productivity loss over the past 50 years of 13% for cropland (Scherr, 1999).

 Increasing degradation of natural resources is already having a negative feedback effect, reducing the potential of agriculture and any new innovations, and making the task of increasing productivity and reducing malnutrition all the harder. For example, soil degradation reduces the potential of agricultural initiatives such as improved water management (IAC, 2004). Current policies and priorities have not, in the main, slowed down this degradation. And despite the existence of many technologies for the improved management of soil fertility in SSA, there has been a poor uptake of these existing technologies by smallholder farmers.

Though contentious, increased applications of synthetic fertilizers are seen by many practitioners as essential for SSA, as reflected in the resolution by AU members to increase fertilizer use significantly by reducing its cost through national and regional level procurement, harmonization of taxes and regulations, the elimination of taxes and tariffs, output market incentives, and access to credit from input suppliers (Chude, 2007). The AU’s recommendation to remove all taxes and tariffs from fertilizer and fertilizer raw materials could increase fertilizer use. However, farmers are unlikely to increase their use unless they have access to markets for the output, they are confident that the expected returns are sufficiently high to justify the cost, they have access to affordable credit to purchase fertilizer and the risks of crop loss (or revenue loss from adverse market conditions) are sufficiently low.

Recommendations for fertilizer use typically involve unsophisticated “blanket high dose” applications while research focuses on fine-tuning high-input recommendations that are particularly inappropriate for the region, given the cost of fertilizer in SSA and the understanding that higher doses of fertilizer are more likely to result in environmental pollution (Snapp et al., 2003). More appropriate, particularly for resource-poor farmers in SSA, are approaches and recommendations that enable farmers to maximize returns
from smaller input purchases (Snapp et al, 2003). Further, as the following discussion on integrated approaches to water and soil management highlights, given the poor state of soils in much of SSA, mineral fertilizer alone may have little impact on yields and therefore the economic justification for increasing fertilizer use.

Pollution and health hazards from agrochemical use including fertilizer and pesticides in SSA are currently less of an issue than in other regions because most farmers cannot afford to apply any, let alone high levels of fertilizer, particularly given its relatively high cost. However, experience from other regions suggests that in parallel with encouraging increased fertilizer use, efforts will be needed to reduce the negative associated health and environmental impacts including soil acidification and water pollution that particularly come from excessively high levels of fertilizer (Weight and Kelly, 1998). Farmers are more likely to minimize the negative environmental effects of fertilizer use if they have access to technologies that enable technically efficient application, typically specific to local soil conditions (Weight and Kelly, 1998). Biological control is an option for integrated pest management and involves augmentation or conservation of local, or introduced natural enemies to pest

populations. There are several examples of where staple and important crops have been saved by biological control over wide areas.

Fifty-seven percent of SSA’s land is “marginally sustainable”, meaning poorly buffered soils with very low soil organic matter and poor water retention (Weight and Kelly, 1998). Addressing one of these problems without addressing the other in parallel is likely to have very little impact on output, and indeed there is a growing consensus that gains in productivity in SSA require an integrated approach to soil, nutrient, and water management rather than undertaking separate research. On farms with low soil moisture and low fertilizer-use efficiency, the addition of chemical fertilizer is likely only to be profitable where there is regular rainfall or irrigation, and already relatively high organic matter in the soil (Masters, 2002). A combination of organic and inorganic sources of nutrients—integrated nutrient management—has been found in many situations to be more effective than using just one approach (Murwira and Kirchmann, 1993; Swift et al., 1994; Ahmed and Sanders, 1998; Bationo et al., 1998; Murwira et al., 2002; Ahmed et al., 2000). Green manure crops can be grown in farmers’ own fields, and there is evidence in West Africa that they can help to revive degraded lands. Yet although green manure technologies have been successfully developed for west Africa, and even though some farmers have adopted them, many farmers see green manure crops as competing with edible and cash crops, and having little observable impact on yields and soil fertility in the short term, and so are reluctant to adopt them.

In some areas of SSA, such as western Kenya, phosphorus deficiency is a critical limiting factor for crop yields, such that without application of phosphorus, investments in nitrogen or nitrogen-fixing legumes has little impact (Sanchez, 2002; Smalberger et al., 2006). Phosphorus can be added in several ways: phosphorus fertilizers; phosphate rock (such as Minjingu rock in Kenya); and phosphate released from biomass such as from Tithonia leaves. Phosphorus fertilizers are relatively costly in SSA and are scarce in some countries, due in part to poorly developed markets, a lack of domestic production, or limited foreign exchange, and so, not surprisingly, phosphorus application in SSA is low (1kg ha-1 compared with 14.3 kg ha-1 in Asia) (Bruinsma, 2003; Smalberger et al., 2006). The use of relatively small applications of phosphorous has been found to be effective at increasing vegetative cover in Nigeria (CGIAR). However, in water excessive phosphorous can over-stimulate the growth of algae thereby depleting the water of dissolved oxygen and harming aquatic life. The addition of phosphorous combined with improved soil erosion management techniques is likely to reduce the potential negative externalities of its application. Further, phosphorous fertilizers may contain cadmium which can enter certain crops including potatoes and leafy vegetables and which is toxic to humans.

Integrating Approaches
Encouraging more integration requires alternative approaches to the “transfer of technology” model that has been common in SSA. There has been criticism of natural resource related research approaches that are predominantly undertaken on research stations rather than collabora-