Cereal-based production systems dominate the smallholder sector in developing countries, reflecting a focus on provisioning of food (calories) as the basic agriculture service. Coupled human natural systems are at the core of agroecosystem design, and it is insightful to consider the viability of diversification options within this production context. Two decades of research in cereal-based cropping systems of the sub-humid to semi-arid tropics is drawn upon to develop functional assemblage theory that address multiple sustainable development goals. Rigorous analysis of tradeoffs among the ecosystem services provided by different functional types illustrates the services provided by diversification with legumes. These include nutrition-enriched food, fuel, saleable products and augmentation of soil resources for improved productivity. We report on temporal dynamics using on-farm transects and trial data from
Results/Conclusions
Our results indicate that soil productivity and active organic matter pools (but not necessarily total soil organic matter) can be built on smallholder farms through management strategies that enhance biological cycling of phosphorus and nitrogen. Specifically, successful approaches involved: 1) incorporating as rotational or intercrops legume species that enhance availability of sparingly soluble phosphorus (e.g., lupin or pigeon pea) and 2) judicious use of small doses of fertilizer or manure. We found that a focus on optimizing calorie production in the short-term limits the range of plant functional types to cereals and short-duration annual grain legume, with negative consequences for long-term ecosystem services. Consideration of diverse performance criteria shifts the focus to combinations of short and long-duration multipurpose legumes and cereals, to provide services throughout the year. Services of particular interest to limited resource households (e.g., widowed and the very poor) included nutrient cycling efficiency; soil building and provisioning of food during the hungry season. Intercrops of early maturing, nutrient-enriched crops – e.g. peanuts - and long-season multipurpose legumes that build soil nutrient biological pools –e.g. pigeon pea – were found to augment a unique bundle of ecosystem services missing on many smallholder farms.
