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Background:In southern Africa, conservation agriculture (CA) has received a lot of research and promotional support from various organizations in the past decades. Conservation agriculture is largely promoted as one of the few win-win technologies affordable to farmers, in the sense that potentially it improves farmers' yields (in the long term) at the same time conserving the environment. This is because conservation agriculture reduces nitrogen loss in the soil, promotes water and soil conservation and improves agronomic use efficiency of applied nutrients. However, some concerns have been raised over the feasibility of conservation agriculture on smallholder farms given constraints imposed by the biophysical and institutional realities under which smallholder farmers operate. The main aim of this study is to answer the question whether conservation agriculture is resulting in tangible livelihood outcomes to smallholder farmers. The counterfactual outcome approach was used to estimate ex post impact of conservation agriculture adoption on one of the key livelihood outcomes-food security. Results:The study that utilized a data set covering 1623 households in Zimbabwe, Malawi and Mozambique found no significant impact of conservation agriculture adoption on Food Consumption Score of farmers in Zimbabwe and Malawi. Possible reasons for the insignificant of CA impact on food security in Zimbabwe and Malawi could include the small land areas currently devoted to CA, and the failure to implement the full complement of practices necessary to set off the biophysical process that are expected to drive yield increases. In Mozambique, conservation agriculture significantly improved the Food Consumption Score for farmers exposed to the technology. A possible reason for effectiveness of CA in Mozambique could be due to the fact that often CA is being promoted together with other better cropping management practices such as timely weeding and improved seed varieties, which are poorly practiced by the generality of farmers in a country just emerging from a war period. Conclusion:This paper provides one of the few ex post assessments of the impact of conservation agriculture adoption on household livelihood outcomes-food security. Given the mixed findings, the study suggests that conservation agriculture farmers in the three countries need to be supported to adopt a value chain approach to conservation agriculture. This entails the introduction of commercial or high-value crops in the conservation agriculture programmes, value addition on farmers produce, access to the necessary support services such as markets for seed, fertilizer, herbicides and equipment as well as reliable extension. We believe that under such circumstances conservation agriculture can effectively reduce food insecurity and poverty in the medium to long term.

To measure the yield and financial returns from five grain legume-maize intercrop combinations over 12 years of cropping, a field experiment was conducted on a loamy sand soil in the subhumid unimodal rainfall environment of Domboshava in north-central Zimbabwe. Inputs and management followed smallholder practice, including partial grazing of crop residues and a zero mineral fertilizer treatment. The intercropped legumes grew moderately well most years. Cowpea averaged the highest grain yield (0.244 t ha −1 ) and haulm yield (1.54 t ha −1 ) over the 12 years, followed by pigeonpea and sugar bean. Intercropped pigeonpea yield was the least variable of the legumes over the years. Maize grain yield was highly variable across years with or without fertilizer and was reduced in years of low (533 mm) and high (1313 mm) rainfall. The pigeonpea-maize intercrop grown without fertilizer produced 0.11 t ha −1 (6.25 %) more maize grain yield per year than sole crop maize, in addition to pigeonpea grain and haulms. Intercropped cowpea (which yielded more than double the above-ground non-grain biomass of pigeonpea) had less effect on maize grain yield. There was no trend to greater benefits from the legumes on maize yield after more years of intercropping. Net present values of annual margins accumulated over the 12 years for sole maize with fertilizer (US$1719 ha −1 ) and without fertilizer (US$935 ha −1 ) were higher than the fertilized and unfertilized intercropping options (US$1017 and US$745 ha −1 ). Pigeonpea or cowpeaunfertilized maize generated more financial returns than the other intercrops, but the low yields and high labour costs for the legumes made the intercrops financially unattractive. We conclude that regularly intercropped pigeonpea or cowpea can to a small extent help to maintain maize yield when maize is grown without mineral fertilizer on sandy soils in sub humid zones of Zimbabwe, and simultaneously provide some nutritious food, but that financial considerations will encourage smallholder farmers to persist with growing low input sole crop maize.