Outcomes

In general the research-extension program has successfully introduced and brought benefits of soybean BNF to thousands of smallholder families, exploding the myth that the crop is too sophisticated for them to manage. The results of work to extend promiscuous soybean to smallholders in southern Africa and Nigeria have already been reviewed (Mpepereki et al. 2000). Promiscuous soybean has enabled farmers with no access to commercial inoculants also to adopt soybean. Up to 50% of soybean produced in Hurungwe district in northern Zimbabwe in the last three seasons (1998-2000) was promiscuous, while in Zambia promiscuous Magoye still forms the backbone of smallholder soybean production (Javaheri, 1996). Promiscuous soybean effectively nodulated with indigenous rhizobia, fixed 82-92% of their N with amounts ranging from 46-73 kg N/ha without inoculation and produced a larger biomass and contributed more N to the cropping system (Table 1).

Table 1. Maize yields for two seasons following soybean in a sandy loam soil in a smallholder farm, Hurungwe, Zimbabwe (1998/99)._

Soybean variety Soybean biomass Maize yields

Maize control Nil 0.19 0.2

Yields of maize after soybean were significantly higher than maize after maize, demonstrating significant residual fertility effects of soybean (Table 1). This is a positive contribution to sustainable food production and security as maize is the staple for many sub-Saharan communities. Residual fertility effects on maize have been consistently obtained under farmer management and boosted adoption of soybean BNF against a background of rising mineral N fertilizer prices and depreciating local currencies.

An important benefit of soybean BNF has been the boost in household incomes from grain sales by farmers, with volume sold from four districts rising from 65 tons in 1997 to over 800 tons in 1999. A critical element in the promotion program has been the consolidation of loads to achieve economies of scale that have enabled the relatively small production of each farmer to be sold on the lucrative commodity exchange as part of a large parcel. Produce marketing is a key element of the conceptual framework for promoting soybean.

A study of the economic potential of soybean showed that the crop was most profitable for the poorest farmers as it had lower input costs but gave the highest return on investment (Rusike et al. 2000). Poor farmers who adopted soybean for the first time between 1997 and 2001 have testified that they earned more money from soybean sales than from any other crop that they have ever grown (Table 2). The significant boost in family dietary protein availability (Table 2) is a critical element of household food security, a key benefit of BNF among poor rural communities.

Table 2. Grain, protein and cash returns from soybean for Tapera smallholder farm in Zimbabwe (1998)._

Soybean variety

Total grain yield (kg ha"1)

Protein from 15% seed retained (kg ha"1)

Cash from 70% grain sold (US$ equiv.)

Magoye

2100

126

471

Local

1900

114

302

Roan

2800

168

496

Nyala

3100

186

560

Average smallholder planting: 0.4 ha; average yield: 0.8 t ha"1; average price: US$360 t"1 (2001). Poor nutrition among the HIV-infected is contributing to the high death toll from AIDS. Significant savings from use of rhizobium inoculants also were reported in Zambia (Carr et al. 1998). Integration of soybean into local diets has driven adoption as soybean is processed to substitute several expensive grocery items that include milk and meat.

Average smallholder planting: 0.4 ha; average yield: 0.8 t ha"1; average price: US$360 t"1 (2001). Poor nutrition among the HIV-infected is contributing to the high death toll from AIDS. Significant savings from use of rhizobium inoculants also were reported in Zambia (Carr et al. 1998). Integration of soybean into local diets has driven adoption as soybean is processed to substitute several expensive grocery items that include milk and meat.

7. References

Carr et al. (1998) In Mpepereki, Makonese (eds), Harnessing Biological Nitrogen Fixation in

African Agriculture, University Zimbabwe/CTA, Harare, Zimbabwe Javaheri (1981) Mimeo Government of Zambia, Lusaka

Kasasa et al. (1998) In Waddington et al. (eds), Soil Fertility Research for Maize-based Farming

Systems in Malawi and Zimbabwe, SoilFertNet/CIMMYT, Harare, Zimbabwe Mpepereki et al. (2000) Field Crops Res. 65, 137-149 Svubure (2000) M.Phil. Thesis University of Zimbabwe, Harare, Zimbawe

8. Acknowledgements

We thank the Rockefeller Foundation for funding our recent BNF research and extension work.

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