Yield gaps, the difference between actual production and what is potentially achievable under optimum growing conditions, are greatest in the poorer parts of the world, and these regions are also the ones that are predicted to be most vulnerable to the combined pressures of increases in population, the effects of climate change, environmental degradation and urbanization.
Poor harvests and reduced farm household income make it more difficult to improve productivity.
A study examining cassava productivity in smallholder farmers’ fields in Kenya and Uganda established that several factors contribute to low yields, including poor soil fertility (the main constraint), water scarcity and substandard management practices. Farmers were aware of the importance of soil fertility, with 62 per cent describing it as a critical factor in low yields, and 22 per cent as the more important cause for low productivity. Applying fertilisers (correctly) would be the simplest and most effective solution, especially if combined with the use of improved planting materials, but for many smallholder farmers both of these remain too expensive and/or out of reach.
In addition, individual constraints to productivity are known to interact with each other to keep yields low. Plants respond to mixtures of stresses differently from individual ones, and therefore maximising yields requires addressing all the problems together, something that is much easier to do for wealthier and better informed farmers than for those with limited resources and poor access to inputs and labour.
Figure 1: The concept of yield gaps among theoretical potential, experiment station yield, the potential farm yield and the actual farm yield
Poor harvests and reduced farm household income in turn make it more difficult to improve productivity in each succeeding growing season. Yield gaps are poverty traps.
This is especially true for women farmers, since they typically have less access to resources than their male counterparts. A study reviewing sorghum productivity in Ethiopia, for example, found that productivity was significantly lower for female-headed households than for male-headed ones because of many socio-economic problems. Furthermore, women were unrepresented in a survey (17% of the total) because many of the questions were intended for farmers who owned the land they farm, and the majority of women either rented or shared their plots.
Other important socioeconomic factors for reducing yield gaps include: contact with agricultural extension agents, in particular in low productivity areas; size of land holding; education level attained by the household head; age; ownership of livestock; the possibility of hiring labour; and production of cash crops, as a spill-over effect on other crops farmed. Most of these factors discriminate against women.
Knowledge of the socioeconomic context in which smallholder agriculture exists is essential. Despite the critical importance of socioeconomic factors in yield gaps, these are often not considered: a recent review of the yield gap literature established that of 62 papers on the topic, only eight included models that considered socioeconomic factors.
It has also been argued that poor understanding of how smallholder farms operate has led to an excessive focus on grain productivity of individual crops. Since managing risks is critical for resource-poor farmers, yield stability may actually be more important than absolute yield. Farmers may also value other parts of the crop in addition to the grain, such as straw for feeding livestock, generating energy or as building material, yet most studies on yield gaps do not take account of these. And intercropping systems, when crops are grown among those of a different kind, may result in higher farm productivity and resilience, and better preservation of natural resources, even if, due to competition, the individual yields of the intercrops are lower than in single cropping stands.
Access to markets and the possibility of either safely storing and/or adding value to farm products are also important in determining the decisions farmers make. What is the point in producing more if you can’t either sell it profitably or keep it unspoiled for later use?
The need to research fully and address the socioeconomic factors that create and maintain yield gaps does not detract from the importance of research on innovation, technologies and knowledge aimed at the same goal. Rather, it calls for a more integrated and nuanced approach to the problem that aims to explore all the complexities, as defined by Figure 2.
Figure 2: Socioeconomic factors that create and maintain yield
Integration is crucial: improved seeds, or suckers for banana or roots for cassava, addressing critical constraints to production will only have an impact on farmers if they can access these materials and the information on how to best use them. This requires a functional distribution system and effective agricultural extension services. Yet fake seeds – grain coloured so as to look like treated seed – remain a problem, which can affect up to 30 per cent of purchased samples, as does fertiliser adulterated with cheap ingredients. Equally, agricultural extension services in Sub-Sahara Africa are typically underfunded and understaffed, with accountability and governance problems, by men who do not appreciate the needs of, and are not appreciated by, women who carry out a large part of farming work and do not reach the vast distances from cities. This means smallholder farmers do not get the services they need and to which they should be entitled.
Policies devoted to closing yield gaps must focus on rural development and the creation of wealth in poor farming communities. Beyond the outlined topics for research, this requires providing or enabling access to sustainable energy sources; to safe drinking water and water for agricultural production; good quality education and health services; access to functioning and fair markets; and suitable financial tools such as credits, insurances and targeted subsidies.
Claudia Canales Holzeis is a plant molecular biologist with a near-decade of experience in plant genetics research. She previously worked as Senior Project Officer for the International Service for the Acquisition of Agri-Biotech Applications (ISAAA), based in the Philippines. A graduate of the University of Reading in Environmental Biology, Claudia Canales gained a DPhil. in Plant Genetics at Oxford.