The introduction of conservation agriculture (CA) for smallholders increased the competition for crop residues between crop and livestock enterprises of the mixed smallholder farming system. Smallholders practicing CA have resorted to using grass and leaf litter in addition to available crop residues. The effect of these different mulching materials on maize (Zea mays L.) growth and yield is not well documented in smallholder CA systems of southern Africa. A two-year experiment was run in 2012/13 and 2013/14 seasons to evaluate the effect of maize residues, grass (Hyparrhenia filipendula (L.) Stapf.) and leaf litter that farmers are currently using and residues from leguminous species, sunhemp (Crotolaria juncea L.) and Tephrosia (Tephrosia vogelii ((Hook) f.)) on maize nitrogen (N) uptake, growth and yield. Significant differences in soil water content across treatments were only observed during March in 2012/13 season. Maize residues retained more soil water and Tephrosia had the lowest soil water content when seasonal rainfall pattern was erratic. Grass and Tephrosia treatments had the lowest chlorophyll content. Conventional ploughing, maize residues and leaf litter had similar chlorophyll content which was significantly higher than grass and Tephrosia treatments. At a site with higher initial soil fertility conventional ploughing treatment out yielded the other treatments by 727–1265 kg ha−1. With more degraded sandy soil conventional practice had 119–430 kg ha−1 more maize grain than the CA treatments. With adequate fertilization, the mulching materials have a similar effect on maize growth in basins and direct seeding. Further studies on different application rates of mulching materials and mineral N fertilizer, and nutrient release patterns of these residues are critical in order to better understand soil fertility management under smallholder CA systems.
Source: Open Access Journals
Authors: O’Dell, D.; Sauer, T.J.; Hicks, B.B.; Thierfelder, C.; Lambert, D.M.; Logan, J.; Eash, N.S.
Published in: Journal of Agricultural Science, 7(3): 32-48, 2015.
Two of the biggest problems facing humankind are feeding an exponentially growing human population and preventing the accumulation of atmospheric greenhouse gases and its climate change consequences. Refined agricultural practices could address both of these problems. The research addressed here is an exploration of the efficacy of alternative agricultural practices in sequestering carbon (C). The study was conducted in Zimbabwe with the intent to (a) demonstrate the utility of micrometeorological methods for measuring carbon dioxide (CO2) exchange between the surface and the atmosphere in the short-term, and (b) to quantify differences in such exchange rates for a variety of agricultural practices. Four Bowen ratio energy balance (BREB) systems were established on the following agricultural management practices: (1) no-till (NT) followed by planting of winter wheat (Triticum aestivum), (2) NT followed by planting of blue lupin (Lupinus angustifolios L.), (3) maize crop residue (Zea mays L.) left on the surface, and (4) maize crop residue incorporated with tillage. Over a period of 139 days (from 15 June to 31 October 2013) the winter wheat cover crop produced a net accumulation of 257 g CO2-C m-2, while the tilled plot with no cover crop produced a net emission of 197 g CO2-C m-2 and the untilled plot with no cover emitted 235 g CO2-C m-2. The blue lupin cover crop emitted 58 g CO2-C m-2, indicating that winter cover crops can sequester carbon and reduce emissions over land left fallow through the non-growing season. The micrometeorological methods described in this work can detect significant differences between treatments over a period of a few months, an outcome important to determine which smallholder soil
management practices can contribute towards mitigating climate change.
Published in Environmental Management, 2013
Ndah, H.T.; Schuler, J.; Uthes, S.; Zander, P.; Traore, K.; Gama, M.-S.; Nyagumbo, I.; Triomphe, B.; Sieber, S.; Corbeels, M.
Despite the reported benefits of conservation agriculture (CA), its wider up-scaling in Sub-Saharan Africa (SSA) has remained fairly limited. This paper shows how a newly developed qualitative expert assessment approach for CA adoption (QAToCA) was applied to determine its adoption potential in SSA. CA adoption potential is not a predictor of observed adoption rates. Instead, our aim was to systematically check relevant factors that may be influencing its adoption. QAToCA delivers an assessment of how suitable conditions “and thus the likelihood for CA adoption” are. Results show that the high CA adoption potentials exhibited by the Malawi and Zambia case relate mostly to positive institutional factors. On the other hand, the low adoption potential of the Zimbabwe case, in spite of observed higher estimates, is attributed mainly to unstable and less secured market conditions for CA. In the case of Southern Burkina Faso, the potential for CA adoption is determined to be high, and this assessment deviates from lower observed figures. This is attributed mainly to strong competition of CA and livestock for residues in this region. Lastly, the high adoption potential found in Northern Burkina Faso is explained mainly by the fact that farmers here have no alternative other than to adopt the locally adapted CA system—Zaï farming. Results of this assessment should help promoters of CA in the given regions to reflect on their activities and to eventually adjust or redesign them based on a more explicit understanding of where problems and opportunities are found.
Published in Agriculture, Ecosystems and Environment, 2013
Andersson, J.A.; D’Souza, S.
This literature review of Conservation Agriculture (CA) adoption among smallholder farmers in southern Africa (Malawi, Zambia and Zimbabwe) analyses the historical background of the upsurge in CA promotion, the various definitions of CA that have emerged since the 1990s, the barriers to its adoption, as well as uptake figures and adoption studies. First tested as soil and water conservation measures, large-scale promotion followed a reframing of CA as a production-enhancing set of practices. Different definitions of what constitutes and is promoted as CA in southern Africa complicates the assessment of adoption across the region, while a commonly used, reductionist notion of CA adoption – as the uptake of minimum tillage – in adoption data collection, casts doubts on the validity of adoption figures. As CA uptake is often also incentivized by means of input support (fertilizers, seeds, herbicides) provided by promotional projects, adoption claims have limited value. Current CA adoption studies are methodologically weak as they are biased by the promotional project context in which are carried out, and build on farm-scale analyses of standard household surveys. A more thorough analysis of farming households and their resource allocation strategies is required to understand the farm-level adoption constraints different types of farmers face. As contextual factors appear key influences on smallholders’ farming practices, studies focusing on the wider market, institutional and policy context are also needed if we are to understand (limited) CA adoption in southern Africa.
Published in Food Policy 34(4): 377-387, 2009
Assessing the effectiveness of a technical assistance program: The case of maize seed relief to vulnerable households in Zimbabwe
Augustine S. Langyintuo and Peter Setimela
The recent economic downturn in Zimbabwe impoverished the majority of households. To assist vulnerable rural households improve their food security, the British Department for International Development implemented a seed relief program from 2003/2004 to 2005/2006 that emphasized recycling of maize open pollinated varieties (OPV). Using data collected from 597 households in six districts in 2006, this study assesses the effectiveness of the program in terms of its targeting of beneficiaries, the flow of information from participating NGOs to beneficiaries on the need to recycle the seeds, and the level of recycling done at the end of the program. The empirical results suggest that the targeting method participating NGOs use inadvertently excludes relatively vulnerable households while including large proportions of relatively well-endowed households in the program. The choice of varieties to distribute is guided more by the ecological adaptability of available commercial seeds and less by preferences of beneficiaries. Notwithstanding the fact that seed selection information is critical in encouraging beneficiaries to recycle distributed seed, not all of them received it. In conclusion, it may be stated that the program undoubtedly contributed to increased food productivity by vulnerable households but its overall effectiveness could have been enhanced through (i) the involvement of the beneficiaries in the choice of types of seed to be distributed, (ii) better targeting of beneficiaries, and (iii) improved information flow between NGOs and beneficiaries.