of irrigated land in SSA despite the claim by Rosegrant et al. (2009) that small-scale irrigation projects are not only more manageable, but also more profitable. Rosegrant et al. (2009) also point out that irrigation projects, regardless of size, are generally only economically viable for cash crop or other high value crop production. They also claim that irrigation is most often utilized when in the presence of complementary inputs and, like Mwendera and Chilonda (2013), rural services. Water rights are clearly an issue for whether or not irrigation is a viable option, although Shah et al. (2002) points to a number of other studies that show that land rights, too, play an important role given the longer term and semi-permanent nature of irrigation investments.

# **_2.5. Farm power and mechanization_**

Traditional agricultural practices in SSA rely on human power channeled through hoes, shovels, cutlasses, and other hand tools to bring new land under cultivation, prepare fields for planting, and harvest crops. Mechanized equipment and/or animal traction can be employed to increase the timeliness of field preparation and expand farm size all while saving labor. The process of moving from hand tools to animal-powered or motorized land preparation devices like tractors is referred to as mechanization and is seen as one way to increase agricultural productivity,<sup>2</sup> and farm profitability when the right conditions exist. The most comprehensive theory of mechanization processes in Sub-Saharan Africa is likely provided by Pingali, Bigot, and Binswanger (1987). From their (now rather dated) review of over 50 sites in Africa, we understand that the use of animal power or mechanized equipment is an evolutionary process of the farming system, not a one-time use decision like some of the other inputs surveyed in this paper, and largely influenced by population pressures. Moreover, major constraints in most smallholder African farming systems (e.g., farm size constraints, livestock disease constraints) exist that prohibit a profitable transformation from mostly human-powered agricultural production to animal or machine intensive operations (Sims and Zienzle 2006).

While studies on tractor use and animal draught power use decisions are far less prevalent than those of the other inputs identified in this paper, the consensus appears to be that reliance on human power for agriculture is still hugely dominant and limits productivity increases (e.g., Sims and Zienzle 2006). In an overview of the current state of mechanization of Sub-Saharan Africa using FAOSTAT/AGS data, Mrema (2011) finds that there were 2 tractors per 1000 ha of arable land in 1980 but only 1.3 in 2003, as compared to the more than doubling of tractor prevalence in Latin American and Asia over the same time frame. Pingali (2007) also observes a decrease in tractor use over time in SSA. Using data from 1998, Clarke and Bishop (2002) report that 65 percent of land under cultivation was done by hand, 25 percent using draught animal technology (DAT), and 10 percent using engine power. Ashburner and Kienzle (2011) show a decrease in mechanization in SSA, claiming that primary preparation carried out by hand tools is currently at 80 percent, with DAT only at 15 percent and the remaining 5 percent using tractors.

> 2 Pingali and Binswanger (1984) found a decreasing relationship between farming intensity and yield per hectare across 52 countries in Africa, Asia, and Latin America. Using the same data, however, they find a positive and significant relationship between farming intensity and labor productivity.

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