Sustainable resource management coupled to resilient germplasm to provide new intensive cereal–grain–legume–livestock systems in the dry savanna

Sustainable resource management is the critical agricultural research and development challenge in sub-Saharan Africa. The accumulated knowledge on soil management gathered over the last 10 years, combined with solid crop improvement and plant health research at farmers’ level, has brought us to a stage where we can now address with confidence the intensification of cereal–grain–legume-based cropping systems in the dry savanna of West Africa in a sustainable and environmentally positive manner.Two sustainable farming systems that greatly enhance the productivity and sustainability of integrated livestock systems have been developed and implemented in the dry savanna of Nigeria. These are: (i) maize (Zea mays L.)–promiscuous soybean [Glycine max (L.) Merr.] rotations that combine high nitrogen fixation and the ability to kill large numbers of Striga hermonthica seeds in the soil; and (ii) miflet [Eleusine coracana (L.) Gaerth] and dual-purpose cowpea [Vigna unguiculata (L.) Walp.]. Improvement of the cropping systems in the dry savanna has been driven by the adoption of promiscuously nodulating soybean varieties (in particular TGx 1448-2E) and dual-purpose cowpea. The rate of adoption is very high, even in the absence of an efficient seed distribution system. The number of farmers cultivating the improved varieties increased by 228% during the last 3 years. Increased production of promiscuous soybean has been stimulated by increased demand from industries and home utilization. Production in Nigeria was estimated at 405,000 t in 1999 compared to less than 60,000 t in 1984. Economic analysis of these systems shows already an increase of 50–70% in the gross incomes of adopting farmers compared to those still following the current practices, mainly continuous maize cultivation. Furthermore, increases in legume areas of 10% in Nigeria (about 30,000 ha in the northern Guinea savanna) and increases of 20% in yield have translated into additional fixed nitrogen valued annually at US$ 44 million. This reflects, at the same time, an equivalent increase in land-use productivity, and with further spread of the improved crops, there are excellent prospects for additional economic and environmental benefits from a very large recommendation domain across West Africa.     

Post-flooding disaster crop diversity recovery: a case study of Cowpea in Mozambique

To restore food security to a traditional African cropping system following a sudden loss of seed, genetic diversity must be re-established. This study examines the extent to which Cowpea diversity was reinstated two years after a flood disaster in Gaza Province, Mozambique. The contribution that seed from various sources made to the recovery was assessed using semi-structured interviews and morphological and molecular data. Data suggest that diversity had recovered to some extent yet there was evidence of a narrowing of the genetic base, with fewer rare alleles and differences in the distribution of allele frequencies. Although the main channels for accessing seed after the flood were seed relief and markets, these sources contributed to minimal and different diversity. It appears that diversity was regained primarily through social networking in the form of loans or gifts of seed from friends and relatives. The results of the study are discussed in relation to seed relief approaches.     

Response of cowpea and soybean to P and K on terre de barre soils in southern Bénin

Good growth of grain legumes helps food security and protection of the environment but this may require nutrient inputs. A participatory technology development activity explored from 1998 to 2000 the responses of cowpea (Vigna unguiculata) and soybean (Glycine max (L.) Merr.) to inorganic soil amendments (P and K) on terre de barre soils with different levels of degradation in southern Bénin. Adingnigon, on the Abomey plateau, represents a level of severe degradation, while Hayakpa, on the Allada plateau, is still relatively non-degraded. Treatments included: (i) an unamended control, (ii) P fertilizer only, applied in 1998 or 1999, and (iii) P plus K applied in 1999. At Hayakpa, yields without fertilizer were generally moderate to high; responses to P were statistically significant and K application had a significant effect on soybean yield in 2000. At Adingnigon, P application had a large relative effect (30–200%) but a small absolute effect (less than 100 kg/ha) on cowpea and soybean yield. Subsequent K application increased grain yields further (approximately 100 kg/ha) but still not up to the cowpea yield potential. When 13 Mg/ha of organic amendment (chicken manure or cotton seed) were applied to severely degraded plots at Adingnigon with prior grain yields below 200 kg/ha, cowpea yields of more than 500 kg/ha were achieved, approaching their biological potential for the zone. It is clear from this study that (i) P and K inputs are needed for grain legumes even on relatively non-degraded terre de barre soils and (ii) inorganic fertilizer alone will not revive highly degraded soils on the terre de barre plateaus of southern Bénin.