Conservation agriculture and rainfall variability in Zambia: is CA a promising option for responding to droughts and floods? Umar BB1, Nyanga PH2 1 Department of International Environment and Development Studies, Norwegian University of Life Sciences, P.O Box 5003, NO-1432Ås. Norway;
[email protected] 2 Geography Department, School of Natural Sciences, University of Zambia, P.O Box 32379 Lusaka, Zambia Keywords: rain-fed agriculture, adaptation, climatic risks, food security, crop production Introduction Smallholder farmers of Sub-Saharan Africa (SSA) face a lot of risks in their agricultural production. For those in dry-land areas, major risks are related to rainfall and other climatic factors. Water stress in the root zone during critical crop development stages is a fundamental constraining factor contributing to the low yield levels of smallholder farms in such environments. Farmers use a range of approaches, to deal with climatic and other risks, such as choice of crop and crop varieties, use of fertilizer, planting density, water harvesting (Aune and Bationo, 2008). Conservation Agriculture (CA) is one agricultural system being promoted in dry-land areas of SSA as a response option to extreme climatic events such as droughts and floods. CA is a tillage sequence that minimizes or reduces the loss of soil and water and achieves at least 30% soil cover using crop residues (Mazvimavi & Twomlow 2009). It has recently been suggested that the main benefit of the basin variant of CA in water scarce tropical environments may be an in-situ water harvesting effect (Enfors et al, 2010). Since smallholder farming in SSA is mostly rain-fed and susceptible to intra and inter seasonal droughts, the water harvesting effects of CA basins could prove to be a solution to this problem. With the adoption of CA, yield levels could be stabilized (FAO 2011). While the benefits of CA in drought-prone regions have been widely documented, performance of CA in high rainfall areas has been more limited. Problems of water-logging from Nkhotakota District of Malawi have been documented (Ngwira et al, 2009). FAO (2011) acknowledged that there were limited benefits of CA in sub-humid environments during years with adequate rainfall as yields could be affected by water-logging. This is one reason why promotion of CA in Zambia has been concentrated on the low rainfall regions. Haggblade and Tembo (2003) noted that the highest adoption rates of basins in Zambia had occurred in the low rainfall regions. While there is literature on performance of basins in low rainfall areas and also for high rainfall areas, there is limited information on the performance of CA basins in drought-prone or low rainfall areas during incidences of high rainfall or flooding. Models of future rainfall trends in Zambia have predicted that low rainfall areas will experience an increase in flooding incidences (GRZ 2007). We report on CA performance during flooding episodes in areas that are normally characterized by low rainfall and droughts. Materials and Methods Three provinces were selected as study areas based on variations in agro-ecology and on past and current efforts in the promotion of CA. These were the Southern, Central and Eastern provinces of Zambia. Questionnaires were administered to 640 randomly selected households between June and September 2007. These were households that were under the Conservation
Agriculture Programme under the auspices of the Conservation Farming Unit (CFU) of the Zambia National Famers’ Union. The same households were interviewed again in 2008 and 2009 although the sample size reduced to 535 in 2008 and 486 in 2009 due to migration due to floods, deaths, and absenteeism. The sampled households were asked questions on their agronomic practices, farming expenditure, and crop yields. The crop yield data obtained from the surveys were correlated with the rainfall data for the areas. Key informants included agriculture extension staff involved in CA and long time residents of the study areas. Two focus group discussions were conducted each consisting of eight CA farmers. Discussions focused on experiences with CA under drought and flooding regimes. Results The farming households surveyed over the three year period allocated up to 25% of their cultivated land to CA. The percentage of total land area under CA increased steadily during the three farming seasons although the average area under CA remained the same during the 2007/8 and 2008/9 farming seasons. The percentage increase was as a result of the reduction in the area under conventional agriculture (CV) (Table 1). The average maize yields were 3.4 tons ha-1 in the 2006/7 farming season but only 0.77 tons ha-1 in the 2007/8 farming season. There were no statistically significant differences in the rainfall received during the 2006/7 and 2007/8 farming seasons (p=0.838). Both seasons had above normal rainfall. The above normal rainfall of 2006/7 did not seem to negatively affect maize yields while that of 2007/8 resulted in significantly lower yields (p=0,003). This finding reaffirms the importance of not only the average amount of rainfall that is received per season but its onset and distribution. ZVAC (2008) observed that the rains experienced in Zambia during the 2007/8 season were atypical not only in their intensity but in their distribution. They covered the usually drought stricken low-lying areas of southeastern Zambia and caused flash floods. FAO (2011) reported that the occurrence of intra-seasonal dry spells that coincide with critical stages of crop growth rather than total seasonal rainfall per se may complicate crop establishment and reduce yields. The same may apply to incidences of flooding. The households seemed to have responded to the floods and the lower yields of the 2006/7 farming season by reducing the area under CV and maintaining the area under CA the following season. Table 1: Land area allocation to CA/CV and Maize yields Season 2006/7 2007/8 2008/9 Average area under CA (ha) 0.22 0.42 0.42 % of cultivated area under CA 11.5 16.5 24.9 Average area under CV 1.69 2.12 1.27 Total cultivated area (ha) per household 1.91 2.54 1.69 Average Maize yield (tons/ha) 3.39 0.77 1.65 Average rainfall (mm) 1046.3a 1086.8a 858.6b CV = Conventional agriculture. This includes the use of mould board plough and traditional hand hoe for tillage. a Means followed by the same letter in row are not statistically different at p≤ 0.05 probability level.
Analysis of the area under CA revealed that the households allocated 0.19ha, 0.31 ha and 0.28ha to basins in the 2006/7, 2007/8 and 2008/9 farming seasons respectively. The figures for ripped areas were 0.04ha, 0.11ha and 0.14 ha respectively. The area under basins was
slightly reduced while the ripped area continued to increase. Focus group discussions and key informants suggested that problems of water-logging were reported in basins during the years of above normal rainfall. The continued increase in ripped area may be a demonstration of the farmers’ confidence in the tillage system under flooding conditions. Farmers reported that they dealt with the problem of water-logging in basins during incidences of above normal rainfall by backfilling the basins completely and/or making ridges. Such sentiments as “we (CA adoptors) were more food secure than our friends who did not use CA…Most of us do harvest quite enough for household consumption either during flood year or drought year while our friends who depend on CV little and mostly nothing…” Other studies have shown that farmers argued that early land preparation and planting associated with conservation agriculture increased chances of survival of the maize crop from floods and increased water retention capacity under CA contributed to higher crop production than under CV during a drought year (Nyanga et al. 2011). We conclude that there is potential for higher production under CA than under CV during incidences of both drought and floods among the Zambian smallholder farming References Aune, J. B., Bationo, A.,(2008). Agricultural intensification in the Sahel - The ladder approach. Agricultural Systems, 98 (2): 119-125. Enfors, E., Barron, J., Makurira, H., Rockström, J., Tumbo, S. Yield and soil system changes from conservation tillage in dryland farming: A case study from North Eastern Tanzania. Agricultural Water Management, In Press, Corrected Proof DOI: 10.1016/j.agwat.2010.02.013. FAO. (2011). Climatic Risk Analysis in Conservation Agriculture in Varied Biophysical and Socio-economic Settings of Southern Africa. Johannesburg: Regional Emergency Office for Southern Africa ( REOSA). GRZ (2007). The National Adaptation Programme of Action (NAPA). Ministry of Tourism Environment and Natural Resources. Lusaka, Government of Republic of Zambia/Global Environment Facility/United Nationsa Development Fund. Haggblade, S. & Tembo, G. (2003). Development, Diffusion and Impact of Conservation Farming in Zambia. Lusaka: Food Security Research Project. Mazvimavi, K. & Twomlow, S. (2009). Socioeconomic and institutional factors influencing adoption of conservation farming by vulnerable households in Zimbabwe. Agricultural Systems, 101 (1-2): 20-29. Ngwira, A. R., Mwale, C.D., Kabambe, P., Wall. P., Thierfelder, C., Bunderson, T. (2009). proposal to release conservation agriculture technology for use by farmers in malawi. Lilongwe, malawi, Chitedze Research Station Nyanga P H., Johnsen,F.H., Jens, A.B (2011) The conservation agriculture project (CAP). Monitoring and evaluation report 2009/2010,Noragric, Ås ZVAC. (2008). Multi-Sectoral In-Depth Vulnerability and Needs Assessment. Lusaka.: Zambia Vulnerability Assessment Committee (ZVAC).
