation, the farmer participatory approach for technology development and dissemination was further developed in about 34 pilot sites each in Thailand and Vietnam and in 31 sites in southern China. Farmers were generally very interested in participating in these trials. After becoming aware of the seriousness of erosion in their cassava fields, they have shown a willingness to adopt simple but effective practices to reduce erosion while at the same time obtaining short-term benefits from the adoption of new varieties and other improved practices. The testing by farmers on their own fields of new cassava varieties and fertilization practices in addition to soil conservation practices was found to be of crucial importance for the adoption of more sustainable production practices. The resulting increases in cassava yields in Asia over the past 10 years have increased the annual gross income of cassava farmers by an estimated 270 million US dollars.
Keywords:cassava
erosion control
farmer participatory research (FPR) and extension (FPE)
Thailand
Vietnam
China
impact assessment
