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Most people are under the impression that vegetables grow best in full sunlight, including the people who should know best. But do they? This is one of the questions a research project in West Java sought to answer. “Traditionally, farmers here have worked on the principle that the more sunlight the better when growing vegetables,” says James Roshetko, a scientist with Winrock International and the World Agroforestry Centre. “When we began our research in Nanggung, just 11% of farmers had any experience of intercropping vegetables with tree crops.”
Working in collaboration with Bogor Agriculture University and Winrock International, the World Agroforestry Centre set up a series of on-farm experiments to evaluate the performance of seven species of vegetables, all with a strong market demand, under three different light regimes, ranging from full sunlight to low light.
For six of the vegetables – amaranth, kangkung, eggplant, chilli, tomato and katuk – production per plant was higher under medium light than under full sunlight. Amaranth, for example, produced 15.3 g per plant under medium light, compared to 5.5 g under sunlight; eggplant produced 833 g and 488 g respectively. When assessed in terms of production per area, amaranth and chilli both achieved higher yields per hectare under medium light than under full sunlight, even though the presence of trees meant there was less space available for vegetables. Furthermore, production costs per kilogram were lower for all vegetables under medium light. Less labour was required for weed control as the tree shade reduced weed growth.
“The research suggests that these vegetables grow best under the conditions which are found in one of the main agroforestry systems practised in West Java, where farmers grow fruit trees, timber trees, banana and annual crops in one integrated system,” says Roshetko. He also points out that the research was conducted during a year of lower than average rainfall, and the vegetables benefitted from being in medium shade as they had lower rates of evapo-transpiration. Nevertheless more research needs to be done on the quality of vegetables under different light conditions, and the appropriate crop rotations, the study provides valuable evidence about the benefits of understory vegetable production. This is precisely the sort of information the extension services need if they are to help farmers improve their productivity.
Long before agrochemical companies developed synthetic pesticides, farmers were using substances found in wild plants to control insects and other creatures that threatened their crops and livestock. However, relatively little research has been done on the subject and knowledge about ‘pesticidal’ plants is scanty. A research programme conducted by scientists from the World Agroforestry Centre, the Royal Botanical Gardens, UK, and the Natural Resources Institute, UK, in partnership with universities in Malawi and Zimbabwe, has shed new light on the importance of these plants for farmers in Zambia and Malawi.
Scientists interviewed over 260 farming families about their use of pesticidal plants and conducted laboratory tests to analyse the active ingredients of selected species and their efficiency. “We found that most farmers were very knowledgeable about the pesticidal properties of a large number of plants,” says Gudeta Sileshi of the World Agroforestry Centre, “although they use relatively few on a regular basis.”
One of the most popular concoctions was made from the leaves of Tephrosia vogelli. This is sprayed in liquid form on vegetables to protect them from insects and used as a dry compound to deter weevils in granaries. The researchers found that it was just as effective as some commercial pesticides. Since many farmers use it as a fertiliser tree – it helps to enhance soil fertility – it is widely available.
However, other useful pesticidal species appear to be suffering from overharvesting and habitat loss, and their use is therefore restricted. Efforts are now being made to domesticate some species. For example, protocols have been developed for the propagation of Securidaca longependuculata and Bobgunnia (Swartzia) madagascariensis, which are high-value pesticidal and medicinal plants.
“More research needs to be done, both on the species used and on duration of time for which the active ingredients are effective,” says Sileshi. Safety issues also need to be better researched. For example, some farmers use an extract of the monkey orange, Strichnos spinosa, to protect their livestock from ticks, but the active ingredient, strychnine, is highly toxic (and also used as a rodent poison). Sileshi believes that green pesticides could play a much more important role in protecting farmers’ crops, livestock and food stores in future, but that will only happen if policies and incentives support the necessary research and development.
In 2010, a farmer-led initiative supported by the World Agroforestry Centre in Cameroon was one of just 25 recipients of the biennial Equator Prize, which recognises and celebrates outstanding community efforts to reduce poverty through conservation. RIBA Rural Resource Centre provides training in agroforestry, nursery management, watershed protection, apiculture and microfinance to the farming communities who live in the mountainous Northwest Region. During recent years, the number of farmers planting nitrogen-fixing tree crops has risen, as have crop yields, and the average number of trees planted per household has increased from 10 to over 120.
RIBA is one of several resource centres which are training farmers on how to domesticate wild species of fruit tree. “The Equator Prize recognises the tremendous work which has been done by the resource centre and local farmers,” explains Zachary Tchoundjeu, World Agroforestry Centre’s Regional Coordinator for West and Central Africa. “It is also international recognition of the importance of the participatory tree domestication approach that we have pioneered.” This story is told in ‘Trees for Change’ Booklet No. 4, The Fruits of Success. |
