technology abandoned it. A 1990 survey found that only 29 percent of the farmers who first used fertilizer under the program kept using it (Tripp, 1993, p. 2012).

Similar programs were launched for maize in Ethiopia, Ghana, Kenya, Malawi, Mozambique, Sudan, Zambia, and Zimbabwe (Smale, 1994; Brinkley, 1996; Howard et al., 2003; Smale and Jayne, 2011). Some programs showed early success before reaching an adoption plateau; however, often adoption gains were reversed and new technologies abandoned. Frequently, adoption depended heavily on controlled prices or subsidies that proved too expensive to maintain. Similarly, researchers are finding that several recently launched campaigns to promote MV technologies with subsides are proving expensive with marginal benefits at best (Ricker-Gilbert et al., 2013; Jayne and Rashid, 2013).

# **7.1.2 Heterogeneous conditions and technologies**

An alternative explanation is that the circumstances that affect the profitability of a given technology are heterogeneous, so it is unlikely that all farmers will decide to use the same technology. In this sense, the choice of technology is endogenous (Mundlak, 1988; Mundlak, Butzer and Larson, 2012). Differences in natural endowments, for example soil fertility or water availability, affect fertilizer response rates, yields, and therefore the profitability of a given technology (Larson and Leon, 2006; Marenya and Barrett, 2009; Jayne and Rashid, 2013). Variable weather adds to the risk of a technology, even if the technology is profitable on average (Larson et al., 2016). Spatial differences in transport and transaction costs affect relative profitability (Xu et al. 2009). In the specific case of maize, Suri (2011) concludes that in Kenya, the differences in the costs and benefits of using maize hybrids explain the differences in choices made by adopters and non-adopters of MV technologies. In short, the market prices and relevant shadow prices farmers face differ, which generates variation in pursued livelihood strategies and employed technologies.

Practical differences in technology preferences is illustrated by Table 2, which shows that input use intensities such as chemical fertilizer and manure application per hectare, the share of intercropped fields, and the percentage of adoption of hybrid seeds are all substantially higher in Kenya than Uganda, which led to the higher maize yields and higher crop income in Kenya than Uganda. Nevertheless, in the case of Uganda, the use of low-input-low-yield technologies are consistent with weather-related yield risks (Larson et al., 2016).

# **7.1.3 The Integrated Maize Farming System**

While research and extension programs often focus on high-yielding seed-fertilizer technologies, another avenue is to adopt integrated soil fertility management systems, which use both organic and inorganic fertilizers. For example, in India, Kajisa and Palanichamy (2013) found that application of organic fertilizer directly increased productivity of upland cereals and also raised the efficacy of chemical fertilizers in low fertility soils. Evidence from Malawi and Kenya shows that intercropping or rotating maize with nitrogen-fixing legumes is another possible way to restore soil nutrients (Snapp et al., 2010; Ojiem et al., 2014).

A more complex integrated maize technology, which seems to work well in populous areas that are also free from sleeping sickness, is examined by Muraoka et al. (2016) and Otsuka and Yamano (2005). In the highlands of Kenya, farmers who adopt this system grow forage crops such as Napier grass and 13