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Inga alley cropping as an agrometeorological service to slash and burn farmers

Last modified July 20, 2007 08:13

According to Chris Geerling (2004) from the Working Group on Ecology and Development of the Netherlands Commission on International Nature Conservation, the wide ranges of (Low External Input) farming systems found in Africa - but the same applies to great parts of Latin America and Asia - is a reflection of the range of variation in the nature and the availability of the natural, economic and human resources, under widely varying geographical, climate, governance and political conditions. Farming systems under these conditions mean playing the given deck of a whole series of low-value cards, with risk reduction as the main operative, rather than maximalisation of production (Geerling, 2004).

By KEES STIGTER

 

According to Chris Geerling (2004) from the Working Group on Ecology and Development of the Netherlands Commission on International Nature Conservation, the wide ranges of (Low External Input) farming systems found in Africa - but the same applies to great parts of Latin America and Asia - is a reflection of the range of variation in the nature and the availability of the natural, economic and human resources, under widely varying geographical, climate, governance and political conditions. Farming systems under these conditions mean playing the given deck of a whole series of low-value cards, with risk reduction as the main operative, rather than maximalisation of production (Geerling, 2004).


Slash and burn agriculture contains several of such farming systems in which coping with risk reduction by farmers destroys forests. In such systems the soil quickly becomes infertile. In an example on the acid soils of the Costa Rican rain forest this was already the case after two years (Elkan, 2005, 2006). According to this author, based on research by the British tropical ecologist Mike Hands, alley cropping with Inga edulis is an agroforestry solution for such farmers in Costa Rica, Honduras and elsewhere that will make it possible to get into (more) sedentary farming as an alternative to slash and burn farming.


Agroforestry essentially has various agrometeorological components (e.g. Stigter, 1988). Alley cropping is an agroforestry system in which crops are grown in alleys formed by trees of which pruned biomass is used as mulch. This is incorporated into the soil for fertility and soil structure (water holding) improvement or spread over the soil as a surface mulch (Stigter, 1984). Surface mulches protect the soil from too strong solar radiation as well as too strong rainfall impacts. They also minimize weed growth by shade and smothering and provide nutrients according to their rates of decomposition (e.g. Stigter, 1984).


Alley cropping in semi-arid areas remained largely unsuccessful due to too low biomass accumulation and too high competition between crops and trees (e.g. Mungai et al., 1995; 2001). It may have there some benefits on sloping lands due to positive effects on runoff and soil loss (e.g. Kinama et al., 2007). In sub-humid to humid areas success with alley cropping on marginal soils is more likely but has also not been without difficulties (Carter, 1995).


In some alley cropping, shade of the trees is important against weeds and surface drying before their pruning. This is also the case in the Inga alley cropping design that therefore has a good set of agrometeorological aspects and may be treated as an agrometeorological service to the farmers concerned, at the same time providing the needed nutrients.


It is the merit of Hands’ work that it first determined in a participatory approach with the Costa Rican farmers the problems of weed infestation and fast loss of productivity after slash and burn had taken place (Elkan, 2005, 2006). They were clearly in need of an alternative. It is another merit of Hands’ work that he found the lack of phosphorus to be the main limiting soil factor due to fast leaching from the soil after slash and burn (Elkan, 2005, 2006).


He then designed a system in which the conditions found in virgin tropical forests were mimicked: minimize weed growth – first by tree shading then by leaf mulches – and recycle nutrients, including phosphorus, through slow leaf decomposition, by using thick leaved nitrogen fixing trees providing sufficient biomass under the local climate conditions without too limiting competition.


After this system worked well with maize crops in Costa Rica, Honduran slash and burn farmers further developed the alley cropping of Inga with maize and beans and with pepper as well as vanilla. Moreover, the trees do provide a not unimportant amount of fuelwood. In Honduras an organic supplement of rock phosphate is used. The main remaining problem is the necessity to have seed orchards of Inga trees because the pruning for mulch prevents fruit setting. This is a seriously limiting factor to the speed with which the system can spread (Elkan, 2005, 2006).


What science now could additionally contribute is a quantification of such systems in the way this was done by Mungai et al. (2000) in Kenya. Together with crop experiments this would ameliorate the design criteria and therefore improve the efficiency of such systems and the possibilities of transfer of their valuable basic merits to still other conditions. This is how design development of agrometeorological services of this kind is at its best, in collaboration with soil scientists, social scientists, botanists, agronomists and ecologists (WMO, 2006).

 

References


Carter, Jane, 1995. Alley farming: have resource-poor farmers benefited? ODI Natural Resource Perspective No. 3, ODA, London, 4 pp.


Elkan, Daniel, 2005. The rainforest saver. The Ecologist, ECOLOGISTONLINE, 8 pp., www.theecologist.co.uk/archive_detail.asp


Elkan, Daniel, 2006. An alternative to slash and burn. In: Farming matters: understanding sustainable agriculture. LEISA Magazine on Low External Input and Sustainable Agriculture, Special Issue (pp. 15 - 16).


Geerling, Chris, 2004. Hunger in Sub-Saharan Africa. Discussion paper available from the author of this paper.


Kinama, J.M., C.J. Stigter, C.K. Ong, J.K. Ng’ang’a and F.N. Gichuki, 2007. Contour hedgerows and grass strips for erosion and runoff control in semi-arid Kenya. Arid Land Res. Managem. 21: 1-19.


Mungai, D.N., 1995. A microclimatological approach to understanding maize yield performance in alley cropping in the semi-arid areas of Machakos district, Kenya. In: C.J. Stigter, F.J. Wang'ati, J.K. Ng'ang'a and D.N. Mungai (Eds.), The TTMI-project and the "Picnic"-model: an internal evaluation of approaches and results and of prospects for TTMI-Units. Wageningen Agricultural University (pp. 111 – 123).


Mungai, D.N., C.J. Stigter, C.L. Coulson and J.K. Ng'ang'a, 2000. Simply obtained global radiation, soil temperature and soil moisture in an alley cropping system in semi-arid Kenya. Theor. Appl. Climat. 65: 63 -78.


Mungai, D.N., C.J. Stigter, C.L. Coulson, J.K. Ng'ang'a, G.W.S. Netondo and G.O. Umaya, 2001. Understanding yields in alley cropping maize (Zea Mays L.) and Cassia siamea (Lam.) under semi-arid conditions in Machakos, Eastern Kenya. J. Environm. Sc. 13: 291 - 298.


Stigter, C.J., 1984. Mulching as a traditional method of microclimate management. Arch. Meteorol. Geoph. Biocl. B 35: 147 - 154.


Stigter, C.J., 1988. Microclimate management and manipulation in agroforestry. In: K.F. Wiersum (Ed.), Viewpoints on Agroforestry. Second renewed edition. Agricultural University, Wageningen (pp.145 – 168).


WMO, 2006. Commission for Agricultural Meteorology (CAgM). The first fifty years. WMO-No. 999, Geneva, 44 pp.

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