Pigeon pea (Cajanus cajan) is a tropical legume native to South Asia. Its high protein content and adaptability to arid environments have made it an important food crop across sub-Saharan Africa. Pigeon pea is a genetically diverse crop with several varieties that differ in time to maturity and plant architecture. A number of these varieties are perennial in nature, with a shrubby habit that helps them last several growing seasons and regrow after harvest.
Currently, concerted efforts to breed perennial pigeon pea are scarce. But the existence of perennial cultivars and the practice of ratooning pigeon pea means perennial pigeon pea could be readily implemented on smallholder farms. Perennial pigeon pea is also particularly promising in that it can be effectively integrated in cropping systems with other essential food crops such as maize and cow pea.
Current use in sub-Saharan Africa
Pigeon pea is an important food crop in several parts of sub-Saharan Africa, providing both a high protein food source and large amounts of fodder for livestock. It is often grown on a smaller scale for non-commercial use than more dominant crops. Smallholders use it both as a perennial and an annual, and it is very important in some areas to ensuring food security.
Mapping priority areas for perennial pigeon pea production
Researchers on the Perennial Grains for Africa project mapped optimal areas for perennial pigeon pea production using geographic data from Malawi, Mali, Ghana, and Tanzania. Perennial pigeon pea production is currently proposed as a strategy to be utilized on marginal agricultural lands that are poorly suited to the production of more dominant crops. Utilizing perennial pigeon pea on marginal areas could improve their soil quality while not displacing a significant amount of current production.
First, marginal agricultural areas were identified by using a combination of map products that identified areas with a combination of marginal land suitability for agriculture, poor net primary productivity, and sub-optimal surface temperature and precipitation. These maps were then combined with maps that identified areas with optimal growing conditions for pigeon pea based on temperature and precipitation. The intersection of these two map products produces, then, a map of areas of that too marginal for the production of important staple crops, but have sufficiently good characteristics for the production of pigeon pea.
Evaluation of tradeoffs by smallholders
Researchers used choice experiments to study farmers‚Äô preferences for attributes of a perennial pigeon pea crop. Choice experiments measure stated preferences of participants as opposed to revealed preferences that come from observed market transactions. Choice modeling is a method used to estimate the marginal value of various attributes of a good and is especially useful when an observed transaction of a good does not occur. Choice experiments are a flexible tool useful for understanding choices and demand for new products or technologies.
Choice experiments were conducted in three districts in Malawi‚Äôs Central and Southern Regions: Dedza, Ntcheu and Zomba. The sample consists of farmers from 488 village households that were interviewed in September and October 2014. Each respondent evaluated five choice scenarios in which different aspects of the proposed cropping system, such as perenniality, soil fertility, and yield, varied.
These estimates were then used to calculate the marginal rate of substitution or willingness-to-pay in terms of maize yield for each of the cropping system variables modified in each choice scenario. Farmers are only willing to substitute about 32 kilograms of maize (per hectare) to get the lower labor and seed requirements associated with a perennial crop. They are however willing to trade 347 kg per hectare of maize yield to get high soil fertility and 131 kg/hectare to get high biomass. The results suggest that farmers would only accept a 2% reduction for perenniality alone, but as much as 20% to have higher soil fertility and 7% to have higher biomass production, which can be associated with perennial cropping systems.
Modeling perennial pigeon pea adoption scenarios
To model the potential demand for perennial pigeon pea cropping systems in Malawi, researchers developed system dynamics models that combine elements from sociological and economic theories of change that stress the importance of peer-to-peer communication in the adoption of new technologies. These models incorporated results from the choice experiments to further quantify farmers’ willingness to replace existing practices.
The two most important controls on adoption patterns were existing maize yield potential and the potential risk for grazing damage on pigeon pea by livestock. Adoption of perennial pigeon pea cropping systems was modeled as being slower in areas with high maize yield potential since choice experiments indicate that farmers inherently value maize more. However, in lower fertility areas with low maize yield potential, models predicted faster uptake of perennial pigeon pea systems. When a 75% reduction of yields by livestock grazing was included in the model, adoption rates were significantly reduced, indicating that the potential benefits of perennial pigeon pea are moot if crops cannot be protected from animals.
Models were then further extended to include greater climate variability, as is predicted by current climate change models for Malawi. Compared to the control systems of maize and pigeon pea monocropping, adoption of perennial pigeon pea systems was more sensitive to climate variability, and adoption rates significantly decline in extreme conditions wherein crops perform very poorly.