Agricultural intensification in West Africa Nutrient dynamics in the Kano close-settled zone in Nigeria show that farming can be intensified without damaging the environment, and in some cases improving it. Small-holder farming in semi-arid areas is being forced to change to compensate for the needs of more people living under conditions of increasingly variable rainfall. As more land is used for agriculture, rangeland areas are reduced, so limiting the availability of animal fodder. The length of fallow periods where soil fertility may be restored is also reduced. This has forced herders and farmers to interact, exchanging crop residues (fodder) for animal manure (soil fertility restoration). As competition for these resources intensifies, some livestock herders started farming land to provide crop residues as fodder and farmers started rearing their own livestock. The Kano close-settled zone in Nigeria is one example of high intensity farming systems in semi-arid areas, which have evolved under local market conditions. The systems of the Kano close-settled zone in Nigeria (Bache and Harris, 1994, Harris, 1994 and Mortimore, 1993) and the Mossi plateau, Burkina Faso (Prudencio, 1993), and Machakos, Kenya (Tiffen, et al. 1994) show that farming can be intensified without damaging the environment, and in some cases improving it. The unique example of the Kano close-settled zone, where population densities of up to 500 per kmē have been reached and farming intensity has been at 100% since 1964 (Mortimore, 1993) without resulting in obvious land degradation, has prompted the study of nutrient dynamics within this farming system to determine if nutrient inputs and outputs are in balance, and how farmers maintain soil fertility. Detailed study The farming system of the Kano zone is based on the cultivation of four main crops (millet, sorghum, groundnut and cowpea), on farmed parkland bearing economically valuable trees and on the production of livestock (mostly small ruminants, with some cattle and donkeys). The long-term rainfall (1906-1985) is 822 mm, distributed in a unimodal pattern between May and September, however in recent years the rainfall has been below average. Rainfall during the study was 565 mm in 1993 and 895 mm in 1994. The study was conducted in a village composed of a farming community in a rural setting, located approximately 40 km east of Kano, about 10 km from any tarred road. The detailed nature of the study meant that it was impossible to consider large numbers of farmers across the Kano zone. Therefore it focused on a case study of a few farmers, which has provided valuable detailed data. The study has monitored the activities of three farmers within the zone through two farming seasons, focusing on the use of livestock manure, inorganic fertilisers, compound waste, the Harmattan dust which bears nutrients, biological nitrogen fixation by leguminous crops and the nutrient content of the harvest of farmers' fields to determine a nutrient balance (nitrogen, phosphorus, potassium, calcium and magnesium in 1993, nitrogen and phosphorus only in 1994). The objective was to identify sources and destinations of soil nutrients, and how they are transferred through the farming so that soil fertility is maintained. Nutrient dynamics The results were calculated for each farmer's field and then combined to provide information on the nutrient balance for each farmer's landholding. The farmers' nutrient balances vary from field to field, depending on fertilisation practices and crop rotations. Farmers may rotate the application of manure or use of inorganic fertiliser across fields over several years. Planting a legume crop ensures a large nitrogen input to that field through fixation. Year to year variability depends on rainfall, and its effect on nutrient removal in yields, and the subsequent effect on fodder and manure supplies for the following year. It is the balance of nutrients over time that determines sustainability. Despite the small scale of this study the results provide a detailed understanding of nutrient dynamics within the farming system allowing us to make informed judgements about what may be happening in the system as a whole, and its potential for sustainability. Farmers practices recycle nutrients through the farming system as much as possible. Nutrients are gained through nitrogen fixation and the use of inorganic fertiliser (nitrogen and phosphorus) and through the Harmattan dust (cations and micronutrients), and lost when crops are sold. The key to the success of the farming system is crop-livestock integration, involving the recycling of nutrients within the system as much as possible. Crop residues, especially those of legume crops, are used as animal fodder. Leguminous residues are transferred to the compound at harvest, where they are used to feed livestock which are tethered in the compound during the rainy season. Small ruminants convert the "free" nitrogen fixed by legumes into manure when legume crop residues are used as fodder. Their manure, together with compound waste, is returned to the fields during the following dry season. During the dry season livestock roam the field grazing cereal crop residues. Occasionally Fulani herds pass through the area, however estimates of the contribution of manure from grazing animals to the nutrient balance proved quite negligible. Farmers did not enter into contracts with herders to exchange crop residues for manure. While millet and sorghum are grown as staples of the farmers' diet, groundnuts and cowpeas are grown to fix nitrogen and provide fodder. Storage difficulties prevent farmers from trying to store these legume crops for their own household consumption. The sale of these crops, and occasionally any excess cereal grain and any unused stalks and fodder earns cash with which farmers can purchase inorganic fertiliser. Farmers can also earn money in other ways, such as labouring, rope and mat making, or practising trades. Population density and labour In studying the Kano close-settled zone we have observed the point in the intensification process at which all land is under cultivation, all palatable crop residues are used for fodder and trees are conserved. As a result we have a better understanding of how the farming system works, and the rational of an indigenous farming system. Northern Nigeria has much higher population densities than its neighbouring francophone countries. Our results contrast with those of other workers. Researchers in francophone west Africa have calculated the amount of rangeland required to support the livestock necessary to provide sufficient manure to maintain annual production of cereal crops on 1 ha without reducing soil fertility (Schlecht et al, 1995, Turner, 1994). Calculations vary, but about 23-40 ha of rangeland is required to support 1 ha of cropland. This corresponds to a cropping intensity of 2.4 - 4.2%. The focus of discussion at a conference on the role of livestock in nutrient cycling in sub-Saharan Africa was the limit to agricultural production as dictated by manure and fodder supply (Powell et al, 1995). Research carried out in Niger, Burkina Faso, Mali and Senegal under similar rainfall regimes does not suggest that these areas could develop farming systems as intensive as that of the Kano zone. Yet results from the Kano zone and other areas show that farming can exceed this land-use intensity for many years. Areas of higher population density are characterised by higher livestock density (Bourn and Wint, 1994, Hendy, 1977), they also have more labour available to transport manure from compounds to fields, and so increase soil fertility. The research results differ because less densely populated areas are subject to labour scarcity, which limits agricultural intensification. In studies carried out in the francophone countries of west Africa with lesser population density and farming systems where average landholding size ranged from 3 - 10 ha, farmers did not find it worth their while to transfer fodder to the compound and tether livestock, then return the composted manure to fields. Livestock holdings were insufficient to provide enough manure to fertilise such large landholdings, even if sufficient fodder was available (Williams et al, 1995). Although some legumes are grown, the farmers have not yet realised the role that legumes can play in providing fodder for livestock, nitrogen through biological nitrogen fixation, and a saleable cash crop to enable purchases of inorganic fertiliser. This discussion shows the importance of labour to agricultural intensification. The introduction of new technology will only succeed if the household is in a position to adopt such new practices, i.e. if there is sufficient labour. Development must coincide with the advent of conditions conducive to change. Frances Harris, Dept of Geography, University of Cambridge, Downing Place, Cambridge CB2 3EN, UK. This paper presents work carried out as part of the study "Nutrient budgets in relation to the sustainability of indigenous farming systems in northern Nigeria" funded by the Natural Resources Institute, UK and carried out at the Departments of Geography of the University of Cambridge, UK, and Bayero University, Kano, Nigeria. ILEIA Newsletter Vol. 11 No. 4 p. 16 References - Bache, BW and Harris, FMA. 1994. Nutrient budgets in relation to the sustainability of indigenous farming systems in northern Nigeria. Outline report of first year's work. Agronomy and Cropping Systems Programme, Natural Resources Institute, UK. - Bourn, D and Wint, W. 1994. Livestock, land use and agricultural intensification in sub-Saharan Africa. Pastoral development network discussion paper, ODI. - Mortimore, M. 1993. The intensification or peri-urban agriculture: The Kano close-settled zone, 1964 - 1986. In: Turner, BL, Kates, RW and Hyden, G. (eds). Population growth and agricultural change in Africa. University Press of Florida. - Powell, JM, Fernandez-Rivera, S, Williams, TO and Renard, C (eds). 1995. Livestock and sustainable nutrient cycling in mixed farming systems of sub-Saharan Africa. Vol II: Technical papers. Proceedings of an international conference held in Addis Ababa, Ethiopia, 22-26 November 1993. International Livestock Centre for Africa. Addis Ababa, Ethiopia. - Prudencio, CY. 1993. Ring management of soils and crops in the West African semi-arid tropics: The case of the Mossi farming system in Burkina Faso. In: Agriculture, Ecosystems and Environment 47, 237-264. - Schlecht, E, Mahler, F, Sangar, M, Susenbath, A and Becker, K. 1995. Quantitative and qualitative estimation of nutrient intake and faecal excretion by Zebu cattle grazing natural pasture in semi-arid Mali. In: Powell et al. 1995. Livestock and sustainable nutrient cycling in mixed farming systems of sub-Saharan Africa. - Tiffen, M Mortimore, M and Gichuki, F. 1994. More people, less erosion: environmental recovery in Kenya. J. Wiley. - Williams, TO, Powell, JM and Fernandez-Rivera, S. 1995. Manure utilisation, drought cycles and herd dynamics in the Sahel: implications for cropland productivity. In: Powell et al. 1995. Livestock and sustainable nutrient cycling in mixed farming systems of sub-Saharan Africa. Further reading - Harris, FMA. 1994. Farmers' management of soil fertility: a case study from the Kano close-settled zone. Research for development in the arid zone of Nigeria. Centre for Arid Zone Studies, University of Maiduguri, Nigeria. - Hendy, CRC. 1977. Animal production in Kano state and the requirements for further study in the Kano close-settled zone. Land Resources Report 21, Land Resources Division, Ministry of Overseas Development. << country/story review