Shirley A. Tarawali

An integrated agro-ecosystem and livelihood systems approach for the poor and vulnerable in dry areas

More than 400 million people in the developing world depend on dryland agriculture for their livelihoods. Dryland agriculture involves a complex combination of productive components: staple crops, vegetables, livestock, trees and fish interacting principally with rangeland, cultivated areas and watercourses. Managing risk and enhancing productivity through diversification and sustainable intensification is critical to securing and improving rural livelihoods. The main biophysical constraints are natural resource limitations and degradation, particularly water scarcity and encroaching desertification. Social and economic limitations, such as poor access to markets and inputs, weak governance and lack of information about alternative production technologies also limit the options available to farmers. Past efforts to address these constraints by focusing on individual components have either not been successful or are now facing a declining rate of impact, indicating the need for new integrated approaches to research for development of dryland systems. This article outlines the characteristics of such an approach, integrating agro-ecosystem and livelihoods approaches and presents a range of empirical examples of its application in dryland contexts. The authors draw attention to new insights about the design of research required to accelerate impact by integrating across disciplines and scales.

Integrating crops and livestock in subtropical agricultural systems

As the demand for livestock products increases, and is expected to continue to increase over the next few decades, especially in developing countries, smallholder mixed systems are becoming more intensive. However, with limited land and water resources and concern about the environmental impact of agricultural practices and climate change, the challenge is to find ways of increasing productivity that do not compromise household food security, but rather increase incomes equitably and sustain or enhance the natural resource base. In developed countries there has been increased specialisation of crop and livestock production. In contrast, the majority of livestock in developing countries is kept in mixed crop/livestock systems. Crops (cereal grains and pulses) and crop residues provide the basis of the diet for animals, e.g. cereal straw fed to dairy cattle or sweet potato vines fed to pigs. Animal manure can provide significant nutrient inputs to crops. Water productivity is higher in mixed crop/livestock systems compared with growing crops alone. Mixed systems allow for a more flexible and profitable use of family labour where employment opportunities are limited. They also spread risks across several enterprises, a consideration in smallholder systems that may become even more important under certain climate change scenarios. Integrated crop/livestock systems can play a significant role in improving global food security but will require appropriate technological developments, institutional arrangements and supportive policy environments if they are to fulfil that potential in the coming decades.

Adaptation of the CROPGRO growth model to velvet bean (Mucuna pruriens): II. Cultivar evaluation and model testing

Velvet bean (Mucuna pruriens (L.) DC. cv.-group utilis) is widely promoted in tropical and sub-tropical regions as a green manure cover crop that can reduce weed growth and soil erosion and enhance soil fertility. To provide these benefits, the crop must attain rapid ground cover and develop substantial aboveground biomass. To assist biophysical targeting of the crop to environments that can provide adequate growth conditions, the CROPGRO model was adapted to simulate velvet bean growth and development. This paper evaluates the performance of the model for phenology, growth, senescence and N accumulation for multiple locations that represent a range of environmental and agronomic management scenarios. Vegetative development, as described by main stem leaf appearance rate, varied linearly with thermal time. Time to flowering showed departures from the linear photoperiod response used in the model. Additional research is required to determine whether the crop is influenced by factors besides photoperiod and air temperature, especially water and nutrient deficits. The linear response to photoperiod did, however, provide reasonable values for partitioning to vegetative, reproductive and senesced materials. Simulation of nitrogen concentration for various plant components matched observed data. Sensitivity analyses evaluating the ability of the crop to provide ground cover, intercept light and develop adequate growth for soil protection and weed suppression indicated that a mean temperature of over 22 °C and a soil moisture holding capacity of at least 100 mm are required. The CROPGRO model proved to be a reliable decision support tool for guiding analyses of velvet bean response to crop management and environmental conditions. Further research, however, is warranted to improve its predictive capability, especially for phenology.

The potential contribution of selected forage legume pastures to cereal production in crop-livestock farming systems

The potential of 3-year-old grazed pastures of Stylosanthes hamata, Chamaecrista rotundifolia and Centrosema pascuorum to contribute to subsequent maize production was investigated in subhumid Nigeria in 1993. All three legume pastures had the ability to give better maize grain yields than native pasture but this was significant only for Stylosanthes hamata and Chamaecrista rotundifolia. For the legume species, maximum yield of maize per kg of N applied was attained at 60 kgN/ha. The subsequent yields of maize could be related to the legume species used, pasture management and the length of the fallow period. Centrosema pascuorum behaved as an annual, and as such there was little legume present after 3 years; crop yield was therefore relatively low. Nevertheless, this species could be useful in 1-year fallow/pasture situations. Maize cropping was economically viable for legume plots only with 60 or 120 kgN/ha and not for native pasture. There were no significant differences in the time required to till or to weed legume pastures as compared with native pasture. Forage legume pastures could also have a positive effect on maize residue yields which represent a fodder resource in addition to the herbage understorey remaining after cropping, the quality of which could be enhanced by the presence of the forage legumes. The use of forage legumes for the promotion of both crop and livestock production in sustainable agricultural systems is discussed. The results of the study are used to highlight the importance of selecting the appropriate legume species, pasture management practices and duration of fallow period in relation to the prevailing farming system to maximize benefits from the legumes.

Characterization of a collection of Aeschynomene histrix in subhumid Nigeria.

A collection of 64 accessions of the South American pasture legume Aeschynomene histrix Poiret was characterized in 1995 at Ibadan in south-west Nigeria in order to test the potential of the accessions as forage plants in subhumid areas and as a trap crop for the parasitic plant Striga hermonthica (Del.) Benth. All accessions had a low biomass production during the first 8 weeks after sowing but soon variations in the collection became apparent. Morphologically, accessions could be classified as having prostrate, decumbent, semi-erect and erect growth habit. The semi-erect to erect accessions grew vigorously and had high dry matter yields. The most frequent disease was Rhizoctonia foliar blight, for which, in general, prostrate accessions had a higher severity. In contrast, plants with semi-erect to erect growth habit were more susceptible to a wilting disease probably caused by Fusarium spp. With an average crude protein content of 16% and 48-h in sacco dry matter and protein digestibilities of c. 50%, fodder quality of 13-week-old plants was similar to that of other tropical forage legumes. As a result of a laboratory experiment to test the potential of A. histrix to act as a trap crop for Striga hermonthica, 13 accessions showing a significant influence on in vitro Striga hermonthica seed germination were identified. Twenty promising accessions were selected for further evaluation. These accessions showed good biomass production and/or high tolerance to diseases and/or significant influence on Striga hermonthica seed germination. Such material has the potential to contribute to both livestock-forage and improved fallow systems with the aim of increasing the sustainability of agricultural production in West Africa.

Potential of Lablab purpureus accessions for crop-livestock production in the West African savanna

The introduction and use of herbaceous legumes may contribute to agricultural intensification, especially in the context of sustainable crop and livestock production systems. In the context of evaluating different legume species for these systems in moist savanna zone of West Africa, the present study involved the evaluation of 46 accessions of Lablab purpureus (L.) Sweet between 2000 and 2002 at Samaru, Zaria in the northern Guinea savanna of Nigeria to identify accessions with the potential to contribute to grain or forage production and those with the potential for multiple use. Grain yields (0·6–2·4 t/ha) with a mean seed crude protein and phosphorus content of 25·3 and 0·46 g/kg, respectively, were obtained. Dry matter yields (leaf: 0·3–3·1, stem: 0·2–4·6, root: 0·03–0·3 t/ha) were produced between 40 and 140 days after planting. Within this same period up to 1152 kg shoot crude protein/ha, equivalent to 184 kg N/ha, were recorded for accessions. Ten accessions that may contribute to grain production, eight accessions that may contribute to forage production and six accessions with drought tolerance were identified. Some white-seeded accessions (Grif 1246, ILRI 4612 and PI 183451) with good grain and forage yield and high-protein content have the potential to provide more and higher quality food for people and feed for livestock. The observed potential to contribute to grain production for protein-rich food, feed for livestock and green manure for soil N improvement suggests lablab may be an acceptable legume option for use in cereal-legume-livestock systems in the moist savanna zone of West Africa.

Relative palatability and seasonal agronomic performance of selected pasture legumes for species mixtures in dry-subhumid West Africa.

Relative palatability and some agronomic traits were studied for nine legumes including Aeschynomene histrix , Centrosema brasilianum (two accessions), Centrosema pascuorum , Chamaecrista rotundifolia , Stylosanthes guianensis (two accessions) and Stylosanthes hamata (two accessions). All species were consumed by cattle but the relative palatability varied according to season. Only the two S. guianensis accessions were positively selected throughout the year. A positive relationship was established between the ability to retain green leaves in the dry season and palatability. Once established, the two C. brasilianum accessions out-performed the other legumes in their ability to stay green and retain leaves in the dry season; related to the ability to retain green leaves under drought conditions, C. brasilianum ILRI 155 was among the most palatable legumes in the dry season. S. guianensis accessions had the highest dry matter (DM) yields and one of them (ILRI 15557) had the highest nutritive value. In contrast with earlier results in the same environment, C. rotundifolia and A. histrix performed poorly in terms of DM productivity. The implications of the agronomic characteristics of the legumes for the management of legume-based pastures in crop/livestock systems are discussed and the concept of legume–legume mixtures, composed of several compatible species, is advocated.

Improving water productivity in crop-livestock systems of drought-prone regions: Editorial comment

Crop-livestock systems in sub-Saharan Africa (SSA) are mostly rainfall-dependent and based on fragmented marginal lands that are vulnerable to soil erosion, drought and variable weather conditions. The threat of water scarcity in these systems is real, due to expanding demand for food and feed, climate variability and inappropriate land use (Amede et al ., 2009). According to recent estimates, farming, industrial and urban needs in developing countries will increase water demand by 40% by 2030 (FAO, 2009). Water shortage is expected to be severe in areas where the amount of rainfall will decrease due to climate change. The lack of capacity of communities living in drought-prone regions to respond to market opportunities, climatic variability and associated water scarcity also results from very low water storage facilities, poverty and limited institutional capacities to efficiently manage the available water resources at local, national and basin scales. The spiral of watershed degradation causes decline in water budgets (Awlachew and Ayana, 2011), decreases soil fertility and reduces farm incomes in SSA (Amede and Taboge, 2007) and reduces crop and livestock water productivity (Descheemaeker et al ., 2011). In areas where irrigated agriculture is feasible, there is an increasing demand for water and competition among different users and uses.

Characterization of a germplasm collection of the tropical pasture legume Centrosema brasilianum in subhumid West Africa

The available world collection consisting of 257 accessions of the tropical pasture legume Centrosema brasilianum (L.) Benth. was assessed between 1993 and 1995 in northern Nigeria to complement existing knowledge on the genetic diversity of this species and to identify accessions with high agronomic potential for subhumid west Africa. The excellent nutritive value and good dry matter productivity of C. brasilianum and its outstanding ability to remain green over extended dry periods confirmed its potential as an important forage resource, especially for the dry season, and indicated its possible role in soil conservation. Two distinct groups, comprising 10 and 11 accessions, were identified for further evaluation in short fallow and pasture systems, respectively. Accessions in the first group had a fast establishment, very high yields in the establishment year and good drought tolerance but yields were low to average in subsequent years. Accessions in the second group had sustained high yields under grazing, a high competitive ability and good drought tolerance.

Assessment of water productivity and entry points for improvement in mixed crop-livestock systems of the Ethiopian highlands

between environmental legislation and the size and geometry of their farms. Amongst the respondents, 89% said that only punitive law enforcement would be able to force them to maintain all the APP (in-farm permanent protection areas). About 88% of the farms that adopted pasture base dairy-MIG, fenced off springs and remaining forests. The use of electric fences in MIG system minimizes animals contact with water, streams and forest areas. Finally, for 91% of the famers interviewed pasture carrying capacity and milk sales increased substantially when they switch from traditional semiconfinement to pasture based dairy.